Well, a few days ago I posted about losing oil without an apparent leak. Well, I was replacing my crankshaft position sensor yesterday and found the leak. Of all the places, oil was leaking OUT of cylinder 7 through the spark plug thread. It is such a small amount of oil I totally missed it when searching on top of the engine.

I guess this means I either have a bad piston ring (unlikely) or a bad valve stem seal. Is there any other way this could happen? As I mentioned in my last post, I replaced the heads with reman units when doing the head gasket job. Is it possible to replace a valve stem seal without removing the heads? Can I get to it through the valve cover?

I'm thinking of adding some type of stop leak product to the engine oil to see if it helps. Any other ideas? Thanks in advance.

 

Are you sure it isn't coming out of the valve cover gaskets and running down into the recess for spark plug 7?

Also, I don't know if it will work on a disco but there is a tool that allows you to replace valve stem seals without removing the head, I used it on an 86 camaro back in the day, worked like a charm. I forget what it's called, but it essentially keeps the valve from falling into the cylinder, while you replace the seal.

 

Thanks for the post. Yeah, I'm sure it's not coming from the valve cover. Maybe the photo doesn't show it well but that plug is covered in oil. Oil then works it's way through the threads and pools on the cylinder head recess for the plug. A little bit runs down the outside o the head but it burns off pretty quick.

I have been looking for a tool to let me change valve seals w/o removing the head. Anyone have any ideas on that procedure?

 

Some old skool methods included - air pressure thru something (sawed off sparkplug) screwed into spark plug hole, air holds valve in place at top dead center, and feeding rope into spark plug hole to fill up cylinder.

 

if you have or can rent a compression gauge you can remove the gauge and attach an air line, the air will hold the valve in place while you use a valve spring compressor replace the seal. But i think you have a bigger issue that is why is oil leaking past the sparkplug? Was it loose? did it not have a washer? was the sparkplug hole helicoiled incorrectly? oil should not be getting past the plug at all never mind to the extent that it appears as a leak.

Now real OLD SKOOL, like as old as me. We would pull the plug, pack the cylinder with rope leaving a 12inch piece hanging, crank the cylinder to TDC. the rope would ball up hold the valve in place. When the seal or spring was replaced you would back the piston down and pull the rope out.
But that is some battle field $hit, that luckly does not have to be done today.