Transmission cooling line popped off while driving

[Thunderbirds]

All,

last night we took the M1123 back out for a test drive after adjusting the tie rod ends. It ran great. Until....


... 10 miles into the drive, we suddenly had ATF squirting into the cab from one of the holes in the deck coming from underneath. We pulled over and found a flexible transmission cooling line popped off the hard line. We lost 90% of the fluid. I tightened it down as good as I could and limped back to the house at 30 mph... Probably shouldn't have thinking back, but it did ok.

At the house I went through all the hose clamps and found I was able to get a turn or two on most of these clamps.

FWIT, If you find yourself underneath the truck doing inspections, take a 5/16 and 1/4" socket with you and give it a test. Just as a preventative measure, I rode over 40 miles without incidence since I got the truck, and then this happened. Also a good idea to have extra ATF in the back.

 

[Mogman]

Glad you made it home OK, hope there was no permanent damage.
Instead of starting a new thread for every little item on your new truck you should start a thread about the restoration/build of your M1123
Something like "the trials and tribulations of my M1123"

 

[Retiredwarhorses]

actualily, folks Should be replacing all hose clamps and rubber hoses…in my shop, we do not reuse hose clamps, or attempt to tighten them further, they are generally loose because the rubber has shrunk as the hoses have dried out.

 

[Thunderbirds]

actualily, folks Should be replacing all hose clamps and rubber hoses…in my shop, we do not reuse hose clamps, or attempt to tighten them further, they are generally loose because the rubber has shrunk as the hoses have dried out.

That is an awesome point. Didn't even think that far. I know what I will be doing this weekend.

Thanks RWH

 

[Mrgior31513]

actualily, folks Should be replacing all hose clamps and rubber hoses…in my shop, we do not reuse hose clamps, or attempt to tighten them further, they are generally loose because the rubber has shrunk as the hoses have dried out.

That's a lot of desert life problems, you learn to check your rubber periodically. All of these ones going for sale in the drier climates, like out of Yermo and such, it should be one of the first things to look at. It's not as bad out in the Midwest, rubber wears out eventually, but it's not nearly as bad. I park my Toyota in a shipping container and keep a bucket of water uncapped to keep humidity in there and it helps a ton.

 

[Thunderbirds]

Now I am a little confused

When I re-attached the cooling lines after my incidence, I could have sworn the line ID was 5/16" or 1/4", just while staring up, and messing with the barb fitting, line and clamp. However, the PM calls for

HOSE,NONMETALLIC MAKE FROM HOSE,P/N 6490610019

which translates to 3/8" non-metallic line.While trying to verify before I spend the $$ on a line I can't use, I ran across this:

Interchange: Power Steering Return Hose – HMMWV Systems

They say in part:

We are of the opinion that using a 5/16″ barb with a 3/8″ hose is an error. The barb itself is 1.5875 mm smaller diameter than the hose, and that means that the hose would have to be tightened considerably just to contact the shank of the barb.

First off, very interesting site, secondly, apparently the Part Manual often calls for a 3/8" hose, even on 5/16" barbs.

For all the experts that work on this a lot, what is your opinion, experiences, thoughts?

 

[Mrgior31513]

For all the experts that work on this a lot, what is your opinion, experiences, thoughts?

I've not worked on those vehicles at all, but I've done a lot of work on a lot of different trucks, cars, forklifts, etc. over the years. As far as general automotive experience goes, measure the barb and size the hose to fit it. If the book is wrong, then the book is wrong. I doubt there is a reason they have larger hose listed in the PM other than a mistake. Rubber lines should fit snugly over barbs. If it is too loose then it is easier for it to come loose in the future and more chance of it leaking. Loose hoses over barbs require significantly tighter (usually over tightened) hose clamps in order to simply get a decent seal, rather than a snug clamp simply helping to make a tighter seal and keeping it from slipping off the barb.

