Anybody herd of micro cracks in 4.0 tfsi?

[Marsolek1]

Took car to dealership was told I have micro cracks in my block and need a new engine.. my cooling system keeps getting bubbles in heater core causing no heat in cabin...I can bleed the air screw every day and 10 min later after driving no heat again... theirs no oil in water and no water In oil... they said they tested the bubbles in cooling system and it's not exhaust gasses. They said it's boost pressure... where could boost pressure be getting into cooling system at? It has a two brand new turbos from recall and pickup tube...

[gk1]

Get a second opinion.

[RLCree]

2 ways, either head gaskets or cracked block. Do a leak down test and you'll find it. I would perform it both at top and bottom dead center. That'll test both the gaskets and the entire cylinder bore.

[Marsolek1]

Is micro cracks a thing with the 4.0 tfsi? I will try leak down test

[Avantly]

If you have some manner of micro fractures I would expect that dye + a pressure test would reveal the location, but if they are small maybe it only leaks when hot. The only thing that would make me scratch my head is that if such cracks exist, it seems that you would have coolant leaking externally and at least have some dried coolant residue around the crack area, and low coolant would be the cause of the air in the system. How much coolant are you losing? The "boost pressure" claim makes no sense to me, I don't have the diagram in front of me but I am not aware of any pre-combustion-chamber location in the block that sees boost pressure other than the intake ports, and if it were leaking in the intake runner then you should be able to see the crack location simply from coolant also escaping into the affected intake port and washing away some of the carbon deposits. Therefore the next step would be to at least add dye to the cooling system and check such an area.
It seems more likely that the source of a "boost pressure->cooling system" leak would be the water-to-air intercooler on the front of the engine. I think you might need to get a second opinion from a shop that knows this engine.

[Marsolek1]

I have to top off coolant dam near every 3 days gallon or so is getting a bit expensive.. their is no signs of coolant leaks outside engine and the bubbles start when engine is hot. I was thinking the intercooler also but one would think the pressure building g in my cooling system is excessive and blowing the expansion tank cap relief loosing coolant.. the black little hard coolant line going to the top of the expansion tank shakes and jiggles when the bubbles go threw the line...I will check my water to air cooler and put some die in coolant and check the intake Valves.. will update soon as I get time from work to tackle project ...thinking I might as well just tare heads off...

[Botbasher]

I was thinking the intercooler also but one would think the pressure building g in my cooling system is excessive and blowing the expansion tank cap relief loosing coolant..

It'll blow out the cap only if you have extreme over pressure (or a weak spring in the cap)... but that'll leave very visible signs!

So what if you have a crack in the intercooler that only manifests when hot and under pressure... but it's not enough to cause misfires... you'll pull the heads to find... NOTHING!! Remember, pressure in the intake goes both ways... positive and vacuum!!

I'd try 2 things before I break into the block.

1) Get a Combustion Gas Detector and test your coolant. That'll tell you if it's coming from the cylinders. If not, move on...

2) Get a Coolant System Pressure Tester (I think both can be loaned from auto parts stores) and do some basic testing before jumping off the deep end! You'll see on the gauge and hear the leak. Remove the Throttle Body and listen to the IC area. Listen around the underside of the tank (common failure point!). Just listen... Hear a hiss or bubbling... BINGO!!! I found my crack in the expansion tank in 30 seconds with the tester... after chasing it around for weeks!!! Returned the tool so fast the parts guy thought I got the wrong tool!

Our motors have enough issues needing them to be removed... don't add simple things like a coolant leak to the list! [up]

Cheers,

KS

[Avantly]

Completely agree with Botbasher on this. I would find the claim that there are "bubbles" or air being forced into the cooling system w/o combustion gas present to be highly suspect for most engines, especially with the claim that your block is cracked/fractured since a cursory look at the 4.0T SSP does not show anywhere that a "cracked block" would introduce anything other than combustion gases into the cooling system.
I don't think you should be driving the car without knowing where the coolant is going. If you have cooling system pressure forcing coolant into the intake manifold (via intercooler) you are risking catastrophic damage as coolant washing down the cylinder walls is guaranteed to cause galling on the pistons and that is going to give your rotating mass and block a very short lifespan.
You need a second, competent party to test for combustion gases in the cooling system; You need a pressure test of the cooling system; This may also lead to a pressure test of the boost side of the turbos (i.e. the entire intake system from turbo to intake valves).
If the dealer can't specify where they think that a cracked block could cause boost pressure to bleed into the cooling system then the involved technician(s) and service manager should be considered highly suspect.

