B6 A4 No Heat Again

[my1stturbo]

What's the best chemical to use for a flush that's safe. I know that this is just a temp solution but want to rule out the core. The heater core was replaced about a year ago and I did have heat after that, but now back to the same symptoms as before. I will see about possibly replacing the core again in the spring but hoping a flush will at least get me through the winter.

I was worried about it being air but I've tried bleeding it multiple times and haven't had much luck. I have a code for an actuator in the HVAC system but not sure it's related. I also tried doing a block test myself to see if I had exhaust gases in my coolant but that tested negative.

Was thinking of trying to pressurize the system to see if it's leaking anywhere and possibly getting air back in the system but haven't found a good way yet.
'
I've read a lot of the write ups on here so familiar that this is a fairly common issue.

[Cybersombosis]

Try flushing the core using the below method. If you changed your core and didn’t change or flush the old coolant, then it may have clogged again if you didn’t get the bulk of sediment out.

https://www.audizine.com/forum/showt...1#post14856965

[EuroxS4]

https://www.youtube.com/watch?v=qMz4gp6xuMY

Use MB citric acid and hot ionized water and run it through the cooling system to get all the sediment out thats on the walls of the coolant pipes. Note this may dislodge such sediment also causing another potential problem but this would be the best way as it will disolve any rust and sediment in the cooling system including blocked passages in the heater core.

[old guy]

I have a code for an actuator in the HVAC system but not sure it's related.

Get the engine up to temperature. Get under the hood and feel the supply and return heater core hoses. If both are equally hot you could have a blend door issue. Thus the actuator code.

[my1stturbo]

Thanks for all the quick feedback. The heater core was changed at the same time as the thermostat so thought most of the sediment would've drained out but maybe not. Last time I checked the hoses the bottom hose was significantly hotter than the top. I had the coolant changed out this week hoping it would help but so far no luck.

I have a bottle of Prestone flush that I thought about using prior to the heater core swap. Either that or the MB flush I would limit to the core itself and just use 2 lengths of hose to get the supply and return to buckets. I recall a thread on here detailing a flush with a pond pump, 2 hoses, a bucket, some boiling water and some type of mesh to filter out any debri from the core.

The A4 has become by 2nd car over the years so it does sit s majority of the time. Possible that contributed as the lack of regular use allowed the sentiment to build up? Or would the swap without a coolant flush be the real cause of the issue.

[old guy]

That would be this thread. Clicky click®️ Unfortunately I still ended up replacing the heater core a year or so later.

[my1stturbo]

That would be this thread. Clicky click®️ Unfortunately I still ended up replacing the heater core a year or so later.

Yes, that's it. I purchased a new Spectra core and the clamp kit so will likely just swap it again in the spring. Was hoping to at least get back to some heat for the winter since the garage isn't accessible at the moment and the colder temps already set in up north.

I'll look up the write-ups for the core replacement and see if it's something I can do over a weekend in the driveway. Had a mechanic do the swap for me last time but he's not around for a while now. I definitely had a coolant leak last time (o-ring on the thermostat tore) so figured air was the reason when the heat went away. Was hoping the coolant flush this week would get the air out of the system but maybe it's the core all over again.

[EuroxS4]

The reason why new heater cores block is because sediment is covering the walls of all coolant pipes and passages. That being said the passages in the heater core are very tiny so it doesn't take much for them to clog again. As mentioned benz citric acid is the best to use, I a\have heard of people running CLR through their cooling system for a day straight with good results. However personally I would go with the citric acid and boiling water solution and run that through the cooling system or just the core.

[my1stturbo]

Cool thanks. Is the citric acid from MB readily available at the parts counter?

[inliner311]

I've used a garden hose hooked to the kitchen faucet to get hot and cold water. Then I've used one of the attachments to connect the garden hose to a coolant line that you can get at the auto parts store and I got a sprayer attachment that had a threaded end to help create more pressure. Also a sprayer will allow you to pulse it which helps to break it up. Run the water both directions multiple times then I put a funnel on the hose then rinsed everything with distilled water.

