Crankshaft rear seal didn't fix the oil leak - ZR-1 Net Registry Forums

QB93Z · 08-10-2009

My problem started with an oil drip from the forward edge of the bell housing on my 1993 ZR-1 (102K miles). I guessed that it was oil leaking from the crankshaft rear seal.

Yesterday I (we) replaced the crankshaft rear seal, seal housing gasket and clutch. Thanks to all who helped.

I drove about fifty miles in the evening and parked it in the garage. This morning I have oil that dripped from the bell housing again.

My conclusion now is that the oil is coming from the transmission input shaft seal.

Anyone have any other ideas where the oil could come from?

Is replacing the transmission input shaft seal easy or will I have to rebuild the whole transmission to do it?

Thanks, Jim

A26B · 08-10-2009

Jim,
When you replaced the rear crank seal, where did you notice the oil leak "mess' in particular? If it's the rear seal, the mess should be confined to an area in the bellhousing between the flywheel & rear of the engine. A tranny seal would be confined to the rest of the bellhousing area, i.e. from the flywheel to the trans side of the bellhousing.

The trans input shaft seal should be accessible by removing the trans input shaft housing, with no further disassembly. Not a big job.....once you get the trans out. Any chance it might be overfilled? Should be level with the bottom of the fill plug.

Pete · 08-10-2009

Jim the trans seal is easy of course after you remove the trans from the car.

I really haven't seen many leaky trans seals but then i haven't seen too many high mileage Z's.

Anyway the seal is easy to repalce no need for taking the trans apart.
It's in the input shaft housing the one with all the allen socket head screws take off the allen screws housing will come off the seal is in the housing.

The other issue is finding the seal, it only comes with the complete gasket set $200+.
I'm pretty sure if you take the seal to your local parts store it could be match up to something like an axle seal.

Gaskets for the the ZF are available from Flatout Gaskets,no seals.
I'm using Flatouts trans gaskets with no issues for over a year.
http://www.flatoutgroup.com/

Pete

Pete · 08-10-2009

Jim also make sure your PCV system is up to par.

If your running one PCV valve or are not 100% the motor will push oil out the seal, seen that on 2 LT5's.

Just a thought or something to look into to.

Pete

QB93Z · 08-10-2009

Jerry, Thanks for the info. Here is the rear seal area immediately after the seal housing was removed, part of the old gasket is stuck at the top. The bolts holding the seal housing were basically finger tight so we thought we had found the source.

The inside of the bell housing was a mess all over. I couldn't determine an area that was the leak source. I cleaned it up so when I pull it again, I may get an indication.

Good to hear about the transmission input shaft seal being easy to replace. When I started this job I got a transmission rear seal from Advance Auto. When we pulled the transmission, it was obvious that they gave me the input shaft seal instead, so it was exchanged for a rear seal. I guess I should have kept it.

Jim

QB93Z · 08-10-2009

Quote:

Originally Posted by Pete

Jim also make sure your PCV system is up to par.

If your running one PCV valve or are not 100% the motor will push oil out the seal, seen that on 2 LT5's.

Just a thought or something to look into to.

Pete

Thanks Pete.

I will check it out.

flyin ryan · 08-11-2009

Sure does look like it was the rear main, doesn't it Jim? Strange...

. Keep diggin'.

tccrab · 08-11-2009

Hmmm..
I was going to suggest the possibility of blow by from the oil box under the plenum dripping down the hole and then out onto the crank.
But I don't see enough crud around the block drain hole.

Rear main seal seems the most likely candidate.
Having a hard time seeing how the front seal on the input shaft of the ZF6 could cause a drip there. I would have thought that the flywheel/clutch/pressure plate would have blocked any tranny oil from reaching the rear main area.

TomC
"Crabs"

flyin ryan · 08-11-2009

Maybe...Just maybe, the seal was hooped from new or somehow was nicked or damaged when installing? Sure looks like that was/is the culprit

.

QB93Z · 08-11-2009

Further investigation, no answer yet.

Here is a picture showing where the oil drips from:

There is no fresh oil on the back or bottom edge of the oil pan:

I checked the oil level in the transmission. Not very accurate, but using the pinky finger test, the oil level seems to be at the level of the plug. It appears that I have not lost any transmission oil.

I will investigate the PCV system to see if maybe the crankcase is feeling pressure. And I will be pulling the plenum to look for oil.

