Cracks in piston heads

[clankilpatrick]

Good evening All,
well the saga continues. After getting the radiator recored, to try and finally solve an overheating problems and sending the head off to be pressure and rockwell hardness tested to rule out any cracks in it , things just go from worse to worser!!
Was cleaning up the block with wet and dry in preparation for putting the head gasket and head back on when noticed a crack in cylinder No 3 from the edge of the combustion chamber towards the outer edge of the piston.:eek: On closer inspection there was also a crack on number 4 piston head right were it would seem that one of the intake valves has come into contact with the head when a timing belt has gone (done by previous owners). All the piston heads have a lovely valve imprint in them. Its even flattened out some of the part No's on one of them!! :mad:
My question and this may be a bit obvious, is what do I do from here? The motor was running beautifully prior to us taking the head off and if we had diagnosed that the radiator was the cause of the heating problems first we never would have taken the head off!
Is this potentally a major problem or can these things take this sort of punishment? Would love to hear from anyone who has had a similar sort of thing happen and what you did.:confused: Leave it; replace with new OE pistons; or possibly some better jobbies such as the ceramic coated flash ones?
Cheers
Dave

[Lucus]

Next step would be engine out, strip down, measure and replace worn/damaged bottom end components (IMHO that is)

[Bareld]

Is there anybody who has seen these cracks before?
Is it a common problem for a td5
Do i need to be afraid to see this when i take my head of.

[langy]

This thread relates to a 300 tdi engine - the damage is from a broken timing belt and the impact of the out -of- timed valves on the pistons. TD5's have a chain drive cam, so the likelyhood of the same damage occurring is low.

[Blknight.aus]

engine overhaul time.

It'll likely soldier on as is for a long time but my luck doesnt run that way.

[101 Ron]

I would drop the sump off and replace the pistons.
The injectors would be worth a look too.
The valves hitting the pistons I believe have not caused the cracks.
These cracks in the piston bowl are often seen in Diesel engines and is related to diesel knock, or the uncontrolled burning period in the combustion process of a diesel engine.
Injector spray pattern , fuel , engine design and the type of load on the engine will have a effect on weither these cracks occur.
If the cracks were small it is some times OK to leave things alone.
In this case the cracks are far too large and the cracks will spread quickly with piston and motor failure your friend some time in the near future.

[clankilpatrick]

Gidday 101 Ron,
yeh, decided to replace the pistons. Was a good opportunity to check everything over in the motor while we had the sump off. Bugger all wear on the big ends and everything else looked fine. Changed the timing belt at the same time. Put everything back together and touchwood the truck is ticking over beautifully and gets up the hill on the way home about another 100m before i have to changedown to 4th!!