Replacing the Fittings for the Oil Cooler to Block on an 8.1L K2500

[Anak]

Vehicle is a 2002 Suburban 2500 4wd with the 8.1L big block. Situation is probably the same for many Silverado pickups with the same engine. I doubt the body lift on the HD line would make any difference.

This is not a complete write-up, but just some notes about the sticky points and solutions I found.

I replaced my oil cooler lines a couple years ago to solve a leak problem. It didn't solve the problem. It reduced it, but I still had a leak at the block fittings. So I ordered new fittings, but hadn't gotten around to replacing them until recently. It appears it is a good thing I ordered the fittings when I did as it appears they are no longer available. If I were smarter I would have replaced the fittings at the same time I did the lines, but none of the write-ups I found seemed to indicate that was typically necessary. It would be easier to do this if the lines were not in the way. Having recently replaced the lines I did not want to pull them all the way out, so I worked around them.

My first challenge was getting the second fitting out of the block (the forward-most fitting). The fittings are installed with a sealant that seems to operate like loc-tite. Mine were very tight. In order to get access and have enough leverage I had to go purchase a long pattern flex head 1/2" drive ratchet. My breaker bars could be gotten into place to break things loose, but there was so little room to swing that I could not reasonably remove the fittings with just the breaker bar. A normal 1/2" drive ratchet could not be gotten into place and there was not enough clearance beneath to include a universal. Here are several pics of the available clearance:







Here are the new fittings, part number 15765610:



All my current internet searches turn this up as no longer available/out of stock. Finding some old stock on ebay would be one option. The other option would be trying to replace this O-ring:



That O-ring is probably inaccessible when the fitting is still in the block. I would not advise trying to replace it without first removing the fittings.

As to the replacement, that is the primary reason I am writing this up. I could not find any information about the required O-ring. So I took an old one and matched it up:



The one with the tape is the old one. New one on the right.



Sorry for the poor focus. Description of O-ring reads O-RING 114 5/8" ID x 13/16" OD x 3/32" Thick. What you are probably looking for is a #114 O-ring.

Removal requires a decent dental pick. I have not tried fitting the new ones in. Having the OEM replacement fittings I went with those. I simply wanted this information available for next time. I expect a good O-ring lube will be helpful for installation of the new O-rings.

Before installing the new fittings I wanted to clean up the threads in the block. There was not clearance enough for a toothbrush, so I cut one in half:

 

[Anak]

With everything cleaned up I installed the new fittings:



While I was able to get the lines out of the old fittings without jacking up the engine or dropping the front axle, I was not so fortunate on re-installation. The rear-most line could not get enough clearance over the diff to line up straight with the fitting. Perhaps if I had tried to thread the fitting even farther into the block I could have made it work, but I didn't want to apply that much torque. I opted instead to jack up the motor, but I did not jack it up by much at all. In fact, I did not do anything to disconnect the motor mounts. I simply took pressure off the motor mounts. Total distance raised was probably less than 1/4". A wood block under the oil pan needs to be sized to avoid putting excess pressure on the drain plug portion of the casting:



Lines were then able to be installed. Note that the forward line does not get a plastic ring. There is no clearance for the ring below the fitting.



Last detail is the bracket which holds the lines to the block. It is just forward of the motor mount. It might not be challenging to get to on a 2wd, but it is a pain on a 4wd. I could only reach it from all the way in front of all the steering components. It is a long reach down the front of the engine and very little room to move a tool back and forth. Removal was not too bad with an electric ratchet, but re-installation was a pain because the bracket has two sides which need to be simultaneously lined up with the threaded hole in the block. It took a while to finally get lucky with that one.



Replacing the fittings did indeed substantially reduce my oil leaks. I am not done though. I think the oil pan is my now remaining leak. Probably have to deal with it in a couple years. Given the truck is over 20 years old I can't complain too much.