The only 'advantage' of a loose hose would be that it would have less chance of sticking to the tube for future removal, but it's never been an incentive for me to make one fit loose. I'm more concerned with it not leaking than I am with 'potentially easier future removal'. If rubber lines stick that bad I'd rather shave them off the barbs and put new hoses on. *It's usually rubber line that's used with fuel and water/coolant that stick, not those used with oils like trans fluid or hydraulic fluid.

 

[Mogman]

I have never seen a GM truck transmission that ran 5/16 hose, 3/8 and larger but not 5/16, I think the TM is correct just possibly a piss poor design.

 

[Mrgior31513]

I have never seen a GM truck transmission that ran 5/16 hose, 3/8 and larger but not 5/16, I think the TM is correct just possibly a piss poor design.

If the hard line is 5/16 would you still use 3/8 hose or go with hose to match the hard line?

 

[Dieselmeister]

I would match the hose to the hard line. Using a hose that is too large will cause too much deformation and stress in the rubber when tightening down the hose clamp to get a good seal. That will lead to an earlier failure of the hose.

 

[Thunderbirds]

... If the book is wrong, then the book is wrong. I doubt there is a reason they have larger hose listed in the PM other than a mistake. Rubber lines should fit snugly over barbs. If it is too loose then it is easier for it to come loose in the future and more chance of it leaking. Loose hoses over barbs require significantly tighter (usually over tightened) hose clamps in order to simply get a decent seal, rather than a snug clamp simply helping to make a tighter seal and keeping it from slipping off the barb....

Thanks, that seems to be the consensus and makes sooo much sense.

I have never seen a GM truck transmission that ran 5/16 hose, 3/8 and larger but not 5/16, I think the TM is correct just possibly a piss poor design.

I also agree with that, however the cooling line connections between the hard lines ARE 5/16" on this truck. The hard lines are anywhere between 1/4" and 5/16" O/D, hard to tell with all the underfloor coating and paint, a 3/8" I/D would never have a fit I could live with.

If the hard line is 5/16 would you still use 3/8 hose or go with hose to match the hard line?

I won't, there is not benefit as the amount of fluids won't be any more than the 5/16" can handle IF the hard lines are in fact that size.

I would match the hose to the hard line. Using a hose that is too large will cause too much deformation and stress in the rubber when tightening down the hose clamp to get a good seal. That will lead to an earlier failure of the hose.

Agreed. So, I probably will get a 10' 5/16" hose for the garage and replace as I come across. Not sure where else that same condition is, but then I'll have some in stock.

That area is also prone to a lot of heat. It may be a good idea to pay attention during the PM checks, while under the truck.


BTW, we finally made a pretty cool "maiden voyage" trip without any major incidence yesterday. It was a 93 degree F day, the cooling kept up wonderfully, never even got out of the blue area, I was able to see the needle follow the load demand, as in rise while driving uphill, less so in the straight away or downhill.

I did have some black smoke out of the exhaust and a bad smell, almost like like burned rubber or oil, on a steep hill at one of the highest altitudes in our area (6,250' ASL) I figured I may have some fuel starvation issue, maybe a clogged injector, or the altitude difference? In your experiences, what are other reasons the 'black smoke syndrome' can appear? I've only had 150 miles with the truck, so we are getting to know each other, but until then I am paying close attention to every symptom, this one got my attention for now.

Thanks everybody.

 

[Mogman]

Now I am a little confused

When I re-attached the cooling lines after my incidence, I could have sworn the line ID was 5/16" or 1/4", just while staring up, and messing with the barb fitting, line and clamp. However, the PM calls for

HOSE,NONMETALLIC MAKE FROM HOSE,P/N 6490610019

which translates to 3/8" non-metallic line.While trying to verify before I spend the $$ on a line I can't use, I ran across this:

Interchange: Power Steering Return Hose – HMMWV Systems

They say in part:

We are of the opinion that using a 5/16″ barb with a 3/8″ hose is an error. The barb itself is 1.5875 mm smaller diameter than the hose, and that means that the hose would have to be tightened considerably just to contact the shank of the barb.