Jim

08-10-2009	#1
QB93Z Join Date: May 2007 Location: Westminster, Maryland Posts: 3,689	Crankshaft rear seal didn't fix the oil leak My problem started with an oil drip from the forward edge of the bell housing on my 1993 ZR-1 (102K miles). I guessed that it was oil leaking from the crankshaft rear seal. Yesterday I (we) replaced the crankshaft rear seal, seal housing gasket and clutch. Thanks to all who helped. I drove about fifty miles in the evening and parked it in the garage. This morning I have oil that dripped from the bell housing again. My conclusion now is that the oil is coming from the transmission input shaft seal. Anyone have any other ideas where the oil could come from? Is replacing the transmission input shaft seal easy or will I have to rebuild the whole transmission to do it? Thanks, Jim __________________ If it isn't fun, you aren't doing it right! 1990 Black ZR-1 - sold 1993 Quasar Blue ZR-1 1994 Competition Yellow ZR-1 1995 Dark Purple ZR-1 Maryland State Coordinator WAZOO Member

08-10-2009	#2
A26B Join Date: Dec 2003 Location: Arcadia,OK Posts: 3,394	Re: Crankshaft rear seal didn't fix the oil leak Jim, When you replaced the rear crank seal, where did you notice the oil leak "mess' in particular? If it's the rear seal, the mess should be confined to an area in the bellhousing between the flywheel & rear of the engine. A tranny seal would be confined to the rest of the bellhousing area, i.e. from the flywheel to the trans side of the bellhousing. The trans input shaft seal should be accessible by removing the trans input shaft housing, with no further disassembly. Not a big job.....once you get the trans out. Any chance it might be overfilled? Should be level with the bottom of the fill plug. __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1*, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed.

08-10-2009	#3
Pete Join Date: Dec 2003 Location: Chicagoland,IL Posts: 2,679	Re: Crankshaft rear seal didn't fix the oil leak Jim the trans seal is easy of course after you remove the trans from the car. I really haven't seen many leaky trans seals but then i haven't seen too many high mileage Z's. Anyway the seal is easy to repalce no need for taking the trans apart. It's in the input shaft housing the one with all the allen socket head screws take off the allen screws housing will come off the seal is in the housing. The other issue is finding the seal, it only comes with the complete gasket set $200+. I'm pretty sure if you take the seal to your local parts store it could be match up to something like an axle seal. Gaskets for the the ZF are available from Flatout Gaskets,no seals. I'm using Flatouts trans gaskets with no issues for over a year. http://www.flatoutgroup.com/ Pete __________________ '91 #1635 PoloGreen 350 LT5 11.09 @ 129.27 11.04 @ 128.86 474RWHP 400RWTQ http://www.youtube.com/watch?v=SFNFOhGGlR4 http://www.youtube.com/watch?v=ZlRIOMwaDYY https://sites.google.com/site/peteszr1garage Last edited by Pete; 08-10-2009 at 01:49 PM.

08-10-2009	#4
Pete Join Date: Dec 2003 Location: Chicagoland,IL Posts: 2,679	Re: Crankshaft rear seal didn't fix the oil leak Jim also make sure your PCV system is up to par. If your running one PCV valve or are not 100% the motor will push oil out the seal, seen that on 2 LT5's. Just a thought or something to look into to. Pete __________________ '91 #1635 PoloGreen 350 LT5 11.09 @ 129.27 11.04 @ 128.86 474RWHP 400RWTQ http://www.youtube.com/watch?v=SFNFOhGGlR4 http://www.youtube.com/watch?v=ZlRIOMwaDYY https://sites.google.com/site/peteszr1garage

08-10-2009	#5
QB93Z Join Date: May 2007 Location: Westminster, Maryland Posts: 3,689	Re: Crankshaft rear seal didn't fix the oil leak Jerry, Thanks for the info. Here is the rear seal area immediately after the seal housing was removed, part of the old gasket is stuck at the top. The bolts holding the seal housing were basically finger tight so we thought we had found the source. The inside of the bell housing was a mess all over. I couldn't determine an area that was the leak source. I cleaned it up so when I pull it again, I may get an indication. Good to hear about the transmission input shaft seal being easy to replace. When I started this job I got a transmission rear seal from Advance Auto. When we pulled the transmission, it was obvious that they gave me the input shaft seal instead, so it was exchanged for a rear seal. I guess I should have kept it. Jim

08-11-2009	#7
flyin ryan Join Date: Aug 2006 Location: Edmonton, Alberta or Phoenix, Arizona Posts: 2,741	Re: Crankshaft rear seal didn't fix the oil leak Sure does look like it was the rear main, doesn't it Jim? Strange... . Keep diggin'. __________________ There are no limit's mans ingenuity, just as mans ingenuity will never conquer the forces & behavior of this planet...Smokey Y.

08-11-2009	#8
tccrab Join Date: Oct 2004 Location: Folsom CA Posts: 1,654	Re: Crankshaft rear seal didn't fix the oil leak Hmmm.. I was going to suggest the possibility of blow by from the oil box under the plenum dripping down the hole and then out onto the crank. But I don't see enough crud around the block drain hole. Rear main seal seems the most likely candidate. Having a hard time seeing how the front seal on the input shaft of the ZF6 could cause a drip there. I would have thought that the flywheel/clutch/pressure plate would have blocked any tranny oil from reaching the rear main area. TomC "Crabs" __________________ TomC '90ZR1 #792 Honorary Pirate [B]If it ain't FUN, you're doing something terribly WRONG. [/B]