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Blown Head Gasket

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Got back from a brief spin last night, went to do my weekly oil check and noticed oil in the expansion tank [:'(] Spoke to Ken Tolfree on the phone last night who checked the car out last week whilst servicing the lux and it sounds like the head gasket has blown, probably down to the turbo overboost the car seems to be producing.

Whilst checking the car last week he noticed an adjustable valve leading to the wastegate on the tubing next to the oil filler cap. I have a photo I can't seem to upload. Anyway, I adjusted the valve as much as I could to release the pressure but it still seemed to overboost although not as bad. I decided last night to remove the valve and tape the tubes together to release the pressure, this resulted in almost no turbo boost at all, I think it is just a coincidence that when I got back the head gasket had blown or could this have been the cause???

The engine seems fine and I didn't even notice anything wrong (apart from the lack of boost) until I opened the bonnet. I must admit I felt sick when I saw the oil in the coolant, first thing I thought was F**k I have broken it [:(]

I need someone to tell me it's all going to be fine, new gasket, flush the sytem good as new???

Please no stories of cracked blocks, blown cylinders etc... I might just start weeping [:(]
 
Cheers Andrew,

I am off to your site to order the gasket [;)], the problem is I do not want to move the car as it is so I will have to wait for Ken to fit me in ( about 3 weeks, booked up and then onholiday, how dare he!!![:mad:]) to flush the sytem and fit the new gasket.

As soon as I do I will book in to get the level 1 kit fitted probably end of may, the clutch will just have to wait (swine car!!!)

Getting fed up not being able to use the car because of one problem or another [:(]
 
I wouldn't bother with the widefire gasket. What's the good of a wider fire ring on one (the head too I believe) side?

Stick to stock or get an MLS gasket like a Cometic.
 
Hi Fen,

I have already ordered the widefire, can't do any harm having a stronger gasket, can it??? especialy if I am going to put on a level 1 kit ?
 
ORIGINAL: Bigglesdan

Hi Fen,

I have already ordered the widefire, can't do any harm having a stronger gasket, can it??? especialy if I am going to put on a level 1 kit ?
Click to expand...


Absolutely not. My point is that the widefire is not any stronger than standard as far as I can see; merely having a wider fire ring on one side of an otherwise standard gasket equates to nothing IMO.

I would also suggest it's somewhat disingenuous to imply a Superchips kit is unsafe. Under no circumstances would I recommend anyone buy a Superchips product but equally I don't think I'd recommend anyone who already has one remove it on grounds of safety. By all means remove it if you want to or if you want to fit something that conflicts with it.

Bottom line is 944 head gaskets, especially Turbo ones, just fail. It's a function of getting old and going brittle and that's far more likely what caused yours to go than the AFR the car is running (and has been for quite some time I expect).

Berg - no, the Turbo has the ports of the Lux style oil/water cooler blanked off or bypassed or something. It is possible to get a leak there still however and it's a good point that if the only symptom is oil in the water that the HG may actually still be OK. Did the car show any other signs like starting on 3 cylinders, excessively pressurising the cooling system etc.?

Bad form IMO that Dan has been persuaded/scared into buying parts that he quite possibly doesn't need after a telephone and web forum diganosis.
 

ORIGINAL: Fen
My point is that the widefire is not any stronger than standard as far as I can see; merely having a wider fire ring on one side of an otherwise standard gasket equates to nothing IMO.
Click to expand...
Here is some interesting stuff about HG failures. Enjoy.

Cheers,

Jim.


 
I take it back. The Widefire isn't even as good as stock.

I haven't read it all but I've read a lot of other Rennlist discussions on HG types and failures.

Obviously lean AFR can cause failure and it's ridiculous to simply replace a blown HG with a stronger one and hope a problem disappears but that is no more ridiculous than not fitting the best HG you can when you fit one. The only fix for blowing HGs in a short space of time is getting the engine mapped to run correctly.

All that said I still believe that many original 951 HGs fail through age alone. If the car hasn't been messed with (or even if it has been but not for a long time) and it's kept properly serviced then it is unlilely the AFR will have changed yet HGs still fail. Lots of people have had them let go and just replaced them and been fine.

On a standard car I'd replace with a standard HG - they last 12-19 years and counting after all. Personally I went with Cometic for my present engine build, not because I think I'll have a problem but because I want to turn the boost up. Because the car was properly mapped to suit the spec will be running (and will be mapped again when I make changes) I don't think I need fear another failure due to not having a deliberately weak HG as a pressure valve.
 
Whilst I mostly agree, threads like this one worry me with going too strong on the HG. Whilst in this case he was pushing the turbo too hard and probably injecting too much water to compensate with a weaker HG I doubt it would have got to the block cracking stage. Whilst with a proper set up it shouldn't happen things can go wrong.
At snetterton last year I had the vacum pipe come adrift from the Fuel Pressure regulator - If I hadn't noticed the AF guage dancing, I could easily of blown the HG. If the HG was super strong what else could I have blown?
Whilst replacing the HG isn't cheap or easy its cheaper than a new block. However I think if you want the best sealing possible a cometic MLS is the one to aim for.

