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DeadSkunk SuperDork
1/28/15 8:33 p.m.

This is just another example to reinforce my belief that modern cars are needlessly complex. I don't need dual temperatures, I don't even need automatic temperature control. I need heat or cooling and a twist knob.

CGLockRacer SuperDork
2/19/15 8:17 p.m.

Another update. I had the coolant flushed and the heater core flushed twice with CLR. After I got the car back, it was much better, but still not great. They got a 10 deg increase in vent temp on the driver's side and a 25 deg increase in the pass side vent. Drove an 1hr + to my GF's and actually had to turn the heat down. Parked the car, went back out to run errands, parked long enough for the car to cool down. Start up to drive back, and the problem was back. berkeley!

This is the best picture of the system I have found.

There is no flap labeled for left/right temp control. In the Golfs with full auto/dual zone control, there is a flapper motor between #3 and #4. I'm wondering if is a common housing and there is a flap in there that has come loose. Of course the only way to get to it is to remove the heater core and dash. DOUBLE berkeley!

Any suggestions from the GRM hive? Thanks!

Fueled by Caffeine
Fueled by Caffeine MegaDork
2/19/15 9:13 p.m.

Sell car. Buy different one.

CGLockRacer SuperDork
2/20/15 7:31 a.m.

In reply to Fueled by Caffeine:

Not an option right now :(

Fueled by Caffeine
Fueled by Caffeine MegaDork
2/20/15 7:58 a.m.

Buy this. Deal with it in the warm weather.


motomoron SuperDork
2/20/15 12:44 p.m.

Last winter, 7 degrees F out. Mrs. Motomoron is driving 90 miles RT to Baltimore daily in her B5 A4 2.8 V6 to be with a seriously ill parent and the heat stops working. I flush core w/ CLR a couple times, it improves some. I figure out the thermostat is stuck open and fix it w/ a remote, inline t'stat from a 70's 320i. Heat improves, is still not great. Then it gets warm and we forget about it 'til this fall. With feeble heat and a nearly gone clutch, she solves the problem w/ a really nice '12 A3 2.0 FWD, sport pack, slick top.

We sell the A4 to a very nice young man who flies from Buffalo to buy it. In winter, with full disclosure the heat is barely operational. He brings his notebook w/ VAG-com, scans the car and has no issue w/ anything he sees. He pays for the car, gets in and drives back to Buffalo.

The next day he calls to ask if I'd noticed the gurgling noise the car had been making. I offer that as punk and metal drummer/motorcycle and car racer of decades I'm well pleased to be hearing berkeleying anything, so no, I didn't. He says he got home at 9 PM and bled the cooling system and now the heat is quote "Like an inferno".

What he did that I was afraid to do was blow through the core w/ compressed air, dislodging a clot of gack that was settled in the bottom of the core. Me, I was imagining a paper-thin corroded core blowing a tube and having to completely disassemble the car outdoors in 7 degree F weather. Which would necessitate my killing myself.

So be more aggressive getting the crap out of the heater cores and bleed the air out very carefully. And verify actual engine op temp - on the A4 the temp gauge position is not an actual linear depiction of temp. It's a made up thing based on temp at the oil filter block.

CGLockRacer SuperDork
3/9/15 8:02 p.m.


I tried to swap out the heater core tonight. I can get 90% of the way there and I'm just stuck. I gave up for the night and reassembled everything.

See this this picture:


This is looking towards the center of the car next to the driver's right shin. The hose clamps labeled "A" come loose with no problems. The pipes are slip fit into each other with o-rings. I cannot get them separated. Any attempt will bends the flanges for the hose clamps on the pipes that come through the firewall (left of pic.) There is a dash bracket, not pictured, that prevents me from moving the pipes out towards the footwell enough to get them apart. There is a nut on the firewall that holds the pipes into a grommet that is supposed to be loosened, but not removed. Of course, you can't see if it is Torx or hex head. I thought I got a torx to fit, and loosened it up some, but that didn't help. And, of course, the only way to get to some of this stuff is to bed over backwards over the door sill or cram my forearms into just big enough to get in, scrape all the skin off coming out areas.

Any suggestions besides kill it with fire?

rcutclif HalfDork
3/9/15 8:52 p.m.

Can you get to the engine bay side of the pipes? Might be able to pull from there to get extra room.

SVreX MegaDork
3/9/15 9:10 p.m.

In reply to CGLockRacer:

I don't have a suggestion to solve your problem, but I do have a suggestion for accessing it better...

Take the time to remove the passenger seat.

I am generally too lazy to do this when working under a dash, but always thankful when I take a minute and do it.

chiodos Reader
3/9/15 9:12 p.m.

I was thinking compressed air as well but knowing forcing air in the coolant system may be hard to get bubbles back out but what if you used a garden hose on the heater core outlet and let her rip to shoot the potential clog out

Knurled UltimaDork
3/9/15 10:23 p.m.

Water and air. Pulse water in, blast it out with air. Add a little water, blast air in to hammer the small amount of water through. You can't hammer with a steady push.

Do this a LOT at work. It takes 20-30 minutes of playing with water and air before you stop seeing crud blowing out. 7 times out of 10 i can get a heater core unclogged, 2.5 of the remaining 10 working well enough that a replacement can be procrastinated a while longer. (Guess what? Replacing heater cores sucks even if you're getting paid to do it. Haven't blown one apart yet.

bigdaddylee82 Dork
3/9/15 10:58 p.m.

Being a modern VW, that bolt has got a pretty good chance of being a triple square instead of a torx, they like to slip the occasional polydrive fasteners in too, but they're usually on engine components.

chiodos Reader
3/10/15 10:59 a.m.

