[V6-12v] Car not getting up to temp in winter...thermostat not the problem

[Austin Franklin]

Hi Poncho,

> An expansion tank top?  Boy that's a new one for me.
> I would be skeptical, but who knows.

I know ;-)  Replacing it fixed the problem.  Old cap, no heat...new cap,
heat.  The excess pressure in the system forces the thermostat open.

> It appears that Audi uses a typical designed cap.
> Basically it is a pressure relief valve that opens
> between 17 psi and 22 psi to relieve excess pressure
> due to over heating.

Excess pressure, yes...but not necessarily due to overheating.

> The
> typical symptom is leakage; overflow because the cap
> won't hold the 17 psi of pressure.

Mine was "clogged", not stuck open...so it held pressure.

> My experience over the years is that the 12V engine
> thermos often stick "open".

My thermostat is fine.  I've tested it...  And, simply replacing it didn't
solve the no heat problem, but replacing the overflow tank cap did.

> You can run from May until October here in the
> northeast and you won't even know you have a problem.
> See how the temp holds on your car when it gets
> colder.

Exactly.  My problem was in the cold months.  With the thermostat being open
all the time, in fall/winter/early spring, it would not get past the first
mark...until I blocked the radiator, then it ran normal temp.

> If you have to
> replace the thermo, use a good OEM from Wahler

I used the Wahler.  I used the Shokan timing belt "kit" and it came with
that.

> And by the
> way, you dont need to pull eveything apart.  The
> thermo can be weaseled out of there without removing
> the timing belt.  A pain, but not major.

I guess that depends on what car.  On my A4Q 12V, it was a major pain.  I
have 70k and it's 10 years old, so I wanted to do the timing belt/water pump
etc. service anyway.

Regards,

Austin