Real seal oil leak?

[clinem03]

I continue to get a lot of oil (?) leakage from under the front of the bell housing between the plate and BH (see photos). It has been a constant leak since the rebuild. I had the clutch and fly wheel replaced a few hundred miles ago, and the leak has been persistent before and after the rebuild of the transmission. We didn't replace the rear seal when the transmission was out b/c it was bone dry. I should also note that the fluid leaking out is always jet black, even when my oil is clean/changed. It tends to flow much heavier when the engine warms up on longer drives.

Could it be anything other than a rear seal leak?

 

[Rustytruck]

Did you locktite the flywheel bolts? as oil can seep through those bolts too. I would make sure your PVC system is up to snuff so your internal engine gasses is not being pressurized and pushing oil out. You need a good source of air in the valve cover and good vacuum on the PVC valve to suck the pressure out.

 

[blubuckaroo]

Any oil running through the bell housing will be really black.
Have you looked at the rear intake manifold "valley seal" and the valve covers? Leaks from those places can track down the bell housing.

 

[clinem03]

Did you locktite the flywheel bolts? as oil can seep through those bolts too. I would make sure your PVC system is up to snuff so your internal engine gasses is not being pressurized and pushing oil out. You need a good source of air in the valve cover and good vacuum on the PVC valve to suck the pressure out.

Not sure as I outsourced the flywheel replacement to a good shop here in the area that works on classics - I plan to head up there this week and will ask. I also have been having other oil leaks that and even blew through two fuel pumps (carters) that were spraying oil out of the weep hole. The 2nd pump blew in less than 100 miles from replacing it. I put on a Airtex pump and all seems to be OK but I'm only ~50 miles in since replacing it. I also have an oil leak just under the crankcase where the oil pan meets the balancer. I recently refurbished the oil pan, added a single Fel-Pro seal but it still leaks out the front. I planned to drain the oil, drop the pan and make sure everything is lined up and add a bit of RTV. I did replace the PCV valve so I hope its working!

 

[clinem03]

Any oil running through the bell housing will be really black.
Have you looked at the rear intake manifold "valley seal" and the valve covers? Leaks from those places can track down the bell housing.

I'm not sure what the rear intake vally seal is? Can you point me in the right direction on that one? Valve covers were cleaned, powder coated and replaced with nice Fel-Pro seals about 500 miles back but I'll double check for leaks.

 

[blubuckaroo]

I'm not sure what the rear intake vally seal is? Can you point me in the right direction on that one?

The seal I'm referring to is the long skinny gasket along the front and rear of the intake manifold. It's often referred to as a "China Wall".
Most of the builders will avoid using the seal that comes in the gasket set, and use a thick line of RTV instead.

Also, when you replace the front crankshaft seal in the timing cover, use the balancer to center the timing cover on the crank before tightening down the cover bolts. Otherwise the seal may not be properly centered, and leak.

 

[clinem03]

The seal I'm referring to is the long skinny gasket along the front and rear of the intake manifold. It's often referred to as a "China Wall".
Most of the builders will avoid using the seal that comes in the gasket set, and use a thick line of RTV instead.

Also, when you replace the front crankshaft seal in the timing cover, use the balancer to center the timing cover on the crank before tightening down the cover bolts. Otherwise the seal may not be properly centered, and leak.

I'll check the china wall, thanks for that! Before I refurbished the oil pan and added a new seal, it wasn't leaking. I really think is a gap in the oil pan seal that is causing the leak not on the timing cover alignment...but I'll double check.

 

[73azbronco]

^^^ this. Back end of intake manifold, look for shiney.

 

[clinem03]

Seems there is some “Shiny” build up but it looks pretty pooled up in that one spot…is this enough to be the culprit of the leak?

 

[gnpenning]

Hit that area with a degreaser or oven cleaner and rinse off. Drive it and see if it reappears.

After your fuel pump issues you need to put a few miles on it anyway.

Did the shop that replaced the clutch say anything about oil on the old clutch?

 

[svastano]

What brand of rear main seal was used? I used 2 Felpro and both leaked ended getting a made in USA rear main from my machine shop and so far so good! about 1600 miles on the motor since that.

 

[clinem03]

Hit that area with a degreaser or oven cleaner and rinse off. Drive it and see if it reappears.

After your fuel pump issues you need to put a few miles on it anyway.

Did the shop that replaced the clutch say anything about oil on the old clutch?

Good call - more to come soon!

 

[clinem03]

What brand of rear main seal was used? I used 2 Felpro and both leaked ended getting a made in USA rear main from my machine shop and so far so good! about 1600 miles on the motor since that.

I did not replace the main seal as it was dry on the trans side...but good to know that the felpro ones are leaking!

 

[clinem03]

Found my leak! Seems it is the intake manifold gasket. Thanks for all the help!

 

[blubuckaroo]

Found my leak! Seems it is the intake manifold gasket. Thanks for all the help!

Good job!
A much easier fix.

 

[clinem03]

So I pulled the intake manifold, restored it, reinstalled it with a heavy bead of RTV and new gaskets (not on the "china wall" part). It stopped the oil blowing out the rear and dripping down and leaking from the bottom of my bell housing. It slowed the oil flow down quite a bit, but I still have oil leaking from the same spot (although slightly less). I think at this point it is likely a rear seal leak. I cleaned the bell housing up this morning and took her for a run to see where the oil is leaking and it appears to be from behind the plate and down the center of the bell-housing....AND now I also see oil leaking out of the shift fork boot - that has to be a rear seal blowing oil into the bell-housing...right?

 

[Timmy390]

Make sure the crank case is vented well. Pressure build up will force oil out the rear seal

Tim

 

[clinem03]

Make sure the crank case is vented well. Pressure build up will force oil out the rear seal

Tim

Thanks, Tim! How do you make sure the crankcase is properly vented? My PCV valve is new and lines are clean, I also have a filter on the passenger valve cover in lieu of running it into the stock air cleaner.

 

[Timmy390]

Thanks, Tim! How do you make sure the crankcase is properly vented? My PCV valve is new and lines are clean, I also have a filter on the passenger valve cover in lieu of running it into the stock air cleaner.

Sounds like you got it covered....Prob not the issue..

Tim

 

[clinem03]

Sounds like you got it covered....Prob not the issue..

Tim

The truck sat for 20 years so I have no clue when/IF the rear seal was replaced. I had the transmission out and the rear seal seemed dry on the trans side so I left it...regretting that!

If oil is now pushing out the shift fork boot, it can't be from anything other than the rear seal - right?