One other thought about your car, is bleeding with the bleeder screw really sufficient to bleed this system? I am not a 4.0T expert by any means but the only guaranteed effective bleeding method I've used on many VAG engines is a vacuum bleed. Coincidentally, a vacuum bleed would also reveal leaks in the system (i.e. the cooling system would not hold the specified vacuum before you begin filling it). If you are not familiar with the vacuum bleeding process, you should look it up, there are many third party vacuum bleeding tools which work well and all you need is the adapter for the VAG coolant cap and a small air compressor. No vacuum pump is required.

[Botbasher]

One other thought about your car, is bleeding with the bleeder screw really sufficient to bleed this system? I am not a 4.0T expert by any means but the only guaranteed effective bleeding method I've used on many VAG engines is a vacuum bleed.

4.0tt don't have bleeders like the 3.0 do. The cooling system high bleed point is the heater core hoses (that silly little hole in the metal pipe).

You can get away with fill & burp, especially if you keep the front right tire elevated, without much drama. Even after I filled and bled from the hole, I had cold air blowing from the heater for about 15 minutes of driving and then it magically cleared itself!

As a final check to my fill, I get the motor hot, open the tank, close it again and then just let it sit for a couple hours, usually overnight. The cooling air in the system contracts and is displaced by the coolant. If I have a lowered coolant level in the tank after a couple hours I know I got it all!

A vacuum bleeder would have made it a little bit easier and definitely faster though! It's not a fast process, but it has never failed and requires no extra tools. So that's a win for me!

Cheers,

KS

[Avantly]

4.0tt don't have bleeders like the 3.0 do. The cooling system high bleed point is the heater core hoses (that silly little hole in the metal pipe).

You can get away with fill & burp, especially if you keep the front right tire elevated, without much drama. Even after I filled and bled from the hole, I had cold air blowing from the heater for about 15 minutes of driving and then it magically cleared itself!

As a final check to my fill, I get the motor hot, open the tank, close it again and then just let it sit for a couple hours, usually overnight. The cooling air in the system contracts and is displaced by the coolant. If I have a lowered coolant level in the tank after a couple hours I know I got it all!

A vacuum bleeder would have made it a little bit easier and definitely faster though! It's not a fast process, but it has never failed and requires no extra tools. So that's a win for me!

Cheers,

KS

I am fairly certain there is a warning in the service information NOT to do specifically what you described. I believe the claim is that ff you run it with air in the system you risk air pockets and hot spots in critical areas causing excessive thermal expansion and potential gasket/etc damage (I have not verified this claim but I have known many VAG engineers and I would be inclined to trust them). I highly recommend you look into the vacuum bleeder systems. You can get a taiwan made one on Amazon for cheap as heck and you can fill the system to 100% with no air in a matter of a few minutes. You should never use it on vehicles that don't mention it (older USA cars come to mind... The vacuum can suck the rubber gaskets on the radiator side tanks... into the radiator LOL) but for VAG cars it is the only way... I would be terrified to run a 4.0T to warm/hot trying to bleed the system, I think you are asking for trouble.

[Audibellybutton]

I am fairly certain there is a warning in the service information NOT to do specifically what you described. I believe the claim is that ff you run it with air in the system you risk air pockets and hot spots in critical areas causing excessive thermal expansion and potential gasket/etc damage (I have not verified this claim but I have known many VAG engineers and I would be inclined to trust them). I highly recommend you look into the vacuum bleeder systems. You can get a taiwan made one on Amazon for cheap as heck and you can fill the system to 100% with no air in a matter of a few minutes. You should never use it on vehicles that don't mention it (older USA cars come to mind... The vacuum can suck the rubber gaskets on the radiator side tanks... into the radiator LOL) but for VAG cars it is the only way... I would be terrified to run a 4.0T to warm/hot trying to bleed the system, I think you are asking for trouble.

