Porsche Enthusiasts Club Forum

Hi all,

Pulled the head off my turbo today due to high water consumption under turbo.
First inspection of the head shows corrosion but more worryingly a crack. Location of the crack isn't across the bore but between a water jacket and one of the holes for the head bolts.

Can this be saved?

Secondly, wondering where my water was going. One of the exhaust valves has a red face.... Not sure if that's an indication. Perhaps the crack is allowing water into the exhaust port and it's going out the manifold. Not water in oil contamination and no signs of a bad HG before removal....
Spark plugs dirty
Compression test strong
Overflow test good
No contamination in oil or water

There was some water out exhaust but no white smoke.

I'm emailing these photos to my local engineer shop too.
Thoughts welcome

Here are the pictures:

Definitely one for an expert opinion, but they can normally be repaired although being around a stud hole is a high stress area...

The red valve is an indication of poor combustion IMO; the other three all look as they should but the red would suggest some contamination in there: I reckon the crack caused a poor HG ring seal next to that water gallery so as you suspect some water was probably getting into that cylinder, although in small quantities given there weren't any other apparent symptoms.

I'd be interested to hear what the engineer's shop say about this. Hope you get it sorted expeditiously!

Thank you, the engineer I spoke to today said the red indicates burning water.
I can't see where the water has got into the cylinder.

I'll have to get te head pressure rested and get a quote.

Has anyone got any ideas where I can get a new one at a reasonable price? Porsche wants £1,600

Also, I meant to ask...

Is a 250bhp head the same as a 220bhp model? When I called Porsche they said my part number for my m44/51 engine has been superseeded but didn't know if the 250bhp was the same.

They're the same. Although I believe the Turbo S and probably therefore all of the 250bhp cars had larger exhaust valves, but I've only seen this written and have no evidence to back it up...

Either way any 951 head will fit.

This is causing me a headache now.

The machine shop called me back. It has been pressure tested and although there is a crack, the location of it doesn't matter and its not causing any water loss.
He said the head was good, could do with a skim just probably isn't causing the water loss since its such a small tolerance just under 3 thou.

So in short the head isn't the source of my water loss.

It is definitely not an external leak. There is no overheating. I've pressure tested the expansion tank, the the coolant system topside of the thermostat is all good including the cap.

So, where do I look for water loss? One of the exhuast vales was red, so water is getting into cyclinder 2. There is no scoring on this cyclinder, slightly on #3 and i haven't inspected 1 or 4 yet.
Any thoughts? I'll inspect the block this weekend and may just skim and fill the crack and stick it back on with a new HG. Perhaps a thicker HG would help?

How old was the head gasket and what condition is the deck of the block in ?

Year old and only 1,000 miles.

Who changed it ? Looking at it's condition I wouldn't have put that head back on without skimming it.

Ouch! I agree with a Pauly's comments above and I'm my experience old alloy heads should always be skimmed when renewing the HG as you nearly always get some deformation somewhere. A pound to a pinch of s£6t I'd bet water has gotten past the HG sealing rings, possibly caused by some movement due to the crack and a poor seal onto the head.

As a rule when changing HG's I always have the head skimmed and I dress the block with a blade and scotch cloth, with a final degrease prior to fitting the gasket and head.

Not to scare you, but it's worth double checking the block liner with a magnifying glass and torch prior to jumping in and popping the head back on though just to be doubly sure.

Were all the other seals changed on the head when the HG was replaced? If not do them now including lapping in the valves, or if the seats have excessive wear have them re-cut (avoid this if poss though as it means re-shimming the springs, big hassle).

Just my a'peth, where does that crack terminate? It may be more severe than it looks and is penetrating the exhaust tract. Replace or repair, do not reuse that head without further investigation.

If it turns out u need a head I have a good turbo head here. Pm for details if required. Thanks

No idea where the crack ends unless it was drilled out. All I can relay is that the machine shop said it pressure tested fine and has slight distortion but not enough in his opinion to use that level of water.

Basically the head is good but should be skimmed if I'm reusing it. So I'm hunting elsewhere to the source of the leak. I've no idea where this could be unless the Pistons rings or liners are damaged

Pardon my ignorance here but are turbo blocks lined?
From my experience with more mundane engines water leakage into the combustion chamber from a cracked head or porous block will decarbonise the chamber and pistons and pressurise the cooling system in a normally aspirated car. I have no experience of turbo engines but I suspect a certain backflow of exhaust gases will be experienced until the turbo has spooled up, hence cooling the exhaust valve with steam in this situation.
Pressure testing with a cold unstressed head is not conclusive imho.
Pop that exhaust valve out and have a look down the port.