333pg333

It's possible Brian but we'd have seen evidence underhood I would think? Either wet or dry coolant witness marks. We'll get to the bottom of it but even if it was coming out of the 2nd tank and dropping on the track, you'd assume that either myself or cars behind would 'notice' this and that there'd still be a couple of drips on pit floor. This track is small (1 min-ish) so even with a cooldown lap I'd think that there would be some visible liquid after each session.

TonyG

If the coolant ain't on the ground, and it ain't in the catch can, and there ain't no coolant in the oil.... then it's being burned in the combustion chamber.

While the cometic head gaskets are great in other engines, they are not really effective in the 951 engine. The stock (or wide fire) seal much better.

You can deck plate it, you can put in larger head studs, but you can't stop the head from flexing and moving around. That's the problem. That's always been the problem. The head casting simply doesn't have the proper beam design and it's just not rigid.

That's the flaw of these engines. And there's no way of getting around it.

And BTW, it's a common trick to use a pressure sensor in the coolant system. This because it allows you to see a broken water line long before the temps go through the roof.
I'd put a wide fire on it and go from there.

TonyG

333pg333

There's pluses and minuses with the Cometics. We did the whole day, broke the club record and could have kept going, or had it been a registered car, driven home. I think I would have to agree that there is block flex even with all the deck plates/big studs/pinned girdle. Short of billet block we may have to just deal with it. There are some other things we need to deal with. Good chance the stock intake is hurting not only upper rpms but by having so much early tq the max peak cylinder pressures are hitting at an early onset and for longer. Perhaps with a custom intake (bigger plenum, shorter runners) we will shift the tq to the rhs and even lessen it a bit. While we would need to rev more and therefore maybe decrease time between refresh, it may also assist in limiting excessive peak cylinder pressures which are the h/g killer. Also by venting the head like Corleone did could help offset the localised boiling.
Is the 16v head any less prone to flex I wonder? Clearly less detonation.
Why is the Widefire better than stock for example?

Paulyy

Note, I've also had the pin hole coolant leak. I couldn't ever find it until it grew and boom, dumped it all!!

I wouldn't to surprised with the MLS. The stock gasket seems like it's got more force pushing back into the head than the MLS.
I guess it's the same as a copper gasket vs a normal exhaust gasket. you cannot compress the copper one so the 2 flanges need to be exactly flat. I believe it's a similar story with the MLS. It does have as much of a crush point as the stock gasket there fore the head and block need to be 100% flat. When it goes through heat cycles, it will move no matter what. That 0.01mm could just make the slightest leak for example.

333pg333

Oh, plus it did turn out to be the H/Gasket after all.

333pg333

All 4 were worn. Spoke to the builder of the motor today and he's worked out something that seems to keep them together. As used on a 997 running 55psi for the Standing Mile. To do with O ringing the head and running separate Gas crush rings. Will pursue this if we finish the 16v motor.

David Floyd

I have a similar failure every 2 years, guess there is enough movement between head and block to cause the breach.

Have a new Cometic on order now, been pushing coolant under boost, so I will change out and good for another 2 years.

Good thing about the Cometic is they don't seem to fail completely.. just leak.

Gas rings sounds like a great solution

333pg333

I'm jealous David...wish we could only do it once every 2 years! :-)

David Floyd

I'm not using the fast pedal enough

Thom

MLS Phuzion headgasket? Curious to hear more about it.

Eric_Oz_S2

I'm having similar problems with leaking coolant under boost for my supercharged s2. Starting leaking after about 6 track days (10 hrs). I'm going to try a cometic. Is .051 thick closest to stock? Is that what is commonly used?

I think stock is 1.1mm and the .04 is a little less than this. Is there any sealing benefit of the thicker 5 plate design? I could probably decrease my cr a little to low 10s with no disbenefit.

Paulyy

Eric what HG do you have? Is it the MLS, if it is, then it'll explain the issue. If its the stock one, probably similar issue but your HG could be deteriorating.

Eric_Oz_S2

I'm using stock at the moment, only 6 track days old.

odurandina

hey,

you all are living in relative affluence (no thrown rods).

KSira

The 16V head should help in several ways. The head itself is a stiffer construction and will also have less peak cylinder pressure according to what I have read. Also the 16v Porsche manual states that the S2 head has increased strength in the studs area and needs less torque when installing.

Did you retorque the studs after heat cycling the engine?