Heater core flush on the C5

[A62TURBO]

I read the article on AW regarding the heater core flush but that was on a B5 chassis. Anybody here can tell me which hose is OUT and which hose is IN? I noticed on our C5's that the hoses are over and under unlike the side to side hoses in the B5. Any info is greatly appreciated, thanks!

[rollerton]

Pretty sure the top one is out? But it doesn't really matter for flushing since you'll want to flush both ways.
I have a pretty solid flush method~ go buy a "drill pump" for $5 at a hardware store (It's a simple drill-driven plump that'll do about 8-10gpm) and a washing mashine supply hose, and a couple other small pieces of hose to adapt the wash mashine hose to the heater core.
Cut that wash machine hose in 1/2 and screw both pieces to the drill pump. Hook the drill pump OUTLET hose to the core and the drill pump INLET hose into a bucket of CLR/ HOT water. Other heater core connection to hose that is also in the bucket.
You've just created your own CLR heater core flush circuit.
Run the drill as long as you want, until the battery is dead or whatever. On our old passat with chronic lack of heat I did this for a few hours, then bled. Worked awesome.
On my B5 S4 with low heat I even installed a Passat aux pump in the core inlet hose to get more flow through, and it made a huge difference.

[A62TURBO]

Wow great info roller, this is great because I don't even need a hose, just a bucket of hot water. Any additives I should use with the hot water?

edit: I just realized you were talking about CLR solution. Thanks for the great info man!!!

[A62TURBO]

Just out of curiosity I checked the expansion tank level and found it to be less than the minimum mark, it took almost half a gallon of fluid. Could that be a cause of my no heat problem?

[rollerton]

Doubt it. But, start the car, let it idle / warm up and feel the hoses at the core. If one is hot and one isnt you're still not flowing through the core.

[A62TURBO]

OK, I'll give the system a check when I get home later. I already bought the drill pump, hose, and CLR. One thing, the CLR says on the back not to use it on plastic, aluminum and a few other metals, what is the heater core made of?

[BLKmamba818]

what does it mean when no heat at all comes out and hot water is dripping on my foot from feet vents, but only on the driver side

[Vinchenzo51]

what does it mean when no heat at all comes out and hot water is dripping on my foot from feet vents, but only on the driver side

I really hope your not serious... But on the off chance your serious, are you sure its hot WATER, and not antifreeze? If you have a plugged heater core or a crack in one, it could be a much bigger issue. Lots of electronics under the carpet that can be damaged if they get wet.

Greg, did you end up fixing your issue? Let me know if you end up needing help ripping out your dash lol.

[BLKmamba818]

I really hope your not serious... But on the off chance your serious, are you sure its hot WATER, and not antifreeze? If you have a plugged heater core or a crack in one, it could be a much bigger issue. Lots of electronics under the carpet that can be damaged if they get wet.

Greg, did you end up fixing your issue? Let me know if you end up needing help ripping out your dash lol.

im not sure what it was, all i know is it would drip on my foot while driving and it was scolding hot. it soaked my carpet for awhile before i could a friend re-route the water coming in my heater core. but now i have no heater in my car and with little money and im not the best one to pull out my dash and try to fix something like this. but so far it has been 3 months since all this happened and i have had no trouble with any electronics from the water.

[rollerton]

Wow. Yeah, water (coolant) dripping on your foot is not good. Pretty sure the A6 heater core is like the B5/A4 heater core and the dash has to come out. From what I hear it's a 10 to 16 hour job for someone who's experienced.

[Vinchenzo51]

I removed and reinstalled a dash in about 4 hours total and I hadn't a clue what I was doing. Can't imagine it taking more than a solid days worth of work for 2 guys.

[A62TURBO]

Wow. Yeah, water (coolant) dripping on your foot is not good. Pretty sure the A6 heater core is like the B5/A4 heater core and the dash has to come out. From what I hear it's a 10 to 16 hour job for someone who's experienced.

I guess it's just one of those engineering marvels, 16 hours....ouch!!!

[new audi guy]

Man i have a 'no heat' problem as well.... has me utterly stumped... even the dealer is stumped!

1. little to no heat comes out, only if i'm at 3500 rpm's do i get a little heat out of it
2. had water pump, thermostate, timing belt done a year ago
3. tried to bleed air out, no change
4. dealer searched for codes on heater flaps, no codes
5. dealer did a 30 minute flush of heater core, no improvement
6. car temp is rock solid at all times, no fluctuations on the dial in the dash
7. engine temp 140
8. had 3 dealer techs discussing, none have a clue, they said it made sense if the thermostat was not working... but i have new thermostat

2004 C5 A6 2.7t

utterly dumbfounded by this... and freezing my ass off on my 1 hr commute to work!

anyone have a suggestion?

[A62TURBO]

You probably just need a new heater core.

[A62TURBO]

Just flushed and bled the heater core, now I have heat!!!! Nothing nasty came out of the Heater core so it probably just needed to be bled. Not having heat when idling sucks, I'm glad it was an easy fix, I would recommend bleeding the hc to anyone with some sort of heat issue.

[mike's machine]

Where are the hoses going to heater core located?
It never blows hot in idle, so I'm assuming I need to do this also...
Are the hoses behind engine which are very hard to reach, or are there easier-to-reach location???
Thanks in advance...

[A62TURBO]

The hoser are to the right of the battery. You should get the car up to temp and pull the top hose off far enough where the bleeder hole clears the pipe, rev the engine a bit to get the fluid moving, once you see fluid come out of the hole and no more air bubbles you should be fine. I went a step further and flush the core, but I didn't really need to.

[mike's machine]

Thanks!

[A62TURBO]

Right when I fix my heat problem the weather forecast for the rest of the week is in the 60's

[BLKmamba818]

but what does it mean when it leaks out of the floor vents? is it def cracked or shld i just try and flush mine as well? cuz its getting cold as hell when im leaving work at night and cant really take it anymore.

[A62TURBO]

Most likely your core is cracked.

[BLKmamba818]

anyone know a good diy video to get me thru this project