Hate to break it to you but I know audi techs that just fill and burp their cars. Of course there is always a by the book way, but it is not the only way that works. I am on my 2nd C7 and I have done burp and fill on both of them. No heat or IAT issues. Of course it takes longer but it definitely works

[Avantly]

Hate to break it to you but I know audi techs that just fill and burp their cars. Of course there is always a by the book way, but it is not the only way that works. I am on my 2nd C7 and I have done burp and fill on both of them. No heat or IAT issues. Of course it takes longer but it definitely works

Yes, I am well aware of VAG techs at dealerships everywhere not following the manufacturer's guidelines "because it seems to work fine". This isn't just a problem at dealerships, nowadays most mechanics dealer and indepentent are too lazy to learn the proper service procedures, it requires reading and learning and heaven forbid they graduate from parts-swapping mechanic status to automotive technician status.

It's just hilarious to me that someone would use that time-consuming archaic method and hope that it gets all of the air out of the system, as opposed to using the cheap and simple vacuum bleed tool and fill the system to 100% in a matter of minutes. The reason I find it funny is because I believe the root cause of many techs not using the right tool is laziness - They don't want to read or learn how to use such a simple tool - And then choose to use a method that takes far longer. Always funny(and a bit sad) when mental laziness creates more physical work, over and over and over.

[Audibellybutton]

Yes, I am well aware of VAG techs at dealerships everywhere not following the manufacturer's guidelines "because it seems to work fine". This isn't just a problem at dealerships, nowadays most mechanics dealer and indepentent are too lazy to learn the proper service procedures, it requires reading and learning and heaven forbid they graduate from parts-swapping mechanic status to automotive technician status.

It's just hilarious to me that someone would use that time-consuming archaic method and hope that it gets all of the air out of the system, as opposed to using the cheap and simple vacuum bleed tool and fill the system to 100% in a matter of minutes. The reason I find it funny is because I believe the root cause of many techs not using the right tool is laziness - They don't want to read or learn how to use such a simple tool - And then choose to use a method that takes far longer. Always funny(and a bit sad) when mental laziness creates more physical work, over and over and over.

Audi says to change the thermostat you need to remove the whole front end. People have found that you can do it without the front end even coming off. There will always be a “by the book way” and a shortcut. What you choose to do is up to you but I was only saying that the fill and burp definitely works. Nobody is saying it’s better than a vacuum bleed

[Avantly]

Audi says to change the thermostat you need to remove the whole front end. People have found that you can do it without the front end even coming off. There will always be a “by the book way” and a shortcut. What you choose to do is up to you but I was only saying that the fill and burp definitely works. Nobody is saying it’s better than a vacuum bleed

You are comparing apples to acorns. There is a big difference between proper bleeding of a critical liquid cooling system and the method which you use to install the correct part with correct torque specs and sealing. Can you get the correct part installed, sealed, and torqued to OE spec with both installation methods? Certainly. In that case you are simply taking a different route to accomplish the same task to manufacturer's specifications. Absolutely no comparison to shadetree hick mechanic coolant bleeding method vs. Audi OE spec. If you want to understand why the vacuum bleeding method is critical for these cars, read up on thermal expansion of materials and find information on just how hot the area can get around an air bubble, especially in the heads and turbos. Your position is not defensible so I don't know why you are trying. Every time you tell someone "AHH JUST DRIVE IT UNTIL SHE'S BURPED, BUD" you're misleading people and potentially putting someone who follows your advice in a situation where they damage their (very expensive) engine.

[Avantly]

And I just want to be clear, it is totally fine that you want to use a coolant bleeding method that the manufacturer considers unacceptable, as long as you acknowledge and inform those whom you are trying to "help" with your advice of this. Some people end up in dire situations where they have no choice but to do things like this, but it is very important to inform people of the correct method, as you will find that many people actually want to learn the right way to perform service procedures, and also wish to minimize risk of damage to their car while servicing it. It is completely fine to tell people the wrong way to do something that "seems to work fine" as long as you also tell them that it is the wrong way to do it (and in this case is something that the manufacturer specifically recommends against).

