help me find my oil leak

[1972BlueC20]

Hey guys,

I'm trying to chase down an oil leak......I've recently replaced my valve cover gaskets with felpro premadry gaskets and I've also replaced my oil sending unit both of which were leaking but they don't appear to be leaking anymore.

Here are pics of the oil leak, it's not really bad but I want to fix it


the oil is coming down from the back of the oil pan between the dust cover and oil pan, and there are droplets that form on the dust cover as well

any ideas where I should start or where you think the likely leak spot is??

[GASoline71]

If you're positive it's not the sending unit, and/or the valve covers... it's either the rear intake manifold seal, or the rear main seal. Both of which are a @!%#& to replace.

Gary

[Grumpy old man]

Looks like the rear main seal , Anytime your trying to find a slow hidden leak clean the area as best as you can and let it dry ,Then use baby powder --Yes, BABY POWDER and dust the area thoroughly and the powder will lead you to the leak .try it ,it works !

[1972BlueC20]

Is the rear main something I can do in my driveway?

If so, can someone tell me the best way to go about it......I think my engine is the original and if so I believe it has the 2 pc seal....I heard those are the ones you can do without pulling the transmission.....damnit, I just had the trans rebuilt......FML

[bob8619]

Looks like mine did a few months ago. Mine was from leaking intake gasket.

[1972BlueC20]

was the intake gasket hard to change??

[geezer#99]

Pull the cover off the tranny. Clean it up. Look inside.
If you had leaks from the sender or valve covers the inside of the bell could be saturated.
Leave the cover off for awhile. Then look for leaks.

[bob8619]

No its pretty simple. Take a flashlight and a mirror and inspect around the intake in the back.

[OSM 70 C20]

Just my $0.02... a bolt on my oil pan was loose. The one between the oil filter and the pan. I was hard to get to as there wasn't much clearance for a socket to get it tight. It leaked pretty good (?) for awhile, but I finally saw it. Just a thought... could be rear main.

[LockDoc]

-
There have been a few people that replaced a rear main seal only to find out later that the oil was coming from the back of the intake. Be sure and eliminate that possibility first.....

LockDoc

[1972BlueC20]

yeah my pan bolts were a little loose too, I went around and tightened all them....also I noticed that what I think is the timing chain cover where it meets the oil pan is also leaking....but the oil doesn't seem to be making it's way all the way back to where the oil droplets are near the back of the pan and the dust cover.

I wish I had the money and time and space to pull the engine and redo the whole thing just for good measure....ahhhh man dreams!!

[asolde]

Make sure your valve covers are straight at the bolt holes. They get dimpled after years of over tightening. Use a ball peen hamer and a good piece of wood to straighten them back out. I put mine back on with hi temp red RTV and lightly tighten. I put a little extra rtv around the back lower side since that's where they leak at. Just my preference.

Check your oil sending unit for leaks

Inspect the rear of your intake manifold around the distrbutor area for leaks. This is not hard to repair but them old intakes are heavy to lift in and out of there. I used my engine hoist the last one I did on the blazer. Do some reading on it. What is important is don't use the rubber gaskets on the rails use sealant. I use the (right stuff) sold at your local parts store. A good 1/4" bead along the rails and a blob of sealant at each corner where the head meets the block will do. I'm thinking this is where your major leak is at.

Your fuel pump cover could be leaking oil, thats a gasket easy fix

Timing chain cover could be leaking but just because you found oil on it dosn't mean it's leaking there the engine/road air could have blown it there.

The last thing you want to do is a rear main seal but it can be done in the truck (pia)

You can buy a dye and add it to your engine oil with a black light you will find all of the leaks.

Good luck Alex

[gscube]

This post was a great. My new C20 thanks you!