OM603 - blue smoke on startup and nailing...
 

Hey guys!

I have a 1987 300SDL with the dreaded #14 cylinder head. The car ran great until this winter. I switched it over to synthetic oil and it slowly began smoking on cold starts. I wasn't too concerned because it would go away after a while.

Well, now it is spring and it has worsened over the winter. Now when I start her up it idles roughly for a little while, then after revving it up and driving for a few blocks she starts to calm down a bit, with the occasional misfire (from cylinder #6)

Further more, whenever I am driving it sounds like the engine is "knocking". Disconnecting the #6 injector seemed to quiet that down considerably...

Any ideas as to what could be causing the blue smoke on startup and the misfiring at idle? Once the car has been running for about 15 minutes she purrs like a kitten and runs real nice.

My theories are:
Valve stem seals need replacing
Turbo needs to be rebuild
Blown head gasket
Cracked head


I am really hoping it is the turbo or valve stem seals as those aren't TOO involved...and a blown head gasket wouldn't be completely terrible since I have a lift...just tedious...

Any ideas?

One possibility..........and the least costly............is a bad glow plug on #6. The blue smoke is typical of a stone cold cylinder with no glow plug assist.

However, I'm not sure of this because it should clear up within about three minutes...........not 15 minutes.

You don't have a bad turbo or bad valve stem seals.

Does the engine consume any coolant on a regular basis?

Is the upper radiator hose very stiff the following morning after the vehicle was shut down? If you release the cap on the expansion tank, does this stiffness in the hose disappear?

ah, forgot to mention that. I did check for retained pressure on the hose and it felt fine. felt like there was a bit of coolant left in there, but no built up pressure.

I did a resistance check on all the glow plugs and they all checked out fine.

Sounds to me like injector problems. Might just pull #6 and have it tested.

As soon as I am back in town ( I leave for a week on friday ) I plan on rebuilding all of the injectors with new bosio nozzles and having them pop tested and shimmed.

If this doesn't clear up my issues then what would you guys recommend? I have no qualms with replacing the head. I love this car and want to keep it running for as long as possible.

You don't need a new set of nozzles yet.

Just switch #5 with #6 and see if the problem shifts to #5. If it does, then the issue is a bad injector.

Damn clever that Brian.

Sounds like bad injectors, or maybe, maybe, a weak IP. As Brian said start by swapping them around and see if the nailing follows it. If it does I would remove all 6 and have the local Bosch shop test them to see what you have. A couple may be in need of new nozzles.

It doesn't sound like GP's those should clear up pretty much right away. Since its coughing for so long its certianly not GP's.

Your IP could be losing prime, my brokers SDL is doing the same thing and so does mine. However mine isn't nearly as bad and clears up within a minute or so. Hers is a bit worse.

But rule out the injectors first.

Mine does the same thing, but only for about 2-3 minutes. I, too, changed over to synthetic oil.

Hadn't thought about the GPs, tho. Need to check them out.

Did a diesel purge today, so will see if that helped things out in the morning.