[SOLVED] Help appreciated finding my oil leak

LsHart said:

Back of intake. Oil pressure sensor good?

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No leak there. I replied it less than a year ago and checked the area with a video probe.

I promised an update today after a second try at replacing the oil pan gasket. I ran the engine for a few minutes then checked for leaks about 1-2 hours later. It didn't have enough time to leak much but I did see a bit of oil forming on the inboard starter bolt. There was also a very light film on the driver side second pan bolt from the rear. Nothing coming from above this area and it's not at the rear corner. I will give another update tomorrow, but it doesn't look like It's leak free.

I'm still not sure but it looks like the oil is coming out of the oil pan gasket. I'll post pics and and a description tomorrow.

Question - Do you guys put sealant completely around the gasket? I'm only putting it in the 4 joints at the corners where the front and rear engine plates mount to the block. I'm using Permatex Ultra Black.

As always, comments are appreciated.

Another Update - The next morning there was one or two drops worth on the floor (pic). They fell from the inboard starter mounting bolt (pic). Since this bolt is very close to the joint of the rear engine plate and the oil pan gasket corner, I couldn't tell which one was leaking. I pulled the starter and cleaned up the area (before and after pics). I'm going to let it sit a while to see if any new oil shows up. If not, I'm going to install the starter, run the engine, take it back off and wait for oil to show. Hopefully I'll be able to finally tell which is leaking.

There was no oil on the driver side bolt pan bolt noted in my last post.

More to come....

hagar said:

Sounds like its rear seal like others have said, but first make sure your pcv system is flowing properly. It takes very little reduction in flow to cause a pressue build up on ls engines, then they can leak oil out of anything once pressurized.

Also check the dipstick tube where the mount for the tube is attached to the tube. I have seen a couple trucks with leaks that people had been chasing, that was the little tack welds that hold the tube to the metal tab/mount. Once those leak, the oil ends up all over the lower side of the engine block.

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Thanks for the ideas. There's nothing on the dip stick tube. Also I did a quick check on the PCV by checking for pressure at the oil fill opening with the engine running. It was sucking not blowing. See my last post for latest progress.

TahoeRestore said:

Another Update - The next morning there was one or two drops worth on the floor (pic). They fell from the inboard starter mounting bolt (pic). Since this bolt is very close to the joint of the rear engine plate and the oil pan gasket corner, I couldn't tell which one was leaking. I pulled the starter and cleaned up the area (before and after pics). I'm going to let it sit a while to see if any new oil shows up. If not, I'm going to install the starter, run the engine, take it back off and wait for oil to show. Hopefully I'll be able to finally tell which is leaking.

There was no oil on the driver side bolt pan bolt noted in my last post.

More to come....

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Oops. I forgot to attach the pics

Update - Looks like a rear plate leak to me. I cleaned up the area and waited an hour or so for oil to show up. Attached are the before and after pics.

If it's clearly a rear plate leak, I'm going to use a shop (giving up my man card) to replace the plate gasket, rear main seal, and refurb the transmission while it's out.

Thoughts?

Dang fresh oil.

That is the very best job I have seen cleaning up the engine and getting very clear photo's showing your leak. Nice Work.

I just completed removing the tranny/transfer case and replacing the Rear Main Seal, Plate gasket, T-bone or Dog bone, and the 6L80 got a new Torque Converter. I chose the Luk and like it a lot. Works great. No leaks at all so far. I hope yours turns out perfect.

Final Update: The Tahoe is back from the shop and not a drop of oil has been seen since. The following work was performed - Engine Rear Plate & Crank Seal, Barbell/dogbone replaced with billet, Transmission rebuild with new torque converter and upgraded parts, Transfer Case refurb with plate that protects from casing wear, New Transfer Case Motor & Encoder which I had bought but not installed yet, Rear Differential - reset pinion & gears plus all new bearings/seals to the wheels, Essentially complete drive train refurb from the back of the engine to the wheels. $4,560 & 4 days in the shop. The estimate to only fix the rear plate seal and crank seal was $1K anyway so I'm pretty happy. Thanks for all the input.

This truck may outlast me.

Awesome! Thanks for the update.

You will probably be good until you reach 340k miles now, LOL.

