Transmission cooler lines - leaking AGAIN

[KenR]

Did a search and couldn't come up with anything newer than a post from 2008.

My 07 Duramax/Allison is on its second set of transmission cooler lines and they're leaking again at the crimp. The truck is out of warranty and the dealership won't warrant the lines they replaced. You'd think GM could make a tranny cooler line that'll go longer than 30k miles before leaking, and if not, at least back up the repair. Didn't know these were consumable parts.

Anyone else have this problem? Anyone have success with custom made lines? I don't want to go through this in perpetuity.

[gophergunner]

I've finally got a decent set for about a year now. My fourth set on my 2006 truck. They say they have 1 year warranty on the parts, but of course they will last long enough to be off that warranty and then they will leak again.

I was looking for something made up, or aftermarket to replace mine last time...would still consider it just in case I need them in the future, but I haven't had any luck finding any.

[DickWells]

I've seen enough complaints in here on those lines to make me wonder why mine aren't leaking in my 04 Sierra, with 112 K on the clock?
I came accross a guy in a truck stop in PA, about 3 years ago, who had leaking lines in a borrowed truck from MA. He had added about 4 quarts of engine oil to the engine, and was swearing at the truck, because he didn't dare to move it! He had started the engine and couldn't find any engine leaks. I had all my tools, and offered to help him and he wouldn't accept any help, so I left. I didn't know about the leaking tranny lines at the time, but I'll bet he put oil in the wrong hole, and that he had trans. fluid all over the ground. I remembered later that the oil on the pavement did look red! Bet he had a fun day ahead of him. He should have accepted my help. With someone to watch while he ran the thing, it wouldn't have taken but a minute to find out where the leak was.

[conway]

I understand that someone installed braided SSteel lines with a teflon inner coating (Titeflex brand SS hose) and silver soldered nuts on the transmission line tubing for the connection. He bought new lines to install the nuts on. Or another option, go to a hydraulic shop and have them make up a replacement with better fittings. Seems that this is a cold weather problem.

[WhiteTruck]

Dick,
You don't have the problem, and likely never will, because it was rare to see them leak until the '06 model year. They must have changed suppliers, because it is very common now. Like it has already been said, shouldn't be that hard to make a decent line.
The braided stainless line repair many have done to the 6.5 engine oil cooler lines was very successful. This would be a good fix, if local resources are available to do this.
Carefully cutting off the existing crimp, and adding a decent constant tension clamp would work too. As conway pointed out, it does seem to mainly occur in cold weather, the hose must relax some then.

[DickWells]

OK, I have Greg's A M lines on my old Sub. Wonder if he makes a set for the DM? Are you there, Greg?
I don't intend to do anything with mine until they start leaking. If it ain't broke ----------.

[unclemikefusny]

While under the truck changing the oil this weekend, I noticed a slow leak around the crimps on one of the transmission cooler lines. Very nice, since I am just out of warranty with 38000 miles on it. My wife noticed spots on the driveway, but I couldn't see the drips with just a casual inspection. This, in my mind, is clearly a defective component problem. Have people been seeing this routinely?

[Splitrimz]

Here is another one with the same problem. 1 Month out of warranty. Dealer replaced two lines, 0ver 500 dollars. I will be contacting Chevy, however I don't hold much hope for any satisfaction. I'll be watching for the first set of aftermarket replacements.

This also started showing up in cold weather, leaking around the crimp on one line.

Maybe the dealer is looking out for me, knowing that the other line is just waiting to happen. <grin>.

[KenR]

The cold weather theory just might be the cause; mine just started leaking again now that the temps have gotten under 30F at night.

Either way, completely inexcusable. The dealer said I'm 900 miles past the warranty period on the replacements...900 miles, like they weren't leaking a week and 900 miles before I took it in...and it'll be over $500 to replace them all over again.

I love these trucks, but spending almost $40,000 dollars on one then dealing with this BS over and over is making me think about ditching it for my old '72 Chevy. Seriously, if you look at cost of ownership over the life of the vehicle they're not even on the same chapter much less page!

[mastertech]

this is a common problem that gm is seeing with all the modle years as a gm tech i see at least 10 a month sometimes the same truck. the rubber hose that is connecting the metal parts at the crimps are where it is leaking the hose needs to be longer there it has a hard bend there that pulls on the hose no fix enless you know some one that can make a hose to fit

[Splitrimz]

I picked up my truck from the dealer this evening..$625 for two transmission lines after they tacked on all the shop towels that got dirty etc. Needless to say I am Pzzed. This comes especially after really pursuing the warranty question I got the "Where did you buy the truck from" question.

