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Mystery leak. Coolant or trans?

Fuel Fire Desire

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Found a couple new drips under the very front of my JL 3.6. Small drips, found weeks apart. Fluid is red and very low viscosity. When compared to fresh coolant (pictured, dripped some out of a bottle next to the Jeeps drip) the color is slightly different, and they mix together well. Not like oil mixing with water. The color more matches what’s in the coolant surge tank.

Leak is coming from the drivers side of the back edge of the radiator. It’s mostly dry, but there’s red fluid on it. Pictured from above and half way down. This is definitely where the leak is dripping from.

The Jeep has needed about a 1/2 gallon of coolant (added to the surge tank) over the past year, but no running leaks found. No coolant in the oil, or steam in exhaust.

Does the transmission fluid have any path through the main radiator (integrated trans cooler)? Or is this definitely coolant?

In either case, more investigating is required, but I’m thinking it’s radiator time.

My worst fear is coolant communicating with the transmission, but since a half gallon has been needed, no trans issues have popped up, and the drips are clear red, I’m thinking not.





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Fuel Fire Desire

Fuel Fire Desire

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mwilk012

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Seems pretty straightforward. You need a radiator.

Your transmission fluid is green.

The radiator has no transmission fluid cooler built in. It is separate.
 
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Fuel Fire Desire

Fuel Fire Desire

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Perfect. My worst case scenario was to have coolant and trans fluid mix within an integrated cooler. If the rad core is coolant only, that’s an easy fix.
 

mwilk012

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Perfect. My worst case scenario was to have coolant and trans fluid mix within an integrated cooler. If the rad core is coolant only, that’s an easy fix.
The transmission fluid heater attached directly to the transmission is where that would happen.
 

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Fuel Fire Desire

Fuel Fire Desire

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It’s unfortunate that this is a common problem from what I’ve briefly read. Radiator leak on the drivers side where the plastic meets the aluminum. That said, it is a relief to finally know where this 1/2 gallon of coolant has gone over the past year/ year and a half. I can easily do a radiator. Head gasket is no bueno, and transmission communication is even worse.

I am right at the end of my power train warranty, but I prefer to do everything myself, and I really don’t want another plastic radiator in there. It is nice to know an all aluminum drop in replacement exists. It’s just disappointing it costs double what a Mopar replacement costs.
 

Beachcomber72

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I am right at the end of my power train warranty, but I prefer to do everything myself, and I really don’t want another plastic radiator in there. It is nice to know an all aluminum drop in replacement exists. It’s just disappointing it costs double what a Mopar replacement costs.
Not saying you don’t have the skills or even proper tools but if you have the Etorque 3.6 I’d highly advise letting dealership address the problem. The coolant system is a pain in the but and you’d also need a vacuum bleeder kit to properly get all the micro air pockets out of the system. That in itself is a huge pain to sort out. Just my .02 cents on the matter.
 
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Fuel Fire Desire

Fuel Fire Desire

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No etorque. I have an early 2018, it’s just a gas engine.

I’m equipped, comfortable and competent to do the physical part R&R, but have not done one with this modern design. I’m still beginning the research on the project, but was initially expecting to be able to bleed off of the thermostat housing, and through the in-line surge tank. Still much reading to do.


If it does wind up being an absolute cluster, I do have family that operates a large/ modern body shop with proper specialty tools/ carts I’d be happy to give business to, (if he doesn’t just show me how to use the machine and loan me a stall after hours).


At the rate this thing is leaking, it’s no big hurry. I first noticed the surge tank was low about a year ago, so it’s probably been happening for closer to 18 months, and only a 1/2 gallon consumed in that time with no drips/ visible leaks until this week. As long as the plastic decides not to rip itself a nice crack (which I’ve had happen before on plastic thermostat housings) I hopefully have enough time to source proper procedure and not just blast the parts cannon.
 

