Valve stem seal advice needed.
 

Hi all!

In replacing valve stem seals on a 190e 2.3 the procedure mentions an air compressor blowing air into the cylinder whilst the spring is removed...can this be done without the air by just moving each cylinder to top dead center instead?

Thanks in advance and have a Happy Thanksgiving!

You can indeed just rest the valve on the piston crown. But this is a little bit of a dodgy solution because the valves go into the cylinder at an angle - turning the crank - raising the piston might cause a geometric lock and a bit of damage to the valve. So don't do that! Make sure you have TDC for each cylinder before you drop the valves though.

The repair manual
 

for my old Norton motorcycle suggesting stuffing a length of rope into the cylinder to hold the valves up. Typical effective but simple British solution for the backyard mechanic.

Yep. Sometimes the old tricks are the best. However, the problem comes if you raise the piston so much you cannot remove the cord, because turning the engine backward to drop the piston a bit is a BIG NO NO on some engines, including the 2.3 IIRC.

On some engines the valve tip can fall below the valve guide making it difficult to pull back up. On some engines the valve will just rest on top of the piston.

Air is used when using a lever valve spring compressor. A twist type compressor ( look up K-D tools ) can be used without air however it becomes difficult to remove the keepers as the valve is trying to fall into the guide.

Look around for one of those 3 gallon carry compressors on junk day / pawn shop / flea market. It will have enough air to do the job if the valves are sealing reasonably well and you don't take too long. If you get into a situation where you must disconnect the air, wrap a rubber band around the valve stem ( at the keeper area ) to keep it from falling in.

If I remember correctly the 2.3 M102 has a domed top head and piston arrangement - I guess the chances of losing a valve in the head are limited with that configuration so long as the piston is at TDC. I know for a fact the compression ratio is such that if the chain breaks interference will result. The M102 is not a "safe engine". However, having never done this before myself I guess it is best to follow the FSM advice.