300D puffs smoke at some starts - valve stem oil seals??

[tedious]

:? Just got the car 1991 300D runs well enough on the road plenty of tug..seems to give some smoke at higher revs - wondered about heater plugs - dont know the history of this car....I am sure the mileage on the speedo is far too small....Have just put some redex diesel cleaner in the tank - gonna change the oil and filter tomorrow cos it looks really black. I hope I am not gonna have to lift the head!

ps no signs of oil in the water and visa - versa.

Little pinky when first started but quietens after 30 seconds or so....

any help gratefully received...thanks

 

[TimN]

What colour is the smoke upon starting. If there is a hint of blue then it is contaminated with oil getting through worn valve seals. You could check the compression if you suspect anything more sinister.

If the smoke at high revs is to be considered unacceptable you could get the injectors serviced.

 

[Andy]

Hi

My advice would be. Stop looking for trouble! If it starts and runs ok. Leave well alone. If the glow plugs are a problem then you will have hard and lumpy strarting.


Try reading war & peace if you need something to do.

Regards

Andy @ www.mercedesservicing.com

 

[dieselman]

Possible glow plug fault. You mention its a bit pinky when first started. That could be a plug not heating fully. Try waiting for five seconds after the glow light goes out, as the plugs continue to heat.
Allternatively it could be a squiffy squirting injector. A dose of injector cleaner is always a good idea before commiting further.

Echo Andy. Dont worry. Mercs do make terrible noises if there is any hint of incomplete combustion.

 

[tedious]

Thanks for the advice guys - Seems to have cleared now after around 350 miles of motorway cruising and a good oil and filter change. Starting is a bit like lumpy gravy but I am gonna change the glow plugs next week.

Its amazing how this car has re-enlightened my interest in home mechanics once more - it seems reasonably easy to get to most things around the engine bay. I am aslo gonna change the transmission oil in the auto box to complete the initial service from me - any advice please? I am gonna get a new filter and rubber gasket from the local dealership...any thing else I need to be wary about?

 

[dieselman]

Change the antifreeze. This engine has an aluminium head which will corrode with old antifreeze in the system.

You say the starting is a bit like lumpy gravy. If after starting the engine is lumpy and missing on one cylinder for about 30s then you have a glow plug down. At £20 each you wont be changing them all just for the fun of it!

 

[tedious]

Hi guys - a follow up - I stripped the head off this beast and took it to a local head specialist. What I did not realise was that some diesels do not use valve stem oil seals at all - and this version of the 3 litre engine does not have valve stem seals on the exhaust valve guides, only the inlets vavles are sealed.

When they took the valves out, turns out the exhaust valves were a little worn on their stems and the guides were worn. I got them to fit new guides to all valve positions and bought new exhaust valves.

Everything back on and bolted down she runs really well and no signs of the smoking after sitting in traffic any more!

Thanks