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Transmission Cooler Hose Replacement


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I finished troubleshooting a red fluid leak that happened on our way north to New Hampshire last month. I initially thought it was a hydraulic fluid leak but as it turns out it is a small leak in one or the transmission hoses going to the cooling condenser. It only leaks when the engine is running.

There isn't much hope in finding a place in the While Mountain area of New Hampshire that is equipped to handle this repair so I plan to purchase a gallon of TranSynd to use for topping off the transmission level until I can reach an Allson shop on our way south back to Florida where I will have the filters changed along with replacing both hoses that run from the transmission to the cooling condenser.

After thinking about my situation for a spell, I think I may try some Gorilla Special Seal Tape of the Flex Tape as a temporary repair until I find an approved Allison shop near me in Florida to do the service and repairs. I will need to clean up the hoses really well with solvent to get the cleanest seal possible.

Edited by Dr4Film
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Just thinking out loud here . . .

I wonder if you can clamp two halves of a pipe with a rubber "gasket" on the hose itself.  Pipe could be anything that is slightly larger than the OD of the hose you're clamping (hose clamps should work, or u-clamps).  Gasket could be a section of bicycle (or motorcycle) inner tube, one layer only.   The idea is to put enough clamping pressure on the actual hole to keep it from seeping out.  Be sure to chamfer all sharp edges. 

Just a thought.

- bob

Edited by cbr046
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2 hours ago, cbr046 said:

Just thinking out loud here . . .

I wonder if you can clamp two halves of a pipe with a rubber "gasket" on the hose itself.  Pipe could be anything that is slightly larger than the OD of the hose you're clamping (hose clamps should work, or u-clamps).  Gasket could be a section of bicycle (or motorcycle) inner tube, one layer only.   The idea is to put enough clamping pressure on the actual hole to keep it from seeping out.  Be sure to chamfer all sharp edges. 

Just a thought.

- bob

I agree.  My fix….clean the hose with acetone.  Get a roll of Gorilla tape.  Double or triple wrap the hose….noting the exact location of the pinhole leak.  Then, and this is optional, wrap one layer of the foam back HVAC tape, the black insulating tape on the refrigerant lines over the leak.  Leave it wide enough for two hose clamps.  Position the hose clamps so that the leak is covered with the bands, solid area if possible.  
 

Others will have to chime in.  Obviously look at it after driving….

Good Luck.  BTW, my air intake hose has a double wall thickness of Gorilla tape.  Monaco cut it too long and bent it so that it had a small split at the web where the coil is located.  Fixed it that way in 2015. 40K later, my OTR shop says it is first class.  I did, I think, also put the silver HVAC metallic tape over it. 

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  • 2 months later...

I finally had some time to get under the rear end of the coach and take apart one huge hose clamp and two HD Zip-Ties which were holding the transmission cooling hoses to the frame. Started the engine up and isolated the seeping to only one of the hoses. I now need to remove one more hose clamp and one more zip-tie to get the hoses separated enough to clean up with Dawn Dish Soap followed with a good cleaning with Acetone as Tom Cherry recommended.

The seeping is exactly where the one hose clamp was holding the hoses in place. The clamp is a thick rubber one with some metal down the center type clamp. I wonder if there might have been some chafing going on with the vibration of the engine that has caused the hose to seep.

I purchased a 14-foot roll of Flex Sealing Tape which I will apply first. Then I plan to cut a small section of large ID hose lengthwise that will cover most of the circumference of the leaking hose and clamp it in place.

That should work for our trip back to Florida coming up soon after Columbus Day.

I am guessing that the most TranSynd fluid that I may have lost on the way up and while running the engine up here is possibly one quart. I will check it one we have the transmission up to temp and sitting in a level spot.

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I've seen a lot of hoses with the entire outer rubber covering completely wore off and the hose still not leak.  The real working portion of the hose is the internal rubber that prevents leaking while the wire braid adds strength and keeps the internal portion from rupturing.  The external covering is more cosmetic, not saying it doesn't help but 90% of the work is done with the wire braid and internal rubber.

Your seep could be originating from someplace else and migrating to where you see it.  Hard to tell.

If your system is the same as mine you probably have a #12 hose from transmission to cooler.  You could measure and have one made and carry it as a spare.  Much cheaper to have one made yourself then having a repair shop do it. 

Shouldn't be hard to change if you have access.  I had to remove my return hose from the cooler so I could install a separate cooler to augment the cooler internal to the radiator.  I didn't loose too much oil when I did this, maybe a quart. 

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If these are AN fittings (or JIC, which I think are compatible), any automotive speed shop would have the hose and fittings to replace the hose assembly.

