Head Gasket Failure?

[Tom Brearley]

Hi,

Having worked reliably for almost 11 whole months, my GT has decided it's unhappy again.

Accelerating up a gentle hill in overdrive, a loud & rapid 'clacking' started coming from the engine. Power and drivability reduced. Accelerating produced severe engine shake. The clacking varied according to engine speed.

A compression test shows that cylinders 3 and 4 have 50psi (while 1 and 2 are around 170psi which is normal). When testing cylinders 3 and 4, there's an audible 'chuffing'.

There's no 'mayonnaise' on the radiator cap or oil-filler cap. There's no white smoke from the exhaust and the coolant level hasn't dropped.

But am I right in thinking this is probably head-gasket failure?

Thanks

Tom

[Bumpa]

Don't know, never having experienced HGF myself. But have you had the rocker box cover off to see if anything is amiss in there?

[Tom Brearley]

I have indeed: all looks normal.

[Dave Wheatley]

99% certainty of head gasket failure in my opinion.

[Ian F]

I think you will find that you have a piece of head gasket missing between 3 and 4 cylinders. If you drive it like this you risk eroding the head and block in that location necessitating skimming of both. A common issue with A series and B series engines.
Usually caused by surfaces not being perfectly flat, head bolts not tight enough or overheating - usually cylinder 3.

Ian F

[Tom Brearley]

"If you drive it like this you risk eroding the head and block in that location necessitating skimming of both."

Annoyingly, I drove it for 35 miles to get home - having been advised it was a cracked exhaust manifold.

[Ian F]

It may be OK, you just need to look. There will be burn marks across that area, but check with a straight edge and feeler gauges. It may always be a weak spot though if you don't get the surfaces refaced

Ian F

[Tom Brearley]

Thanks All.

If anyone can recommend a classic-friendly garage in the Exeter area, I would be grateful. The one I have used before (at Tipton St John) can't book me in until late September - and I'm not that keen to do the job myself.

[Not_Anumber]

It is very easy to get the head off a B series engine with basic tools, nothing to be wary of. Take the head into any engine engineering workshop to have it checked. Leave instructions for them to skim it if needed and if so to advise you whether the level of damage would necessitate skimming the block (generally less likely to be needed). Order a new head gasket of a known make. Reassembly is the reversal of dismantling, ensure you have a feeler gauge and a spare hour to adjust the tappets. Enjoy driving it again.

[Vic Butler]

The best gasket is a Payen.