A few hours after I arrived home today I noticed a light puddle/film of oil under the transmission. I checked to make sure it was oil and not power steering or transmission fluid. I drained the pan and only got about 3 3/4 quarts out of it, so I lost about 1.5 quarts. I could see a few drops in a path down the driveway.

Under the car the entire oil pan is dry except the back where it meets the bellhousing. Oil is leaking out there and from that point backwards there is a nice film of oil on everything, mainly just the trans.

Engine is a stock 2002 5.3 with a carb, LS1 oil pan, mated to a Muncie.

Oil pan bolts were nice and snug, any ideas on what this could be? Thanks

 

could be the rear main. Also check to be sure it isn't coming from the top of the engine. Oil pressure sensor, back of a valve cover ect.

 

rear main seal or the oil sending unit on the top of the engine at the back..

 

Check the flexplate bolts. Crank should be drilled through. Common place to leak. Especially if you've taken the flexplate off and on.

 

Thanks for the quick replies. Didn't see any oil leaking from the top near the valve covers or oil sensor. When you say the crank should be drilled through, do you mean the holes where the flywheel bolts to the crank?

I'll most likely be taking the trans out today to see what I can find.

 

The older 5.3s have a problem of the rear cover gasket breaking and leaking. Also the rear main seal. Done a few here.

 

Took a second look at the oil pressure sensor (which has the top plastic part broken off since apparently I wasn't able to properly guide an engine stand around my garage) and it looks like there is some oil pooling around the base of it. Not a lot, but could most of it have dried up?

 

Oil doesn't evaporate, but on a vehicle in motion, with lots of moving/spinning parts, it's highly mobile.

Another possible spot - where the oil passages go through the pan right by the oil filter. Pretty sure I sprung a leak on the Jeep after installing a Melling 10296. Can idle or cruise for hours with no issue, but pressure is high enough at high RPMs that it squirts out there. I neglected to change the oil pan gasket there when I last installed it and should have.

I also mated it to a 4 speed initially(out for T56 now). One of the interesting things about the LS is that the oil pan actually is part of the rear mating surface for the bellhousing and such. SOO if the oil pan is not meticulously aligned(and perhaps sticking past the rear of the block even a little), when you bolt the bell/trans on(and then beat the heck out of it by driving it) the oil pan can get pushed out of position and develop a leak quite easily.

All of the other suggestions are spot-on. Don't take my lengthy explanation as trying to convince you this is more likely than any other possibility.

 

Thanks for the help. I put the oil back in and ran the car for a few minutes. It didn't take long for the oil to seep out of the sensor and make its way down to the pan/bellhousing.

A plug should do the trick, this sure beats taking out the trans) Thanks again.

 

Nice find!

 

Sometimes, the "gods" are smiling at you!
Buy a lotto ticket tonight.