Oil viscosity and leaking rear main

J

JBill

Well-known member
I've got what seems to me a pretty bad oil leak in the rear main on a newly professionally overhauled engine (only about 500 miles on it). I'm using a multi-grade oil (10-30). Would a straight weight (30) help any? I'm guessing probably not, but just wondered.
 
10-30 and straight 30 would have the same viscosity at engine running temperatures; the straight 30 would have a higher viscosity only when cold. So if you have a leak when the engine is running, single-weight probably wouldn't help much.
 
Changing oil is grasping at an unattached straw. Same thing happened to me a few motors ago. Something's wrong and your rebuilder should make it right. It's not going to fix itself. My guy guaranteed his rebuilds for life, but I had to pay for the motor pull and reinstall--twice!

Steve
 
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After making sure the drain tube is clear on the rear main, and after setting the clearance for the rear main, I apply a thin layer of silicone sealer to the cap and bolts, and to the ends of the pan gaskets. This picture shows the gasket I used on Mark's engine the other day, which is rather stiff. I prefer the cork, but with care, either should be fine. Also be sure to install the gasket for the rear of the cam. I should have installed it for this picture, but I was intending to show the rear main sealing I use.
 
Is the leak there all the time ? I overfilled my crankcase with oil once ( 1/2 a quart )and had a leak at the rear of the pan .It left quite the mess .After draining about a quart the leak disappeared . The dipstick is not always accurate .
 
Richard Lorenz said:
Tom: In your upper photo, it looks like the opening where the aluminum insert is exposed might not be sealed completely.
Click to expand...

Not sure where you mean, since the oil slinger isn't an air tight seal. Where the cap meets the block I'm quite sure I have no gap. I also put some blue silicone under the castle nuts, altough it doesn't show any excess squeezed out.
 
JBill said:
I've got what seems to me a pretty bad oil leak in the rear main on a newly professionally overhauled engine (only about 500 miles on it). I'm using a multi-grade oil (10-30). Would a straight weight (30) help any? I'm guessing probably not, but just wondered.
Click to expand...

Where is the leak showing up? From behind the flywheel inspection plate or from the opening in the bottom of the flywheel housing typically holding a large cotter key? Possibly from the rear of the pan and then following the front side of the flywheel housing?
When is it leaking? While it is running, after it is shut down, both?

Leaks....the Devil is in the details of assembly!
Your engine builder won't like to hear there are leaks but he will probably want to make it right! Give him a call!
Good Day!
Dave in MN
 
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Tom Wesenberg said:
After making sure the drain tube is clear on the rear main, and after setting the clearance for the rear main, I apply a thin layer of silicone sealer to the cap and bolts, and to the ends of the pan gaskets. This picture shows the gasket I used on Mark's engine the other day, which is rather stiff. I prefer the cork, but with care, either should be fine. Also be sure to install the gasket for the rear of the cam. I should have installed it for this picture, but I was intending to show the rear main sealing I use.
Click to expand...


Tom

In the top picture you show a glob of sealant where the bearing cap and pan gaskets meet. If that's a silicone based sealer and you let it set up, isn't the installation of the pan gonna "cut" that glob in half?
Do you install the pan prior the silicone curing?

Thanks
Leo
 
spinelll said:
Tom

In the top picture you show a glob of sealant where the bearing cap and pan gaskets meet. If that's a silicone based sealer and you let it set up, isn't the installation of the pan gonna "cut" that glob in half?
Do you install the pan prior the silicone curing?

Thanks
Leo
Click to expand...

Yes, that blue silicone was applied a few seconds before the picture was taken, and the pan was installed a few seconds after the picture was taken. As mentioned I do like the old cork gaskets better than this new style. This is the first time I used this style of pan gasket, but I find it a bit stiff.
 
Guy who is driving his A 365 days this year had a rear seal issue in his posting, I think he switched to 30wt and had less of an issue or even solved it
30 wt ND here
 
Check your oil tube cap. If its not venting it will pressurize the block sending oil out the rear main. We had the same problem and only after pulling the engine and dissasembling it did we figure out it was something as easy as a oil tube cap.
 
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