Pitted piston - head gasket failure

[MorrisJohn]

My car suffered head gasket failure (see photo) between cylinders three and four.

The cylinder head has cleaned up well and it’s all very smooth to touch, with no signs of warping or score marks.

All four cylinders are nice and clean and feel perfectly smooth.

The only cause for concern is some pitting on the no.4 piston crown (see photo). It appears slightly jagged on one side. It’s going to be removed and inspected, but what are your thoughts on replacing it?

From the photograph would it cause you any great concern?

[philthehill]

I have seen worse and still in service.
You are right to strip out the piston and see what the total damage is before making any decision.

[MorrisJohn]

Thanks Phil.

[JOWETTJAVELIN]

The piston is damaged - replace it is my advice.

[Nourish]

Or put it back together and give it a compression test. If it's low gearbox off and drop the crank and have a look at the piston.

[pgp001]

Nourish

Forgive my ignorance, but I dont understand why you would remove a gearbox and then the crankshaft just to inspect a piston.
I would have thought removing the sump and taking off the big end cap, then lifting the piston out from the top with the head off would be quicker.
Have I missed something ?

Phil P

[philthehill]

I agree with Phil P.
To examine the piston in question there is absolutely no need to remove the gearbox or crankshaft.
Phil J.

[Nourish]

Yeh your right - my apologies

[MorrisJohn]

Thanks gents. New pistons and big end shells it is.