Coolant pressure relief valve raised when engine warm?

[gusmagoo]

Hi everyone,

Quick question, I've recently noticed that the black plunger type relief valve (the one with a sort of spring clip on it) located just forward of the water reservoir cap on my 2004 C2 tiptronic appears to rise when the engine is at normal running temperature (as if open) and falls back down again when it's cooled down.

I'm not losing any water (that I can see anyway) the car has no visible leaks and never goes higher than 82 degrees on the temperature gauge. I'm led to believe that this shouldn't be happening and am not sure if it is safe to drive this weekend.

My water level appears to be steady midway between Min and Max whith a cold engine, and rises a little when warm.

Can any one suggest a reason for this rise and fall, (of the valve) and is it safe for me to drive the car? No other warning lights or issues to the best of my knowledge, thanks in advance.

[Loren]

Yes, that is normal behavior.

[ericinboca]

Many, including me, will open it manually and lock it in the open position to allow any trapped air, after coolant system work, to escape. On my 986S track car, I never close it.

[gusmagoo]

Ah I see, for some reason, it has been suggested that this is not normal by a few people over here in the UK.

I hadn't noticed it before, and thought perhaps it should only rise if the system was OVER pressurized, possibly highlighting a problem.

If Loren says it's normal, thats good enough for me. I will question my friendly UK forum members for some clarification on this one! I will drive it happily this weekend and as usual, keep an eye on my temperatures and fluid levels.

Many thanks for your help everyone. :thankyou:

Edited April 16, 2011 by gusmagoo