oil leak on bellhousing... - Chevelle Tech
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post #1 of 58 (permalink) Old Nov 24th, 19, 8:31 PM Thread Starter
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oil leak on bellhousing...

Hey fellas, changed my oil today in my new (to me) 70 Chevelle. I noticed a pretty good amount of oil on the outside of the passenger side bellhousing and around the starter. It drips down to the bottom of the bellhousing and when driving, it looks like it's getting slung down the transmission and the rest of the undercarriage. I wanted to make sure I don't misdiagnose this as a bad rear main seal. The engine was rebuilt recently, so I wasn't expecting an oil leaks, but from research I've done on the forum, it sounds like people experience oil leaks pretty often on freshly rebuilt engines. I'm going to put it up on a lift tomorrow afternoon, but just wondering yals thoughts first. The forum seems to point to either rear main, galley plug, cam plug, or rear corner of valve covers. But with the oil being on the OUTSIDE of the bellhousing, does that rule out the rear main?? Thanks.
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post #2 of 58 (permalink) Old Nov 24th, 19, 9:41 PM
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Re: oil leak on bellhousing...

i would look around the passenger side valve cover for oil leaking

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post #3 of 58 (permalink) Old Nov 24th, 19, 10:06 PM
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Re: oil leak on bellhousing...

Check the distributor gasket. I had mine leak from there. Had to double up on the gaskets but that resolved it...
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post #4 of 58 (permalink) Old Nov 24th, 19, 10:15 PM
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Re: oil leak on bellhousing...

It could be from the valve cover gasket, the back of the intake manifold where it seals to the block especially in the corner where the intake and head come together. If you have a BB with a passenger side dipstick it could be coming out where the tube inserts into the motor.
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post #5 of 58 (permalink) Old Nov 25th, 19, 8:05 AM
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Re: oil leak on bellhousing...

Adam,
I would get a bottle of leak tracing die at the parts store and put it in the oil. Drive it for a while and then look for the leak with an Ultraviolet light. With a fresh engine the clean oil can be very hard to see to determine where it is coming from. With the die in it and the UV light you should be able to find it pretty easily.

If it is on the outside of the bellhousing I doubt that it is the rear main seal.
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post #6 of 58 (permalink) Old Nov 25th, 19, 9:00 AM
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Re: oil leak on bellhousing...

Check the dipstick tube as well. ALSO, if using a mech fuel pump, it could also be leaking there. I've had this issue.
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post #7 of 58 (permalink) Old Nov 25th, 19, 12:53 PM Thread Starter
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Re: oil leak on bellhousing...

Quote:
Originally Posted by 427L88 View Post
Check the dipstick tube as well. ALSO, if using a mech fuel pump, it could also be leaking there. I've had this issue.
Dipstick tube looks to be ok. Fuel pump looks clean. It's definitely leaking on the back side somewhere.

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post #8 of 58 (permalink) Old Nov 25th, 19, 12:59 PM
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Re: oil leak on bellhousing...

Quote:
Originally Posted by vtchopperdude View Post
Dipstick tube looks to be ok. Fuel pump looks clean. It's definitely leaking on the back side somewhere.
Are seeing any of it on, or dripping off the flywheel/flexplate dust cover? That's where I have a leak on my car. That's why I was curious.

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post #9 of 58 (permalink) Old Nov 25th, 19, 1:07 PM Thread Starter
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Re: oil leak on bellhousing...

Quote:
Originally Posted by BillK View Post
Adam,
I would get a bottle of leak tracing die at the parts store and put it in the oil. Drive it for a while and then look for the leak with an Ultraviolet light. With a fresh engine the clean oil can be very hard to see to determine where it is coming from. With the die in it and the UV light you should be able to find it pretty easily.

If it is on the outside of the bellhousing I doubt that it is the rear main seal.

Bill thanks for the advice! This was my weekend plan. Just trying to get people's advice on potential spots that are prone to leak on these motors.



I put it on my buddy's lift this morning before he opened up (owns an exhaust shop), and it's definitely wet mid way up on the bellhousing and dripping down. I noticed some RTV silicon (or similar product) at the rear of the intake manifold. It was definitely put there during the engine rebuild because it has been painted over. So, that's a potential location??



There is some leakage on the drivers side, but not nearly as pronounced as the passenger side. What's weird is none is dripping on the exhaust. I don't have any smell of burning oil, ever. But it definitely leaks more once warmed up. I notice when I start it and back it out of the garage, no drips, but after I come back from a drive, there is noticeable drips on the driveway if I don't immediately pull it in the garage over some cardboard. It runs great, so I don't think it's a major leak, for now, but I want to get it squared away before it becomes an issue. I just hate leaks!!!!!


So, I think the rear main can be ruled out. The origin is higher up. The valve covers have leaked/weeped in both Mustangs I've owned, and my dad's Willys, but not this much, so I am leery to rule them out. But, for it to leak enough to sling it down the undercarriage lends my thoughts to something that is pushing out more oil when under pressure and warmed up. The valve covers shouldn't be under pressure, right? The PCV valve is on the passenger side cover, and routed to the manifold, which looks to be correct. It does have a T fitting and splits into a much smaller tube that goes into the firewall (not sure about that....!!!). But, with it freshly rebuilt, I don't suspect the PCV valve to be the issue.


Thanks again everybody for the inputs. Looking forward to finding this pesky leak! I like the underside just as clean as the top side!!!


Thanks, Adam

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post #10 of 58 (permalink) Old Nov 25th, 19, 1:11 PM Thread Starter
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Re: oil leak on bellhousing...

Quote:
Originally Posted by BillyGman View Post
Are seeing any of it on, or dripping off the flywheel/flexplate dust cover? That's where I have a leak on my car. That's why I was curious.

Yes, at the very bottom, it drips, but I believe it is coming from higher up and making it's way down to the lowest point. However, the back of the oil pan is bone dry, so if it were the rear main, then I'd expect the back of the oil pan to be drenched. Mine is not. I can reach my finger between the oilpan and dustcover and it's drity and greasy but not really oily.

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post #11 of 58 (permalink) Old Nov 25th, 19, 1:12 PM
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Re: oil leak on bellhousing...

Don't rule out the rear main yet.......

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post #12 of 58 (permalink) Old Nov 25th, 19, 1:19 PM Thread Starter
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Re: oil leak on bellhousing...

Quote:
Originally Posted by blue_69_malibu View Post
Don't rule out the rear main yet.......

roger that

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post #13 of 58 (permalink) Old Nov 25th, 19, 1:32 PM
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Re: oil leak on bellhousing...

Sent you a PM

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post #14 of 58 (permalink) Old Nov 25th, 19, 1:55 PM Thread Starter
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Re: oil leak on bellhousing...

Quote:
Originally Posted by BillyGman View Post
Sent you a PM
Got it, and replied. Did you get it??? It doesn't show in my sent box....

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post #15 of 58 (permalink) Old Nov 25th, 19, 3:24 PM Thread Starter
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Re: oil leak on bellhousing...

Here are some pictures
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