In reply to Knurled:

Good to know the tried and trued method from the field.

pjbgravely Reader
3/10/15 12:32 p.m.

I know you are too far alone for this but I noticed no one mentioned back flushing the core. I have in the past used adapters to hook the core up to a garden hose, using a valve to modulate pressure. running large amounts of water through the core for periods of time, reversing flow each time can bring a plugged core back to life.

CGLockRacer SuperDork
3/19/15 8:15 p.m.

I give.

I got the hoses removed. The yellow are hose crimp clamps from HF to keep the coolant from coming out.


Then got the bolt loose (red arrow, buried in between the pipes). It is a 5.5mm. It also has a torx, but I couldn't get it lined up properly. The head of the bolt is very short, so it is difficult to keep the socket on it. And I'm working blind because my hands and forearms are crammed in behind the engine.


I have removed the driver's right side kick panel and heater core cover here. This shot would be in the center console next to my right shin. Heater core in place.


These are the two berkeleying junctions that I cannot get apart. Hoseclamps removed in this shot. You can see a bracket in the left side of the shot. I removed the lower bolt and actually bent it out to get more room.


This is as far as the heater core comes out.


There is no fore/aft movement of the heater core because it is contained in the heater box. I have to move the pipes forward or backward. The pipes are held with a clamp against the firewall. The bolt in the first shot is loosened, not removed, according to the factory manual to give you wiggle room. I loosened the bolt until I could feel it come out completely and turned it in only one turn. I had the most wiggle room possible. The pipes that lead through the firewall will not move.

I'm going to the VW dealer tomorrow at lunch to show them these pictures and see if they can help me. Again, the factory manual (a friend got me .pdf files of all the manuals) does not have the dash coming out. They just don't tell you how to separate the pipes from the heater core.

Why VW, why?!?! You make the heater core so accessible, but then impossible to remove! Car designers really need to work on the cars they build. I bet they'd make much simpler designs.

daeman Reader
3/20/15 12:11 a.m.

Before you head off to vw, seeing as you have your coolant lines off the heater core, put a garden hose into one of the fittings and see what the flow thru the core is like. Doesn't make much sense to pay money to vw, or go to the extent of removing the core if it turns out that there's nothing wrong with it.

Given the age of the car, the external condition of the core, and the fairly internally clean pipes, coupled with the fact that your heat is uneven left to right i wouldn't be real confident that the core is the fault.

You checked your cooling left vs right yeah?

Don't be super intimidated at the idea of pulling the dash if you have to, they are usually installed as an assembly and whilst not fun, isn't going to be some kind of dark magic keeping it in there. Think about it this way, if the old core is so hard to get out, do you really want to risk damaging a new one while trying to install it if that ends up being the fault.

Ian F
Ian F MegaDork
3/20/15 4:54 a.m.

Personally, I'm amazed you can access the core without taking the dash apart. That alone is an improvement over most modern cars, even back to the 80's and 90's. On some it's like they hung the damn core/blower motor on the assembly line and built the berking car around it... But I suppose it's one of the side effects of designers needing to reduce NVH. The blower is a loud thing and the deeper it's buried the less that noise will be heard. Driving a classic car will remind one of this.

Looking at your picture and the exploded diagram, I'd say the only thing holding the firewall pipes to the core is simply the friction of the o-ring seals between the pipes and the core (get new ones!) and the gasket to the firewall. It will likely require some effort to break that seal and push/pull the pipes into the engine bay. By trying to pull the core out before breaking that seal, you've made your life harder as there's now tension on the joint. Yes, breaking that seal will be easier said than done.

CGLockRacer SuperDork
3/20/15 6:23 a.m.

In reply to daeman:

The core has been flushed twice with CLR, and the entire cooling system has been flushed.

In reply to Ian F:

There is a clamp that holds the pipes to the firewall that is inaccessible. That is the bolt that needs to be loosened, but not removed. You can see it between #21 and #31. The pipes are bonded to it somehow. I get about 1/4" of freeplay after loosening the bolt.

Thanks for feedback, everyone.

Ian F
Ian F MegaDork
3/20/15 8:21 a.m.

Ah... interesting. Looks like a real kick in the nuts... The only thing I can think of is with the bolt loosened and the engine side hoses removed, there may be enough free play in the grommet to allow the pipes to pivot at the firewall and pull out of the heater core. They will be very tight and not want to come free. Make sure you have a pan or something under them as when they come loose they'll dump coolant all over the place.

Again, you'll need new o-rings. Once that seal is broken it's unlikely they'll seal correctly again. And lord knows you don't want to separate all of this again to replace them.

jimbbski Dork
3/20/15 8:58 a.m.

Cut the pipes and replace with rubber hose.

daeman Reader
3/20/15 8:24 p.m.

Yeah, fair enough, that'll account for it looking clean. But it worked for a period of time and it makes no sense that it'd block solid just cause you've stopped the car. That's much more symptomatic of an air lock being the culprit. The hoses are very high up on the fire wall and the core appears to be slightly higher again, it makes bleeding the system a royal pita. Some cars the only way to get all the air out is using a vacuum bleeder or elevating the front of the car quite substantially and even then it can still be a real pain. Even my nearly 30 year old Mazda ute is a bastard to bleed due to the placement of the heater core.

Ian F
Ian F MegaDork
3/21/15 7:58 a.m.

Agree on the bleeding thing. While I never had a problem with it during my first two timing belt changes, on the 3rd I replaced the t-stat as well, which drained even more coolant out of the block, so I used a vacuum bleeder. Not terribly expensive - about $75 from thetoolwarehouse.net

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