Must Ie overhaul my engin after 36000 on the clock

I think You're trying to ask if You need to overhaul Your diesel engine after You've gone around 36,000 miles. If so, the simple answer is... No. That's really nothing at all. Even if You meant 360,000 miles, it's still not enough that You'd generally need to do an engine rebuild. Typically, You'll want to rebuild if there are worn engine bearings or poorly seated piston rings. Depending on the quality of the engine, You might be able to hit much higher miles on a diesel before this becomes necessary.