Anyone else having leak problems? I changed the oil to synthetic at 1k miles and I noticed the rack was seeping. I wiped it off. Got underneath it again today at 4300 miles and the rack is still seeping. Not leaving a puddle, but there is a trail about 6" long were it has leaked down to the A arm mount. To make it all worse I noticed the rear main is leaking pretty bad. No spots on the driveway, the whole underside of the bellhousing/oil pan/crossmember area is covered in oil. Im guessing this much seepage is not normal

 

Oil leak is a common issue on the 07/08 GMT900's. Rear main and/or Crank Position Sensor O-ring is the likely culprit. I had both replaced on my truck last summer with less than 4K miles on it.

 

I just switched to mobil one 2 weeks ago and no leaks yet...I have 2200 miles.

 

13000 no leaks.

 

vmax2007......how long did the dealer take to do the repair? Did they put up much fuss?

Im pretty busy this upcoming month and can't really do without the truck for more than a couple days.

 

Which "attempt"?

The first attempt: They changed the oil pan gasket, oil cooler line manifold gasket. Strike one!! (Same day service)

Second Attempt: They changed the Rear Main Seal. Swing and a foul tip (I think it was leaking too, but my oil leak was still there). (2 day service)

Third Attempt: Crank Position Sensor replaced. Home Run!!! No more oil leak!!! (same day service).

If there is oil on/near your starter mounting bolts, it IS the Crank Position sensor. The CPS is mounted above the starter someplace.

Here, read this thread over at GM-Trucks: (post #19 has pics of mine).

http://www.gm-trucks.com/forums/inde...20service&st=0

Ignore the red/yellow highlights, that was from the search function.

Dealer was awesome about it. Oh, and do NOT let them touch your oil pan gasket, it is NOT the source of your leak, I would bet my truck on it.

 

its clearly leaking through the gap in the bottom of the bellhousing.

 

So was mine, that is the lowest point of the engine. Take the large (approx 2") inspection cover off and stick your finger in there under the flywheel and see if you feel oil (I recommend doing this with the engine off and the keys nowhere near the ignition...). You can see from my pics in above link that I had drips on the bottom of the bellhousing, near that semi-circular hole, as well as on the starter bolts. The oil on the starter bolts was from the CPS O-ring leak. I am not 100% sure if the rear main was ever leaking though. I never felt oil in the inspection hole and the oil on the bottom of the bell housing could have followed the bell housing/engine seam all the way down. But after the Rear Main seal was changed, I still had the oil leak from the CPS o-ring, but it didn't seam to be as bad at the bell housing. It was still there, just not as bad. So, I still don't know for sure if the rear main was leaking or not? But I suspect BOTH the rear main and the CPS O-ring, and possibly even the oil cooler line manifold had been leaking (oil did collect around that area too...see pics).

 

I had a leak at the oil cooler line o-ring. I looked like it was the rear main to me. The dealership cleaned it up and then ran put UV dye in the oil, let it run for a while and then they hit the back of the engine with a black light.

The mechanic thought it was the rear main too, but decided to test it to be sure. I'm glad he did! It's been about 6 weeks since they stopped the leak. So far, so good.

 

Took it in for repair yesterday. They said the rear cover was leaking and they are waiting on parts. Not sure what they are replacing, but I assume the rear cover seal. Supposed to have it back today.