best sealant hose barb against transmission fluid

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1,680
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CT
2003 jeep grand cherokee, 4.0L, on the transmission oil cooler at the radiator, there's a 3/8" rubber hose connecting the cooler metal lines to the metal lines that run from the transmission. I cut one of these off last year to do a transmission fluid change. It recently started seeping at this connection point so i replaced the hose and used permatex aviation on the barb then put the hose on but it is still seeping. I reused the oem clamps, the spring loaded kind where you squeeze the tabs with pliers and it expands so you can remove it. I'm wondering if these aren't providing enough clamping force so I'll be replacing them with good hose clamps. I know when I initially removed the hose, I had to cut it off with a razor blade because it was practically glued on there with whatever sealant chrysler used. So, does anyone know what sealant chrysler may have used? And what sealant should I use? Any application advice? Any advice on the type of hose I use? thanks.
 
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21,640
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Apple Valley, California
Those spring clamps are a 1 time use only. That and I bet that the replacement hose has a smaller O.D. Just put on some regular worm clamps. No sealant needed or used.
 
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25,172
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Upstate NY
while you are there splice a Magnefine filter into the return line. While I have reused those OEM clamps, if they leak, replace them. I have a Magnefine in my 2001 Jeep Cherokee 4 cyl.
 
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2,097
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kansastan
 Originally Posted By: 1 FMF
2003 jeep grand cherokee, 4.0L, on the transmission oil cooler at the radiator, there's a 3/8" rubber hose connecting the cooler metal lines to the metal lines that run from the transmission. I cut one of these off last year to do a transmission fluid change. It recently started seeping at this connection point so i replaced the hose and used permatex aviation on the barb then put the hose on but it is still seeping. I reused the oem clamps, the spring loaded kind where you squeeze the tabs with pliers and it expands so you can remove it. I'm wondering if these aren't providing enough clamping force so I'll be replacing them with good hose clamps. I know when I initially removed the hose, I had to cut it off with a razor blade because it was practically glued on there with whatever sealant chrysler used. So, does anyone know what sealant chrysler may have used? And what sealant should I use? Any application advice? Any advice on the type of hose I use? thanks.
I'll second what Chris and Tom said. You shouldn't use ANY sealant on a hose barb. Not only is it unnecessary- it's more likely to cause problems than prevent them. The rubber hose is plenty flexible to seal if properly clamped onto a hose barb in good condition. Like Chris said- the replacement hose might have a slightly smaler OD than the original hose... and you'd do well to replace the clamps. While I generally like OEM spring clamps, I've found it difficult to find good quality aftermarket ones- and the OD of the hose has to be EXACTLY the right size for the clamp to work properly. If in doubt... just get screw clamps. They're cheap and adequate. Like me.
 
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588
Location
Chicago, IL
Check the barb for burrs and or corrosion. I've casting flaws on cheap aftermarket parts (like the prestone flush kits). It just hit it with a file and it clears it right up. For your application, I'd look and see if the barbs haven't gotten rounded off or gunked up. (Or, make sure you are using the right rubber tubing for the application- it's possible the tubing isn't quite right for trans fluid and because the tubing is stretched out at the barb, it lets some weep out.)
 
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35,975
Location
ME
You can also get hose good and hot, maybe not dunked in boiling water in your example but at least steamy hot from a tea kettle for example. Then it's soft and pliable and really conforms to the ridges of the barbs.
 
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19,479
Location
Chicago Area
Spring clamps are nice. An even pressure from the whole circumference. But since you have a problem, use 2 screw clamps 180 deg apart. It will not leak.
 

1 FMF

Thread starter
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1,680
Location
CT
went to a better store on the weekend and got a length of actual transmission oil cooler hose. It is 3/8 hose but the O.D. is larger than typical 3/8" fuel hose which [censored] sold me on the second go around. It was probably the combination of the oem spring clamps and the [censored] hose I bought the first two times, although the hose the first time was trans. oil cooler hose from parts america. picked up some permatex trans rtv and gave it a try, didn't coat the whole barb but only about 1/2" wide at the point where the hose reaches to when fully pushed onto the barb. let the rtv set an hour, then installed the hose with correctly sized hose clamps, and finally no leaks. http://www.permatex.com/products/Automot...RTV_Sealant.htm
 
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