Fixed oil leak on oil cooler line block

[LRob]

Ive been a member here a while but havent posted a whole lot though I should. Truck runs fine and has been mostly trouble free since i purchased it in 2014. 2009 Tahoe 5.3 w/ max tow package.

I has had some oil consumption issues that i've done the DOD disable w/ newly designed valve cover install. Lately its been plagued with oil leaks, so i pulled the pan and did the gasket, and while I was in there I did the O-ring for the pick up tube and the AFM shield for the oil pan. I probably dont need it since i tuned out the DOD, but it was only an $8 part and I was already in there. Anyhoo the oil pan gasket did slow down the leak a little, but didnt completely fix it. I purchased some UV dye to put in the oil and found that it was leaking from the plug on the side of the oil cooler block. Please see attached pics. I modified a 3/8ths hex to fit in the small face and pulled the plug to find a hard piece of plastic acting as the O-ring. I went and purchased a small o-ring kit and a 9/16th o-ring fit. I also applied some thread tape as well, before re-installing it. The pic has a 8mm wrench, its actually supposed to be 3/8th. Slip the short hex into the plug then the wrench over the hex and torque down the plug. I wanted to share this since I didnt find much on this and figured it would be able to help someone.

 

[donjetman]

Most folks don't have an oil cooler. Mine had a blockoff/bypass adapter that has a gasket that is prone to leaking.

 

[drno4]

New here. Active on a Toyota forum (our other vehicle), but I do the repairs on our '03 Yukon Denali XL as well. This is exactly what I've been looking for, as that plug is leaking on mine, too. Thank you for taking the time to share your experience and the details. Helpful!

As a bonus: Search on this site "mystery oil leak" (thread started by username "Aeterna") -- for some reason the site would not let me share a direct link here. Post #13 on that thread mentions this same issue, but your post here includes more detail. Thanks again.




ETA: removed the plug in question today and inspected its hard plastic conical o-ring. No cracks, chips, deformities, nothing. Hmm. Not what I expected.

In this case, the o-ring sits completely inside the female thread receptacle--unlike, for example, a common oil drain plug where the edge of your crush washer is visible underneath the head of the drain plug, even after tightening. This design allows this plug to seat all the way into the threads, and bottom out, rather than stopping short a couple of millimeters as it would with a washer under the bolt head.

Because of that unique design of the o-ring, and because mine still seemed to be in good repair, I decided to clean up the area and reinstall the same plug and original o-ring...but this time, added a bead of red high temp Loctite around the circumference of the o-ring for some extra insurance. Tightened things back up guttentite (can barely get my hands up there, let alone my torque wrench).

Will continue to watch it closely and see if drips persist.

Thanks again for your post.

 

[rickybo6by]

Ive been a member here a while but havent posted a whole lot though I should. Truck runs fine and has been mostly trouble free since i purchased it in 2014. 2009 Tahoe 5.3 w/ max tow package.

I has had some oil consumption issues that i've done the DOD disable w/ newly designed valve cover install. Lately its been plagued with oil leaks, so i pulled the pan and did the gasket, and while I was in there I did the O-ring for the pick up tube and the AFM shield for the oil pan. I probably dont need it since i tuned out the DOD, but it was only an $8 part and I was already in there. Anyhoo the oil pan gasket did slow down the leak a little, but didnt completely fix it. I purchased some UV dye to put in the oil and found that it was leaking from the plug on the side of the oil cooler block. Please see attached pics. I modified a 3/8ths hex to fit in the small face and pulled the plug to find a hard piece of plastic acting as the O-ring. I went and purchased a small o-ring kit and a 9/16th o-ring fit. I also applied some thread tape as well, before re-installing it. The pic has a 8mm wrench, its actually supposed to be 3/8th. Slip the short hex into the plug then the wrench over the hex and torque down the plug. I wanted to share this since I didnt find much on this and figured it would be able to help someone.

View attachment 241204 View attachment 241205 View attachment 241206 View attachment 241207

thank you so much. changed my gasket today. and boom big drop right from that bolt. will be doing your fix in the morning.

 

[09_4WD_YUKON]

Got to fix this leak myself. What do yall think the temp gets down there? What oring material would be needed? I'm assuming rubber would not hold up. Also, the thread tape mentioned above, was that just regular teflon tape? Or something else?

 

[Geotrash]

Got to fix this leak myself. What do yall think the temp gets down there? What oring material would be needed? I'm assuming rubber would not hold up. Also, the thread tape mentioned above, was that just regular teflon tape? Or something else?

I would use Viton if you can find it, otherwise an automotive o-ring would be fine. Temps won’t exceed 250°F.

 

[Blackcar]

I like to use this product on automotive fluid threads.