[EuroxS4]

I would assume thats something a benz dealer would stock. If not just purchase online:

https://www.fcpeuro.com/products/mer...s-000989102511

[MoRbiD]

J plug?

[my1stturbo]

J plug?

Replaced the j plug with the thermostat about a year ago.

[my1stturbo]

Took the car for a quick drive before and realize I have 2 things going on. I cleared the hvac codes and did a reset of the actuators before I took the car out. After letting the car get up to temperature i have luke warm at best heat on the passenger side, and what feels like AC on the drivers side. Scan of the hvac points to a failure in G220, which if I recall is a real pain to get to. I'll go ahead and order the flush from FCP but looks like I might still have an issue if I don't get the flap changed.

[Mike Tries]

The reason why new heater cores block is because sediment is covering the walls of all coolant pipes and passages. That being said the passages in the heater core are very tiny so it doesn't take much for them to clog again. As mentioned benz citric acid is the best to use, I a\have heard of people running CLR through their cooling system for a day straight with good results. However personally I would go with the citric acid and boiling water solution and run that through the cooling system or just the core.

I had absolutely no heat, and I tried using CLR on mine. It worked better than expected. It's been a couple months now, and heat is still strong, but it could always clog later. I'll report back if it does, but if anybody is wondering, I just flushed out my heater core with a garden hose for a while. Low pressure, high flow. Then I capped off the bottom heater core pipe and filled from the top with CLR. Left it overnight, flushed it like crazy the next day, hooked it back up, and had heat for the first time since I bought it.

EuroxS4, running CLR through the entire coolant system sounds enticing. I wonder if there is any danger to this, though? I worry about the CLR attacking some of the seals or hoses or metals that you might find elsewhere in the system. It seems like pretty benign stuff, as long as you're not made of Calcium, Lime, or Rust, so it might be worth trying to clear out the crud from the rest of the cooling system.

[Turbo510]

"The cary company" has a fact sheet showing the recommended does and don'ts of CLR. I don't have personal experience with it, but they caution using it to clean car "radiators".


https://www.thecarycompany.com/facil...eaners/clr/faq

[my1stturbo]

Thanks for that. I had tried CLR in a diluted solution cycling it through in the past years ago on a different core with not much success.

Order the MB flush so will try to find best ratio and get that going when it comes, only using it in the core for now. If I can get the heat restored for the winter I'll do another full flush in the spring if I start to notice anything developing in my coolant bottle.

[walky_talky20]

I'll add a suggestion for a nifty tool called the "Blast-Vac":



It runs about $60-$80. Connects to an air compressor (~70-100 psi) and your garden hose. You control the water flow with an adjustable dial and you have a trigger to release the kracken, I mean the air pressure. From the website: It "creates a unique vortex air/water blast for powerful cleaning applications."

You know how you turn on the garden hose to wash your car and the hose still has air pockets in it so it does this aggressive air/water blasting thing until the line clears? That's exactly what this tool does, but does it on-demand. You can get some very aggressive water blasting effects going on. We flushed out an engine block and hit the ceiling once.

Anyway, I used this to get heat back on my winter B5 the other day. Here it is hooked up:

IMG_9861.jpg

This is what came out. Brace yourself:

IMG_9863.jpg

Actual poop. That's what came out.

Yes, I did accidently spray myself in the face with this substance. I will never recover.

[EuroxS4]

I would not be putting 70-100psi through the heater core as the system is not designed for that amount of pressure. Your just asking for a problem.

[walky_talky20]

It's metered through an orifice within the gun to create the proper vortex cleaning effect. It is quite literally made for flushing heater cores and radiators and such.

From the website:
Perfectly suited for quick and efficient cooling system flushing. Simply attach it to radiator or heater hoses and you're in business.

Does a really fantastic job. Pressure does not really build within the core as long as the other end is open. It's more about getting the water "upset" as it goes through core to loosen the things.

