Oil Leak - Rear main and front sensor

FL335i · December 29, 2015

I've been watching the front of my block. behind the belts, there is a 3 bolt cover about 3" dia with a sensor. Wet in that area as dirt and such stick to it. I've wiped it clean twice and it's come back twice, slowly. So I'm on vacation this week and take it in today. Get a call 3hrs later about a rear-main leak. I never even knew my rear main was leaking. I do my own oil changes too.. figure I would of noticed it. So the dealer is addressing both leaks. In some ways I'm glad they found the rear main. The scary part is how did I miss that leak. I've never had any drops on my driveway. Is the rear main a common leak? I have the 5.3L.

Brianibew · December 29, 2015

I have the leak on the front of the engine about the middle of the block. Let me know what they did to fix that.

FL335i · December 30, 2015

^I almost did that myself vs even having the dealer mess with it. It looks like 3 torx screws and an O-ring behind the cover. But I have a warranty... figured let them mess with it. next thing ya know I'm out of a truck for 3 days b/c of a rear main leak that came out of left field.

FL335i · December 31, 2015

Update. I stopped by the dealer. They were very cool showing the me truck and the leaks, and talking to the tech. It's not my rear main. it was the flex plate bolts that were leaking. So the good news is he didn't have to drop the oil pan and do a rear main seal. I'm very happy about that. Factory sealed engines are never duplicated. The bad news is he still had to pull the transmission, exhaust and driveshafts. But they were correct, thing was leaking inside the bell housing. The solution was re-install the flex plate bolts with the white bolt thread sealer dope. He used an AC Delco tube, looked just like the version I got from Autozone for my K5 project. I used that stuff on my intake manifold bolts and the Harmonic Damper bolt. So I'm not as disappointed as I originally was over this deal. I'm actually glad the dealer found this. So heads up to fellow 14's... check for oil leaks at the bell housing. Knowing this, I would remove the flex plate inspection cover before my warranty is up....

As for the damp spot on the front of the block that was the whole reason I took the truck in (LOL).... tech really didn't want to mess with it. I was OK documenting it. I just don't want it leaking like a sieve the day after my warranty is up. We left it as he'd check some other 5.3's and see how they looked. I wasn't going to throw a fit. Tech was doing a huge job for me already on the flex plate bolts. Worst case is the dealer does the front leak when it gets worse down the road or I'll buy the gasket and do it myself in 15 minutes. Small stuff is one thing. Pulling a trans is another. I'm keeping things in perspective here. I'm happy thus far with the dealer and tech. This whole experience is proof that talking to the tech and getting under the car is priceless. I'm in industrial construction. After a few emails and calls to the engineers I tell them to suit up boys and come out to the field so I can show you why what you designed will not work Takes 3 seconds for the light bulb to go off. our society needs more hands on in your face time with problems. It's not a bad thing.

Edited December 31, 2015 by FL335i

20SierraL8T24 · January 2, 2016

I have a little oil around the tin plug on the front of my tranny. I'll take a couple pics tomorrow during the day. After reading the last post, I may have an issue.

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FL335i · January 2, 2016

^That's what mine was doing. You got a leak from the either the rear main or more than likely the flywheel bolts. Oh, FYI.... I still don't have my truck back. I am driving a new Canyon loaner. Nice little truck, but I miss my 5.3 and the AFE I want the job done right. I'm not pushing them.

Beni · May 14, 2022

Regarding your front engine leak you mentioned "I'll buy the gasket and do it myself in 15 minutes". What gasket are you referring to? i have the same issues with the front and rear leaking as you and want to fix it myself. i got the rear, but not sure about the front - what gasket I'd need?