2004 2500hd rear main leaking 6.0

Mighty HD · July 5, 2006

I have had an oil leak that the dealer can not find now for months and months. It leaks on the ground in the driveway/garage and I have given up.

The truck has 16k on it, oil changed every 2k, M1 5w-30 or 5w-40. By the bible.

When we left for our 500 mile trip to our destination I cleaned underneath the truck and got all the oil off the bellhousing and oil pan. It was spotless. By the time we got there it was smoking from oil on the exhaust, and completely soaked underneath. Obviously there is a leak somewhere

Or there WAS.

The oil level stays just a pinch under total full with 6 quarts.

Once we got to the inlaws, I then again cleaned underneath the truck and got all the oil off, scrubbed everything down with a brush & degreaser. Yes I'm a bit anal.

The oil level just dropped a hair. Most people wouldn't notice it.

So the drive back -- 500 miles, 65-75mph, a few stops here and there.

I check once we get home and not a single drop of oil anywhere.

What gives?

mmmikkke · July 6, 2006

Could your pcv be malfunctioning as in sometimes not v-ing? That would let pressure build up in the crankcase pushing oil out through the easiest path, which could be the rear main.

IIRC, GM modified the pcv installation so it's not a serviceable item, because incompetent mechanics were leaving it unplugged. So this one could be a bear to fix.

99Silver6.0 · July 8, 2006

Or your engine has some serious blow-by and its building up some crazy pressure in the case. Has your dip stick been push out the slightest bit???????? Cadillacs use a vented oil filler cap you could try. That rean mainis a beeyatch! When I built my motor I went through 2 of those dam seals. They are hard to get seated around the crank snout! You CANNOT oil them and feeler gauges rip them up. I had to buy a special tool that looks like a ring compressor to install the rear engine cover/main seal.