Hello fellow Benz enthusiasts, I'm new to your forums! I'm in the process of chasing down the infamous M103 oil consumption problem with my 1991 300SEL. I'm having difficulty finding specific specifications for valve guide to stem clearance (new or at wear limits).
Secondly, has anyone here had experience with driving the guides out and installing new ones? Did you use a air hammer or did you do it by hand? Was there any noticeable change in ID of the new guide when it was installed to the point that it needed to be reamed open?
Motor has 140,000 miles on it with good compression (176 to 184 PSI). Figuring it could be a result of a leaking head gasket or valve stem seal failure. I'd like to clear this potential cause off my list while I have the head off.

Thank you for your help!

Most of us, including me, have our heads rebuilt at a machine shop. I have seen people use dry ice to shrink the guides to force them out...and doing the same in reverse to install. Then lapping the valves to the seats, without any griding. New stem seals and used guides. Beating them out may work, but installation I would never try with an air hammer. A press, maybe.

I paid $300 in labor and about the same in parts (incl gasket and bolts) after all the dust settled for my head. 12 guides, 12 seals, skimmed 0.005" (and timing cover), 12 springs.

If you are on a super tight budget, try fixing the oil leaks the M103 is notorious for before anything else (stem seals too). Your consumption may be less than you expect and something tolerable around 1000 miles per quart. At 322k, mine is minimal after a 1000 mile trip with some speeds at 90mph for extended time. Probably around one quart per 3000-4000 miles. Granted mine is all sealed up with a very slight valve cover leak that pisses me off.

Oh, I read something about the rubber seal in the valve cover that seals the PCV system causes leaks. I removed one and it fell apart by hand. Easy for oil mist to be sucked up and consumed!

Hopefully 'S-class Guru' chimes in, he has had his car since new I believe and and give you the full scoop on loss versus consumption.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

If you can move a >new valve < in the guide ,replace the guide .Check the valve stem as well as the guide it may be the valve thats worn .

Back in the day we did everything in-house. I've done plenty of M102's, 103's, and 116/117's. The guides were checked for wear using a go/no-go gauge. If replacement was required we knocked them out the old fashioned way using a drift specifically made for the guides being replaced, and installed the new ones the same way. I wouldn't be surprised if you can find everything you need on Ebay............

Back in the day we did everything in-house. I've done plenty of complete valve jobs on M102's, 103's, and 116/117's. The guides were checked for wear using a go/no-go gauge. If replacement was required we knocked them out the old fashioned way using a drift specifically made for the guides being replaced, and installed the new ones the same way. The only thing we didn't do was flatten a warped mating surface.

I wouldn't be surprised if you can find everything you need on Ebay............

Very inaccurate method...........

Most manufacturers' maximum acceptable worn guild clearance is on the order of 3 to 3.5 thou.

Changing guides should be left to a shop with the proper equipment. The head is usually heated in an oven to about 400F and the guides are chilled in refrigerator. Upon removal from the oven the tech quickly taps out the old guides and taps in the new. Then the head is placed back in the turned off oven and allowed to cool very slowly.

Slight distortions invariably arise, so reaming is almost always necessary and final clearance should be about one thou.

Duke

“1000 mile trip with some speeds at 90mph”
That reminded me of some extended cruising in the 91 300e 4Matic at the same speed! And that’s when it had about 200k on the clock. Incredibly smooth and quiet. Another great MB that I was sorry to see go (sold with about 240k).

That car leaked / burned oil since the day I bought it with 60k. It started with adding 1 qt. before each 5000 mile oil change and progressed to 2 qts. between changes (about a quart every 1250 miles). The type of oil made a difference (15W40 worked best for me). I’m sure I had internal leakage, but there were also external leaks (front cover and valve cover). I thought I was burning more before I sealed the external leaks. Make sure you take care of those if you have any.

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07 E350 4Matic wagon, 06 S430 4Matic, 99 SLK 230
retired W210 (x3), W124, W126