Bob Rouleau

I learned something interesting just yesterday from the head tech at my dealer. There has been a rash of blown coolant hoses. Now, we all know about the usual fittings on all the Mezger engines. This is a twist on the same "dump the coolant" story.

He discovered that the cap for the system is supposed to release pressure at 15 lbs/sq in.

In fact in cars with blown hoses, the caps tested at 30 lbs! It appears that rat her than release the extra pressure harmlessly, the overpressure blows hoses. He tested a half dozen caps in stock and all tested at 30 lbs. He ordered a new batch and many of those were also wrong!

He now tests the coolant caps on any Mezger engined car that comes in for service.

Best,

ilko

Thanks for sharing this info Bob! Has this only been limited to 997 GT3s? The coolant cap is a shared part among all 986, 996, 987, and 997 cars.

Nizer

Interesting data point but if excessive pressure from faulty cap were the issue wouldn't rubber hoses be expected to let go before epoxied fittings?

Jamie_GT3

I think that's what he's saying, in addition to the epoxied fittings, now hoses are blowing as well...

chardonet

Thank you for the information. I am headed to my dealer next week, and will mention this. I hope there will be a fix with the caps.

F1CrazyDriver

Anyone know how we can get the one's on our car tested ?

Which equipment is required ?

993GT

Thanks for the info Bob!
Funny enough was just pondering the 'performance' of my expansion bottle/'rad' cap early today...

CRex

Many thanks for this most important info. Does anyone know where we can buy a batch of proper-spec'd cooloant valves?

ShakeNBake

+19.5

Texas RS

Bob,

Thanks for the info. I have an '11 RS, I had a coolant leak at about 3000 miles that was diagnosed as a coolant cap issue. Dealer replaced it and I thought all was good, and it was until earlier this year when I had a coolant hose blow out at a DE event. Fortunately it didn't cause a accident.

Steve W

Thanks for the info. The coolant caps are actually a little more complicated. They are something of a 2 stage pressure release which releases steam at 1.4 bar (20.2 psi) and release liquid at 1.8 - 2.0 bar (25.9 - 29.4 psi), the stages differentiated by the volume/speed of release. The cap numbers have changed through 4 iterations, to the current 996.106.447.04, although I don't know what the differences between them are. Below is a section from the Cup car manual, which use the same cap as all the street GT cars:

ShakeNBake

I'll bet the 991 GT3 does not use the same coolant cap as the cup

kyrocks

I had a coolant hose blow (near right front tire) on my previous 2011 GT3 with 2000 miles on it.