First off, very interesting site, secondly, apparently the Part Manual often calls for a 3/8" hose, even on 5/16" barbs.

For all the experts that work on this a lot, what is your opinion, experiences, thoughts?

This was very confusing to me as I have changed a ton of hoses on HMMWVs and have never put a 3/8 hose on a 5/16 hard line.
I have a M1097R1 4 speed truck on my lift and measured the hard lines to the transmission.
I have no idea where your lines came from but the hard lines on that truck (and likely every other HMMWV I have worked on) measure 0.375 OD which is exactly 3/8"

 

[Retiredwarhorses]

There in NO 5/16 hose anywhere on a hmmwv….period.
all transmission soft lines are 3/8, the only other size used is 1/4 on the fuel injection pump from the fuel filter and on the
fuel tanks return.

 

[Dieselmeister]

I did have some black smoke out of the exhaust and a bad smell, almost like like burned rubber or oil, on a steep hill at one of the highest altitudes in our area (6,250' ASL)
Thanks everybody.

Could be bio sludge. Several years ago I was in Wyoming, and filled up at a Safeway in Laramie (apparently you get what you pay for). As I was driving over a 9000+ foot back roads pass towards Colorado, the engine started sputtering, and I could barely keep it running, by keeping the pedal on the floor. The amount of smoke belching out would have made the Rolling Coal crowd jealous. This went on and off for about 20 minutes. I didn't want to stop in the middle of nowhere, and have the engine quit, so I kept going until I got to a real gas station, and topped it off with good diesel. When I opened the fuel filter, it was packed with this greenish, almost jello like glob of whatever it was. I dont know how that stuff even made it through the fuel line. Running a 6.5 NA at 9000 feet without sludge is hard enough, but after that it ran fine.

 

[Thunderbirds]

Could be bio sludge. Several years ago I was in Wyoming, and filled up at a Safeway in Laramie (apparently you get what you pay for). As I was driving over a 9000+ foot back roads pass towards Colorado, the engine started sputtering, and I could barely keep it running, by keeping the pedal on the floor. The amount of smoke belching out would have made the Rolling Coal crowd jealous. This went on and off for about 20 minutes. I didn't want to stop in the middle of nowhere, and have the engine quit, so I kept going until I got to a real gas station, and topped it off with good diesel. When I opened the fuel filter, it was packed with this greenish, almost jello like glob of whatever it was. I dont know how that stuff even made it through the fuel line. Running a 6.5 NA at 9000 feet without sludge is hard enough, but after that it ran fine.

Dang,I've heard of the slime. In this case, I just replaced the fuel filter this morning. (Yeah, I know, @Mogman already reprimanded me... ) The filter looked ok, but I am sure it was pretty clogged, as the truck runs so much better, just around the driveway. I'll be doing a test run to breakfast shorlty.

Thanks for the input, everybody!

 

[Thunderbirds]

This was very confusing to me as I have changed a ton of hoses on HMMWVs and have never put a 3/8 hose on a 5/16 hard line.
I have a M1097R1 4 speed truck on my lift and measured the hard lines to the transmission.
I have no idea where your lines came from but the hard lines on that truck (and likely every other HMMWV I have worked on) measure 0.375 OD which is exactly 3/8"

There in NO 5/16 hose anywhere on a hmmwv….period.
all transmission soft lines are 3/8, the only other size used is 1/4 on the fuel injection pump from the fuel filter and on the
fuel tanks return.

I stand corrected, I was mistaken. The line I was looking at was the fuel line, just like @Retiredwarhorses stated, and it was NOT the line I reconnected but that is what I remembered. In my feeble mind I mistook all the lines for the same size.

Here is what the mess under the truck looks like: