My 1973 280 needs the valve seals replaced. It burns oil like crazy, which fouls the spark plugs and carburetor and makes the oil solid black, as well as, of course, blowing plumes of smoke from the tailpipe. I have done quite a bit of research on the job and it still seems daunting, very daunting. I don't have nearly enough expertise do to the job myself, but I have even less money to pay someone to do it so I'm my own mechanic :-/ I am 17 years old and this is my first car. I have been restoring a 1971 Jeepster Commando, so I have basic experience working on a cars, but the Jeep is substantially simpler than the Mercedes... German engineering. I bought the car with the problem, and just drove it around for a while letting it smoke (almost a year actually, but I don't commute very far). Driving it like that takes such a toll on the engine that now it's performance is so poor it is completely un-drivable.

Anyways. I have the service manual on pdf and it doesn't really make the procedure very clear. Getting past the camshafts and chain is what befuddles me the most.
Also, to crank the engine to get each piston at TDC I will have to remove the radiator, correct?

Does anyone who has done this have anything to say about this? Step by step guide? If anyone has made a video of the procedure they would be my hero , but I've scoured the internet and found no such thing.

Every single bit of advice helps.

Welcome to the forum.

Yes, the M110 is not one of the easier Mercedes engines to change valve seals on.

First you need the right tools.
A valve spring compressor is a must.
You may find one in the tool loaner section on this forum.

Also moving the piston to TDC to remove the valve springs may do you no good, because the valves can still move down some what till they hits the piston.
This makes it at least much harder, if not impossible, to remove or install the valve keepers.
You need to pressurize the cylinder with compressed air, that will keep the valves at there highest point, in there seats.
So you need some kind of an adapter to screw into the spark plug hole and attach a air hose to it.

You also need a magnet, one of this cheap telescopic ones from the auto parts store will do, to fish the valve keepers out.

An other added difficulty is the fact that the 73 M110 still uses 11mm exhaust valve shafts, this thicker shafts limit the distance you can push the spring down to get to the keepers.
You will see that the 9mm intake valve shafts are much easier to work with.

Only remove the cam followers or rockers and the thrust pieces from the cylinder you are working on.
Make sure you install them again in the same position.

Then pressurize the cylinder.
The engine may turn a little as the piston moves down under the air pressure.

Hit the top of the spring retainer with a aluminum or brass punch to loosen the keepers.

Now push the spring down and fish the keepers out with the magnet.

After removing the springs and the retainer you can remove the old valve stem seal.
There are special pliers available for that purpose but a screw driver should be enough to pry the seal of the guide.

It is also a good idea to check the guide for looseness, it is not uncommon for this guides to be loose in the head.

Next install the new seal.
Use a condom, a small plastic sleeve that is normally delivered with the valve seals.
It slides over the top of the valve , so you don't destroy the seal lip on the keeper groves of the valve.

One way to install the keepers is to put them into the spring retainer before you place the retainer on the springs.
Keep your finger on top of the keepers while you carefully push on the retainer to compress the springs.
With a lot of luck the keepers may just fall into place.

Another way is to lightly magnetize a screw driver and lower the keepers on the tip of that screw driver into position when you compress the springs.

Which ever way you do it, there will be a lot of fumbling and some foul language.

__________________

76 240 D. Bought in 1998 for $25.
85 300D. Got it for free with a bad engine. ( Sold )
60 Unimog 404. What was left of it, was given to me. Now powerd by 617A.
88 560 SEL. Bought without engine and trans. Now powerd by 617A.
67 250 SE. Cuope. For resto or sale.
64 220SE. For resto.

you might want to practice on an engine in a pick&pull if you fear hurting yours.

you should stop if you find a wobbly guide, as that is a far worse problem than a bad valve seal and has some of the same oil consumption symptoms some times.

To hand crank the engine around, you can reach up from the bottom under the fan and a 3" extension should be sufficient. No need to remove the radiator. Removing the plugs will make hand cranking easier.

-CTH

__________________
- cth350@gmail.com
http://www.111lakeside.com/

It's not likely that whatever ails the engine can be fixed in situ--that head will almost certainly need to be removed and rebuilt.

