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Discussion Starter · #1 ·
A couple of year ago I installed a set of Red's Auto Rehab 1/2" transmission lines in my 2006 2500HD. It worked fine for a while and then started leaking at the connection at the lower radiator. I took it apart today and it was very loose where the 45 degree "adapter" screws into the cooler inside the radiator. Assuming that was the problem I tightened it up as much as I dared (I can't get a torque wrench on it), then reassembled and took it for a drive. It's still leaking just as bad as it was before. Below is what the set looks like along with a close-up of the offending connection (this is from their website, mine is still on the truck).

The O-rings do not appear damaged. It's really hard to see down there but I'm assuming the connection pushed into the cooler and the O-rings seal between the line and the cooler and that the face of the cooler is compressed against and seals on the inside of the radiator. Is this correct?

So what could cause this to leak if the O-rings aren't damaged? It is not leaking water, just transmission fluid. I can replace the O-rings if that's the problem but it's a fairly long operation so I want to be reasonably sure that will work before I start (just letting the truck idle won't cause it to leak, I have to re-assemble everything and drive it a bit).

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Have you tried contacting the manufacturer? Often they know the most common failure issues. Saves time.
 

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A couple of year ago I installed a set of Red's Auto Rehab 1/2" transmission lines in my 2006 2500HD. It worked fine for a while and then started leaking at the connection at the lower radiator. I took it apart today and it was very loose where the 45 degree "adapter" screws into the cooler inside the radiator. Assuming that was the problem I tightened it up as much as I dared (I can't get a torque wrench on it), then reassembled and took it for a drive. It's still leaking just as bad as it was before. Below is what the set looks like along with a close-up of the offending connection (this is from their website, mine is still on the truck).

The O-rings do not appear damaged. It's really hard to see down there but I'm assuming the connection pushed into the cooler and the O-rings seal between the line and the cooler and that the face of the cooler is compressed against and seals on the inside of the radiator. Is this correct?

So what could cause this to leak if the O-rings aren't damaged? It is not leaking water, just transmission fluid. I can replace the O-rings if that's the problem but it's a fairly long operation so I want to be reasonably sure that will work before I start (just letting the truck idle won't cause it to leak, I have to re-assemble everything and drive it a bit).

View attachment 646464

View attachment 646465
I have the same kit (5/8 though) and had the same problem, but with the upper fitting. Discovered something I had not known when I first installed them back in like 2012. And here it is:

Install 2 o-rings back to back at each of those fittings that go into the cooler. One o-ring will provide a back stop for the other taking up the slack that is causing the leak. Do one fitting at a time or the cooler could fall inside the radiator.

I know, sounds stupid. But look at the fitting pic above and you will notice that very little of the o-ring sticks past the washer. Most of it sits down inside the washer. You can't use a smaller ID washer either as it won't slide down over the threads. So, just use 2 o-rings. Go for Viton material if you can. Been maybe 4-6 years since I did that and no problems since.

I tried calling Red's years back when this happened and could get no one. Found the instructions for a similar kit and that's where they actually instruct by design to use 2 o-rings per fitting.

Happy trails.
 

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^^^ Also, for future reference since you have this kit, if you ever get limp mode, a Christmas tree lit up dash or some other Twilight Zone issues, check the ground wire on the passenger side right near where the hoses run. Cost me over $450 for the dealer to find mine had been damaged from the hose rubbing it. Broke and made sporadic contact causing all kinds of erroneous codes and mysterious issues. The 5/8 hoses were overkill and a real PITA to run, being so stiff. And here I thought I got everything tight and safe when I first did it. Live & learn.
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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Soooo, maybe not a kit I should to my wish list, or?
 

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Soooo, maybe not a kit I should to my wish list, or?
It depends. At the time I needed a new mousetrap because the GM OEM lines leaked at the crimps and so did the OEM replacements as GM, at the time, saw no need to make better crimps. So, the options were having a shop make a set using the old solid portions or buying a different mousetrap. There were so many stories about guys having to replace their OEM lines regularly. So I went a different route. Had I got the 1/2 inch instead of the 5/8 (they're hyd hoses) and had Red's instructed 2 o-rings per fitting, there'd a never been an issue. Today, there may be better options, but weren't at the time. Btw, I went with the 5/8 because I thought I may need the extra cooling fluid carrying capacity here in the Vegas desert.
 

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Thank you. Is one able to guard against the ground wire problem easily?
 

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Thank you. Is one able to guard against the ground wire problem easily?
Yea, just do a better job than I did. lol

It was really tight trying to fish hard 5/8 hydraulic hoses. I thought I got everything right, of course. I even wrapped places on the hoses with extra rubber and used several zip ties to prevent abrasions and movement. But I obviously missed a spot. The dealer found it after much looking and just fixed the broken wire, routing it so it won't happen again. After awhile, the hoses get hard and will cement in place. So set them right the first time and they won't move. Vibrate, but not move.

Also, save money and headaches and just buy the 1/2 inchers.
 

