[urq] Cooling System question

[Chris Miller]

I'd replace the cooling overflow bottle cap if you are concerned about pressure in the system; I believe that is the pressure relief valve in the cap.

Easy ways to test for the head gasket leak (into the combustion chamber) include checking the plugs; the really clean cylinder may be leaking; also there are test strips you can use in the coolant to see if there are combustion gasses present.

As for possible leaks:

If it is leaking to the outside of the engine, not into the cylinders, I think you'd see a stain on the block.   Pull the lower engine cover and see.

The later cars came with an after run electric cooling pump, I believe; not sure when that started.  They are plastic and can crack and leak.  Do not check them when hot as they can break open and douse you and cause a severe burn.  Similarly the control valve for the heater core is plastic and can crack.

Another possible spot for a leak is the water pump; sometimes they seep but it would be difficult to see with the belt guards in place.

There is also a small tube across the front of the block, behind the inner belt guard against the block.  On my 20v motor, it has a rubber hose on each end; I think that is the water return feed from the turbo.  The feed is below the turbo off the block.

Chris

-----Original Message-----
From: urq-bounces at audifans.com [mailto:urq-bounces at audifans.com] On Behalf Of Keith
Sent: Saturday, October 13, 2012 4:27 PM
To: urq at audifans.com
Subject: [urq] Cooling System question

Evening All,
I have some curious goings-on with my quattros cooling system. On occasion but not always there are one or two drops of coolant on the garage floor. The system does indeed lose a little, but so little as to be unable to trace the source. The running temperature is absolutely normal but the cooling system remains pressurised even when the engine has cooled right down. The engine runs fine.  I have searched on line for possible causes of the system remaining pressurised, some suggest a leaking head gasket. Obviously I do not want to remove this just to look and there are no other signs that I am aware of to suggest HG failure. I will be surprised and not a little disappointed if the HG is failing because the block was Wills ringed when I built it (10yrs ago though) to ensure a good seal around each cylinder and I don;t thrash it (in fact my friend ridicule my mechanical sympathy for my car!) I guess the question is: should I be concerned? Are there any tests I could do to confirm/deny HG failure given the current minimal outward symptoms? The amount of residual pressure in the system when cold is what concerns me the most though.
Any ideas/suggestions gratefully received (as always).
Regards
Keith

‘87 WR
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