Too much coolant pressure means blown head gasket?

[Ranger]

Holy ****, pls tell me I don't have a big problem here!

'99 with 32k mi. Spent Fri/Sat at the track for a DE. No overheating problems. Started spewing coolant out of the top of the overflow container after a couple sessions. No sign of container leaking. I interpreted that as it was responding to an overpressure condition and releasing coolant as designed(?). Coolant was at very top of container. While still pretty hot we pulled out some coolant until it was down to min mark. Estimated total coolant removed (spewed and "pulled out") as a liter. Last session of the day my "add coolant" dash light came on. Since temp was still ok, I drove 30 min home.

Last night, once the motor was cool I added water/antifreeze up until halfway between min/max level. Added ~3/4 liter.

This morning at the track not only was it spewing out of the overflow tank, but it was also leaking out of the F/R radiator. I interpreted that as confirmation of my "overpressure" theory. Dash gauge indicates operating temp remains absolutely normal. I opened the overflow container cap and coolant came out. I figured "ok, that's as much as wanted to come out, so I'm ok". Next session more spewing (but less). No leakage from radiator this time. However the "add coolant" light was back on.

Overflow tank was empty at this point. Since I knew that the coolant capacity was high, and the temp guage continued to show no abnormal activity at all, I chose to continue.

After each successive session I'd have a little coolant spray around the overflo tank. Each session seemed to have less and coming out. Dash temp indicator remained fine. I know that a very serious indicator is when you temp guage goes high, then falls back down to normal or lower (when your coolant is pretty much gone), but that didn't happen.

So I can't understand how I can be a liter low on coolant, have no apparent over heating problems, yet have spewing coolant. And not just from the overflow cap, but also 1 incident of it coming out of the radiator too. I can't seem to make the symptoms fit a "bad cap" explanation. The fact that it leaked out of the radiator too that one time just seems like some kind of "the problem is too much pressure, not just a leak" smoking gun. So I'm worried that cylinder compression is leaking into the coolant. There is no sign of contaminated oil or coolant, but it's not like I drained anything to really look.

Oh pls mighty Renntechers, give me good news.

Edited April 7, 2007 by RangerGress

[Loren]

You need to find the source of your leak.

If it is external - that is actually good. A bad hose, or radiator, or coolant tank, or cap are cheap compared to coolant in your oil.

I would pressure test the coolant system (to locate the leak) and I would change the oil and look for coolant in the oil (not a good sign - but if the oil is clear of coolant then you can be pretty sure that the leak is external).

[Chuck Jones]

You need to find the source of your leak.

If it is external - that is actually good. A bad hose, or radiator, or coolant tank, or cap are cheap compared to coolant in your oil.

I would pressure test the coolant system (to locate the leak) and I would change the oil and look for coolant in the oil (not a good sign - but if the oil is clear of coolant then you can be pretty sure that the leak is external).

Not hijacking this thread...and this is sort of relevant to the issue at hand about testing systems...but I have one of those Stant kits for pressure testing cooling systems....but it only has the adapters for American cars. It's the nice chrome kit with the pump and pressure gauge on it. Is there an adapter that would allow me to use the pressure tester on Porsches?

I saved the old cap I had when I had to buy the new one due to leakage.....and I was wondering if it would be feasible to make an adapter out of that cap and would that work for pressure testing? What pressure does the 996 run at?

[Ranger]

You need to find the source of your leak.

If it is external - that is actually good. A bad hose, or radiator, or coolant tank, or cap are cheap compared to coolant in your oil.

I would pressure test the coolant system (to locate the leak) and I would change the oil and look for coolant in the oil (not a good sign - but if the oil is clear of coolant then you can be pretty sure that the leak is external).

Not hijacking this thread...and this is sort of relevant to the issue at hand about testing systems...but I have one of those Stant kits for pressure testing cooling systems....but it only has the adapters for American cars. It's the nice chrome kit with the pump and pressure gauge on it. Is there an adapter that would allow me to use the pressure tester on Porsches?

I saved the old cap I had when I had to buy the new one due to leakage.....and I was wondering if it would be feasible to make an adapter out of that cap and would that work for pressure testing? What pressure does the 996 run at?

How 'bout this for a theory. What if the coolant system pressure is proportional to RPM and fluid level......And I have a weak hose/connection at my F/L radiator, and an even weaker overflow tank cap. Therefore I'd get a radiator leak at high pressure and a overflow leak at medium high pressure. That would fit the symptoms, but is dependent on my assumptions of coolant system variables. Thoughts?

Edited April 8, 2007 by RangerGress

[slbates]

Check your spring type hose clamps for the source of the radiator leak. I have had two that have leaked. I think Porrsche released a TSB on this, but I just bought a stainless screw clamp from Lowes since I didn't want to wait for the "official" Porsche version. The cap can leak...even the new style is not immune to leaks.

[Ranger]

Check your spring type hose clamps for the source of the radiator leak. I have had two that have leaked. I think Porrsche released a TSB on this, but I just bought a stainless screw clamp from Lowes since I didn't want to wait for the "official" Porsche version. The cap can leak...even the new style is not immune to leaks.

Entire problem turned out to be the cap. I'd researched the cap issue but I misunderstood the nature of the problem. It's not that it leaks, it's that it "doesn't leak". That is to say, it doesn't allow pressure release when it should because it's valve gets clogged. So pressure builds up until coolant starts coming out all over the place.

Thanks for all the input gents. -Scott

Edited April 11, 2007 by RangerGress