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2001 S8, dash fans all work at all speeds but car insists on only blowing cold air. Flushed the heater core and not much dirty liquid came out. refilled the coolant to the right height (made sure no air was in there) and drove it around but still only cold air.
Anyone got any ideas? I know heater core unit replacements cost a lot because it's such a pain to get to. NEED HEAT FOR THIS UP COMING WINTER!
Whats the engine temperature like? Is it running cold?
How did you flush the heater core?
The D2 has two heater cores. They are actually relatively easy to remove compared to other cars I've owned, though only if you have to!
they have two heater cores??? the one i flushed was very easy to get to
I back flushed and flushed this one (pictures) using just water from a gardening hose. Engine temp is fine, its exactly where it should be even after driving around. on a side note before i bought the car, the dealership that had it had replaced the thermostat.
They're the bleeder screws.
The two hoses on the plenum side lead to a small electric pump (Rest mode on the climate will run this with the engine off).
Four hoses come off the pump to the heater cores which are either side of the HVAC air intake (centre top of your first pic - should have a plastic mesh grill on top).
Flushing the hoses from the bleed screws may only flush as far as the pump.
Also, no heat isn't necessarily a coolant issue. The HVAC adopts an air mixing approach to heat and cool air using directional flaps. If theres a problem with the flap motors, or the signal from the climate module, that will also result in no heat.
You heed to scan the climate unit with VCDS (VagCom) to check for faults.
Any clicks coming from behind the dash? Flap motors often break gears.
I went to O'reillys and got a OBD2 scan. All that showed was "Air System Insufficient Flow Bank 1" which is the reason my check engine light came on. Had this problem before but my mechanic said it was due to the hose being loose. He tightened it and the check engine light came off, just came on a little bit ago so going to tighten it again and see if the light comes off.
not sure of the difference between VCDS and OBD2 so not 100% sure the climate control was fully scanned thru ; there was the mesh grill over the HVAC but I took it off. As of now there is no noise coming from behind the dash and the directional flaps work perfectly fine. do note that after flushing I turned the fan on and it kind of nasty stink, going to turn it on and see if it still smells. Should I flush out the other hoses?
No smell anymore- also no water leakage into the cabin
OK, that was going to be my next question - people often report coolant leakage onto passenger front carpet when heater cores give way.
What sort of smell did you have - I take it you know the coolant sweet type smell (very distinctive).
The HVAC does have drains at the bottom which go through nipple tubes which drain behind the heat sheild above the catalytic converters, mainly meant for aircon condensation but may work to drain coolant from heater cores if they leak.
However, I would have thought a leaking core would give you a coolant smell through the vents regardless.
Access around the HVAC is very restricted, however if you look to the outside of the HVAC air inlet in the plenum area, you will see two hoses running down each side which connect with metal pipes about 3 or 4 inches from the interior wall of the cabin.
The metal pipes connect directly with the heater cores (NOTE:the pipes are not actually part of the cores, they are a press fit with o-ring seals held in place by the clip you see on the outside. Leave the clip in place unless you intend to remove the cores. Disturbing these pipes too much may result in losing seal integrity with the cores).
Removing the hoses either from the core pipes, or from the electric pump housing will give access to flush the cores.
I've also read somewhere that there may be bleeding problems caused by the this dual system and the electric pump. I don't know myself and I'm not sure I believe it. Bentley is no help in this regard, as it says to fill the coolant system from empty using a vacuum pump, and the cooling system diagram ends at the bleeder screws!
Also, just a thought - on the centre three front interior vents there is a small wheel with a blue and red dot. That needs to be on Red for the centre vent to run through the HVAC. If it's on Blue it's getting fresh air regardless of Climate settings.
VCDS is proprietary software from RossTech. It is a comprehensive suite that gives detailed access to all the cars modules. It's doesn't just read and reset fault codes like most OBD2 code scanners (though that is obviously one of its functions), it can also be used to change settings and functionality of the various modules and to log various values for fault diagnosis, for interests sake, or to make changes.
It also uses a General User Interface on a Windows compatible system (laptop), rather than a limited access screen on an OBD2 scanner, so you can more easily read and understand whats going on.
It is not VAG software as such (which is restricted to approved workshops), but can do just about anything a VW or Audi dealership can do (if you know what you're doing).
for a fully functional (licensed) version it's reasonably pricey, but most would say it's worth the price and pays for itself the first couple of times you use it.
Last edited by twentysevenlitres; 10-07-2014 at 06:24 PM.
not sure of the difference between VCDS and OBD2 so not 100% sure the climate control was fully scanned thru ; there was the mesh grill over the HVAC but I took it off.
OBD2 scanners only read the generic emission codes (engine module only) that set off the CEL...will read same codes on all brands of cars sold in North America since 1995, but no other modules.
VCDS is VW/Audi specific and will read all the cars modules...HVAC, ABS, Engine, Trans, etc....
Smell was that of dog poo; but if it matters it did smell a little like coolant for around 30 seconds from when I added the new coolant. Fan was on red - i've put it to blue and everything in between with no luck.
I found the hoses (these silver and black ones right?)
probably going to end up trying to flush these
10-06-2014, 07:52 PM
* S8 NO HEAT *
