Oil and Transmission Cooler Lines Leak?

FishinDVM · December 17, 2019

2014 GMC Sierra 5.3 L83 @ 95k. So, I have been noticing a strange smell in the cab right after start up, or when idling at a light. Not horrible, not every time... its subtle, and when I do pick up on it, its difficult to place. I have smelled burning oil, exhaust, and gasoline in my days... and while I think it fits in that category somewhere, it doesnt match either of those perfectly. I was leaning towards transmission fluid when hot, or differential fluid when hot, simply because im not familiar with the smell of either. So, I read somewhere that someone else had a similar issue and had low level diff oil or a slow leak, so I figured its probably time to change them all anyways as I have never done it. So, I changed my oil, rear diff, transfer case, and front diff fluids the other day. All of that went fine, but I came across the issue, I believe, while under there.

What I found, was a small/slow leak built up on the skid plate / underbody shield. It is on the passenger side, behind the radiator, but in front of anything differential related. When I looked up, a few hoses had "oil stained" connections. The fluid was a lightish brown/orange color? Tiny amount. The main source seems to be where a "crimp looking" joint connects black rubber tubing to aluminum tubing. I know nothing about oil cooler and tanny cooler lines, but if I follow this tubing forward, it inserts into the lower drivers side of the radiator. I have attached some pictures. I'm guessing they are tranny cooler lines? If so, is leaking at the crimp connection a common problem?

Also, I have an AC condenser leak at the same spot as everyone else... the weld on the dorsal drivers side. I assume, as long as Im ok not having AC, its ok to wait on this? Just to clarify, the AC condenser is strictly AC and doesnt communicate directly with anything else right? I only ask because I have ignored that issue for a while now thinking it wasnt an urgent fix, so im hoping it doesnt have some sort of dual purpose. Back on topic, as for clarification on the oil/tranny cooler line photos, I'm all ears. Thank you, Chris

FishinDVM · December 17, 2019

davester · December 17, 2019

Yes, it's common for the oil and transmission cooler lines to leak at those crimps. Some people replace them with oem or 3rd party lines, that typically are crimped the same way, and eventually fail the same way, others will take the old lines to a hydraulic shop, and the shop will crimp hydraulic hose onto the lines using a better connector, and those will typically not fail (well, I haven't heard of them failing), but it's more difficult to reinstall the lines as the hydraulic line isn't as flexible as the oem line.

CamGTP · December 17, 2019

Yup.

I just spray mine down with cleaner every now and then, keep them looking good LOL. I don't care enough to replace them, so cleaning them is easier.

davester · December 17, 2019

Oh yeah, it also happens to the power steering and hydroboost lines if you have them...

gone_fishing · December 17, 2019

I have the same leak in the same area on my 14 Sierra. Never noticed a burning smell though. Looked into replacing the hoses myself. They are kind of expensive and look like they might be a pain. Decided to monitor it and that was a couple years ago now. Hasn't gotten any better but not any worse. Never seems to leak enough to make it to the floor (collects in plastic belly pan). I pressure wash the engine a couple times a year and clean those hoses off pretty good.

15slvrDbl · December 21, 2019

Been a problem area for Better than 20 years for automakers. Why no one has come up with a better connection who knows.

swathdiver · December 21, 2019

These are serviceable parts, they were not made to last forever. I had these exact some lines in my '82 Olds Diesel and Buick Grand Nationals. Back then, the lines burst on me at about 7-8 years, can't remember anymore. The lines in my 2009 are weeping still like the OPs photos. Not leaking, weeping. My replacements are still collecting dust in the garage...

CapitalTruck · December 23, 2019

Anyone just try clamping trans cooler hose onto the metal portion of the lines? (Cutting out leaking rubber section)? I replaced the lines on my 2wd, but it looks like major heartache with the 4x4 as the lines run under the axle. That doesn't look like fun.

davester · December 23, 2019

6 hours ago, CapitalTruck said:

Anyone just try clamping trans cooler hose onto the metal portion of the lines? (Cutting out leaking rubber section)? I replaced the lines on my 2wd, but it looks like major heartache with the 4x4 as the lines run under the axle. That doesn't look like fun.

I did that for the lines to & from my power-steering cooler, earlier this year, and so far (it's just been a couple months) they are fine. I did replace the oil & transmission lines with ACDelco ones a couple years ago when I noticed them weeping, and the other PS lines with whatever NAPA happened to have in stock...

Edited December 23, 2019 by davester