oil leak from heck!
 

Ok so Im working on a friends truck and we are having one heck of a time getting rid of an oil leak. Alil background. 1994 s10 with a 383 sbc vortec. So far what we have done.

Balancer seal is leaking.
Replaced balancer seal. Still leaking
Then replaced plastic timing cover. Still leaking
Removed cover found double roller chain rubbing on cover, replace cover and installed hd timing chain. Still leaking
Replaced balancer. Still leaking.
Installed a sleeve to balancer, still leaking.
All gm parts used.

This is were we are at. Next option is maybe to try an aftermarket metal cover. Any ideas?

I never even knew there was such a thing as a plastic timing cover for sbc. :confused59:

When there are multiple oil leaks, I would look at your crankcase ventilation system. Sounds like pressure is trying to escape anywhere it can.

That would be my exact response -- bad PCV valve or that system failure somewhere.

In addition to the above, are you sure the leak isn't from the front of the oil pan where it meets the timing cover? They make a thin and a thick front seal depending on the oil pan used; if you use the thin older style pan gasket/seal it will leak badly with the later oil pans, and most aftermarket pans.

Excessive pressure - based on all your efforts to date.
PCV and breather condition?

Condition of crank snout?

The front pan to cover seal design is poor at best.

Most builders I know rely on the Right Stuff: http://www.permatex.com/products/our...he-right-stuff

Mating surfaces cannot be too clean.....I have a new Milodon pan and cover, engine assembled in the shop with the Right Stuff and it still weeps a little oil. :bang:

Getting that area to seal with the motor in the car is tough not to mention a real PITA.

I was also thinking pcv system. Its not coming from the pan that we made sure. We were actually able to see it make its way outta the crank seal. Imma look into the pcv system next.

Also how are yo guys installing the balancer? Hammer and socket or with an installation tool?

I had a guy use a large hammer and crack the thrust bearing. This caused the crank to move forward which made contact the cover and kill the seal in a matter of seconds.
Might be a good idea to install the balancer with the cover bolts a tad loose pan dropped, then tighten them after the balanced is on.

Does this engine have the crankshaft sensor mounted in the timing cover? We had a 4.3 that we could not find the leak on, pulled the wire off and oil ran out of the connection. Just a thought to add to the others posted.

Ok well pcv system was non existent for some reason. Added pcv check valve to one valve cover with hose running to intake vacuum. Other valve cover has a breather installed. My question is we checked vacuum and its only pulling 5-7 in at idle. Shouldnt it be more along the lines of 14in? Still leaks now after pcv but not as bad as without.

Also balancer was always installed with tool, and last time we installed cover we left loose till balancer was installed.

No crank sensor in cover, sensor hole molded closed

I don't want to be the bearer of bad news -- but it is IMPOSSIBLE to compress liquid ---- (think hydraulic rams etc - that's why they use it!) so ANY oil path that was created when leaking -- will continue to leak until you put a new seal/gasket where it's needed. You can tighten bolts til the cows come home and it will leak.

Check your vacuum source.... there is MANIFOLD vacuum and there is PORTED Vacuum.... which doesn't create vacuum until the throttle blades are opened. YOU want MANIFOLD vacuum.


With no photos etc nobody knows where you're pulling your vacuum source from.

Ok will try and snap pix tomorrow.

On a small block chevy, you need to silicone the inside of the balancer snout as well. Otherwise, the oil will travel between the crank gear and balancer snout, then out the snout.

You'd really need to explain that one to me..... :>)



What I've always done is to use a little gasket sealer (never silicone since it will not stand up to oil and gas) on the keyway in the crank/balancer.

Also - what a lot of people FAIL to do, is to put a little oil on the balancer exterior surface that meets the SEAL ---- fail to do that and you ruin the seal surface on the first fire up.

Check the crankshaft sprocket key. I had the same problem you describe. Replaced the key and no more leak.

We used gm gray rtv on the balancer key, always have. Its not leaking from there. I know it from the seal and I'm almost 100% sure its due to excessive crank case pressure just finding the easiest way out.

As per request the pix of the pcv hose hook up.

http://i281.photobucket.com/albums/k...913_085916.jpg
http://i281.photobucket.com/albums/k...913_090052.jpg

Goes from pcv to port on carb base

Well that part looks okay to me...


Remember though -- once you've established a path for oil --- unless you reseal them and start fresh.


Did you pull a vacuum measurement from under the carb?? 5 to 7 inches sounds like you might have a big azz cam? Otherwise I would be wanting to see 10 to 17 inches.

If you don't have a big cam --- then you might want to perform a LEAK DOWN test and see where the issue is.

As far as I know the cam isn't huge. Gonna have him pull me specs. We checked for vacuum leaks and found none. The engine does have low mileage, less then 1000mi. Once he gets back from vacation ill jump back onto his truck and see what else we can find. Thx for the help and direction.

I had a similar problem with a front seal leak and it all boiled down to a bad front crankshaft bearing.

Sounds like the engine is unhealthy.