T-stat change advice

Tue Jul 22 14:51:04 EDT 2003

Matt,

OK, you may indeed have a thermo not closing all the way, but expect that
you will see some coolent temp changes dependent upon thermal input,
ambient, and fan switch points anyway.  I just had a 3B thermo fail closed,
thankfully a slow failure with ample warning, allowing commpletion of a 1200
mile trip thru the Calif dessert.

You may not be able to peal back the PS pump without unbolting the supply
line at the pump, as this line loops around under the pump and travels  thru
an oil cooler in front of the AC cond and rad.  That supply line loop under
the pump is your big access limiter from the top, unless you can remove the
rad side plastic air duct, which should provide straight in access from the
side, in front of the rad.

Bernie

> From: Matt twentyV <matt_20v at yahoo.com>
> Date: Tue, 22 Jul 2003 13:11:17 -0700 (PDT)
> To: Bernie Benz <b.benz at charter.net>
> Cc: 200q20V mailing list <200q20v at audifans.com>
> Subject: Re: T-stat change advice
>
> 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
> way.
> 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...
>
> Matt
>
> --- 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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