[Audibellybutton]

You are comparing apples to acorns. There is a big difference between proper bleeding of a critical liquid cooling system and the method which you use to install the correct part with correct torque specs and sealing. Can you get the correct part installed, sealed, and torqued to OE spec with both installation methods? Certainly. In that case you are simply taking a different route to accomplish the same task to manufacturer's specifications. Absolutely no comparison to shadetree hick mechanic coolant bleeding method vs. Audi OE spec. If you want to understand why the vacuum bleeding method is critical for these cars, read up on thermal expansion of materials and find information on just how hot the area can get around an air bubble, especially in the heads and turbos. Your position is not defensible so I don't know why you are trying. Every time you tell someone "AHH JUST DRIVE IT UNTIL SHE'S BURPED, BUD" you're misleading people and potentially putting someone who follows your advice in a situation where they damage their (very expensive) engine.

Its apples to apples. 2 different ways of reaching the same outcome. A fully bled coolant system. Like I said before, It definitely works and thank you but I am very familiar with cooling systems and how they work. I do not have air bubbles in my coolant system. "Drive it until its burped" just because you dont know how to bleed a coolant system without a bleeder does not mean everyone else shares the same disability. And I get it, thats what your service advisor told you what to do. Nothing wrong with that. You want a cookie or something? Like I said before, the fill and burp definitely works. I forgot the anecdote that it might not work for the average clueless person that needs his hand held so maybe just stick to doing it your way.

[Avantly]

Its apples to apples. 2 different ways of reaching the same outcome. A fully bled coolant system. Like I said before, It definitely works and thank you but I am very familiar with cooling systems and how they work. I do not have air bubbles in my coolant system. "Drive it until its burped" just because you dont know how to bleed a coolant system without a bleeder does not mean everyone else shares the same disability. And I get it, thats what your service advisor told you what to do. Nothing wrong with that. You want a cookie or something? Like I said before, the fill and burp definitely works. I forgot the anecdote that it might not work for the average clueless person that needs his hand held so maybe just stick to doing it your way.

No, it isn't, and I think you're just too arrogant to admit it. You aren't risking some damage due to air pockets if you use a different sequence of parts removal and installation to replace your thermostat. Absolutely no comparison and anyone capable of very basic reasoning (which I assume you are capable of) can see that. Again, your position is indefensible and I don't know why you are trying.

[Audibellybutton]

No, it isn't, and I think you're just too arrogant to admit it. You aren't risking some damage due to air pockets if you use a different sequence of parts removal and installation to replace your thermostat. Absolutely no comparison and anyone capable of very basic reasoning (which I assume you are capable of) can see that. Again, your position is indefensible and I don't know why you are trying.
Again we come back to the same point. Just because you don’t know what you’re doing doesn’t mean everyone else doesn’t. How are you risking damage if there is no air bubbles in your system? Like I said I know Audi techs that do this religiously in practice. It definitely works you just don’t know how to bleed the cooling system without a vacuum bleeder lol

[AudiGuy84]

Absolutely check your intercooler, I had mine leaking internally and was consuming coolant at a small level to not cause a misfire but I’ve seen really bad ones also


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[AudiGuy84]

316608


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[Avantly]

Again we come back to the same point. Just because you don’t know what you’re doing doesn’t mean everyone else doesn’t. How are you risking damage if there is no air bubbles in your system? Like I said I know Audi techs that do this religiously in practice. It definitely works you just don’t know how to bleed the cooling system without a vacuum bleeder lol

1) You "know audi techs" that do something that the manufacturer specifically tells you not to do. So now you know why people criticize dealerships nowadays for doing bad work. Fascinating that you admire this gross departure from an easy manufacturer-recommended bleeding solution and instead take the longer, harder route. Maybe this allows them to charge some extra hours of labor? And if air pockets/hot spots cause future failure, more money for them.

2) There absolutely are air bubbles in the system when you run it to "bleed" it. Running the engine gets everything hot, the air expands, by expanding more of it can escape, rinse and repeat until the air pockets are minimized. During this running with air in the system is when air pockets can cause excessive heat (and therefore thermal expansion) in critical areas which is what can cause immediate or future failure. That is what you are calling for. Vs. using a vacuum bleeder and in a matter of a few minutes filling the entire system and leaving minimal, if any air.

