overheating 4000q

[Bruce Bell]

87 is correct for the thermostat. Did you replace everything, radiator etc.,
because of the overheating problem? You said you flushed the system after
all the replacements. Did you suspect some of the parts? Could the radiator,
if used, have some blocked cores?

My first thought is you are running a bit lean (creates extra heat). Check
injectors system and control pressure. It also wouldn't hurt to make sure
you aren't running too much ignition advance. Set it at the factory spec 8
degrees or better yet make sure you aren't running more than 34-36 degrees
total advance. It would be interesting to see the plug colors after one of
these overheating runs.

Good luck

Bruce
98 A4 2.8qm 70,000
87 4kq 300,000
84 quattro 50,0000

-----Original Message-----
From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com]On
Behalf Of George Nimmer
Sent: Tuesday, September 10, 2002 10:37 PM
To: quattro at audifans.com
Subject: overheating 4000q


I have a puzzling problem with my '85 4000s quattro overheating.  It has
156k miles on it.

Again, it only overheats when driving for 15 mins or more, at greater
than 70mph, when outside temps are 90+.  It does this whether or not the
A/C is on.

It runs cool as a cucumber when the A/C is on high and I'm stuck in
traffic, driving in the city, or crusing at only 60mph, even when
outside temps are 100+ degrees.

I have replaced the water pump, thermostat, coolant expansion tank, all
coolant hoses, the radiator, radiator fan, water temp sender, and
flushed the coolant more than a few times.  I'm running a 50/50 mix of
distilled water and G12, and there are no leaks in the system.  In
addition, I had the coolant system pressure tested at the local VW/audi
independant shop, and had them ensure there were no air bubbles stuck in
the system.

What other components could I possible check???

The engine starts and runs marvelously, revs cleanly and smoothly all
the way to redline.  it is meticulously maintained, and I've taken
several recent ~500 mile drives without any problems whatsoever (with
the exception of the aforementioned overheating under certain conditions
situation).

Ideas?

Thanks.