Porsche diagnosis - makes sense?

[djohnson]

Any comments gratefully received.

As I have mentioned my car (996 C4S) has been with a local Porsche franchise for resolution of serious coolant loss. Following initial inspection last week they said that the issue was excesive pressure in the cooling system causing the coolant to exit via some sort of release valve into the engine bay where apparently it evaporated due to the heat. The exact cause could only be located via removal of the engine and detailed investigation. They have just called to say that the cause was a front radiator which has been replaced under warranty.

Does this make sense? I'm no mechanic but can a radiator fault really cause execessive pressure in the system? There was no leak onto the garage floor so its not as simple as a leaking radiator.

[sportsandclassic]

Sounds like a story to me !!

[Merritt]

Could be possible...?

If the flow through the rad is blocked and the water on the inlet side of the rad is getting very very hot, it would be pressurising the system with high temp steam..?

Let them change it under warranty - if it doesn't work, you've got a new rad out of it, take it back and get them to look at it again!

Steve

[phelix]

Where is the fill cap located; it should vent excess pressure to prevent rad damage.

[911wise]

I can smell something and its not coolant, is maybe something you should say when you pick the car up. Unless its a common problem can't see how they could pin point it so accuratley without actually sitting, watching and waiting for it to happen again. Sounds like an over complicated answer to give some reason as to why they've been messing you around for the past few weeks.

[ballcock]

Dave , I had posted here , and decided to delete it , as I was (probably erroneously!) quoting someone from another thread .. PM me if you want more details , I think it's unfair of me to make a possibly misinformed quote public.

[Boosted LS1]

Maybe they pressure tested the system and initially thought there was a restriction inside the engine somewhere before descovering it was the radiator thus not needing to remove your engine. It could be plausible. I wouldn't worry for the time being. Drive it and see what happens.

Boosted.

[sportsandclassic]

Hi which radiator ?

left right or centre ?

Thanks

mike

[hartech]

I don't know if this helps but we have had a problem where a pressure relief valve rubber sealing ring had split and allowed coolant to come out of the expansion tank exactly as described. It filled up the recess in the tank and dripped away. It was on a Boxster but the same would apply.

However we have also had more cases when an over pressured system was caused by a small cylinder or cylinder head crack. Often this also shows as what looks like smoke from one of the exhaust pipes (if it is the cylinder) or mush in the coolant (if it is the head). It can sometimes crack the expansion tank bottle as well (although they can crack anyway).

DON'T YET UNDERSTAND HOW THE RADIATOR WOULD CAUSE OVER PRESSURING UNLESS THE TEMPERATURE IN THE SYSTEM FIRST ROSE beyond normal running temperature because pressure can only be present throughout the system (not just in one part of it) and if the temperature rose due to a blockage it would register on the dashboard dials and warning lights.

Sorry if this is worrying - it usually is not as serious as a first look at the possibilites suggests as you always have to consider a worst case scenario as well as all the simple ones.

Baz Hartech

[djohnson]

sportsandclassic said:

Hi which radiator ?

left right or centre ?

Thanks

mike

Left and right apparently.

Got the car back so I guess I'll see how it goes.

Thanks for replies.

[ballcock]

Hope that's the end of it for you Dave ...