head gasket life?

[deeman940]

i replaced the head gasket around 5 yrs ago shortly after i bought my 940. i used an Elring gasket with Elring bolts. It would appear it has gone again, is this normal? i would of expected to get a bit longer out of one but i know it is a known common issue...

[john.wigley]

I would say that is abnormal, 'deeman940'. We ran 240s, 740s and a 940 in period for many years and never had to replace a HG. I took my last 740 from 11 to 29 years old and from under 100 to over 170 thousand miles without removing the head.

What was the reason behind the need to replace yours? If the car overheated, it is possible that your head is warped, which, if not corrected at the time, could result in premature failure at a later date.

Regards, John.

[deeman940]

Originally Posted by john.wigley

I would say that is abnormal, 'deeman940'. We ran 240s, 740s and a 940 in period for many years and never had to replace a HG. I took my last 740 from 11 to 29 years old and from under 100 to over 170 thousand miles without removing the head.

What was the reason behind the need to replace yours? If the car overheated, it is possible that your head is warped, which, if not corrected at the time, could result in premature failure at a later date.

Regards, John.

i replaced it because it was leaking. i had the head skimmed when it was done....

[griston64]

What psi are you running ?

The problem isn't exactly the excess boost itself, but the heat and detonation caused by the boost. When you shove more air into the cylinder, you have to shove enough fuel in there to keep the proper fuel mixture. If you have more fuel than air, they mixture leans out and burns super hot. The heat can cause hot spots which lead to detonation and pre-ignition. The heat and shock forces from the detonation eat away at the head gasket causing the leak.

[deeman940]

Originally Posted by griston64

What psi are you running ?

The problem isn't exactly the excess boost itself, but the heat and detonation caused by the boost. When you shove more air into the cylinder, you have to shove enough fuel in there to keep the proper fuel mixture. If you have more fuel than air, they mixture leans out and burns super hot. The heat can cause hot spots which lead to detonation and pre-ignition. The heat and shock forces from the detonation eat away at the head gasket causing the leak.

my AFR's are bang on....shouldn't be a problem. 18psi 1.2 bar

[Forrest]

In my experience the original hg gives up at about 150k miles. I’ve not had a replacement fail yet. 1994 B200FT replaced at 145k miles in 2007 now on 278k. 1997 B230FK replaced at 157k miles in 2012 now on 227k.

Both still completely stock performance though.

[Familyman 90]

You need to investigate and establish the cause of failure before you can draw any conclusions.

[Laird Scooby]

Originally Posted by deeman940

i replaced the head gasket around 5 yrs ago shortly after i bought my 940. i used an Elring gasket with Elring bolts. It would appear it has gone again, is this normal? i would of expected to get a bit longer out of one but i know it is a known common issue...

Couple of questions Damo - did you clean out the threads in the block for the head bolts, did you renew the head bolts and lastly, did you retorque the head (by slackening each 1/4-1/2 turn then retorquing through entire procedure) after 600 miles when you retensioned the timing belt?

Any of those will compromise the life of the HG but there are a few other factors that can influence it. Also you may need to consider an uprated HG if you're running 18 psi of boost.

[griston64]

Originally Posted by Laird Scooby

Couple of questions Damo - did you clean out the threads in the block for the head bolts, did you renew the head bolts and lastly, did you retorque the head (by slackening each 1/4-1/2 turn then retorquing through entire procedure) after 600 miles when you retensioned the timing belt?

Any of those will compromise the life of the HG but there are a few other factors that can influence it. Also you may need to consider an uprated HG if you're running 18 psi of boost.

The Elring gaskets should be fine Dave as the Overboosting guy has used them to 600bhp + on a Redblock

Damo did say he used Elring bolts as well so assume they were new at the time

[Laird Scooby]

Originally Posted by griston64

The Elring gaskets should be fine Dave as the Overboosting guy has used them to 600bhp + on a Redblock

Damo did say he used Elring bolts as well so assume they were new at the time

Thanks Mark - i looked twice but somehow still missed the bit about the bolts at the time, brain cell was still half asleep.

That leaves the other options i suggested then or perhaps the block needs decking.