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usual source of exhaust smoke on start-up/after idling
Make sure you have identified the true cause of your smoke at startup as there are multiple causes and the valve guides leaking is not the first one on the list.
The main reason is oil vapor vented from the oil tank condensing on the interior surfaces of the intake manifold and then this oil is ingested at startup. If the oil is overfilled just a little the problem is accentuated.
The question was about valve stem seals, not valve guides.
aam993,
Thanks for the insight.
Once again I'm a little confused about the terminology. All I could find on "valve caps" was in the picture below and it seems our engines do not have them.
I did make the assumption that the original poster was speaking of the guides as these are often sighted as a root cause for oil leaking into the combustion chamber. I am clearly not an expert at internal engine componentry but looking in the PET exploded parts view how would one avoid having the valve stem slip down the rabbit hole once the collet is removed to replace the valve stem seal? Is there a special tool for this?
I also found the definition of the stem seal:
"Different than other seals in the engine, valve stem seals play an important role in lubrication. Valve stem seals allow a controlled amount of oil to lubricate the valve stem as it moves in the valve guide. The amount of oil that passes by the valve stem seal must be precisely controlled."
Over the years I have only heard debate about worn guides contributing to oil consumption never the seals, is there a functional reason why they are not a potential root cause in our engines, or was this cause simply overlooked and the seals were just replaced when the guides were during a top-end rebuild.
Sorry for all the questions but inquiring minds want to know as they say.
aam993,
looking in the PET exploded parts view how would one avoid having the valve stem slip down the rabbit hole once the collet is removed to replace the valve stem seal? Is there a special tool for this?
Andy
Andy, there is an air chuck that will screw into the spark plug hole. With the engine set so both intake and exhaust valves are shut, you pressurize the cylinder. The air pressure holds the valve shut so you can remove the valve springs and replace seals.
I have used it on small block chevy’s, but not these engines.
Over the years I have only heard debate about worn guides contributing to oil consumption never the seals, is there a functional reason why they are not a potential root cause in our engines, or was this cause simply overlooked and the seals were just replaced when the guides were during a top-end rebuild.
Replacing valve guides is necessary if there is excessive sideplay in the valves: http://forums.pelicanparts.com/porsc...ml#post4831341
Why folks assume worn guides, commit to top-end rebuild with engine out in presence of oil leaks I don't know.
To OP, similar to other 911's the valve seals can be replaced with the engine insitu , but it's tedious. As someone else mentioned, you'll need the an air adapter for compressed air to keep the valves seated while removing the spring and retainer to get to the seal. You'll need a valve spring compressor to work in tight space. Be sure to stuff every crevice with a rag to keep the retainers from dropping somewhere you can't reach them. I would be sure to have a couple extra retainers on hand. Tedious.
I happen to have an extra set of new Porsche brand valve stem seals...pm if you're interested
Smoke on start up would likely be lower exhaust valve seals since not a lot of oil sits up too and they see less heat.
Lowers are definitely easier.
uppers have very little room for compressor with cam towers in place. You may want to call pelican if they will work.
More room around the spring for a tool On lower springs Very tight on the upper springs. You’ll need to research to find a compressor tool fits. Here is the clearances for the tool on the upper springs. You may have to search a little for a dial type compressor that will fit.
Great, thanks for the pictures.
Did you have to use special tool 9237 (https://www.search-vehicles.com/deta...675386587.html) for seal removal and/or special tool 9569 for installation? These are mentioned in factory shop manuals for valve seals.
Andy, there is an air chuck that will screw into the spark plug hole. With the engine set so both intake and exhaust valves are shut, you pressurize the cylinder. The air pressure holds the valve shut so you can remove the valve springs and replace seals.
The poor man's method uses a soft nylon rope. With the piston at the bottom of the intake stroke, insert a length of rope into the spark plug hole (don't lose the end!), then turn the engine and let the piston mush the rope against the valve faces to hold them closed as it comes up on the compression stroke. Kinda brute force, but the air pressure thing always made me nervous given how sticky some of the keepers can be.
As for the two tools listed on Pelican, I don't think they will work. Even if you were able to use a stud temporarily on the valve cover bolt hole to mount the compressor, I am not sure the spacing is right. might be worth a look or a call to pelican.
Here is is mounted on earlier 911 and you can see the location of valve cover hold down.
I'd look for a small overhead valve spring compressor with a dial to compress axially,. They are fiddley but you can likely get the job done with one on the lower exhaust valves.
As for the other tools mentioned, they are easier to work around. Getting the old seal out is easy if you're not worried about damaging it with pliers. Getting the new one on and seated just requires a cutting a piece of thickwall plastic or copper tubing with an i.d. just over the dia of valve stem to push it down to seat it. To stretch the seal over the stem, a small piece of thin plastic that wraps around the circumference of the valve stem, rolling the outer end a little tighter to pass inside the valve seal and allows you to slide over the stem, removing the plastic sleeve.
You could use the threaded foot from the pelican tool and make a small plate with a couple stand-offs, tap a hole for the threaded foot. Sorry for the rough sketch.
You could use the threaded foot from the pelican tool and make a small plate with a couple stand-offs, tap a hole for the threaded foot. Sorry for the rough sketch.
05-18-2021, 02:59 PM
valve stem seals replacement with engine in
I was the original poster.
