T-stat change advice

Matt twentyV matt_20v at yahoo.com
Tue Jul 22 14:11:17 EDT 2003

Hi Bernie, yes the temps take forever to warm up.
Sunday morning 70mph steady on the freeway in 82F
ambient it dropped from 187 peak driving to the
freeway down to 182-183.  Can reach 190 in severe
stop/go.  The water and oil temp guages also suggest
temps are low (oil temp guage barely reaches first
hash mark above 60C, water 80C).  The T-stat was not
replaced when the 3B was installed (which was the
obvious time to replace it, doh).   So original
Tstat, and 3 sensors suggesting low temps.  MFTS
was replaced when the motor was swapped.  I'll put
money on the Tstat being at least partially stuck
open.  DFI only if certain that IAB.
I hadn't thought of moving the PS pump, silly as I
went that route when I replaced the radiator and
T-stat back with the 7A.  I'll look at it again
tonight.  BTW on that job I didn't remove the pump
just unbolted from the mounting and swung out of the
I am trying to get everything perfect before
ratcheting up the boost chip.  For those that
remember, I originally was running very rich,
with low gas mileage (16-18).  New O2 sensor,
repaired wiring on IM temp sensor, and replaced ECU
code of unknown origin with stock, and now the engine
is running much better.  Block 000 channels 8 and 9
are right where they are supposed to be, and can see
23-24mpg at steady 70mph, though still 17 in heavy
stop-n-go traffic.  Only thing left that is not
perfect are the engine temps...


--- Bernie Benz <b.benz at charter.net> wrote:
> Hi Matt,
> What does the VC show as the warm up temp profile?
> And the VC must be
> reading from the 3B ECU temp sensor on the back of
> the head, right?
> Anyway, if a stuck open thermo, the warm up temp
> profile would be very slow
> and never reach anywhere near 185F unless you were
> really pushing on a 100+
> day.  So, I don't believe that is your problem.
> So, what's wrong with 185F op temp within a spec of
> 185/205F?  DFI if IAB!!
> And, unless you have previously calibrated the temp
> sensor and VC together,
> your readiings can be off by 10F.
> You are using the 7A thermo housing on your 3B, I
> assume?  You should be
> able to reach the housing hold down bolts thru the
> 7A's plastic side duct,
> where the housing's outlet pipe comes thru to
> connect to the lower rad hose.
> Once you get the thermo housing loose, I don't know
> where you go from there
> but, IMO, removing the IM won't help much.
> DFI if IAB!
> Bernie
> > From: Matt twentyV <matt_20v at yahoo.com>
> > Date: Tue, 22 Jul 2003 10:27:19 -0700 (PDT)
> > To: 200q20v at audifans.com
> > Subject: T-stat change advice
> >
> > Subject car is a '91 coupe quattro with a 3B
> engine.
> > I want to replace the T-stat as the engine temps
> > are a little low as read by VAG-COM block 000
> (hovers
> > in mid 180s vs. spec of 185-205) and radiator gets
> > warm immediately after starting.
> > Looking at the engine, I don't see how to get at
> > it without taking off the intake manifold.  Is
> there
> > a magic way to do this, or just bite the bullet
> and
> > pull the IM?  The coupe engine bay is a little
> more
> > cramped than the 200, the radiator is just a few
> > inches from the IM.  If pulling the IM is the
> > recommended course I can justify it better by also
> > replacing the MFTS and after-run sensor.  Any
> other
> > DFY-if-IAB-but-makes- sense-if- your-are-in-there
> > items?
> > TIA,
> > Matt Rooke
> > '91cq//20vt
> > '00S4//30vtt
> >
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