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.

 

[2017sltXL]

I had an 07 XL with a 5.3 that I bought used with 225k on the clock, knew the history of it well, knew it went through a quart every 3k miles.
It had never been opened up, believe it or not. It has some leaks I knew about before I bought it, rear main being one of them.
Front main and PS pump I did right away, but with no time to address the rear main right away I did try a rear main seal conditioner.(Blue Devil IIRC)
I'll say it did work pretty well and reduced that leak to the point it would not drip. Still had some windage leak on the bell housing but barely.

That said I used it as a band aid until I had access to a hoist where I could replace it and change the pickup o-ring.
I'm not a fan of those additives because it's not some magical thing that affects just the rear main, it "conditions" any seal it comes into contact with.
I also did run an engine cleaner about halfway through ownership. That was a mistake however because it knocked a lot of garbage loose and kept plugging up the VLOM screen under the OP switch. The first time it happened I thought the old girl was about to give up the ghost, but then after pulling over to the shoulder with 0 psi, running normally, put two and two together and made it home fine with that annoying bell going off because I had zero psi, at least according to the gauge.
The only good thing was I could change that screen blind folded by the 3rd time lol.

 

[Chevymec]

I know you said you checked the oil sender, but did you check the cam sensor below it? They can leak also. My drivers side valve cover gasket was rock hard and had a good leak down the block, but also the rear main cover gasket has been leaking for a long time.

 

[nick0789]

Probably not everyone else’s preference but I’ll start at the top of the engine and work down until I see oil or residue. You might get lucky and it be valve cover gaskets, it may be more of a PITA repair.

Have you double checked the oil dipstick area? Where the tube meets the block.

I usually have less luck starting at the bottom and working my way up because of all the grime that builds up underneath.

Keep us updated!

 

[2591tdj]

I have a

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!

2002 with the same mileage and same leak. The oil change place and a mechanic both said rear main but neither removed skid plates and did a thorough examination. I feel pretty sure that they are correct, tho. Repairman wanted $800 (several years ago) to replace it and said that he pulls the engine rather than the tranny and TC to replace the RMS. Both said to keep driving it until the leak gets really bad or my oil consumption gets too high. So, I’m still driving it despite oil pools on my driveway daily. Funny, I rarely have to add oil between 3,000 mile changes.

 

[West 1]

I am older and work slow, I do have a tranny jack and a couple floor jacks. My Oil Pan Gasket replacement did not fix my leak but with the pan off I could see the leak was coming down the starter side of the block from the Rear Main Seal cover plate gasket. I spent 1/2 day or more pulling the drive shafts and transfer case. Exhaust from the manifolds to the connection behind the tranny. Removed the Torsion bars and then unbolted and dropped the tranny down and out. I changed the tranny pan gasket and filter while the tranny was out. The next day I installed the new Rear Main Seal into the cover plate and then on to the block. I do have an alignment tool for this but these Teflon Rear main seals are self centering. You do need to install these on the crankshaft clean and dry, no oil, no grease, no assembly lube. There should be a plastic installation guide. Slip that over the crank and push your new seal and plate into position. Let the seal center itself. Torque the mounting plate bolts evenly into place using multiple steps and this part is done. I waited till the next day to start putting the tranny back in. Working alone, with no lift it took me maybe 4 hours to get the tranny and other parts back in. Another hour to get the tranny fluid installed and all air out of that system. It is not a fun job. With no experience there are many things that can go wrong. If your shop quoted $800 for this job when todays shop hourly rates are $150 that sounds like a very fair price.

With a lift and good tools it can be done much faster but there is nothing easy about a rms leak repair. As far as pulling the engine for this repair I don’t know. The tranny bolts are difficult to get to in these cars and for me pulling and installing those took up a large part of the time. Pulling the engine or pulling the tranny these bolts have to come out. Once they are out the rest of tranny removal is straight forward.
I should mention to be fair, I live on the West coast, almost every bolt is not rusted and comes out when needed. In the rust belt states many of these might break or be stuck.

 

[2591tdj]

I am older and work slow, I do have a tranny jack and a couple floor jacks. My Oil Pan Gasket replacement did not fix my leak but with the pan off I could see the leak was coming down the starter side of the block from the Rear Main Seal cover plate gasket. I spent 1/2 day or more pulling the drive shafts and transfer case. Exhaust from the manifolds to the connection behind the tranny. Removed the Torsion bars and then unbolted and dropped the tranny down and out. I changed the tranny pan gasket and filter while the tranny was out. The next day I installed the new Rear Main Seal into the cover plate and then on to the block. I do have an alignment tool for this but these Teflon Rear main seals are self centering. You do need to install these on the crankshaft clean and dry, no oil, no grease, no assembly lube. There should be a plastic installation guide. Slip that over the crank and push your new seal and plate into position. Let the seal center itself. Torque the mounting plate bolts evenly into place using multiple steps and this part is done. I waited till the next day to start putting the tranny back in. Working alone, with no lift it took me maybe 4 hours to get the tranny and other parts back in. Another hour to get the tranny fluid installed and all air out of that system. It is not a fun job. With no experience there are many things that can go wrong. If your shop quoted $800 for this job when todays shop hourly rates are $150 that sounds like a very fair price.

With a lift and good tools it can be done much faster but there is nothing easy about a rms leak repair. As far as pulling the engine for this repair I don’t know. The tranny bolts are difficult to get to in these cars and for me pulling and installing those took up a large part of the time. Pulling the engine or pulling the tranny these bolts have to come out. Once they are out the rest of tranny removal is straight forward.
I should mention to be fair, I live on the West coast, almost every bolt is not rusted and comes out when needed. In the rust belt states many of these might break or be stuck.

Thanks for the excellent discussion of the steps you went thru. I grew up working on vehicles, plus my dad owned an auto parts store and a garage that I worked in during my teen years. Now that I’m retired I no longer have the desire, place to work or proper tools to tackle such a job (more lack of desire than anything else) so I’ll bite the bullet and pay a mechanic when the time comes.

 

[adventurenali92]

I just tackled my oil pan on my 2006 LQ4 6.0 because the crappy shop that replaced my pickup tube o ring in June of 2022 didn’t use the brand new genuine GM pickup tube and o ring that I brought them to use and the cheap crap they used failed which resulted in oil pressure loss on a highway drive down off the mountain. I have had an oil leak forever and in December I replaced the crank pulley seal hoping that would take care of it, but not so much. Anyways I could tell that the timing cover behind the crank pulley was always wet and covered in crud. So while I was into the oil pan to do the pick up tube seal, I also pulled the drive accessories and replaced my timing cover seal, and another crank pulley seal. Basically all the oil that was leaking out the timing cover seal ended up and the bottom of the pan which made it look like a rear main or pan gasket leak. Had done those two already. After buttoning up the oil pan with a fresh GM pickup tube o ring and new timing cover it’s been dry as a bone. So you could be leaking higher up and at the front of the engine with the timing cover or crank pulley seal.