M103 Head Done, Still using oil
 

Car:1989 300E M103

I recently had the head fully redone on my M103 at 249K miles by my indy mechanic, a mercedes indy shop which I've been using for years. I've been tracking oil usage for the last 5 months and it's still using a quart about every 6-700 miles. I pulled the plugs and they all show signs of oil usage. I took it back to the shop, and they took a look. Their conclusion was that oil must be coming up through the rings because all spark plugs showed oil usage. Although I don't have the numbers in front of me right now, the compression was fine and even. They also looked at the head through the spark plug holes and said it looked clean.

I'm trying to consider my options of what to do. I was considering using rislone ring seal to see if that may slow down the oil use. Any other suggestions?

If you have good compression and the car runs fine, my guess would be the valve guide seals. They have to be replaced about every 75k miles on the M103. Just had mine done on my '89 300CE and as with you, I was using a quart about every 700 miles or so. No problems with the operation of the car, just a pain to keep having to add oil.

Did they replace the valve guide seals? That's my guess. Pretty simple if you have the right tools. The bottom end of these M103 engines are pretty indestructible and should go twice what you have before having to do a ring job.

yes, seals as well as some guides were replaced. One guess may be that the intake and exahust seals were reversed but I think it is unlikely that this would be the case on every cylinder.

I'm not familiar with that car or engine, but are there other places for oil to get into the intake? Vacuum pumps? Breather system?