Henkel 56531 LOCTITE 565 White Thread Sealant - 50 mL Tube at SkyGeek.com

Henkel 56531 LOCTITE® 565 White Thread Sealant - 50 mL Tube - Visit and view our entire SkyGeek, Shop Supplies, Aerospace Sealants, Thread Sealant, Henkel Loctite 565 Thread Sealant, section at SkyGeek!

skygeek.com

 

[gooffeyguy]

I need to do this also.

I replaced the gasket for the oil cooler lines last year but I'm still getting a small leak from that area above the filter. It's either the gasket leaking again or this plug.

 

[89Suburban]

Most folks don't have an oil cooler. Mine had a blockoff/bypass adapter that has a gasket that is prone to leaking.

I just ordered one of these, need to get this done on mine.

ICT Billet Block-Off Plate 551621; LS Oil Cooler Delete Plate for 97-17 Chevy LS | eBay

Engine Oil Port Block-Off Plate Model or Series:LS Oil Cooler Delete Plate. Oil Cooler Delete Plate for LS series GM V8 engines. Fits all LS series pans except GTO front sump oil pans, dry sump pans LS7, LS9,etc., and LS4 pans.

www.ebay.com

 

[George B]

I need to do this also.

I replaced the gasket for the oil cooler lines last year but I'm still getting a small leak from that area above the filter. It's either the gasket leaking again or this plug.

Was it your plug? I am in the same spot. Replaced the gasket and still have a leak.

 

[rdezs]

Ditched the OEM oil cooler lines and block on a 6.0 last year. The design is problematic. Went with steel braided.

 

[j91z28d1]

for anyone curious, since I didn't see it mentioned. that's a bypass valve the o ring is on.

you can buy the valves by themselves too. I wanna say it's 4 to 7psi? when cold the oil cooler is decent restriction. especially at higher rpm flow rates. probably when warm too at high flow rates. good to have a bypass in there.

 

[solli5pack]

for anyone curious, since I didn't see it mentioned. that's a bypass valve the o ring is on.

you can buy the valves by themselves too. I wanna say it's 4 to 7psi? when cold the oil cooler is decent restriction. especially at higher rpm flow rates. probably when warm too at high flow rates. good to have a bypass in there.

So do non oil cooler trucks with the blockoff plate have that plug/valve also? I've changed the pan gasket twice and re sealed the block off plate more times than I can count and still have a leak around the oil filter. At this point I assumed I have a rear main leak even though it looks clean in the inspection hole.

 

[j91z28d1]

So do non oil cooler trucks with the blockoff plate have that plug/valve also? I've changed the pan gasket twice and re sealed the block off plate more times than I can count and still have a leak around the oil filter. At this point I assumed I have a rear main leak even though it looks clean in the inspection hole.

nah, only the oil cooler lines have the bypass.


have you tried one of the billet block offs with an o ring seal? mine wasn't that, but cheap to make sure. mine I'm sure is the pan gasket.


for yours, did you rtv the corner of the gasket? it seems common for the plate the rear main in it can leak and not the rear main itself. same amount of work to get to it thou.

 

[solli5pack]

Yes with the RTV...and waited 24hrs before starting the truck...and also have the billet block off and use some RTV on that also....I think I'm going to order a factory plate and try and Reseal it one more time...it really looks like it's coming from the plate but there's oil everywhere so it's hard to tell.

 

[donjetman]

From 2020 to 2023 I had a ICT brand billet plate when I installed my own oil cooler . No leak.

In 2023 when I removed my self installed oil cooler, I reinstalled the stock oil cooler block-off plate & bolts with a Felpro # 72435 gasket.

I always put a thin coat of RectorSeal T+2 on gaskets. No leak.

 

[rdezs]

The trick on the OEM 10 mm bolts for that block off plate is to torque them correctly. Too loose and they leak. Too tight and it works the plate and it leaks. You need an inch pound torque wrench... Can't remember exactly what the book called for, I'm thinking it was around 108 inch pounds. You can easily exceed that with a short quarter drive ratchet and two fingers .

And a side note... Once the oem blockoff plate has been torqued too far, it's warped and won't seal right. A thicker aftermarket one will yield more success and is more forgiving ..... But if you go much tighter, you risk pulling the threads.

 

[kittenmcnugget]

JUst went through this on my 6.2 and this was the best explanation so far, so i thought i'd add what i noticed.

This plug is a #10 ORB or MS Boss O ring port/plug. You can get these steel plugs with o rings for $2 some places. Also, this was intended to o ring seal, so the added teflon can potentially obstruct the seal. The listed o ring size is a 910, but as mentioned Viton would be ideal for temps if you can find them.

Thanks for the above info to get me on track.