I can't figure out if you're just too arrogant to admit your defective position, or you're just another dope smoker know it all (i.e. Idiocracy, "water is for toilets, brawndo is what plants crave", etc). Either way, please don't mislead people by telling them that your method is considered acceptable by the manufacturer. If you want to describe your method at least mention that the only approved method to minimize risk of damage from air bubbles/air lock/etc is vacuum bleeding. Vacuum bleeding is fast, easy, and is the method these cooling systems were designed to be bled with. If you really don't believe me, read some SSP's related to the cooling strategies and the actual reasons behind the electric circulation pumps in these cooling systems. You will need an 8th grade reading/reasoning level to understand them.

[Audibellybutton]

1) You "know audi techs" that do something that the manufacturer specifically tells you not to do. So now you know why people criticize dealerships nowadays for doing bad work. Fascinating that you admire this gross departure from an easy manufacturer-recommended bleeding solution and instead take the longer, harder route. Maybe this allows them to charge some extra hours of labor? And if air pockets/hot spots cause future failure, more money for them.

2) There absolutely are air bubbles in the system when you run it to "bleed" it. Running the engine gets everything hot, the air expands, by expanding more of it can escape, rinse and repeat until the air pockets are minimized. During this running with air in the system is when air pockets can cause excessive heat (and therefore thermal expansion) in critical areas which is what can cause immediate or future failure. That is what you are calling for. Vs. using a vacuum bleeder and in a matter of a few minutes filling the entire system and leaving minimal, if any air.

I can't figure out if you're just too arrogant to admit your defective position, or you're just another dope smoker know it all (i.e. Idiocracy, "water is for toilets, brawndo is what plants crave", etc). Either way, please don't mislead people by telling them that your method is considered acceptable by the manufacturer. If you want to describe your method at least mention that the only approved method to minimize risk of damage from air bubbles/air lock/etc is vacuum bleeding. Vacuum bleeding is fast, easy, and is the method these cooling systems were designed to be bled with. If you really don't believe me, read some SSP's related to the cooling strategies and the actual reasons behind the electric circulation pumps in these cooling systems. You will need an 8th grade reading/reasoning level to understand them.
You are talking yourself into circles. Like I said fill and burp definitely works.

[Avantly]

Goodness gracious you just keep going. Give all the bad advice you want, and I'll keep working to lead people to the right way to do things no matter how hard you try to mislead them. I have to say, encouraging people to do something that the manufacturer specifically says can cause engine damage it's a pretty crappy thing to do, but it's a free country so you can just keep on doing it.

[Audibellybutton]

Goodness gracious you just keep going. Give all the bad advice you want, and I'll keep working to lead people to the right way to do things no matter how hard you try to mislead them. I have to say, encouraging people to do something that the manufacturer specifically says can cause engine damage it's a pretty crappy thing to do, but it's a free country so you can just keep on doing it.

You’re the one that’s booty tickled because I said fill and burp works. It does. Many Audis have lived long lives into the 200-300k+ mile range without ever seeing a vacuum fill. You are talking yourself in circles because nobody said a fill and burp is better than a vacuum fill. The key word in the fill and BURP is to BURP you are not risking engine damage. You face engine damage if you fill and DONT burp. Hope that’s easier for you to understand since I spelled it out for you. I don’t give bad advice. Show me some people that damaged their motor because they did a fill and burp

[RLCree]

I've used fill and burp on every car I've ever owned and worked on in the last 25 years. Not once have I had an issue. These are cars man, not nukes. Come off it already.

[Avantly]

I've used fill and burp on every car I've ever owned and worked on in the last 25 years. Not once have I had an issue. These are cars man, not nukes. Come off it already.

Oh, look at that. Another shadetree who knows better than the manufacturer, giving bad advice. "I've been doing it for 25 years" LOL. Just look at that statement, and compare the cooling systems of the cars that you've "worked on for the last 25 years" to anything like the 4.0T. Have you ever opened an SSP before and taken the time to understand the cooling system in these engines? If you did, you would surely understand the reason for VAG's cooling system.

