Hey guys. New to the forum here.

Just a little about myself...I'm 18 and heading off to Rutgers this fall.

My first car and first love is a 1994 E320 Coupe and my newer car in relative terms is a 1975 280S that I'm restoring with my uncle.


Anyway, I need to replace the valve stem seals in my M110 engine because it burns major oil.

I know it's the stem seals because acceleration is smooth and there's no hesitation so that rules out bad compression/rings.

Also, when I'm on the highway, and I'm doing whatever speed, if I go over 3500 RPM, let off the gas then get back on, huge plume of gray smoke.

So what's the easiest way to go about changing the valve stem seals and how long am I looking to spend at doing this?

Thanks!

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1975 W116 280S - SOLD
1994 W124 E320 Coupe - Gone

CURRENT - 1974 450SEL - 1987 560SEL

It is quite a job.

I am a very experienced hobby mechanic and i would probably not attempt it. i suggest getting a haynes manual or fsm or better, both,, and see what's involved.

Good luck

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Im having some dealer technicians who I work with help me. One of them said he just did it on his Honda prelude...

any other advice please?

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1975 W116 280S - SOLD
1994 W124 E320 Coupe - Gone

CURRENT - 1974 450SEL - 1987 560SEL

The factory manual says the cambox must be removed to replace the valve seals. Pulling the cambox on that engine is almost as much work as removing the head. I did manage to replace the valve stem seals on my grey market m110 a long time ago w/o removing the cambox. You need to correct spring compressor and a lot of patience. I put each cylinder at TD and let the valve rest on the piston.

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as ever
Paul

1989 560SL
1987 300SDL
1987 300TD
1983 BMW 633CSi
1972 280SE 4.5

Would you mind further elaborating or referring me to a good DIY or info place?

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1975 W116 280S - SOLD
1994 W124 E320 Coupe - Gone

CURRENT - 1974 450SEL - 1987 560SEL

This has been discussed a number of times on a couple of the forums here.

You basically need to remove the sprockets from the cams, remove about 2/3 of the head bolts, remove the rocker arms, and pull the cam box/cams off. Then, as stated, you bring each cylinder to TDC, remove the keepers, springs and old valve seals, and install the new seals. Then re-assemble in reverse order. A good source in the Haynes manual for the "123 twin cam."

It is a lot of work. And, when they smoke like that, you will almost certainly need valve guides as well, which does require pulling the head.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

I do not know the valve guides used on your engine. The valve guides on the single cam can wear so bad the small cutback that the seal sits on can be missing or damaged even on some guides. Those guides can get really worn at elevated milages.
The guides themselves are usually sourceable at reasonable cost. They require a closer tollerance reaming than american guides. Putting on a new set of valve rubbers may or may not be enough.

The M110 is a great motor. Good luck with getting it done. How about some more pic's of your 280S. A 79 was my second Mercedes. It was a magnificent highway cruiser.

- Peter.

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2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S

If it helps any details the engine/car only has 77k miles on it...so can it still be guides or just be seals? or Both?

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1975 W116 280S - SOLD
1994 W124 E320 Coupe - Gone

CURRENT - 1974 450SEL - 1987 560SEL

Verifiable 77k?

77K is young, but not off the chart. In any case, you should wiggle the valve stems with the springs off, and if there is anything more than the smallest amount of movement, you will need to do the guides to fix the problem.

By any chance, does your car have the vacuum pump at the front of the cam box? There is a diaphragm inside it that can break and smoke under the conditions you describe.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Not a clue. But this picture may help...

__________________
1975 W116 280S - SOLD
1994 W124 E320 Coupe - Gone

CURRENT - 1974 450SEL - 1987 560SEL

By some documentation, owner history, and brake pedal wear we're pretty sure.

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1975 W116 280S - SOLD
1994 W124 E320 Coupe - Gone

CURRENT - 1974 450SEL - 1987 560SEL

Thats the vac pump located right front w/clear lines running to brake servo and intake manny. Diaphragm looks to be okay. Airline and banjo bolt to manifold oughta be real dirty w/engine oil if it aint.

Nah, dont be so fast..... most common prob with ridiculously low mile cars hibernating for decades is rusted/cracked rings and/or pitted bores from condensation alone. Heck, rusty rings will actually eat grooves in bores - seen this myself. Y'all caint rule out lousy bores and rings without at least running wet/dry comp test first.

Otherwise valve guide seals are DIY difficulty probly 8 of 10, filled with hazards. But if thats what ye wanna do, we'll talk ye through it. Needs special tools: valve spring compressor, air compressor w/spark plug hole adapter, valve adjust wrenches. DIY reconnoitre 10-12 hrs workin slow. DIY'd valve seals on my 220Sb m180 SOHC and took me 2 days under the hood, including trip to dealership for 2nd set of seals after screwin up and busting couple of em. Takes magic touch to set em right. No doubt 6 or less billable hrs if professionally done by an MB indie who done it before - and thats probly what the car deserves. Sorry but yer dealership 'honda pros' lost it when sayin bores are fine "based on performance." Could be true with rice-burners but sure as hell aint true for MB's.. Had one oil guzzler Benz (formerly seized engine) that ran *perfect* after knockin it loose, daily driven more than 3 yrs. All the while drinkin 1 qt oil per 2-300 miles. Nasty rusted bores and rings no doubt.

IF it did turn out to be pitted bores or rusted/cracked rings...is it worth it to do it myself or hire someone or just buy a new engine from a donor?

The thing with buying a new engine is it's such a young engine and I don't want it to go to waste...but I still want to be cost effective.

__________________
1975 W116 280S - SOLD
1994 W124 E320 Coupe - Gone

CURRENT - 1974 450SEL - 1987 560SEL