So, I recently bought an 02 tahoe last Thanksgiving, never noticed any leaks, checked fluids weekly, etc. Went and took the easy way out and got an oil change from local oil shop, noticed small drips while parked. Took it to them, got under it with them, wasnt the bolt or filter, does have a decent amount of oil residue but it almost seemed like it was coming from above and around rms, havent had time to pinpoint all of the othe possibilities, but wanted to say it only leaks for a few moments after parking. Not sure how bad of a leak is coming out while driving, have had to top it off a couple times but I also commute 1hr to and from work. A rms should leak constantly correct, even if its slow drips. The first 5 mins after I shut it off, a decent amount of drops are seen under it, but it never grows anymore than that.

TahoeRestore said:

Final Update: The Tahoe is back from the shop and not a drop of oil has been seen since. The following work was performed - Engine Rear Plate & Crank Seal, Barbell/dogbone replaced with billet, Transmission rebuild with new torque converter and upgraded parts, Transfer Case refurb with plate that protects from casing wear, New Transfer Case Motor & Encoder which I had bought but not installed yet, Rear Differential - reset pinion & gears plus all new bearings/seals to the wheels, Essentially complete drive train refurb from the back of the engine to the wheels. $4,560 & 4 days in the shop. The estimate to only fix the rear plate seal and crank seal was $1K anyway so I'm pretty happy. Thanks for all the input.

This truck may outlast me.

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That price is low.

That is a lot of work to have done for $4500. Not too bad. I hope it all works well now.

Corydolo said:

So, I recently bought an 02 tahoe last Thanksgiving, never noticed any leaks, checked fluids weekly, etc. Went and took the easy way out and got an oil change from local oil shop, noticed small drips while parked. Took it to them, got under it with them, wasnt the bolt or filter, does have a decent amount of oil residue but it almost seemed like it was coming from above and around rms, havent had time to pinpoint all of the othe possibilities, but wanted to say it only leaks for a few moments after parking. Not sure how bad of a leak is coming out while driving, have had to top it off a couple times but I also commute 1hr to and from work. A rms should leak constantly correct, even if its slow drips. The first 5 mins after I shut it off, a decent amount of drops are seen under it, but it never grows anymore than that.

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Determining if it's RMS or Rear Plate Gasket....

I suppose it doesn't matter much because either leak requires transmission removal and both RMS seal and rear plate gasket should be replaced at that time. My shop quote was ~$1K, but I chose to refurb the whole drive train at $4.6K. However, I was able to determine it was the rear plate by removing the starter, cleaning the three way joint and waiting (see pic in the thread above). I was trying to make sure it wasn't the oil pan gasket before spending a lot of money. You could try removing and looking through the inspection plate. A video probe helps. As others have said windage and the spinning flex plate can throw that oil around. Mine was clean in the bell housing (see pic) because the leak at that corner wasn't going into the bell housing.

Thoughts on observing how long it leaks after parking....

See pic of oil dipstick with the oil pan removed. The resting oil level is below the top of the oil pan. This should mean that all oil leaks except for the drain plug should stop after the truck sits for a long while. Of course there's a lot of oil on the internal engine parts and surfaces that will continue to seep out of leaks above that joint.

Some parts under pressure, like the oil pressure sensor, leak most when the engine is running. However that oil travels down the outside of the engine and could continue to drip at the bottom.

The Rear Main Seal is mating with a rotating shaft and should decrease leak rate after shutdown, but again has to travel down surfaces inside the bell housing to get out.

Bottom line: It's not very definitive to observe how long it leaks after parking, but if you clean a lot on the outside and keep in mind the paths and timing for the oil to appear, it helps a little.

I've just started noticing an oil leak on my 2001 Yukon (265k mi) too on the garage floor. It seems to leak even after sitting for a long several days.This post has been VERY helpful. I also need to have a stripped fill plug on my T-case removed/replaced/drilled (whatever). Last shop said T-case would have to be removed to do so. I love my Yukon so I may be spending some money to fix both these in the future. I'd like to know before going into it where to focus to, so this has been illuminating. Thanks.

grizzlyak said:

I've just started noticing an oil leak on my 2001 Yukon (265k mi) too on the garage floor. It seems to leak even after sitting for a long several days.This post has been VERY helpful. I also need to have a stripped fill plug on my T-case removed/replaced/drilled (whatever). Last shop said T-case would have to be removed to do so. I love my Yukon so I may be spending some money to fix both these in the future. I'd like to know before going into it where to focus to, so this has been illuminating. Thanks.

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Welcome. You may have seen this elsewhere....If that transfer case is opened up, have the case saver plate added. It shouldn't cost much more ($25?) and can prevent a hole from being rubbed in the outer casing.

Thanks for this.