As I said before, anyone is free to take the ignorant route and ignore VAG's specific and only endorsed process for ensuring that air is removed from the cooling system before starting it; Some may do it because they feel they have no choice, others do it because they are just too lazy to understand why they shouldn't. My only concern is people who don't know better being misled by people like you. I know this sounds absolutely crazy to you, but when the designers have determined that a specific service process is required to mitigate or eliminate the risks of engine damage, we actually believe what they say! Especially for such a critical system!!

I realize forums like this attract the dopehead know it all type, but please stop giving bad advice.

[RLCree]

Oh I promise you the 4.0 is one of the least complicated thing I've ever seen/worked on. You say VAG knows best, but they're also the company that brought us the 2.0, rear mounted timing chains and habitually failing PCV valves. Point, maybe they don't know it all. Clearly you do though. Dopehead, ha. Whatever my guy.

[Avantly]

Oh I promise you the 4.0 is one of the least complicated thing I've ever seen/worked on. You say VAG knows best, but they're also the company that brought us the 2.0, rear mounted timing chains and habitually failing PCV valves. Point, maybe they don't know it all. Clearly you do though. Dopehead, ha. Whatever my guy.

Because of design issues on the 2.0 engines, you assume that the engineers must not know what they are doing? You also seem to believe that the same engineering teams design every single engine? Tell me, when you design engines, they must be absolutely perfect, right? You must have decades of automotive engineering experience to make a statement like that. (Ok, ok, that was sarcasm)

"The 4.0 is one of the least complicated thing(s) I've ever seen/worked on". If I didn't think you made that statement sarcastically, I'd say that it was outright admission of how little you know about cars in general... Lol nice try.`

Have you ever used a vacuum tool to fill and bleed a VAG car? Maybe you are opposed to it just because you've never cared to actually read the service information and use the VAG method. Once you do, you'll never want to hot-spot "burp" any car ever again. Guys love these things so much they try them on older USA cars that they shouldn't (and sometimes suck in the rubber gaskets on the radiator side tanks on certain radiator designs, lol). If you are going to continue to tell people that the shadetree hot-spot "burp" method is ok, maybe just be kind and mention that VAG condems that method? This way, those who actually have the motivation to learn the correct way to do these critical service procedures won't be misled?

[Gunnarrrrr]

you guys are literally getting trolled by a guy who made his account last week


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[Avantly]

you guys are literally getting trolled by a guy who made his account last week


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Excuse me? Recommending that people follow the only method that VAG endorses, and recommending against a method they condemn, for an engine that costs upwards of $10k is trolling?

No way this forum is full of that many people with room temperature IQ, if anyone is "trolling" here it's you guys recommending this shadetree method. Or is this just how you drive away people who actually know what they are talking about?

[TexasDfwS4]

There are plenty of DIY,S for bleeding systems and you don’t need the Vag solution to do it. This site is for people that can turn a wrench and want to save money. If Avantly looks at some of YouTube’s DIY,s he can see that it not difficult to do, but if he,s afraid of damaging his car then he can pay Audi.

[Alabama]

Get a Coolant System Pressure Tester (I think both can be loaned from auto parts stores) and do some basic testing before jumping off the deep end! You'll see on the gauge and hear the leak. Remove the Throttle Body and listen to the IC area. Listen around the underside of the tank (common failure point!). Just listen... Hear a hiss or bubbling... BINGO!!! I found my crack in the expansion tank in 30 seconds with the tester... after chasing it around for weeks!!! Returned the tool so fast the parts guy thought I got the wrong tool!

Seems reasonable when free. ECS sells a filler unit for under $85. Maybe if qcrazy sees this thread we'll get another experienced opinion.

[freshjive]

Ex audi tech here. I just wanted to say that i have done both the fill, run, top up, drive, top up and the vacuum fill method. The outcome will be the same both. One will just require less work when bleeding. One will require less need for top up after. You won't hurt the engine doing either method. They aren't that fragile. If you don't fill the coolant that will obviously damage the engine. The cooling systems will 'self bleed' for the most part to a certain extent. In my experience the older vehicles were always more a pain the bleed even when pulling the heater core hoses. I can't remember the last time i ever had to pull heater core hoses to bleed a newer Audi. Also with the new vehicles you can activate test plans to open up all the coolant valves to help with that.