Here's a video by South Main Auto using the OTC Blast-Vac. He explains how to "go easy" with the tool especially if the core is very plugged up. Unfortunately he does not catch the junk coming out of the core, which is always the most fun part! :

[inliner311]

My heat wasn't that good so I tried to flush it. The heat was fine while the car was moving but if I idled for a couple minutes the temp from the vents would go down. I actually was looking into that blast vac and came across a picture of someone doing this which I had all the stuff already to do it. Same concept as a blast vac which is adding air to the water from the hose to get some agitation. I end up pulsing it for no longer than second or two so it wasn't putting too much air in. I also didn't clamp the hoses going into the heater core while i was flushing it so if there was too much back pressure the hose would just blow off. It end up working real well and I'm getting better heat than I've ever had. For me a lot of fine particles came out. I flushed on both sides multiple times.

I did try to flush it was a threaded sprayer attachment first so it was fairly clear before. I wouldn't put air in as a first step. It probably a final step once you get it pretty clear with normal water pressure. Like I said it cleared alot of fine particles from the heater core, basically it was like panning for gold but small red particles were coming out. I was maybe getting a teaspoon of particles out each time I put air through it.

I got warm air from the vents before the temp guage on the dash even started moving when it was under 40 degrees outside. I didn't think that was possible with this car.

[walky_talky20]

Love the DIY Blast-Vac. That's pretty neat.

[1.8TFan]

Agreed, my '04 is having heat issues. I initially thought I had a bad blower motor or resistor but after finding my TIP disconnected the fan works properly with the correct vacuum.

I checked my heater core and noticed some crystalized pink coolant where it appears it's either leaked or been bled in the past. I'm planning on pulling it soon and trying to flush the coolant system of sediment.

inliner311, where exactly are you connecting the water/air at under the hood? Are you connecting directly to one of the heater core lines?

[inliner311]

Agreed, my '04 is having heat issues. I initially thought I had a bad blower motor or resistor but after finding my TIP disconnected the fan works properly with the correct vacuum.

I checked my heater core and noticed some crystalized pink coolant where it appears it's either leaked or been bled in the past. I'm planning on pulling it soon and trying to flush the coolant system of sediment.

inliner311, where exactly are you connecting the water/air at under the hood? Are you connecting directly to one of the heater core lines?

You need to disconnect both heater core lines at the firewall and hook up two lines. One to connect to the air/water and one to discharge the water, just like you would normally flush it. I would put a bucket under the discharge one to see what comes out. Then alternate which one you are using to put air/water in. The amount of times you have to switch really depends on how clog yours is. I would start with the top heater core line so you are blowing it through in the reverse direction the heater core would normally flow. How it's flowing through with normal water pressure (not with air) should give you a good indication of how clear it is.

[my1stturbo]

So I'm leaning, at least a little, toward issues with my flaps. I noticed last night that I have semi heat on the passenger side of the car, but what feels like A/C on the driver's side. I have a code for a bad flap on the driver's side. Just haven't figured out how to get my hands in that sport to change it.

[EuroxS4]

So I'm leaning, at least a little, toward issues with my flaps. I noticed last night that I have semi heat on the passenger side of the car, but what feels like A/C on the driver's side. I have a code for a bad flap on the driver's side. Just haven't figured out how to get my hands in that sport to change it.

No that's jut the heater core getting blocked up again. Standard. If you had issue with flaps it would be the same across the board. When flushing those cores I recommend boiling hot water and citric acid and run and the flush in both directions alternating to get as much build up as you can out. I also recommend flushing the insides of coolant pipes and hoses to get rid of build up on the all of the pipes. This is standard when doing a good flush.

[my1stturbo]

Thanks. Notice some coolant under my oil cooler tonight as well so I'll take a look at that and see if I can flush the core again.

[Puddin Tane]

Two more old threads worth a look

OG's nice simple rig for heater core flushing. He used Prestone Super Flush, but Mercedes Benz citric acid flush could be used instead.

OG's method for doing the whole cooling system this way. Cleans out every drop of old coolant so you can put in all new. Coolant degrades over time and needs replacing just like motor oil.