Before doing anything I'd make sure that the diaphragm in the vacuum pump isn't leaking--if it is an enormous amount of oil will be sucked out of the cam tower and into the manifold to be burned along with the fuel until the carbon buildup finally affects the plugs and valves


Tim Kraakevik
kraakevik@voyager.net

Are you sure you don't have a blow-by problem? How would oil get in the carbs if only the valve seals are leaking?

>You need to pressurize the cylinder with compressed air, that will keep the >valves at there highest point, in there seats.

This does not work well with old engines, as the rings/valves do not seal well and thus it's easy to accidentally push the valve down. Ie. the air pressure does not hold the valve with a lot of force.

__________________
Csaba
1972 280SEL 4.5, silver

True, air will bypass the rings.
You will hear and even feel air blowing out of the crank case.
I should have mentioned that cylinder or adapter has to be connected to a compressor that can replenish the pressure ones it drops.

__________________

76 240 D. Bought in 1998 for $25.
85 300D. Got it for free with a bad engine. ( Sold )
60 Unimog 404. What was left of it, was given to me. Now powerd by 617A.
88 560 SEL. Bought without engine and trans. Now powerd by 617A.
67 250 SE. Cuope. For resto or sale.
64 220SE. For resto.

If inlet stem seals are leaking, pulsing in the inlet ports will carry the oil back into the intake manifold and carb.

I've found it easier/safer to get the piston near TDC, thread some thin rope into the spark plug hole, then bring the piston up until it compresses the rope against the head/valves.

__________________
1981 300TD 310k miles
1970 280sel 172k miles
1966 230 Fintail 162k miles

"Where are we going? And why am I in this hand basket?"

I was pretty sure it wasn't that, because the valve openings expand with the hot engine, and it doesn't smoke that much until the engine is up to tempurature. But incase that was the issue I got a piece of hose and connected the intake manifold to the brake booster, bypassing the vacuum pump. I was testing how that worked out and it did seem like less smoke at first, but I didn't get a chance to bring the engine all the way to temperature. The spark plugs are so fouled that the engine wont idle without stalling and it would take at least four minutes to go from 0 to 60. To keep the car drivable for the past year I've been replacing the plugs each time I change the oil; and it's time for an oil/plug change. That doesn't do anything about the carbon building everywhere else inside the engine though.


Regarding the rings, I've done a compression test and all the readings were fairly similar to each other, no outliers, but they were all low around 105 psi. Isn't about 160 psi the norm with most engines? I think I saw on wikipedia once that there was a low-compression version of the M110 (maybe it had to be tuned down for US regulations at the time )

Also, just another quick thought, recently I've been thinking about selling the car. What would you guys say about that? I paid $1,500 for it.

You mean when it's running, or when I have compressed air hooked up to the spark plug hole? When it's running I can hear hissing, but it seems like a normal sound of the engine. I can't feel air flowing from anywhere except the fan.

I suggest you establish a baseline for this engine and really diagnose it. Compression readings seem low but that doesn't really mean anything as it depends on altitude, your gauge etc. You need to perform a leakdown test to see where the blowby is from. You may find it needs head work as well as rings.

As others have suggested, an M110 is probably not what you want to learn these cars on, there are easier Vintage MB engines to work on, let's put it that way... The parts, tools and machine shop work for a ring job and doing the head work you might need will get up to $1500 right quick...

Is the oil pressure good ? what does it read at idle? with good clean oil, not dirty old oil.

I really think the job would yield better results if you pulled the head. It probably would not take THAT much longer, you could check the valve guides(most probably worn out),de-carbonize the head/valves(if it has been burning oil it will need it) and evaluate the cylinders for wear to see if it is a candidate for new rings. If the valve guides are worn out, new seals are a short term bandaid-it's a lot of work to change them without knowing the condition of the guides.

__________________
Tony H
W111 280SE 3.5 Coupe
Manual transmission

Past cars:
Porsche 914 2.0
'64 Jaguar XKE Roadster
'57 Oval Window VW
'71 Toyota Hilux Pickup Truck-Dad bought new
'73 Toyota Celica GT