valves new or used?
 

How do you determine if you shouild re-use the existing valves or install new ones, specially on fouling cylinder.

a machinist can measure
 

the edges and see how worn they are. if not too worn they can resurface them and go. on a diesel the exhaust take a beating and often the intakes are good even after 200k miles.

tom w

Thanks, what does it mean a burnt valve? Is actually a valve that has a section burnet away, edge wise or carbon buildup on a valve?

A section burned away. Always an exhaust valve AFAIK. It leaks so you have low or no compression in that cylinder. Often exhaust valves have to be replaced but not intake, in my limited experience.

Mike

Thanks for the info, the exh valve has carbon build up but nothing burnt away. compression was ok.

You should also carefully mic the valvestems. If the wear is close to or exceeds .001" the valve should be replaced.

Duke

I agree with duke, measure at the top and bottom there should be very little taper, look for pits and grooves were the valve sits on the seat

thanks guys.

Valves rarely burn in a Diesel engine.

I have indeed seen a burnt intake on a gas engine. It was a 56 Ford with a leaky intake manifold which leaned out one cylinder burning the intake valve at that cylinder.

Your machinist will be able to tell by looking at the valves if they can be reground or not.

Good luck,

re-use valves or replace?
 

Not at all unusual for intake valve stems to be worn out on a MB diesel. The valve does not rotate (it is held in a fixed orientation by a pin sliding up/down in the guide to keep the intake shroud oriented.)

Wear is th econsideration, and how the engine will bedriven. Racing purposed argues for all new. Normal operation (anything less than WOT and redline) means reused determined by condition--worn stems, worn spring keeper grooves, warped, pitting, top too thin after re-surfacing--all mean use new one.