Hi gentlemen……. I’m following up with this old thread regarding oil consumption in my 250 SL. I have just removed the head, and found several things that cause questions. I need some advice before proceeding. But let me provide some history first………….
A new MB short block along with a rebuilt head was done in 1984. The valve stem seals used in that head assembly were white Teflon on the intakes and black Viton on the exhausts. The exhaust valve guides had the groove cut to hold the seal in place. These exhaust guides are consistent with the MB Service Manual which says that 250 SL engines after 000618 should have the exhaust valve guide with the groove cut in the top, and use exhaust sealing rings manufactured by Freudenberg. My engine number is 129982-10-001704.
Oil consumption since 1984 (after 60,000 miles) has dropped to something less than 500 miles per quart.
In 2003, I made an attempt to solve the oil consumption problem. My focus was on the head (not bad rings), so I removed the Cam Cover to make a head inspection. As stated above, the valve stem seals were white Teflon on the intake guides and black Viton on the exhaust valves. These seals actually looked good. The only problem I found (again….this is back in 2003) was that the cyl # 3 intake valve guide was loose in the head. I temporarily coated the outside of the guide with JB Weld, staked the head around the guide with a center punch, installed MB valve stem seal kit # 108-586-00-05, and ran the engine until today (2/12/09). Obviously, I should have questioned this back in 2003, but that was before finding this forum and I just trusted MB to give me the correct seals for my engine. So the question………. Is the MB valve stem seal kit # 108-586-00-05 intended for the newer 250 SL engine? I ask this because both the intake and exhaust seals are all white Teflon type. I cannot tell whether the exhaust seals have the internal ridge for the grooved guide.
When I removed the head today, I found that all of the exhaust valve guide seals had “popped” off the guides. Intake valve guide seals in 3 cylinders had also “popped” off, and these 3 cylinders had copious amounts of black, oily deposits. The other 3 cylinders had the intake valve stem seals in place and the combustion chambers were clean. Pretty good evidence that oil is going past the intake valve guides.
The MB Service Manual specifies using valve guide seal installation tools. So here is my 2nd question………Do you guys use these tools (one for the exhausts and one for the intakes) or are there other techniques equally effective? Where do I get such a tool?
When I inspected the head today, the cyl # 3 intake valve guide that was loose back in 2003 and “temporarily repaired” seemed to be in place. This was one of the cylinders where the intake valve guide seal had stayed in place too, and the combustion chamber was good and clean…….free of oily deposits. Obviously, I will have this guide replaced before the head goes back on. But my 3rd question is this…………how can I tell if the guides are loose in the head? They feel tight, but I did not tug on them with pliers and I did not drive on them with a mandrel/hammer to see if they moved. I’m afraid to do that!!
Aside from the possibility of loose valve guides, it appears that my oil consumption problem may be due to the following: (1) wrong installation technique on the valve stem seals since I did not use the MB Service Manual recommended installation tools and/or (2) the wrong seals were installed in 2003. I see no evidence that oil leakage may be going past the ball studs.
I appreciate your comments and advice on how to get this little jewel back on the road.