[s-cars] An overheating '93 UrS4

[Vincent Fregeac]

Last option is a torn head. I had this on my S6. The head gasket is not
perfectly tight any more and some cylinder pressure is released in the
coolant and oil lines during boost, the air bubble blowing of the coolant
when the engine gets hot - I does nothing to the oil, at least in my case.
An easy way to diagnose it is to drive the car until it's warm then release
the pressure cap. If the level of coolant goes up, it indicates some bubbles
in the coolant, probably coming from the cylinder pressure.

Besides, the coolant smell in the cabin is probably coming from the air
release valve on the driver side of the heater, BTDT on 3 Audis.



Vincent

-----Message d'origine-----
De : s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] De la part de Igor Kessel
Envoyé : 21 février 2005 19:33
À : Audi S-list
Cc : Lawrence Bardfeld
Objet : [s-cars] An overheating '93 UrS4


Folks,
today my friend Larry stopped by to let me pressure test the cooling sys 
in his '93 UrS4. Larry indicated that the coolant would slowly disappear 
from the reservoir and within a week or two it trigger the alarm int he 
central display. There was also a strong smell of coolant in the cabin, 
only when the heater was on.

I pressure tested the car to 23psi. There were no leaks whatsoever. I 
also checked the dipstick and the cap for foaming. There was no coolant 
in the oil and there was no oil in the coolant. This pretty much rules 
the head gasket out of the equation.

I took the car for a spirited a test-drive and safely made it back to my 
garage half hour later. Larry was not so lucky. He left my house 
shortly, but in 15 minutes I received a SOS call on my cellphone. To cut 
the long story short Larry limped back into my garage an hour later in 
the car that was overheating and spewing coolant from the reservoir cap 
spout all over the engine compartment.

The symptoms are as follows:

1. The upper radiator hose is hot
2. The entire radiator is cold except for the tiny area around the upper 
radiator hose
3. The engine idles at the second slim hash mark at 13:00
4. After a while the valve in the pressure cap blows releasing a geyser 
of coolant
5. Heat is coming into the cabin, thus I am sure the coolant circulates 
throughout the heater core
6. The lower radiator hose is cold

My immediate guess that either the water pump has lost or spun its 
plastic impeller or the thermostat got stuck closed or both. Also the is 
a leak in the heatercore and/or its hoses. Does anyone have any other 
opinion?

-- 
Igor Kessel
two turbo quattros _______________________________________________
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