Beachcomber72

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An ALLDATA account would be your best friend in this situation. Proper specs, r/r data, fluid capacities and vacuum procedures. As you will still need the vacuum bleed:pump kit I believe.
 

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I just did mine two weeks ago, same engine (no e-torque) and its was a straightforward drain, unplug, remove, reinstall, refill through expansion tank, no special tools needed, the air bubbles will eliminate themselves through the recirculation of the fluid by the pump in your expansion tank.

I would suggest you remove the headlights, I did it on mine and it makes it way easier to access the bolts. you also don't have to remove the trans cooler or other smaller coolers, you just unbolt them and then you can lift/push one aside (the top one) and leave the bigger front one there just moving the side hoses a bit to let your rad pass-by as you remove it. its a fairly easy job, I took my time and it took me about 3 hours I would say if I remember correctly.

Mine's been keeping its coolant level since then,I had a similar issue where mine was leaking on passenger side but same area, the joints where the aluminium clips to the plastic endcap.
 

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I also replaced my OEM radiator (wasn't leaking) as a proactive action since I had 86,000+ miles on my JLUR in 39 months. I have numerous friends whose OEM radiators leak on the drivers side. I installed a cold case and it was easy and straight forward (it was my first radiator removal/install ever). I also replaced the three main hoses, the water pump and the thermostat since I was in there. I recently towed a 2700 lb off-road trailer to Moab for Jeep Jamboree and had to climb 5000' in elevation and then bounce between 5000' and 7000' a number of times. The engine temp never went over 226Ëš on 6-7% grades and when it did, it would go back to 217Ëš and cycle. Running without the trailer I see ~10Ëš lower coolant temps than the OEM radiator registered. The cold case definitely runs cooler than the OEM radiator when off-roading as well.

My oil temps were in the 250Ëš-260Ëš range, but I found that they cycle to 244Ëš and then go back. I believe my oil temps are higher due to using the aluminum Dorman oil cooler housing, which seems to have a higher heat soak than the plastic OEM unit (ran up to 244Ëš max). I am running Amsoil Signature Series 0W-20 so I am not worried about the oil temps since they have been tested for 200 hours at 320Ëš without issue. One interesting tidbit is when the oil temp hits 257Ëš the pressure goes from 32 psi to 75 psi, which must coincide with the fan running to cool the coolant, which cools the oil cooler. If running at 2900 rpm or higher with the 3.6 V6, the oil pressure is also ~75 psi and runs the fan on high as well.
 

_olllllllo_

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An ALLDATA account would be your best friend in this situation. Proper specs, r/r data, fluid capacities and vacuum procedures. As you will still need the vacuum bleed:pump kit I believe.
The JL V6 thermostat does not have a bleed screw and filling through the reservoir tank and running will bleed the system. I have drained it twice and simply run the engine to get most of the air out and then drive through the neighborhood and let it cool and top the coolant off. It appears from all accounts they have improved the system to eliminate air pockets like the JK dealt with.
 

mwilk012

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No etorque. I have an early 2018, it’s just a gas engine.

I’m equipped, comfortable and competent to do the physical part R&R, but have not done one with this modern design. I’m still beginning the research on the project, but was initially expecting to be able to bleed off of the thermostat housing, and through the in-line surge tank. Still much reading to do.


If it does wind up being an absolute cluster, I do have family that operates a large/ modern body shop with proper specialty tools/ carts I’d be happy to give business to, (if he doesn’t just show me how to use the machine and loan me a stall after hours).


At the rate this thing is leaking, it’s no big hurry. I first noticed the surge tank was low about a year ago, so it’s probably been happening for closer to 18 months, and only a 1/2 gallon consumed in that time with no drips/ visible leaks until this week. As long as the plastic decides not to rip itself a nice crack (which I’ve had happen before on plastic thermostat housings) I hopefully have enough time to source proper procedure and not just blast the parts cannon.
It is extremely simple and takes less than 2 hours start to finish.

there is a thread here with every step posted in it.
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