Knocking Mercedes diesel engine

The OM615 (possibly OM616) from my 1969 Merc 406D with a nasty rattling sound at idle. The sound goes away when the engine is revved, recurs back at idle, whether the engine is hot or cold. The sound seems to be coming from the back of the engine, possibly a loose tappet?

Category:

Autos & Vehicles

Tags:

• 406D
• OM615
• tappet

[uranian23]

finally got around to fixing it. 2 of the injectors were really caked up with carbon; new nozzles, and the engine runs fine again.

[uranian23]

turns out it was just the injectors. added some injector cleaner (which is essentially paraffin, much cheaper to buy in this form) to the fuel tank, problems much improved. still needs a new nozzle on one injector, but this has been a very effective temporary solution.

[inphiknit]

I would adjust the valve clearances first, they may just be very out of adjustment. You will need two 14mm wrenches bent to the correct shape to reach the adjustment nuts. Good luck

[uranian23]

thanks. that was our first thought, so we had the rocker box cover off, but then the 2 guys helping, both who had decades of experience of working on coach engines, couldn't see how to adjust the valves. it is at least successfully imported now, though the guy who did the MOT managed to mess up the lights in the process...now with the headlights on, the indicators and brake lights don't work! definite project, our old merc.

[luffe1966]

Weak oil pump??

[uranian23]

thanks for the thought. still trying to get the damn thing imported, so i'm unable to do much with it at the moment.

[mmarkomann]

@uranian23 so what? there are more than 50 years old cars running like the wind...

[dopendao]

i love those vans

[eddimull]

I actually had a tappet come off because of the locking nut on the valve clearance adjuster wasn't tightened down enough. It looked/sounded like a gasoline engine missing on one cylinder.

[carl6405]

Pull off the oil pan. Check that the sump filter is not clogged up, preventing oil from reaching the top of the engine.