M180 valve stem seals underway - PeachParts Mercedes-Benz Forum

joshhol · #1 08-20-2016, 09:05 PM

Finally dove into the valve stem seal job on my fintail that I've been meaning to do for a long time. With the carbs/manifolds out of the car, if I drop a valve it's not too much more to pull the head.
Definitely is a little daunting at first having not done stem seals before but after much effort on #1 intake, #1 exhaust went a little easier. That being said I only did one cylinder today as it took a little bit to refine my techniques.

One annoyance is that when you remove the valve cone halves, the springs extend to a point where it's difficult to remove the spring compressor tool. Have to pry down on the spring retainer to get the tool out.

Also, the stem seal on the exhaust valve is odd. It's rubber and it sits up in the top of the sealing ring retainer (#3 in pic) but it doesn't look like it does much to seal the end of the valve guide. Two options to install it: slide it over the valve and then put the sealing ring retainer with springs and spring retainer over the valve and hope it seats into the top of the seal ring retainer. OR, seat the seal into the seal ring retainer all the way in before putting the seal ring/springs/spring retainer assembly over the valve.
I used the latter method as in the former, it looked like the seal ring retainer would just push the stem seal down on the exhaust valve.

One neat thing was using my leak down tester to control air pressure input right at the cylinder.

Not sure that this job will make much of a difference as I see signs that suggest a valve job will be needed sooner rather than later. Oh well. . .

muleears · #2 08-22-2016, 12:15 PM

What made you decide to do the stem seals? Burning oil?

gmog220d · #3 08-22-2016, 04:27 PM

What style spring compressor are you using? The ones that look kinda like a puller can be a pain sometimes. Just curious . . .

joshhol · #4 08-22-2016, 07:48 PM

I've got this kind. Oh yeah, I have to crank down the adjusting nut all the way to get enough room to get the rocker arm out. One more thing to do.

Muleears, she uses some oil but doesn't smoke an inordinate amount. I just figured with the manifolds off, now would be the time to do it.

From what I can tell in the records, the engine was rebuilt in 1983 and this build has about 150,000 miles on it. But to my untrained eye, it looks like a valve job is in the not too distant future. The cam and rocker surfaces look like they've seen better days. The intake valve on #1 could move a bit in the guide, more than the exhaust valve. It will be more informative doing the rest of the cylinders.

What do you guys think about doing a leak down test at this time? I have the air supplied to the cylinder through my tester but I have no way to warm the engine. Seems results won't be reliable.

joshhol · #5 09-05-2016, 05:28 PM

The stem seal job is done. One more small step to getting this thing moving again, it's on the upswing hopefully.

I took some readings with my leak down tester while holding the valves up even though I couldn't get the engine to operating temp.

Cyl #1 had the worst loss. 42% air loss with air felt escaping from the exhaust port. I may have been wrong earlier in saying the intake valve guide on #1 felt loose. I could go back and remove the valve springs again on #1 to check but what's the point. This probably explains the ashy condition of the #1 spark plug noted in an old post I made.
Cylinders 2 - 6 were ok with a range of 6 - 10% loss. Cold engine.

I hadn't noticed much of a miss before, she always idled pretty nicely.

Question is driving on it the way it is, will further damage occur to the lower end? (Incomplete combustion causing gas to wash the cylinder walls?) If I were to pull the head, I'd want to remove the block and replace front/rear and lower pan seals (assuming the cylinders were ok). If I pulled the engine, I might as well remove EVERYTHING and make this a rolling chassis, have the whole carcass media blasted and fix all the rust, then put everything back together. And, I don't have time for that right now.

When running, I only put maybe 1,000 miles a year on it. (can't drive it in winter, horrible swamp a$$ summers means I use the VW A/C when it's unbearable, and I use the 300D more than the fin. Very selective about where/when I use it)
I may be able to begin tearing it down in another 5-7 years when I'm out of the military and I don't have to worry about dismantling a car and then getting orders to move.

joshhol · #6 09-05-2016, 05:31 PM

BTW, don't rely on air pressure alone to keep the valves up. Move the piston up without fail.

Air escaped the cylinder when trying to re-seat the valve cone halves on exhaust valve #6. The valve dropped but the piston kept it from going all the way.