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Discussion Starter · #9 ·
Thank you mp06011999. My kit did come with two O-rings per fitting which isn't obvious in the pictures. Maybe they just shrunk or something? I do know it's not very tight. It came off and went back in very easily. One thing that bothers me is that you can't really tighten the fitting by screwing it in since it won't line up with the hose the way you need. I then have to "back it up" 1/4 turn or so to line up with the hose. I'm sure that is why it has the nut to tighten things up but it still makes me nervous. It's the only fitting I have to do that with and it's the only one leaking.

I was going to write the manufacturer today if I hand't had any comments here yet so I guess I'll do that and hopefully can get some new O-rings from him. I wish I could get my head in there and inspect things a bit closer to see if there are any cracks but damn there's a lot of stuff in there.
 

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Thank you mp06011999. My kit did come with two O-rings per fitting which isn't obvious in the pictures. Maybe they just shrunk or something? I do know it's not very tight. It came off and went back in very easily. One thing that bothers me is that you can't really tighten the fitting by screwing it in since it won't line up with the hose the way you need. I then have to "back it up" 1/4 turn or so to line up with the hose. I'm sure that is why it has the nut to tighten things up but it still makes me nervous. It's the only fitting I have to do that with and it's the only one leaking.

I was going to write the manufacturer today if I hand't had any comments here yet so I guess I'll do that and hopefully can get some new O-rings from him. I wish I could get my head in there and inspect things a bit closer to see if there are any cracks but damn there's a lot of stuff in there.
It might be worthwhile to get one of those cheap inspection cameras that attach to a smartphone to help you inspect things a little closer (y)
 

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Thank you mp06011999. My kit did come with two O-rings per fitting which isn't obvious in the pictures. Maybe they just shrunk or something? I do know it's not very tight. It came off and went back in very easily. One thing that bothers me is that you can't really tighten the fitting by screwing it in since it won't line up with the hose the way you need. I then have to "back it up" 1/4 turn or so to line up with the hose. I'm sure that is why it has the nut to tighten things up but it still makes me nervous. It's the only fitting I have to do that with and it's the only one leaking.

I was going to write the manufacturer today if I hand't had any comments here yet so I guess I'll do that and hopefully can get some new O-rings from him. I wish I could get my head in there and inspect things a bit closer to see if there are any cracks but damn there's a lot of stuff in there.
O-rings seal between the line (fitting) and the cooler and that the face of the cooler is compressed against and seals on the inside of the radiator. Is this correct?
^^^This is correct. In addition, the hose to fitting seals in tranny fluid via a compression fitting.

First, make absolutely certain what fluid is leaking.
Second, make absolutely certain what connection was loose / got loose. Is it hose-to-fitting, fitting-to-cooler or the cooler to the radiator. It is easy to mistake as I'll explain.

Since both top and bottom fittings are pulling the cooler against the radiator, it is easy to think both are tight & proper when only one is. It is also possible to have removed both fittings from the cooler at the same time during install and then allow the cooler to slip down or the seal to. And that is a real problem. And it is possible to have a misaligned o-ring boogering up everything except the compression fitting.

The only seal for coolant is that seal inside the radiator. You are correct. But it requires two good and proper fitting o-rings to take up the slack of the fitting's washer-to-wall-of-radiator that then pulls the cooler tight against the seal inside the radiator once the fitting is snugged to the cooler.

The tranny fluid only seals in two places. One is the compression fitting where the hose attaches to the fitting. THAT can be super tight. The other is the o-ring seal of the fitting to the cooler. That will seal without being super tight so long as the o-rings are good and sitting correctly. If the o-ring that is buried in the washer is not sitting perfectly inside the washer, the other actual t-fluid sealing o-ring that fits inside the cooler while resting against this buried o-ring will not sit perfectly (in one plane) and can leak tranny fluid. And of course bad or bad sitting o-rings will not provide the proper back up that pulls the cooler tight to the radiator and then you can leak coolant.

I know it's a lot, but I spent some time thinking about it more, recalling it and wanted to be thorough for you. After you are 100% certain what fluid is leaking, the above should get you there. Let's just hope it isn't the coolant seal inside the radiator. I hear that's no fun. Otherwise, if it isn't, new and proper fitting o-rings with a good snugging and really tight on the hose-to-compression fitting should do the trick.

I remove the air box and everything there. But most of my issues were the upper fitting so I don't recall all what had to come out for the bottom one. Maybe the wheel liner?
 

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Discussion Starter · #12 ·
There is no question it is transmission fluid or which fitting it's coming from. Definitely not from the hose but from the fitting-to-radiator. There is no water in the transmission fluid or vice-versa so I assume that seal is working ok. I'm assuming it has to be the o-rings even though they look fine. It seems a bit loose so maybe they shrunk?

I wrote the manufacturer and he replied quickly with the size. For those wanting to know, #910. So I'll bet getting some viton o-rings and give it another go I guess.

When I first installed them I removed the wheel liner. This is the only fitting that seemed to require that and I guess it did make things easier to install the lines, but if I did it again I would not remove the liner. I removed only the air box this time and dealing with the liner in place wasn't nearly as bad as taking it out and putting it back in, not to mention the fasteners lost or destroyed. Live and learn.