@OP. Are you loosing coolant at all? Do you have any faults stored for the V50/51 coolant pump for the cabin?
Do you find yourself with a lack of heat when the coolant is low? (which is expected)
I'd be looking at your intercooler core if you find yourself leaking coolant. Very common on the 4.0T platform.
Thermostat/water pump leaks from the seals are also common. Depending on how bad the leak is it will show signs of the pavement where you park once it cools down.
If theres nothing you're seeing on the ground i would replace the intercooler core as it is most likely your issue.

[Avantly]

Ex audi tech here. I just wanted to say that i have done both the fill, run, top up, drive, top up and the vacuum fill method. The outcome will be the same both. One will just require less work when bleeding. One will require less need for top up after. You won't hurt the engine doing either method. They aren't that fragile. If you don't fill the coolant that will obviously damage the engine. The cooling systems will 'self bleed' for the most part to a certain extent. In my experience the older vehicles were always more a pain the bleed even when pulling the heater core hoses. I can't remember the last time i ever had to pull heater core hoses to bleed a newer Audi. Also with the new vehicles you can activate test plans to open up all the coolant valves to help with that.

@OP. Are you loosing coolant at all? Do you have any faults stored for the V50/51 coolant pump for the cabin?
Do you find yourself with a lack of heat when the coolant is low? (which is expected)
I'd be looking at your intercooler core if you find yourself leaking coolant. Very common on the 4.0T platform.
Thermostat/water pump leaks from the seals are also common. Depending on how bad the leak is it will show signs of the pavement where you park once it cools down.
If theres nothing you're seeing on the ground i would replace the intercooler core as it is most likely your issue.

Your statement directly contradicts statements from VAG. Look at the cooling system design for the 4.0T in the SSP for an example of why. It is a beautiful piece of engineering. Then, read up on all of the proven damage cases where air in the system results in excessive vapor temperature, damaging plastic parts of the cooling system or worse yet, causing excessive thermal expansion in areas that will cause problems later. Don't get me wrong, if people want to do it the hard way and "burp" it that's fine, but anyone with some common decency will at least mention to the person asking about bleeding that the method is NOT recommended by VAG due to the damage potential. They designed the engine, they require the vacuum bleed for a very good reason, and the fact that it takes much longer to "burp" the system while running is proof that you are running it with air in the system, i.e. potential for hot spots.

You are correct that the engine most likely will not appear to be "hurt" after the process, the damage caused by such excessive heat is not expected to show up until later, i.e. previous studies/articles regarding damage to engines from running them with air in the cooling system. One I recall specifically was in regards to radiators with plastic tanks, and what the excessive heat does to the top of the tank where the vapors collected. Overheating the plastic makes it brittle much more quickly; Similar damage to rubber, etc.

No offense but maybe this attitude is why so many people complain about poor quality dealer service nowadays. Sad if you can't even get the dealer techs to follow procedure when the OEM tells you that there is damage potential. Might as well take it to a ford dealership... Lol

[freshjive]

My statement comes from real world experience. Yes the SSP on that 4.0T is good information but it still doesn't exclude it from basic automotive principle. The sole purpose of vacuum bleeding the cooling system is to remove as much air in the cooling system and replenish it with coolant basically making the bleeding process none existent. Its for efficiency. And like i also stated later in that post that there are test plans that you can execute to open up the coolant valves in the system. So long as your coolant pump is working, our thermostat isn't stuck closed or a faulty coolant reservoir cap; there really shouldn't be a worries in something going wrong.

I 10/10 will vacuum bleed a cooling system because i don't have the time nor want to waste time trying to get coolant circuiting in the heater core. In all the cooling system repairs I've done i can let the vehicle idle for 5-10 minutes and within a minute of me driving the vehicle out of my bay I will have full heat in the cabin.

No offence taken. The reason why people complain about the poor quality of dealer service work is very complex but can be broken down quite simply.
1. They have someone not motivated to work or put forward clean work.
2. Lack of training from a schooling/technical stand point and factory service training.
3. People are cheap and people want their car done yesterday. Lack of awareness is what i would chalk it up to.
4. Some people are just absolutely clueless when i comes to applying basic common sense with vehicles - From both a customer perspective and dealer tech perspectively. Perfect example - 4.0T oil strainer recall that came out a couple years ago. Absolute nightmare stories coming out of that thread. Imagine bringing your vehicle to an audi dealer for a recall but they end up keeping your vehicle for 3 months. I've been doing turbos on that engine long before that recall came out - imo should have been released years before. That is in and out day job. No reason for it to take a week let alone 3 months? What was the reason? Lack of experience.
5. Most dealers aren't willing to pay top dollar to keep good techs around unless they actually care about customer retention.

