Okay, well I fired up my LS1 today, and I am seeping a good amount of oil out of the bellhousing. I'm new to LS1s, but from my experience that's a rear main seal.

The car was hit in the front, my theory is that it knocked the crank a bit, and messed up my rear seals (or bearings... ).

My plan is to pull the motor (which really sucks, cause I just got it fired tonight), pull the tranny off and yank the covers and pan to see what's going on. Then, replace the bearings (main and rod) as I see no way to avoid it once I get in there. Is there an actual seal that could be bad as opposed to a bearing? The engine seems to run fine, but I currently have no way to check oil pressure, beyond I know that there is oil up top, so it does have pressure. All in all a depressing find, but it could have been worse. I think that my block and internals are probably fine, minus bearings (which may be okay as well). It runs fine, and has good compression (and runs smoothly at that).

I figure that since the engine is coming apart, I have to put a cam in. LOL, there's really no excuse to take it apart and not put a cam in...

Hell, I guess I have to port my heads too...

...this is getting expensive...

-Cliff's Notes-

My LS1 is seeping oil at the back. Could this just be a seal and not need new bearings? Car was hit in the front, but runs fine and has oil pressure.

Advice? (Be gentle, my wallet hurts already)

 

Can't follow your theory really. More likely the rear seal is damaged or your clutch master is leaking (if you have a manual). Bearings would not cause a leak.

 

It's an auto-

My theory is that the rear main has failed at 51K miles, so it's not likely to have worn out, most likely physical damage. Engine came from a car with a major front impact, which most likely pushed the crank back a little bit, damaging the main seal, and possibly unseating or scoring a bearing, thus necessitating their replacement.

I'm no mechanic by any means, a computer geek by trade actually. Just throwing around my best guesses. I've got bearings coming, as I figure I might as replace them anyway. Have a nice rebuilt motor to start with.

I'm not super familiar with LS1 internals, just wanted to make sure there wasn't anything terribly different from any other small block I've worked on.

 

If the rear main seal is suspect, I'd just pull the trans and flywheel and access it that way. If there was a problem with the bearings, you'd have some horrible noises and metal on the drain plug

 

I just hate to pull the engine/tranny and swap gaskets/seals and have it be bearings. Is there a way to inspect them without pulling them? The motor is in an RX7, so there is really no way to pull the tranny without pulling the motor/tranny together because of space, and for the cost of new bearings/bolts I think it might just be worth the peace of mind. I'm happy to save money if there is a way to inspect them though.

 

I agree that a rear-engine leak is most likely the rear seal - I've got to replace mine soon on my LS1, also. Just make sure it's not the valve-cover gaskets trailing into the bellhousing and masquerading as a rear-seal leak. I don't know how hard it is to pull the tranny in the RX-7, but that's the easiest way to replace the seal in-vehicle on most cars.

If a seal fails quickly (like in this 51K case), it might be that the crankcase is pressurizing, causing seals to fail. To check for pressurization, disconnect and plug the crankcase breather hose (NOT the PCV valve hose), then remove your dipstick and hook up a vacuum/pressure gauge to the distick tube. Run the engine at idle and at about 2000 rpm. You should not see pressure on the gauge - usually there will be a little bit of vacuum that decreases with engine RPM. If you see even a slight amount of pressure during this test, you've got a crankcase pressurization problem. It's not all that unusual on these motors, considering the high compression. It's caused by blow-by, but can often be fixed using a large-orifice PCV valve that will suck away the pressure faster.

I just recently "fixed" this problem on my LT1 car. The previous owner put a new rear seal in the car just 20K miles before I got it, but it was still leaking from there and at the valve covers. The owner gave up and sold the car to me cheap. I found what I was suspecting - a pressurizing crankcase - and I made my own orifice-type PCV valve that did a better job than the original valve. The car still idles dead smooth, and the blow-by problem really isn't any big deal (compression test is good). But now the motor doesn't leak a drop from anywhere. I didn't even have to replace the seal!