[200q20v] Old thermostat information reposted

QSHIPQ at aol.com QSHIPQ at aol.com
Thu Mar 1 10:29:03 EST 2001

Here's some information wrt water thermostats.  All -oil- thermostats for 
*all* I5's are the same since 1982@ 100c (and the same part number for all 
those years too).  FYI, I believe I have somewhere (if I find it, I'll post) 
a TSB that indicates that if customer complaints arise from overheat (hot 
climates) change to the 80c thermo (urq TSB).  Otherwise, the application is 
87C for all I5 engines.  This is a common thermostat available from a variety 
of sources (shares the application in Alfa Romeo's if I remember correctly).  
If you have an urq, you are probably better off with the 80c since this car 
runs hot most of the time anyhow (a must do if you deleted the aux rad).  As 
a rule, I install the 87C thermo on all cars other than my urq's, since you 
can get oil blowby on the cylinder walls when it gets really cold with the 
80c thermo (btdt).  I've also messed with the fan thermostat on my cars (3pin 
are the later I5 apps, the 2 pin the earlier), but didn't find a whole lot of 
difference running a cooler fan switch, YMMV.  The 7blade fan from the later 
turbo cars is a great upgrade, and makes a bigger difference than any 
thermostat IME.  FYI, the 7blade fan is a bolt in mod for the 44 chassis 
cars, but the urq's will *not* bolt in without some trimming or changing the 

A tech at audi AG told me quite a few years ago, that what you really want to 
watch is the head temps.  You should be in the 205-215F head temps in the 
hottest conditions, this is where the I5 operates "best" in terms of thermal 
efficiency.  The english translation was basically, go to 100c and turn all 
on to keep it there "at all prices" <costs> (meaning big oil cooler, rad fan 
on high, etc)


Subj:   Thermo part #'s
Date:   95-08-13 12:00:03 EDT
To: rdh at sli.com
CC: quattro at coimbra.ans.net

I know Dave Lawson posted em..... and Glen Powell has too....  Yo guys.....
Oops found em.....  Ok per Dave L (4-20-95) here you go:

035-121-113        80C thermostat
035-121-113B      87C thermostat

The Fan switch choices are as follows:

AUDI PN             APP

321-959-481E     2-pin  95-84C
823-959-481D     2-pin  82-77C
823-959-481E     2 pin  70-75C
823-959-481F     2-pin  92-87C
811-959-481       2-pin  95-90C  (86-87 coupe)
321-959-481       3-pin  93-88C/85-80C
321-959-481D    3-pin  102-91C/95-84C


BTW, I found a oil thermo in my pieces parts bin that is a 83C thermo, but I
don;t know the app, anyone help on this?  It is an easy swap, but this one
was off my Rally car.....

Scott Justusson

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