LB7 Oil Cooler Leak - Diesel Bombers

Chevy/GMC Duramax 01-04 LB7 Discussion of Chevy and GMC Trucks with LB7 Duramax Turbo Diesel Engines

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Old 06-10-2013, 10:13 PM
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Join Date: May 2013
Posts: 5
Default LB7 Oil Cooler Leak

Iam suspecting an oil cooler leak on my truck, truck hazes a little white smoke at idle and clears up once i get on the throttle. injectors have been replaced recently, along with all the cups and seals. and i have had them checked again just to be sure. My coolant is strting to look a little dark and appears to be a dark film forming in the coolant tank, when i crawl under the truck i can see oil forming on the oil cooler and dripping on the drive shaft, its not very much of a drip but its there. I can also see what appears to be a little bit of a whiteish milky color in oil dripping from the cooler. Ive ordered the gaskets and o-rings for the cooler but not sure to go about doing this job, iam pretty mechanically inclined. any tips or ideas would be greatly appreciated. Also dos this sound like im on the right track?
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Old 07-16-2013, 10:40 PM
Diesel Fan
Join Date: Nov 2009
Posts: 39

I recently did this job. Mine was leaking coolant from the rubber gasket between the cooler and the block.

Not really hard to do but it's hard to tell what to unscrew to get it off. There are 4 bolts that go thru the cooler to the block. You must also disconnect the pipe from the back of the water pump (2 nuts). I also had to back one tranny to motor bolt out some so I get the cooler to clear it.

On the cooler 2 bolts on top and 2 bolts on bottom. One of them is a bit of a bitch to get to.

Edit -2 more nuts on the coolant to block elbow.

Last edited by Back-in-Black; 07-16-2013 at 10:59 PM.
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Old 11-28-2014, 08:22 PM
Join Date: Nov 2014
Location: Fort Worth, Texas
Posts: 2
Default Paladin

Looks like I'm having a "bad oil cooler" experience as well.

I'd been tracking a leaking hydraulic line problem and didn't realize some of that mess was probably engine oil. My Dexcool is getting a burnt burgundy tint. So I'm probably there. I'll do a pressure test on the cooling system with the filter off to confirm. Original Dexcool was a continuous leak masking the cooler issue as well due to continual replenishment. Not loosing any coolant just now, oil level has been constant. New water pump has been on about 400 miles.

This on a 2001 GMC 2500HD, SLT, 4x4, 288K. Recently bought, very used. Needed a water pump first thing. Transfer case only had about 8 oz. of lube in it (no visible leak), Heavy deer proof front bumper, winch, headache rack, gooseneck hitch, possible lift pump, new batteries last week.

Last edited by Paladin; 11-28-2014 at 08:39 PM.
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