Summit Racing or Jegs would also have the parts, if you can do the assembly yourself.  The reusable AN fittings don't require any special crimpers to install, just be careful cutting it, the braid is sharp, and be sure to flush the hose after assembly to make sure there's no debris left inside before installing.

Jim J is correct, it's very unlikely that anything you do on the outside of the hose will actually slow down the leak.

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On 9/10/2022 at 2:59 PM, jacwjames said:

Your seep could be originating from someplace else and migrating to where you see it.  Hard to tell.

The only wet area on the entire outside of the hose is where the fluid is seeping out. If it was leaking from the inside someplace in a different location, I would think that the outside casing would be somewhat wet also along the path to where it is actually dripping.

10 minutes ago, Ray Davis said:

When mine was seeping, I bought a package of shop towels & wrapped one around the leak each day until we got home. 

I would check the oil level and change the towel each day.

I just need it to stop for our trip back home plus give me enough time to find a shop to make up the hoses for me.

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5 minutes ago, Dr4Film said:

I just need it to stop for our trip back home plus give me enough time to find a shop to make up the hoses for me.

Yeah, I understand however I didn't feel like I was going to stop my leak so I just wanted to absorb the seep & stop the mess until we got home.

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  • 2 weeks later...
On 9/11/2022 at 5:38 PM, Ray Davis said:

Yeah, I understand however I didn't feel like I was going to stop my leak, so I just wanted to absorb the seep & stop the mess until we got home.

Well, after attempting a temporary repair, no joy!

I have the area stuffed with Bounty "picker uppers" and will monitor the towels after each day's drive. I have enough Bounty to drive across the country, LOL. Plus, I always carry a supply of TranSynd fluid for topping off. Luckily the fill tube is accessible from the rear of the engine compartment.

We will be leaving for Florida on the 12th of October.

Edited by Dr4Film
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Richard,        
I don’t know the diameter of the hose, but if it’s 5/8 or 3/4 you might want to try using a hose barb.  If you have enough slack, you could cut out the leaking area and insert the barb and clamp it.  If you don’t have the slack, pick up the necessary length of hose and use 2 barbs. 
If you don’t want to try the repair before your trip, you could still pick up the barbs and hose and have them ready for a roadside repair.  I’ve included a link to Amazon for the nylon barbs.  I know you can get brass ones at Lowes, etc.  if you elect to get the nylon ones, make sure they can take the heat.

I don’t know what route you’re taking to Florida, but if you’re taking 95, I’m about an hour east of Richmond.  If you get in a jam, get ahold of me.

Dan

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Richard,          
That’s a smart move.  95 from Boston to DC is a white knuckle trip.  I did that way too many times in the 70’s.  I’d rather play leapfrog with a unicorn than take that route.

As an alternative to taking 81 to 77, you could take 81 to Winchester VA and take 66 to 17 South.  It will hit 95 at Fredericksburg VA.  Nice roads for RV and very little traffic.  If you take that route you’ll avoid the Virginia and NC mountains.

Dan

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4 hours ago, Dr4Film said:

Thanks, Dan. 

We will be over on I-81 taking that to I-77 then down to I-95 in South Carolina.

Done that a time or two.  My favorite would be to exit off 81 @ US 17 and head back towards Fredicksburg.  I have done that all the way from 81 down…or got on I66 (memory) and head east towards DC, then pick up 17.  17 is a piece of cake.  Then follow I 85 down and pick up either the east beltway around Richmond (preferred) of stay on it.  At Petersburg, it splits and stay on I 95 south until you get home.

Many folks like Fred White swore by that route and we had friends in Hartford that did it that way.

Good Luck.  Safe Travels.

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16 hours ago, dandick66 said:

Richard,        
I don’t know the diameter of the hose, but if it’s 5/8 or 3/4 you might want to try using a hose barb.  If you have enough slack, you could cut out the leaking area and insert the barb and clamp it.  If you don’t have the slack, pick up the necessary length of hose and use 2 barbs. 
If you don’t want to try the repair before your trip, you could still pick up the barbs and hose and have them ready for a roadside repair.  I’ve included a link to Amazon for the nylon barbs.  I know you can get brass ones at Lowes, etc.  if you elect to get the nylon ones, make sure they can take the heat.

I don’t know what route you’re taking to Florida, but if you’re taking 95, I’m about an hour east of Richmond.  If you get in a jam, get ahold of me.

Dan

Dan's idea is a good one.
I'd definitely use brass barbs though, those nylon ones can weaken with heat, as well as vibration can break them.
I know the cooler loops on automotive transmissions don't run a lot of pressure, and I suspect the same is true on the Allison.

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