Thank you for all your help.
 

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There is no question it is transmission fluid or which fitting it's coming from. Definitely not from the hose but from the fitting-to-radiator. There is no water in the transmission fluid or vice-versa so I assume that seal is working ok. I'm assuming it has to be the o-rings even though they look fine. It seems a bit loose so maybe they shrunk?

I wrote the manufacturer and he replied quickly with the size. For those wanting to know, #910. So I'll bet getting some viton o-rings and give it another go I guess.

When I first installed them I removed the wheel liner. This is the only fitting that seemed to require that and I guess it did make things easier to install the lines, but if I did it again I would not remove the liner. I removed only the air box this time and dealing with the liner in place wasn't nearly as bad as taking it out and putting it back in, not to mention the fasteners lost or destroyed. Live and learn.

Thank you for all your help.
Thanks for o-ring size info. I'd say new o-rings will prolly be the issue. Fingers crossed and make sure they're sitting perfectly within the washer. Good luck with it and let us know. I never had tranny fluid, coolant cross contamination either.

I've had my passenger wheel liner out so much that the aftermarket access door you cut into the liner for fuel filter replacements has never been used. I bought one of these and a bag of GM pushpins years ago.

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Discussion Starter · #16 ·
Thanks for o-ring size info. I'd say new o-rings will prolly be the issue. Fingers crossed and make sure they're sitting perfectly within the washer. Good luck with it and let us know. I never had tranny fluid, coolant cross contamination either.

I've had my passenger wheel liner out so much that the aftermarket access door you cut into the liner for fuel filter replacements has never been used. I bought one of these and a bag of GM pushpins years ago.

View attachment 646562
I couldn't find the o-rings locally and had to order from Amazon. They are here now so I know what I'm doing this weekend.

What do you mean by "sitting perfectly within the washer"? I don't have them out yet again but I recall the washer basically sat on top of the o-rings but not really snugly. You just sort of pushed it on and then screwed the fitting in.
 

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I couldn't find the o-rings locally and had to order from Amazon. They are here now so I know what I'm doing this weekend.

What do you mean by "sitting perfectly within the washer"? I don't have them out yet again but I recall the washer basically sat on top of the o-rings but not really snugly. You just sort of pushed it on and then screwed the fitting in.
See how in your pic you can only see one o-ring sticking out beyond the washers?
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From memory... I believe the o-rings are small enough to sit inside the ID of the washer. And not big enough not to. But to make sure they are not part in the ID and part out, like pinched. The first o-ring sits entirely inside the washer ID and not against the face of the washer. The second o-ring then sits against the first one that is completely captured within the washer. The first one providing the backstop for the second. The second one actually doing the sealing. The first one is just a spacer, of sorts.

Make sense? It should when you have it apart. And if I'm misremembering, let me know. But I believe THAT was my seeping issue. I did not know to make sure the first o-ring sits inside the washer rather than against the face of it.
 

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Discussion Starter · #18 ·
See how in your pic you can only see one o-ring sticking out beyond the washers?
View attachment 646725


From memory... I believe the o-rings are small enough to sit inside the ID of the washer. And not big enough not to. But to make sure they are not part in the ID and part out, like pinched. The first o-ring sits entirely inside the washer ID and not against the face of the washer. The second o-ring then sits against the first one that is completely captured within the washer. The first one providing the backstop for the second. The second one actually doing the sealing. The first one is just a spacer, of sorts.

Make sense? It should when you have it apart. And if I'm misremembering, let me know. But I believe THAT was my seeping issue. I did not know to make sure the first o-ring sits inside the washer rather than against the face of it.
The o-rings do sit inside the washer, that all looks as you describe.. If there was a difference in size between the old ones and the new ones I put on today I couldn't tell. But at least I feel confident that I do not have an o-ring problem.

I do appear to have a not-tight-enough problem. The 45-degree fitting was pointed somewhat down and left. If you were looking at it face-on it would be facing about 5 o'clock. The problem is it's not tight like that so you have to use the lock washer (don't know if that's the actual name) to snug it all down. I'm assuming that's how it's supposed to work. What apparently happened is the weight of the hose pulled it down some more which loosened it and it leaked. It did it again the second time. Today when I replaced the o-rings I turned it to about 11 o'clock and re-routed the hose to come from slightly above. It was a tight fit with the air intake for the inter-cooler there but we got it done, plus I got it a good bit tighter. Unfortunately it's still leaking. A whole lot less this time, just a drop or two after 15 minutes or so of driving, and the hose won't pull down on it again, but I don't feel like it's done.

I'm looking for a set of crows-foot wrenches so I can put a torque wrench on it. If I can't fit that in there then I'll find me a shorter, thinner wrench. Right now the only 1" wrench I have is a good 18" long and really thick. The adjustable wrench isn't any better. I just can't get ahold of it to give it the 1/4 turn or so I think it needs. But I'm almost there.

Thank you again for your help.
 

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I checked my lower fitting the other day and it's pointing at about 7 or 8 o'clock. The hoses are pretty cemented into their positions after being on since about 2012.

Did you get yours figured out?
 
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