2.0 is leaking from chain box, how hard a fix?

[EarlyPorsche]

Ok my 2.0 is leaking from behind the chain box. Its not the cover gasket as I replaced that. So now I need to replace the O ring or gasket or whatever is behind the box, any clue exactly what it is, I figured it was a large O ring against the head and gasket to the block, anything else? Has anyone done this before? I know I have to take the camshaft sproket off, How do I go about not messing up timing?

I was thinking I take the cover off and mark the chain on the sprocket and then somehow mark the sprocket on the chain. I could then take it all apart and if the came or crank spun on me I would just want to line up my marks again. I could also then install my tensioner stops too.

[304065]

Get out the exploded parts diagram. There are three ways oil can leak out of the chainbox. They are through the cover gasket, which you say you replaced, through the end gasket where the chainbox end fits against the case, and from the intersection of the cam tower (not the head) and the chainbox.

To fix the oil leak you should remove the chainbox and verify that all the surfaces are flat and dimensionally correct-- when an engine is rebuilt sometimes people flycut the heads, which moves the centerline of the camshaft closer to the centerline of the crank, and the chainboxes have to have an equal amount of material removed to compensate or the cam will bind. If this isn't done correctly, a leak will result.

You should not try to get away with just removing the cam sprocket. Unless you remove the valve springs, one of the rockers will be pushing on one of the lobes of that cam, which will turn it one way or the other when the gear is removed. Far better for you to follow the cam timing procedure on that cam, and check the other one while you are at it. Otherwise you will never know that the timing was correct to begin with, or correct when you are finished, and that can get $$,$$$ real quick.

Just my .02, I have the same leaks and have been thinking about it a lot lately in the context of my coming rebuild.

[john walker's workshop]

if the engine is set to TDC #1. the cams will stay in position with the tensioners removed. just be gentle when you remove the sprocket and don't let the chains get pulled in either direction.

[Grady Clay]

There are actually four gasket/seals between the chain housing and the other structures:
Chain housing cover gasket (901.103.191/2.03).
Chain housing to case gasket (901.105.103.03).
Joint ring to cam housing gasket (901.105.197.00).
Joint ring to chain housing O-ring 67.5x75.4x4 (999.701.124.40).


Another oil leak possibility is the big pin that holds the tensioner. Inspect the epoxy seal on the forward (cylinder) end. That is between the chain housing and the #1 or #4 cylinders and visible from underneath. A leaking cam oil hose or fitting can appear as if the chain housing is leaking.

After 30+ years, there also a possibility of casting failure.

Best,
Grady

[shbop]

"i feel for you, but i can't quite reach you."


Too good!

[304065]

Wow, Grady, that is an excellent analysis. I didn't think of the pin itself but I suppose that could work loose as well or the epoxy could crack.

As far as casting failure, do you mean a crack or porosity or both? I have heard of using Glyptal to seal a porous casting but I suppose replacing the chainbox would be easier.

[Gunter]

Wayne's book on engine rebuild would help you with this.
Page 157-58 explains the whole assembly plus advises about the 0.5 mm max float between thrust plate and chain housing.
I actually had to leave out the gasket between housing and case to observe that float.

[EarlyPorsche]

Hmm. Sounds amazingly complicated. I know the engine was rebuilt about 15,000 miles ago. I do not know if it was fly cut. If I take the chain housing off and it is verified true by a machine shop how can I know if I need it milled down. The other side is not leaking so it leads me to believe it is a simple pull it all apart and replace everything non-metal. I think I will try the top dead center trick rather than try and retime anything.

So set TDC, loosen and remove cam nut. Will the gear fall off or do I use a puller? Then off comes the housing? Replace all seals gaskets and epoxy plug and reverse installation?

[EarlyPorsche]

Is that right?

[Gunter]

The sprocket comes off without a puller. But look for the pin and mark the location in the holes on both parts of the sprocket if you want to keep the cam-timing.
Set at TDC, remove chain cover, open the cam nut, compress tensioner and remove, mark the pin-location, pull sprocket and wiggle it out from the chain.
Now look at the thrust plate assembly to see what "float" you have. Is it concentric in the bore of the chain housing? A little off but still within the max 0.5 mm required? If it isn't almost concentric, the large O-ring will not seal. Check the axial play at this time before opening the 3 small bolts.
To check the gasket, you have to pull out the whole assembly. Open the 3 bolts and make sure that you keep the shims together.
Does the gasket look o.k.?
Do you have wayne's book? If not get it and read page 157-58.
Determine first where the leak is coming from. You may not have to remove the chain housing or do any machining to it.
Machining is usually only done to get the right float.
Sometimes the gasket between chain housing and engine case is omitted to get the right float for the large O-ring. Then Loctite 547 can be used for sealing. Do you see a gasket?
It would be soooooooo much easier if you get Wayne's book and study this issue first. It is somewhat involved. On re-assembly, the right side sprocket has the dished side inwards for correct alignment.
After you remove the cam sprocket, take a picture in situ so we can see the float before you remove the sprocket assembly.