Chasing Down Oil Leak – 2005 Tahoe 5.3L

[Danzigman]

I’m trying to track down a pretty bad oil leak on my 2005 Chevy Tahoe (5.3L). It recently started leaking a significant amount of oil. I already replaced the oil pan gasket, but unfortunately, that didn’t fix the issue.

While I had the pan off, I took a look at the flexplate to check for any oil residue—nothing visible there. My understanding is that if the rear main seal were leaking, I’d likely see some oil on the flexplate, right?

The leak seems to be coming from the passenger side of the engine. I also noticed a bit of oil around the oil filter area. A while back, I replaced the oil cooler block-off plate with a billet version that uses an O-ring, so I’m not sure if that could be suspect again.

I checked the oil pressure sending unit and it doesn’t seem to be the source either.

Any suggestions on what else I should be checking? I’m open to ideas—this one’s been tricky.


Thanks in advance!

 

[Marky Dissod]

How well can you clean off as much of the engine as possible?
I've had a rear main seal leak for a while now, almost no oil on the flexplate (manuals have flywheels).

Usually (not always), oil leaks like this are internal. If you don't find anything soon, remove the intake manifold.
Bet you find the leak under the valley cover.

Where else could an oil leak hide?

 

[Danzigman]

You’re right—good catch, and I’ll admit I started my weekend a little early…

I did a decent job cleaning everything off, so I could get a better look. At this point, it very well could be the rear main. I’m sitting at around 197k miles, and the leak issues seemed to start after someone recommended I run an engine cleaner before an oil change early last year. I guess it cleaned out the wrong spots, because what started as a small leak has gradually gotten worse.

 

[OR VietVet]

Yes, likely the rear main. With that mileage. Especially if never been done.
I waited, while reading, for you to say it but you did not. Did you do the oil pickup tube o-ring while the oil pan was off?

 

[West 1]

Fixed my 2003 Yukon 5.3L a few months ago, like you I had replaced the oil pan and the block off plate gasket. It was the rear main seal gasket that had failed on mine and I have read this is very common. Mine only put out a spot on my garage floor, maybe between a quarter and a 50 cent piece size spot. I wanted it dry so I fixed it. Ton of work to pull the tranny/transfer case to do this job but I am dry again, zero leaks. Mine came down right at the starter and looked like a pan gasket leak. Should I have fixed it, NO, but I hate leaks so it got done. Do some reading to make sure you get the new rear main seal in and aligned proper. You don't want to do this job twice.

 

[Marky Dissod]

... the leak issues seemed to start after someone recommended I run an engine cleaner before an oil change early last year.
I guess it cleaned out the wrong spots, because what started as a small leak has gradually gotten worse.

Only engine (oil?) cleaner I'll ever run is Valvoline Restore & Protect.