My third AR…

[dan normile]

Are you bleeding it at the pipe in the valley near the power steering pump/aux pump? Or, are you bleeding it at the upper heater hose? On my '02 allroad, you reveal a bleed port on the upper heater hose by carefully slipping it back off the pipe. The pipe leading to the heater core has a bleed hole that is exposed once you slip the hose back. This is the highest point in the cooling system and best location to bleed. In fact, the upper hose on my car has an icon printed on it that shows this bleed vent hole.

[ShelbyM3]

Are you bleeding it at the pipe in the valley near the power steering pump/aux pump? Or, are you bleeding it at the upper heater hose? On my '02 allroad, you reveal a bleed port on the upper heater hose by carefully slipping it back off the pipe. The pipe leading to the heater core has a bleed hole that is exposed once you slip the hose back. This is the highest point in the cooling system and best location to bleed. In fact, the upper hose on my car has an icon printed on it that shows this bleed vent hole.

I am bleeding from the heater core hose itself. Thank you for the suggestion!

I’ve never actually bled the cooling system using the crossover bleeder. I’ve used that on a bunch of B7’s, though. It has a crush washer under it and I don’t want to deal with it. Engine temps have always been great, it’s the heat that’s lack luster.

Sorry, I just saw your message. Messages are terrible about loading on my phone.

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[jbain2]

Are you bleeding it at the pipe in the valley near the power steering pump/aux pump? Or, are you bleeding it at the upper heater hose? On my '02 allroad, you reveal a bleed port on the upper heater hose by carefully slipping it back off the pipe. The pipe leading to the heater core has a bleed hole that is exposed once you slip the hose back. This is the highest point in the cooling system and best location to bleed. In fact, the upper hose on my car has an icon printed on it that shows this bleed vent hole.

This. Just slide the top hose off. It runs through the firewall. It has a bleeder port. Put a rag underneath and when the coolant starts to come out after things get hot, just slide the hose back over the bleeder holes.


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[Avantly]

Heat when at higher throttle but not idle *could* be just some air trapped.

Do you have access to a vacuum fill tool so that you can do the OEM fill procedure? They are pretty cheap nowadays. Once you vacuum fill a VAG car you'll never do the ridiculous "I think I can burp this without the right tools" process again. Full fill in a minute flat! If you are confident in full fill and still have poor heat, I would also make sure that you don't have an issue with one of the HVAC air doors or cabin temp sensor (maybe you have already done this, I didn't see mention of it in the thread but could have missed it).

I haven't seen a blocked heater core in a C5 yet but if someone ran the wrong coolant/mixed coolants anything is possible. I'm not sure I would use CLR to flush a cooling system, it is quite aggressive in higher concentrations and you may be fighting against gelled up and dried coolant (and not mineral scale/rust blockage) in which case I'd question how well it would even work.

[Audibot]

Heat when at higher throttle but not idle *could* be just some air trapped.

Do you have access to a vacuum fill tool so that you can do the OEM fill procedure? They are pretty cheap nowadays. Once you vacuum fill a VAG car you'll never do the ridiculous "I think I can burp this without the right tools" process again. Full fill in a minute flat! If you are confident in full fill and still have poor heat, I would also make sure that you don't have an issue with one of the HVAC air doors or cabin temp sensor (maybe you have already done this, I didn't see mention of it in the thread but could have missed it).

I haven't seen a blocked heater core in a C5 yet but if someone ran the wrong coolant/mixed coolants anything is possible. I'm not sure I would use CLR to flush a cooling system, it is quite aggressive in higher concentrations and you may be fighting against gelled up and dried coolant (and not mineral scale/rust blockage) in which case I'd question how well it would even work.

I'm never going back from not having a vacuum bleeder again either. Makes it easy plus gives you an idea if there's a leak while not pressurized

Having personally done the CLR treatment and alternating forward and back flushing, it has worked for me. Of course, mine was definitely because someone put the green coolant in. Agree you need to be careful, and I recommend a final "flush" with distilled to remove any garden hose water.

[ShelbyM3]

I’m good on the bleeding. Know how to do that. As far as a vacuum bleeder goes, I’ve had 2 different ones in my Amazon cart for 2 years plus, I just don’t have a good compressor at the moment. I’ve always used my Lisle funnel set in the past without too much headache for the engine and then bled the heater core after a day or two. THIS one has been bled 4 times now with a little air three of the four times. I must have a good bubble stuck, or it’s filthy. Heat was again not great on my way into the hospital this morning.

My first Allroad had a clogged heater core, too. Back then I just changed it because I didn’t have space or time to dink with it. Last night I purchased some supplies to flush this one with a garden hose and some BlueDevil 3-in-1, which is supposed to help with rust. Based off my other 2.7’s rear main seal coolant passages being severely clogged with deposits and needing a new heater core, I’m gonna assume this one is in the same boat.


