Brand new main seal leak. Advice?

whackit · 05-01-2010, 10:40 AM

Hi Folks,

I just ran in my new motor, which ran great. I had to pull the motor again to address a leaky transmission gasket. When I was removing the motor I noticed a drip from the bellhousing joint. It wasn't blue so I new it was engine oil. I pulled the flywheel and sure enough. Leaky main seal. This seal is a brand new viton seal. no scoring on crank. what's up? does anyone have advice? replace it or just leave well enough alone?

Emery G. · Emery G.'s Garage

how long did you run the motor with the new seal?

AlfonsoR · 05-01-2010, 12:14 PM

OK, please do not get offended with the obvious questions:
1. was the seal lubricated when installed?
2. are you sure the seal is square?

other questions
3. how many miles on the engine & did you notice a groove on the crank sealing surface?
4. Did you inspect the seal to make sure it wasn't damaged or deffective when you pulled it out of the box? Sometimes people return stuff and the part is damaged or part was just defective from the factory. If you remove it, inspect to see if the spring is there on the back side of the seal. Although some new seals don't have the spring anymore.
5. Are you sure you installed the input shaft from the transmission correctly?

I would replace it. It should not leak.

whackit · 01:55 PM

Motor ran for about 100 miles.

Seal was installed dry in case, lip lubed with oil. It looks like it is leaking from the crank side of the seal not the case side.

Crank was in good shape. no grooves or scores.

It is straight. It is installed even with the bottom of the chamfer on the case.

Seal looked good when installed.

docrodg · 05-02-2010, 03:14 AM

Could be that the dry install caused the lip to grab allowing it to leak. Other possibilities are improper alignment when installing tranny (even if finally aligned right), worn main bearings, crank runout, and out of round crank end. It looks like the shaft is not centered in the seal in the picture

E Sully · E Sully's Garage

I had a similar leak when I rebuilt my 3.2. When I installed the second seal I set it a little shallower and it has been dry since.

whackit · 05-02-2010, 03:08 PM

Quote:

Could be that the dry install caused the lip to grab allowing it to leak

Quote:

It looks like the shaft is not centered in the seal in the picture

Only the case side was installed dry lip was oiled. Shaft is centered. Picture is taken off center so it looks as though it is not centered.

Quote:

I had a similar leak when I rebuilt my 3.2. When I installed the second seal I set it a little shallower and it has been dry since.

when you say shallower do you mean more or less into the actual case. right now my seal is installed to the bottom of the chamfer. I think when I reinstall I will make flush withe the case. This would make it less deep into the case.

cgarr · cgarr's Garage

Were you able to check the seal on the crank before the engine was assembled? I ask because I have had seals so old "in sealed kits" that they were not even tight on the crank. I have soaked them in oil before too: Its a rather easy install but any chance the spring came off?

AlfonsoR · 05-02-2010, 04:41 PM

Quote:

Originally Posted by whackit

when you say shallower do you mean more or less into the actual case. right now my seal is installed to the bottom of the chamfer. I think when I reinstall I will make flush withe the case. This would make it less deep into the case.

Some manufacturers, like BMW, sell seals that come with a spacer. You install the spacer first, then bottom out the seal on the spacer. This of course, ensures that the seal lip is ridding on a "virgin" surface.

E Sully · E Sully's Garage

Your photo looks just like my first seal did, to the bottom of the chamfer. The second one was installed less into the case. Both of my seals looked new. It worked for me.

lindy 911 · lindy 911's Garage

Actually, most manuals say to install the seal flush with the outside of the case not all the way into the seal bore. I'm not sure why it would make a difference as the crank diameter is the same in both locations but it seems to. Mine is flush with the case and does not leak.

Lindy

Trackrash · Trackrash's Garage

Not to hijack, but I recently replaced my flywheel seal and still have a noticable leak between the motor and trans. I also replaced the trans input seal.
In my case it didn't look like the crank seal was leaking, but I replaced it anyway.

My question is, what is the chance of one the the metal plugs in the case leaking?

It's a '71 motor which was rebuit in 1985, and has been driven about 80K miles since.
It runs fine and only uses about a quart of oil every 1000 to 1500 miles. There is no mess on the rear bumper, just on the bottom of the trans and my garage floor. The trans oil level does not seem to have dropped.

whackit · 05-05-2010, 08:02 PM

Quote:

My question is, what is the chance of one the the metal plugs in the case leaking?

They will leak if the factory seal (epoxy) is cracked or compromised but you will see it weeping from the area. Solution is to thoroughly clean off old sealant and put a new layer of JB weld on there.