Advice on smoking '79 300SD

Hello, I'm looking for opinions and advice. My 300SD began smoking (blue/white)fairly abruptly about six months ago. At the time it had been spending most of its time in storage. I drove it into the mountains and it did fine, but shortly after that it began smoking, especially at start up. While idling it shakes badly and feels like a cylinder is missing. While moving it is smooth and accelerates reasonably for 295K. I don't know how it could be significant, but I've recently noticed it runs smoother when the A/C is on.
I've taken it to two shops and the first advised the compression is too low (185 in one cylinder, approx. 210 in the others). They'd like to replace the engine and won't rebuild it.
I just took it to another shop and had it re-checked, they advised one cylinder is at 250, the others are at 260,275,275 and 325. While running, the compression in #3 goes up to a minimum of 350, the others are at 400-425. He's also advising the engine probably needs at least rings and sleeves, but if he finds significant wear it will need a rebuild.
In searching this forum I've found several similar situations where the recommendation has been to keep driving as long as the engine continues to start.
Any thoughts or suggestions? If it's okay to keep driving it, it will be an almost daily driver.
Thanks,
Jason

[SW]

If it starts and you are satisfied with the performance, then run it as long as possible. Keep maintaining it and watch the oil level. When you mention that the ac makes it run smoother, it tells me that you might have a vaccum leak somewhere. I don't know how a vacuum problem would affect the performance of the engine. However, I recall disconnecting a vacuum line in the central locking circuit while the engine was running and the engine immediately started stumbling.

[can-do]

Greetings,

Unless you're looking to be the speed racer of MB diesels, I'd run the engine as it is. I would look to see if your vacuum line coming off of the vacuum pump going to the filter housing has oil dripping from it while it's running though, could be a vacuum pump seal gone bad pumping oil into your intake. As mentioned before, if it starts and gives reliable performance, why sink money into parts that won't cause any irreversable damage to the engine. If you rebuild now or later, you will still, at the least end up resleeving with new cylinder liners, new pistons, rings, bearings, and probably have the head redone. You can't do any harm to a running diesel engine unless something disconnects like a connecting rod that makes contact with another part other than the liner, those will be replaced in a rebuild anyway, and they're cheap to buy at any rate. Get your money's worth out of what you have, and watch the oil level.


Charles

[Edited by can-do on 06-10-2001 at 11:00 AM]

Thanks, and I'll definitely check the vacuum lines.
Jason