I have now read enough on the internet to realize that these transmission lines are a big "hidden" problem with Chevy. I am considering starting an on-line blog to see just how far reaching the problem is. A lot of diesel owners don't know about this or other diesel pages.

I have read about various fixes but most run in the range of $500-600. I never tried to get a hose made at NAPA, I may just look into that when the weather gets more accommodating.

Whomever comes up with a solution at half the cost is going to do well.

There, I now fell better! <grin>

[painthorsemom]

We just bought a used '06 that had leaking lines while it was on the lot. I had read about the problem before I bought it so I knew to look for it. The dealer just replaced them yesterday for us and the truck has less than 38, 000 miles on it. Now that it's getting much colder up here in NE PA, I hope I don't have the same problem again for a while. You would think that GM would do a permanent fix for this. It wouldn't be very hard to do!

[conway]

The temperature dropped to a cold 60 degree F. I got the dreaded leaking lines on my 07 but they are being covered by warranty. Waiting for the parts to come in.

[gophergunner]

I'm not sure if the lines are steel or not....the colour always made me think they were aluminum but I have never actually checked for sure.

But I've had leaky power steering lines for a while now. About $500 in hoses just to replace them all.....just the cost of hoses.

Now I figure I will replace them once, take my old ones and cut the tubing where the rubber hose is crimped to it, then have a new hose made with compression fittings. It worked very well on my off-road Toyota, I don't see why it won't work on the Duramax.

And if it works for the power steering lines, why shouldn't it work for the tranny cooler lines? They probably see much less pressure anyways. Only problem I can see is if the tubing is some goofy metric size that makes it difficult to find compression fittings for.

[DmaxMaverick]

I'm not sure if the lines are steel or not....the colour always made me think they were aluminum but I have never actually checked for sure.

But I've had leaky power steering lines for a while now. About $500 in hoses just to replace them all.....just the cost of hoses.

Now I figure I will replace them once, take my old ones and cut the tubing where the rubber hose is crimped to it, then have a new hose made with compression fittings. It worked very well on my off-road Toyota, I don't see why it won't work on the Duramax.

And if it works for the power steering lines, why shouldn't it work for the tranny cooler lines? They probably see much less pressure anyways. Only problem I can see is if the tubing is some goofy metric size that makes it difficult to find compression fittings for.

Do not use compression fittings on the PS/PB lines! The pressure can be too great (can peak over 2K PSI). Flare or swage only. You could use compression fittings on the return line, though. You can DIY with a flare kit and some Aeroquip AN fittings (any speed shop should have them, as well as Summit or Jegs). Measure the inside diameter of the hoses, and the outside diameter of the hard lines for the correct size. If they are metric, use the next inch size up for the tubing, but the hose should match, regardless if inch/metric (just make sure the couplers are the same size). Flares are very forgiving when it comes to matching sizes (which you can't do with compression fittings), and you can get "adapter" hose fittings with different hose to flare sizes (example: fit #6 hose to #5 tubing, which is common). AN number sizes represent 1/6ths of an inch (a #4 is 1/4", #6 is 3/8", etc.).

[MikeyB]

AN number sizes represent 1/6ths of an inch (a #4 is 1/4", #6 is 3/8", etc.).

Just so there is no confusion. I think you mean each an number is 1/16th of an inch.
Dang fractions!

Mike

[conway]

I am curious if the leaking cooler lines can be pinpointed to 6 speed trannys and ones that have had work done on them (e.g. TransGo Jr.). I understand that the phenomenon strikes newer trucks so maybe the six speed trannys have a slightly higher pressure that is causing the crimp to let go.

[madmatt]

I've been told this issuse has something to do with cold weather idling.

[gophergunner]

Well its about that time again, time to replace transmission lines once more....

Doing an oil change and I was just having a look to see whats going on under the truck, and sure enough the tranny lines are leaking. Must have just recently started as none of the fluid has hit the ground yet.

So about 45000 km's on my 4th set of lines...has been just over a year so no more parts warranty for me.

So if I can't (or shouldn't) use compression fittings on the power steering lines, can I use the compression fittings on the transmission lines? Or should I just flare the lines like was suggested for the power steering lines? I dug up my last set of tranny lines, so I will attempt to make a new set for myself using the tubing from the old set.

This is seriously frustrating and annoying. I'm not even on my 4th set of tires yet.

[KenR]

I've been told this issuse has something to do with cold weather idling.

I dunno - Mine started leaking again right when the weather started cooling off a bit, but I wasn't idling the truck any more than usual.