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[ShelbyM3]

Heat when at higher throttle but not idle *could* be just some air trapped.

Do you have access to a vacuum fill tool so that you can do the OEM fill procedure? They are pretty cheap nowadays. Once you vacuum fill a VAG car you'll never do the ridiculous "I think I can burp this without the right tools" process again. Full fill in a minute flat! If you are confident in full fill and still have poor heat, I would also make sure that you don't have an issue with one of the HVAC air doors or cabin temp sensor (maybe you have already done this, I didn't see mention of it in the thread but could have missed it).

I haven't seen a blocked heater core in a C5 yet but if someone ran the wrong coolant/mixed coolants anything is possible. I'm not sure I would use CLR to flush a cooling system, it is quite aggressive in higher concentrations and you may be fighting against gelled up and dried coolant (and not mineral scale/rust blockage) in which case I'd question how well it would even work.

How would you go about troubleshooting the HVAC system? I have not looked into that.

Air flow is great, A/C works great from all vents, and the three setting for air flow all direct to defrost, upper, and lower vents.

I’m really leaning towards the heater core itself. Coolant looked quite new when I purchased it and I’ve obviously changed out a lot during the lock carrier swap, but who knows what has happened in the 23 years she’s been on the road. Based off my 2003 Allroad, I imagine it’s more rust and engine block debris mixed with dirt than it is wrong coolant type issues.

All of this kinda makes me want to drain the block, too. But, I only have one drain bolt and I think they went NLA recently.


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[Avantly]

For the vacuum bleeders, I have one made in Taiwan, I can't remember the brand but it has been great for years now. A good friend of mine got a different brand also made in Taiwan after previously having a china made one that was junk, his Taiwan one is also working great. I think as long as it is made in Taiwan (or at least just not made in china) you can't go wrong.

I have never done a block drain on these cars, though I wish they had block drains on both sides that I could install fumoto valves on like I have for other cars.

If I was approaching the car knowing nothing other than what you have described, I would first make sure that the air temperature quickly transitions from COLD (on coldest setting) to "room temperature" (on hottest setting) to make sure something isn't wonky with the blend doors. If that test passed, and I suspected a blocked heater core, I'd likely be trying to back flush it with water by removing both hoses and connecting a garden hose to force water through in reverse. It sounds like you are prepared for this with the garden hose adapters. You have to be careful with this, typical water pressure from the tap can be 30-50psi and you do not want to over-pressurize the core and make it asplode if it is the plastic side tank type. If water freely flows through the core in reverse as well as forward and no crap comes out of it, it is still possible that you have some manner of scale deposited on the inside of the core causing thermal transfer issues, but at least it is flowing and maybe it's time to try something to de-scale it (Audibot indicates that he has used CLR for cooling systems with success, and CLR sure is good at dissolving built up scaling in a lot of applications).

Keep in mind with the 2.7T you have this "short circuit" flow path which is dominant in the plugged heater core situation, this keeps the engine from overheating. So it is entirely possible that even a partially restricted heater core could force flow through this short circuit path and make it very difficult to bleed the core.

It has been a very long time but around 12 years ago when I got my first 2.7T and did the timing belt, I had no vacuum fill tool and had an absolute hell of a time bleeding the heater core, I wondered it if was a little restricted. I ended up bleeding it by disconnecting the heater core hoses a little and getting coolant to flow through it (and got coolant all over the place). I didn't have any problems after that. The coolant in the car when I got it was quite neglected and was not VAG coolant, it was green. The next time I did a coolant drain and fill in that car, I had no problems. Maybe running the correct coolant for a while broke up whatever was restricting the core, or maybe I just needed to have the car parked on an uphill slope when bleeding it, not sure lol.

[ShelbyM3]

This is my 2.7 on the engine stand when I tore it apart. This is why I want to do a block flush, but I’m not entirely sure how much of that would come out just from water flow, or honestly if this 2.7 looks similar.

The HVAC all checks out. Air flow and temps are good, minus heat.

I know I’ve got good flow and coolant getting to the core, when I slip my 90 degree pick in there to loosen the hose and slip it off coolant will shoot out along the pick and I get a good geyser from the bleed hole. The return line is hot and the hose clamp singes my fingers.

I plan on using my Lisle funnel to fill the heater core with the degreaser stuff I got just using gravity, letting it soak for a couple hours, and then flushing it with a hose. After that, I’ll hook the Lisle funnel back up and try to flush as much tap water out with distilled water, and then send it.


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[ShelbyM3]

Found my block drain bolt I had stashed away for Dana, but I kept the factory bolt in good spec so hopefully the o-ring holds up and I can just reuse it. Or maybe swap it to Dena, depending on what happens. It is in fact NLA, I called Audi today and the parts clerk said April 2020 they went NLA. Along with most other fun in my life…!