[Puddin Tane]

A detailed tutorial for flushing MB with pointers that translate to this job, for example doing a pre-flush with Shout stain remover first to make rust, scale, etc. "naked" for the flush solution. Some people warn that the MB flush is extremely aggressive and can actually cause leaks. You sure don't want that with a heater core

[inliner311]

Finally got some cold weather (20F) to see how my heat is after the DIY blast vac flush. I'm still getting warm air before the coolant temp guage starts moving. Best heat I've gotten from this car since I've owned it. If you have access to an air compressor, I'd say it's the way to go. It's like less than $10 in parts from the auto parts store.

[DPDISXR4Ti]

Good thread. Just this Winter I've noticed that my car doesn't provide heat as well as it used to. It could be my imagination, but it seems to take a little longer to heat up, but always makes it to the dead center gauge position (which I realize is a bit forced). The possible slower warm-up had me thinking that the thermostat might be hung open a bit.

I guess the next best step would be to look for HVAC error codes.

[JDCinATL]

I chased heater problems for a cold winter, with no good results. Tried the OG approved method, nods to Fletcher!!!, with little effect. Got tired of being cold a couple years ago, went for a Rockauto replacement. Not too bad replacing if you use compressed air to get all the remaining coolant out of the core before servicing. Now I have perfect heat every day. Took a few months to get rid of the solder smell as the new core heated up, but now all is perfect! When you get tired of failing heat every winter my suggestion is to bite the bullet and get er done!

[CJM_RVA]

My car hasn't had heat since I got it (December '21) so this thread is timely for me as I'm good and tired of being cold. Previously I didn't have any air coming out at all unless I set the system on recirculate, that turned out to be because the flap that admits outside air to the blower was stuck shut. Tried replacing that actuator with no success, but I was able to carefully open it manually and leave it there. At some point I do need to investigate if I replaced one bad actuator with another (junkyard part) or if it's an issue with the wiring harness, but all the other flaps work fine so it's either just that connector or the actuator itself. However the air I get is still cold no matter what temp I set it to or which vents I direct it out of.

So now the question is why no heat. And that's no heat at any time--not on cold start, not at operating temperature, not at idle, not in motion. It doesn't feel like a thermostat or air bubble issue because, among other things, the temperature gauge always seems to be where it should be and I haven't noticed any other driveability issues. I've never actually gotten around to checking the heater core supply/return hoses for a temperature differential - if there's one there, then I guess it's flush or replace? If not...could it be the cabin air temperature sensor that's gone bad?

[inliner311]

My car hasn't had heat since I got it (December '21) so this thread is timely for me as I'm good and tired of being cold. Previously I didn't have any air coming out at all unless I set the system on recirculate, that turned out to be because the flap that admits outside air to the blower was stuck shut. Tried replacing that actuator with no success, but I was able to carefully open it manually and leave it there. At some point I do need to investigate if I replaced one bad actuator with another (junkyard part) or if it's an issue with the wiring harness, but all the other flaps work fine so it's either just that connector or the actuator itself. However the air I get is still cold no matter what temp I set it to or which vents I direct it out of.

So now the question is why no heat. And that's no heat at any time--not on cold start, not at operating temperature, not at idle, not in motion. It doesn't feel like a thermostat or air bubble issue because, among other things, the temperature gauge always seems to be where it should be and I haven't noticed any other driveability issues. I've never actually gotten around to checking the heater core supply/return hoses for a temperature differential - if there's one there, then I guess it's flush or replace? If not...could it be the cabin air temperature sensor that's gone bad?

The easy way to check is just to feel the hoses by the firewall for the heater core when the car gets up to temp. If the bottom is hot but the top is cold then you heater core is plugged up. I would a couple different methods suggested above to flush before replacing the heater

[my1stturbo]

So I got the control module under the driver's side replaced. Still no heat, but the code is gone and the heat is at least even across the board from driver's to passenger side again. Will go back to looking at the core.

[EuroxS4]

Citric acid flush in boiling water to remove or dissolve as much of that scale inside the core as mentioned previously.

[SideMirror]

Irontite ThoroFlush (468-9110-16) https://a.co/d/49d3pDS

I am going to try this to clean out my heater core and radiator from stop leak additive. I bought the car with no heat and after tearing down the entire engine. There's a thick layer of this stuff everywhere. The machine shop called out the stop leak.

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