Hose leak... transmission cooler hose???

darleyhavidson · March 3

Purchased a "CPO" 2022 GMC Sierra 2500HD recently and am slowly learning the ins and outs of the truck. I found what appears to be a leaking hose covered in dirt/sludge. It is on the passenger side and routes under the radiator. I am assuming this is a transmission cooler hose but am not certain. Picture attached for reference. If it is a transmission cooler hose leaking, is this covered under the GM powertrain or bumper-to-bumper warranty?

dh

davester · March 3

probably one of the transmission lines. I can't say for sure, but gm likely will say it's a wear part. they commonly need replacement for leaking at the joints where it switches between the metal tube and the rubber hoses. But see if that crap goes all the way to the radiator or cooler up front , maybe it's the fitting that's leaking.

darleyhavidson · March 3

8 hours ago, davester said:

probably one of the transmission lines. I can't say for sure, but gm likely will say it's a wear part. they commonly need replacement for leaking at the joints where it switches between the metal tube and the rubber hoses. But see if that crap goes all the way to the radiator or cooler up front , maybe it's the fitting that's leaking.

I appreciate the advice, I will look it over tonight.

GMCustomerService · March 19

On 3/2/2026 at 9:11 PM, darleyhavidson said:

Purchased a "CPO" 2022 GMC Sierra 2500HD recently and am slowly learning the ins and outs of the truck. I found what appears to be a leaking hose covered in dirt/sludge. It is on the passenger side and routes under the radiator. I am assuming this is a transmission cooler hose but am not certain. Picture attached for reference. If it is a transmission cooler hose leaking, is this covered under the GM powertrain or bumper-to-bumper warranty?

dh

Congratulations on your recent 2022 GMC Sierra! We're so happy to have you a part of our GMC family. Please know, warranty coverage is ultimately determined by our dealers after a diagnosis is performed. We are happy to help aid in connecting you with one in your area to have this potential leaking concern addressed. If interested, simply send us an email to [email protected] that includes your forum username in the subject line. From there, we will be able to provide our most prime support.

Another JR · March 24

A “CPO” truck should have a bumper to bumper warranty for the initial period of ownership. The dealer should be able to tell you if leaking transmission cooler line replacement would be covered under your warranty without any diagnosis needed.

carkhz316 · March 24

Its either the engine oil cooler or transmission oil cooler line. Both engine lines and 1 of the trans lines go the right side (as pictured) and the other trans line goes towards the left side (if the gas engine). I can about guarantee its leaking at the crimps. I just had to replace/ repair mine last fall right after warranty expiration (of course). When I had them out, I could spin the hose around on the hard line while it was still crimped. They're just made so cheaply as the hose was also very hard like plastic. I bought new Goodyear oil cooler hose and used crimp-style AC line ferrules to rebuild mine along with a cheap hydraulic crimper. They've been fine since.

The dumb thing is that engine oil cooler lines are covered under powertrain warranty, but trans cooler lines are not. But, since you have the CPO b-t-b warranty still, they should be obliged to cover the trans cooler lines as well, though don't be surprised if you're met with the typical bullshit lip service where they tell you that its deemed 'acceptable seepage' and will deny the warranty claim. Then, the day after warranty is expired, suddenly it turns into a danger-critical repair that they need to perform, paid for out of your pocket of course.

darleyhavidson · March 25

1 hour ago, carkhz316 said:

Its either the engine oil cooler or transmission oil cooler line. Both engine lines and 1 of the trans lines go the right side (as pictured) and the other trans line goes towards the left side (if the gas engine). I can about guarantee its leaking at the crimps. I just had to replace/ repair mine last fall right after warranty expiration (of course). When I had them out, I could spin the hose around on the hard line while it was still crimped. They're just made so cheaply as the hose was also very hard like plastic. I bought new Goodyear oil cooler hose and used crimp-style AC line ferrules to rebuild mine along with a cheap hydraulic crimper. They've been fine since.

The dumb thing is that engine oil cooler lines are covered under powertrain warranty, but trans cooler lines are not. But, since you have the CPO b-t-b warranty still, they should be obliged to cover the trans cooler lines as well, though don't be surprised if you're met with the typical bullshit lip service where they tell you that its deemed 'acceptable seepage' and will deny the warranty claim. Then, the day after warranty is expired, suddenly it turns into a danger-critical repair that they need to perform, paid for out of your pocket of course.

I crawled under the truck the other day. That hose is the engine oil cooler line. I bought the transmission oil cooler lines thinking it was the issue. I wrapped the engine oil cooler line in fusion tape (at the connections) to prevent any leaking or further issues. I will give the dealership another chance to make it right, though.

I appreciate the feedback and sharing your experience. I thought about changing out the engine oil cooler lines myself, but looked like quite the job of trying to route the new lines to get in place.

carkhz316 · March 25

Its not too bad if you're mechanically inclined, but you may as well utilize your warranty if you can. You deserve that privilege when they can't make stupid simple things last anymore.

Another JR · March 25

They have been using these swaged part-hose-part-metal-tube assemblies for at least 40 years, and they have been failing at the swage after several years for just as long. My 93 K2500 has 160k miles and is on its fourth set of oil cooler hoses. They are designed for ease of factory assembly - not longevity. I do them myself, but it’s a messy, frustrating job because the quick connect fittings are difficult to disconnect in the tight access space.

carkhz316 · March 25

All my previous trucks didn't start to see cooler hose seepage until 10 years/ 150k miles on average. My current truck was dripping at half that. Thats what I'm underwhelmed by.

They're actually quite easy to disconnect. Routing them out and back in a bit more work.

Another JR · March 25

8 hours ago, carkhz316 said:

All my previous trucks didn't start to see cooler hose seepage until 10 years/ 150k miles on average. My current truck was dripping at half that. Thats what I'm underwhelmed by.

They're actually quite easy to disconnect. Routing them out and back in a bit more work.

I agree they are easy to disconnect if you can get your fingers around them. On my K2500 the access is poor.

I think the swage seal fails due to aging and heat damage to the flex hose material, and not mileage directly.