I did a fuel filter change on Dena today. Lots of nasty debris came out of the filter housing. I wonder if this isn’t the factory filter. Granted, a few of those pebbles came from me getting it out, but most were from it draining into the pan.




And the C5 curse of Dena continues. Yup, I said it. Ugh. My driver’s front window regulator took a dump on me while I was doing the fuel filter. I can’t help but laugh. Sounds like nails on a chalk board and won’t go all the way up. I’m not entirely sure what is going on because I hear a loud pop and scrape when it gets to the top of its travel, which is not fully shut, and everything appears in tact. I fished around and finally noticed a strand or two of the braided cable broke and it’s getting stripped back and shoved through the pulley system. New regulator on order.


I’m able to slide the window closed, , with my hands, thankfully.

I haven’t had to do one yet, but I knew the time would come. I have a rear driver’s unit for Dona and now a front driver’s unit for ole Dena. Don’t you have to remove the frame from inside and pull the whole unit out of the door skin or something fun!? Researching, again.


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[ShelbyM3]

Hey look, more junk in a dirty bucket!

I flushed my heated core today and I have heat at idle now. It’s gonna get cold in about 2 weeks, or so. And then comes the rain…


Battery tray has a little bit of surface rust I’ll leave for now. A good vacuum for good measure!


Let the Blue Devil sit for an hour and then back flushed it. While I waited I cleaned up the battery tiedown with a wire wheel.


Even just gravity filling the Blue Devil I had chunks coming out.

I used this little adapter off The Amazon and it worked, but it leaked right out the box. Piss!

Went back, forwards, and then back around, again. Was clear the last time. Happy to say I’ve got heat at idle. Job. Well. Done….said no C5 owner ever.



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[Avantly]

Glad you got it figured out! I can't quite tell from the pic but the stuff in the bucket sure looks like the stuff in the coolant passage of your block in that other picture you posted!

[ShelbyM3]

Glad you got it figured out! I can't quite tell from the pic but the stuff in the bucket sure looks like the stuff in the coolant passage of your block in that other picture you posted!

I know, I only use my phone and it’s not great.
It’s like sand, but made out of rusty engine metal and mineral deposits. I’m fairly certain all the junk comes from the engine block and makes its way up and over into the supply for the heater core and never comes back partially blocking the inlet feed on the core.


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[Audibot]

I do not miss flushing out that garbage. Glad you got it done and that coolant is looking nice

[Avantly]

Gosh this makes me want to flush out all my 2.7T's before it's too late xD

[ShelbyM3]

Gosh this makes me want to flush out all my 2.7T's before it's too late xD

It’s these darn cast-iron blocks. I don’t think there’s any way to really prevent it.

I thought you were getting rid of all of your 2.7T’s, anyway?


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[Avantly]

It’s these darn cast-iron blocks. I don’t think there’s any way to really prevent it.

I thought you were getting rid of all of your 2.7T’s, anyway?


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I have decided that I will keep one 2.7T car, my first Audi from almost 15 years ago, an '04 S line A6 but the rest are going. I don't want to sell someone a car that's going to have a ridiculous cooling system issue right after I sell it so I have been putting 4-6 hours a week into going over the 2.7T allroads with a fine tooth comb and trying to fix every little thing. I am almost done with belt/water pump/chain adjusters/alternator and a bunch of other crap on the nicest one (that is going first), the car is absolutely pristine in every way with only 113k miles, I found it in Utah so no corrosion, and I would feel terrible if a year later the cooling system clogged up and the new owner had to give some independent shop a ridiculous amount of money to sort it out!!!

[ShelbyM3]

I have decided that I will keep one 2.7T car, my first Audi from almost 15 years ago, an '04 S line A6 but the rest are going. I don't want to sell someone a car that's going to have a ridiculous cooling system issue right after I sell it so I have been putting 4-6 hours a week into going over the 2.7T allroads with a fine tooth comb and trying to fix every little thing. I am almost done with belt/water pump/chain adjusters/alternator and a bunch of other crap on the nicest one (that is going first), the car is absolutely pristine in every way with only 113k miles, I found it in Utah so no corrosion, and I would feel terrible if a year later the cooling system clogged up and the new owner had to give some independent shop a ridiculous amount of money to sort it out!!!

What a guy! That’s really awesome of you. Secretly, it’s the part I like about my Allroads, finding and fixing the little things. But, it can become overwhelming.


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[Avantly]

I'm scarred from purchasing 2 different cars in my adult life from sellers that went overboard to conceal major issues that ended up costing me much money and causing much misery. These were not Audis, but it was just such a horrible experience. Most people I know depend on a single car to get them to work, to the store, etc, they don't have several half-running spares like many of us car enthusiasts do. I would rather not sell a car at all and let it rot in my backyard than sell it to someone and have them experience something even remotely similar to what I experienced with those 2 lemons. So many people nowadays are barely getting by, and a bum car could push everything over the edge into financial ruin!