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Transmission Gauge Leaking, Solution??

2K views 30 replies 4 participants last post by  JBTJ 
#1 ·
2002 TJ 4.0L
32RH Transmission
Sunpro Mechanical Gauge
B&M Transmission Cooler

Hello all, last week I went on a wheeling trip to Silver Lake Sand Dunes in Michigan. Drove my Jeep from Detroit to Silver Lake, roughly a 4 hour drive, then on the dunes, to back home. The Jeep handled really well, and besides this leak that I am having, I didn't manage to break anything else.

Anyways, I had installed a Mechanical Trans Temp Gauge in the Jeep to monitor the temp while wheeling. I had cut the trans cooler lines, where the fluid goes back into the trans after it has been cooled so that way I got the actual temp inside the transmission. When I cut the line, I used a T-Fitting, and some other fittings as well and connected the sending unit into the T Fitting. The T Fitting also of course came with compression fittings that were used to clamp down on the ends of the lines. Finally, I had used Red Threadlocker to seal any other possible gaps.

From the time I installed the gauge, throughout the whole wheeling trip, it held up very well. But the temp must have gotten to hot or something on the way home on the freeway, and caused some kind of leak. I began to smell burning trans fluid on the way home. When I parked it, I crawled under the jeep and saw the Fittings at the cooler lines were leaking, down onto the burning hot exhaust pipe, causing the smell.

The leak is getting progressively worse, it is leaking all over the exhaust, driveshaft, axle, and everything else.

What would be a good way to go about fixing this? Is there some way I can seal this whole T Fitting Unit better so that there are no leaks? And if it comes down to it and I have to pull off the T Fitting, can the compression fittings be reused or will I need new ones?

Thank You!
 

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#3 ·
I'm assuming that's compression fittings.. normally should be fine but compression fittings can be a little temperamental at times.

I did a similar thing, but I used fuel hose and brass barb fittings from Home Depot. I slipped it over the steel tube from the trans and used a hose clamp. Still fine after 6 years.

BTW I wonder why you would put the probe on the return line, which is by far the coolest point on the whole circuit. I put mine on the hot side coming out of the torque converter (before any cooling) to monitor the highest temperature, though a lot of installs put the sensor on the pan which on mine is a bout 30 -40 deg cooler (according to an infrared probe).

An interesting effect of the hot side reading is you can see right away when torque conditions are causing a heat rise (such as a sustained steep grade), well before the actual trans heats up that much.
 
#4 ·
jay-h said:
I'm assuming that's compression fittings.. normally should be fine but compression fittings can be a little temperamental at times.

I did a similar thing, but I used fuel hose and brass barb fittings from Home Depot. I slipped it over the steel tube from the trans and used a hose clamp. Still fine after 6 years.

BTW I wonder why you would put the probe on the return line, which is by far the coolest point on the whole circuit. I put mine on the hot side coming out of the torque converter (before any cooling) to monitor the highest temperature, though a lot of installs put the sensor on the pan which on mine is a bout 30 -40 deg cooler (according to an infrared probe).

An interesting effect of the hot side reading is you can see right away when torque conditions are causing a heat rise (such as a sustained steep grade), well before the actual trans heats up that much.
Interesting, and I put it in the input cause I wanted to monitor the temperature that was going into the Trans. If it was hot (like above 190) then I would know the temp inside the of the Trans. I know the temp going out is hotter but that will be cooled anyway
 
#5 ·
I've been thinking more about your leak problem.
If they are indeed compression fittings, that may be part of the problem (can't tell for sure from the pictures) . Compression fittings don't like flexing especially on hard (steel) tube (as opposed to brass) . Consider flare fittings or even fuel hose.
 
#6 ·
If what’s leaking is at your compression fittings, tighten tighter. If not, use a turn or 2 of Teflon tape. Worked for me. I also have a sensor on both output and input lines so I can monitor the 2. I'm more concerned with output temps though.
 
#8 ·
Scary..I used teflon tape on all of the threads and those ended up turning out fine. However it is still leaking from exactly at the sensor sending unit which is impossible to fix. Im just going to pull the sensor and patch things up.

Is there a fitting that just seals off entry? As you can see in the pics I have the T fitting, where the point of the T is, is where the sender is. I want to plug the sender hole completely.
 
#9 ·
Is it leaking from the pipe thread or the straight thread? Properly applied teflon should seal the pipe thread.

Not sure what you mean by plug the sender hole? side question, but is the sender a (tapered) pipe thread or a straight thread?
 
#10 ·
It is leaking from that exact spot where the red arrow is pointing. There are no threads at that part, just the sender unit can slide up and down, kinda hard to describe unless you seen in person. I simply want to remove the unit now and plug the hole, I was just curious if you can get a close ended fitting to plug it.
 

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#11 ·
If you're simply removing the sender unit, use a pipe plug in the T (with teflon), removing the unneeded fittings.

From the description 'slide up and down' it sounds like the sender unit is supposed to be clamping against a surface that's not in your setup. Without seeing a picture of it, it's hard to visualize.
 
#16 ·
JBTJ said:
With my experience with compression fittings, used on AC systems. All you need to do is tighten it up. Put 2 wrenches on it and go for it. It won't take that much more umph to seal it up.
The lines are fine, it's the sender unit itself
 
#19 ·
Well I ended up plugging the hole, ended up stopping the leak. Added some tranny fluid to it but I added a bit more than I should have, what's a good way to get some out without dropping the pan. There's enough extra in there that it probably isn't safe to keep in there.

Just one problem after another :D
 
#23 ·
JBTJ said:
I wish I could understand your problem. I have that exact same setup on mine. No leaks. Though I did have to make sure the compression fittings were really tight and I used 1 wrap of Teflon tape around the threads on the sending unit.
It's hard to explain lol basically the sending unit is attached to that thin metal hose line with the fluid in it that warms up. When I go to turn the sending unit threads into the T fitting, it is snug (and wrapped in Teflon). The problem is, the thin metal line can be pushed up or down in the unit itself. When this happens, it creates an opening causing a leak.
 
#24 ·
It's hard to explain lol basically the sending unit is attached to that thin metal hose line with the fluid in it that warms up. When I go to turn the sending unit threads into the T fitting, it is snug (and wrapped in Teflon). The problem is, the thin metal line can be pushed up or down in the unit itself. When this happens, it creates an opening causing a leak.
And that line is a compression fitting? On mine the sending unit screws into the T fitting and the electrical connection is made at the end. Nothing moves. You got the B&M kit?
 
#26 ·
JBTJ said:
And that line is a compression fitting? On mine the sending unit screws into the T fitting and the electrical connection is made at the end. Nothing moves. You got the B&M kit?
No it is not, simply screws in. I have a sunpro mechanical gauge. I had a B&M, but it only lasted a year ended up being defective. I just have bad luck with gauges lol
 
#29 ·
JBTJ said:
Was this a kit for transmissions or was it something you pieced together?
It is a oil temperature gauge, same concept though. It wasn't specifically labeled Trans temp but regardless it didnt leak for over a month. Didnt start until after my wheeling trip
 
#31 ·
Okay, you have one of those. Hope it doesn't start to leak at the gauge, then you will have ATF all over the inside of your JEEP. :thumbdown: Per the instructions, it's a NPT thread design. So it would appear that there is not enough sealant on the threads where the capillary tubing goes into the "T" fitting. Personally, I would not use this design. I know you had bad luck with B&M one time. But that is what I use and have been using for years and years and not once had a problem. I would buy the B&M kit that was designed for this application. That way you won't have to worry about a possible leak inside your cab.
 
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