Back to Dans car is there any water in the oil? or just oil in the water? Its unlikely reducing the boost would break it and if it was triggering the overboost protection this would indicate standard chips unless it is really boosting high. How much boost was the in car guage showing or were you off the top of the scale?

Tony
 
I have been experiencing turbo boost (according to the gauge) off the scale as in beyond the 2 bar, to the stop. There is, as Andrew rightly diagnosed a brass adjustable valve leading to the waste gate which I unscrewed as much as the spring would allow. This eased off the boost a bit but would still hit the stop when pushed.

I removed the valve and taped tubes together thinking this would then put more pressure on the wastegate making it open and release some of the boost pressure. This simply caused almost no boost at all, this is the bit I don't understand. Surely without the brass valve in place this is the standard set up, so why was I getting no boost??? Also, can superchips alter the amount of boost and how??? surely it has to be mechanical???

With respect to the head gasket, I am now completely unsure as to what to replace it with, I am sure that I don't want this happening again. I have had the car 4 months and hardly used it as I am scared something is going to blow up and it is beginning to drive me nuts [:mad:]
 
Sorry to add to the head ache!

Standard lasted 14 years and failed possibly due to overboost situation.

The brass valve would have been there to compensate for a weak wastegate spring without it the wastegate could be opening early. Does the pipe come direct from a bolt on the hard pipe (balck runs & runs to the intercooler) and then down to the wastegate or does it dissapear under the inlet manifold through some metal pipes?

Ideally you want to know what chips you have and what boost they were designed to run with.

Some photos of the brass valve and pipes its mounted in might help us to help you.

Tony

 
I had this brass valve system on my last road car,a Rover Vitesse Sport.The valve is just a screw down needle valve which normally in the fully closed position,leaves the engine on standard boost and allows the blow off valve after the wastegate to operate under control of the ECU(these sometimes have adjustable potentiometers to allow boost level to be adjusted).The blowoff valve is norma
ly solenoid operated.
By cracking open the needle valve little by little,no more than 1 to 2 full turns max,you allow boost pressure to escape via the needle valve in a controlled way rather than the blow off valve in a big way.This keeps the engine on boost in a progressive more flattened profile without the sudden cutoff you get if you just turn up the boost pressure.If you fully open the needle valve this leads to rapid overboost and the blowoff valve operates rapidly,it feels like you've run into a wall.In this state it is possible to blow headgaskets.
 
Personally I would put it back together with a standard gasket (that lasted 14 years). Set the valve back to where it was and then get the car on a Rolling road that can measure the Air Fuel Ratio (Normally about £55). If you are chronically lean, then further investigation of the valve and chips is in order. If the AFR is fine then you just have to accept that head gaskets do wear out.

If it is the Superchips solution then there are better and safer chips on the market now, but why replace it for a few extra BHP if the AFR is ok?

I've only ever owned old cars and two of my previous ones (non-Turbo, totally standard) wore out their head gaskets after 100k miles or 10 years. One was because the radiator fan had failed and the car was running hotter than it should.
 
Cheers Jim, I said " No stories of cracked blocks" [:(]

Vitesse, Cheers for the info [;)]

Paul, Ideally I would like to get the car back to original spec, (well maybe with a boost enhancer to stop the lag) I am really not bothered about extra bhp, the car is fast enough for my liking as standard.

As far as the chips go, do the superchips also have a fuel cut off for overboost as I have never experienced the (hitting the wall sensation) that some others have experienced, the car just keeps on pulling all the way???

Does anyone know of another mobile specialist that I could get out to replace the gasket, don't want to have to wait 3 weeks for Ken???


 
I am not 100% positive but am fairly sure that all these chips remove the overboost cutoff. That's how it lets you get more than 0.85bar boost. This is why it's always recommended that chipped Turbos have a second, accurate boost gauge in the car that goes past the 1bar boost of the in-dash gauge. If you suddenly hit 1.5bar boost the dash gauge will just read 1bar so you don't know until you see your pistons come through the bonnet [:eek:]

I do know that the Guru/Promax chip that I have still uses the knock sensor and will retard ignition if it detects pinking/ knocking.
 
I believe the guru chips do have an overboost protection as well it is just set around 21PSI so too late for most of us - I assume (but dont know for sure) it cuts the ignition should we hit it.
Tony
 
We'll test yours at the Dyno Day Tony as your one of the few with a big enough Turbo to hold it at that pressure [:eek:]
 
Right Chaps,

It looks as though I have a buyer for the Lux [:D] which means I can concentrate on getting Turbo sorted [:)]

Firstly, KLR and DME chips? would you suggest Guru or standard?

Head gasket? Wide fire or standard?? (If standard, Andrew would you consider swapping Wide Fire for original???)

Can I remove the brass valve and replace with Standard boost enhancer??? (Brass valve is in a differnt place than I have seen standard boost enhancers which is near air filter box)

How can I test the wastegate to see if it has a weak spring? (hence the brasss valve fitting)

Thanks as always for your help [:)], I know I am beginning to sound like a stuck record [:(]


 
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