[Avantly]

My statement comes from real world experience. Yes the SSP on that 4.0T is good information but it still doesn't exclude it from basic automotive principle. The sole purpose of vacuum bleeding the cooling system is to remove as much air in the cooling system and replenish it with coolant basically making the bleeding process none existent. Its for efficiency. And like i also stated later in that post that there are test plans that you can execute to open up the coolant valves in the system. So long as your coolant pump is working, our thermostat isn't stuck closed or a faulty coolant reservoir cap; there really shouldn't be a worries in something going wrong.

I 10/10 will vacuum bleed a cooling system because i don't have the time nor want to waste time trying to get coolant circuiting in the heater core. In all the cooling system repairs I've done i can let the vehicle idle for 5-10 minutes and within a minute of me driving the vehicle out of my bay I will have full heat in the cabin.

No offence taken. The reason why people complain about the poor quality of dealer service work is very complex but can be broken down quite simply.
1. They have someone not motivated to work or put forward clean work.
2. Lack of training from a schooling/technical stand point and factory service training.
3. People are cheap and people want their car done yesterday. Lack of awareness is what i would chalk it up to.
4. Some people are just absolutely clueless when i comes to applying basic common sense with vehicles - From both a customer perspective and dealer tech perspectively. Perfect example - 4.0T oil strainer recall that came out a couple years ago. Absolute nightmare stories coming out of that thread. Imagine bringing your vehicle to an audi dealer for a recall but they end up keeping your vehicle for 3 months. I've been doing turbos on that engine long before that recall came out - imo should have been released years before. That is in and out day job. No reason for it to take a week let alone 3 months? What was the reason? Lack of experience.
5. Most dealers aren't willing to pay top dollar to keep good techs around unless they actually care about customer retention.

Completely understand your points, and nice to talk to someone who does use the vacuum bleeders at least sometimes. The vacuum bleeding process makes filling/bleeding the system so much faster I just can't imagine doing it any other way.

Wouldn't you agree that for engines like these VAG designs with numerous high points in the system which have both feed and return traveling downward, that there is obviously something behind the service documentation warnings that the vacuum bleed procedure must be done? As I said multiple times before I am not stating that the standard "burp" procedure won't work, I am simply stating that VAG will not approve that method for many of their engines, and this combined with previous articles and studies showing why running a cooling system with air in it can and will cause damage, I just don't see why a person would not mention this to someone when they ask about bleeding the system. As a tech with experience, you can likely gauge when the system appears to be clear of air, though if you work on many brands I am sure you have run into those vehicles in the past, not necessarily VAG ones, which will trap some air for several drive cycles until you get it really hot and then suddenly you are low on coolant again a few days later. Now imagine someone who comes to a forum with no such experience, I just think that telling them to do the burp procedure without mentioning that VAG would not approve it is just irresponsible. The vacuum bleed tools are cheap and they work so well. If you only work on VAG cars then you only need the VAG adapter which makes it even cheaper. Heaven forbid we tell some inexperienced forum member to do it the non-approved way and then have them end up damaging an engine with a price tag this high... I am sure you know, damage is cumulative, what you do now may burn you many thousands of miles down the road.

There are a lot of procedures which can be cut shorter with shortcuts and provide the same end result, but this is one that I won't ever take a shortcut on. Sure, I've been ASE master certified for almost 3 decades and worked on EU cars for more than half of that and am confident that I can guess with reasonable certainty when a majority of the air had been purged from a system using the non-approved method, but why waste the time when the vacuum bleed is approved and works so dang well.

Anyway, your response is much more sensible than the others, even though we are not 100% in agreement with each other. I just won't endorse mentioning the "burp" method to a n00b without mentioning the right way to do it. A lot of people really like to learn the right way to do things, even nowadays...