Diesel Demise

[hiho]

The combustion chambers

All cylinders have cracks between the valves.
Note the impression on the valves from the cutouts in the pistons. Is this from normal running? If it is then GET THE RIGHT THICKNESS HEAD GASKET!!!









Note: No.s 3 and 4 were taken without flash.

[hiho]

And finally...

The Shim.....



The head....



Let this be a warning to you....

[hiho]

Biodiesel deposits in the combustion chamber

Just a note regarding the carbon deposits (or lack thereof) on the piston crowns and in the combustion chambers in the preceeding photos, the car was run on straight biodiesel for 500kms immediatly prior to death and on mostly biodiesel (70%+) for 5000 kms before that. Biodiesel has been ruled out as a cause of death.

Im not sure what a diesel combustion chamber should look like with regards to carbon buildup. I assume that as diesels run lean most of the time there should be less carbon deposited as it gets burned off again during lean running when compared to petrol motors. This motor is much "cleaner" in the combustion chamber than petrol motors that i have stripped after less than 10,000 kms (carburettored) but how does it rate compared to GLD's running dinodiesel?

Any ideas???

[gldgti]

bio d and dino aobut the same

the biodiesel tends not to be worse than dino diesel for carbon buildup, but may not be better either.

those cracks between the valve seats are a usual thing in these engines, ...unfortunate but usual...

[brackie]

Sorry I'm late...

The amount of carbon build up in diesels is a direct result of fueling, however cylinder head design plays it's part in removing carbon on the exhaust stroke. Well designed exhaust ports and system will improve the removal speed of gas and particulates so reducing build up. VW got it pretty right and most of the heads and pistons that I've seen have been very clean. Pay attention to the "smoke screw" (max.fuel at the govenor) as if this is allowing too much fuel to enter the combustion space as well as being blown out of the exhaust carbon will build up.
I've seen plenty of diesels with large amounts of carbon in the head but never to the point where performance has been affected.
The "ghosts" of the valves or combustion space seen in the pics are common and probably nothing to worry about, although if the motor has been apart before I would be checking the piston protrusion above the block and making sure I fitted the correct thickness gasket.