Loosing oil...sometimes

[Chas]

i think i have a problem with my oil return holes....when i go out on the freeway for more than 30 mins i start seeing smoke....then i stop and look under it...its raining oil!...looks like its hitting the exhaust and smoking...not coming from the exhaust itself...and i cant really see where its flowing from....i thought it was a rear main seal , but i can drive it all over town and loose only a spot or 2 on the cardboard i keep under it....my question is , could it blow oil out of the valve cover gasket ? i was thinking it would blow into the cylinder but im thinking its coming out from the valve cover...the rear end of it , making it hard to see where its coming from....it only does this when i run at freeway speeds for more than a few mins.......im looking for opinions before i pull the entire motor and start doing something i may not need to....i am gonna pull the heads and have the valves done and the edelbrock manifold bead blasted this off season......so if its the returns , what is the best way to clean them other than a coat hanger?

 

[cntrhub]

Take a long flat mirror, like say 3" X 5" and place it behind the rear intake manifold. I think you might have a sealing failure between the heads and the intake manifold. The mirror will give you a nice view of the hole area of the back end of the block. take a paper towel and wipe it across the bottom of the intake manifold. If it comes back wet with oil, that may be your leak. If it comes back dry and caked black, it's weeping and not leaking. A weep is a very slow sweating leak that dries from heat. An out and out oil soaked paper towel is a flat out oil leak.
The way to finding an oil leak, is to look at the upper most point of the engine. When a leak forms, it could run right over a seal area and trick you thinking it's a seal.
Now you have a closer idea if it's leaking out of the valve cover, or the intake manifold with that long mirror.
Use a drop light or flashlight to brighten up the dark areas of the rear engine bay. You'll get the right angle and light to get a good shot at what you're looking at.

 

[red70vette]

Likely candidate is the valve cover gaskets. Also realitively cheap fix.

When were they changed? Do you know what kind of gaskets were installed?

I changed to composition cork gaskets from Dr Rebuild and have been leak proof since. Applied gasket seal to the valve cover side and I can remove covers without replacing the gaskets. I was going to use Fel Pro gaskets but since I had to do some other engine work I used the composition cork with the intention of changing later. At $7.00 a pair they seal great.

 

[DDLS3]

The valve cover gaskets get my vote as the primary suspect. I had a similar problem and replaced them with high quality cork impregnated with rubber gaskets. They were $15 at the local parts store.

 

[Chas]

Many thanks...

thanks for the feedback...sounds like im on the right path....and it sounds like an easy fix....this place rocks!

 

[JohnZ]

If it happens primarily at steady freeway speeds, it's probably a failure in your PCV system (clogged PCV valve); you're building presssure in the crankcase, and it will then blow oil out of the weakest gasket or seal to relieve the pressure.