Strange Coolant Leak??

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Jwrigh12

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Hi All!

So my family and I went out of town for a funeral this weekend, and my 2014 1500 (5.7 Hemi, 8sp transmission, 160k miles) was sittng for about 4 days.

Came home and checked underneath like I usually do, to find decent size puddle around the area of the oil drain plug. I say there only for area reference.. the plug itself was not wet.

I believeit's coolant. Check the oil cap and dipstick... no contaminaction detected. Coolant resivour is full and no sign of contamination there.

Upon further inspection, there seems to be coolant drips on some bolts connected to the front of what I believe is the transmission case?

Any ideas would be awesome as I'm a bit stuck.
 

crash68

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On the side of the 8spd transmission is the Thermal Management Unit, it uses engine coolant to both heat and cool the transmission fluid. The design of the the TMU was changed as some had issues with the o-rings leaking.
 

crash68

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If your not seeing trans fluid leaking also, it's probably just a coolant leak. The transmission fluid is on the thin side and there a whole procedure on how to check the level as there is no dipstick.
I'd take a good look at the hoses and connections to see if you can determine where it's leaking from.
 
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Jwrigh12

Jwrigh12

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As far as I can tell, there's no trans fluid visible...but I also cant see the source yet.

Ive read the fill procedure on the transmission a few times (plans down the road to do a drain and fill and possibly install the larger pan). Would it be worth cracking the fill plug loose, and sucking a small amount of fluid out to check the condition, or would that be asking for problems?
 
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Jwrigh12

Jwrigh12

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Got the chance to get under the truck this morning an took a couple pics. All this is fresh. Last night I sprayed it all down with brake clean, cleaned off the dirt, grime an old fluid. All that appears to be new leakage.

Any ideas where to start? @crash68
 

crash68

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Any ideas where to start?
The circle on the picture are where the coolant lines attach to the TMUScreenshot_20230125_160724.jpg
Although your leak looks like it maybe on the back of the engine. Not sure if the Hemi has coolant passages on the intake that could leak, as it maybe coming from the top of the motor
 
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Jwrigh12

Jwrigh12

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Hmmm. I'll have to have a look back there. Will also check the TMU and lines going to it.

Is it just me, or is this TMU just not a well coveed topic? Can't seem to find much of any info on it...
 

BuschLatte420

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On the side of the 8spd transmission is the Thermal Management Unit, it uses engine coolant to both heat and cool the transmission fluid. The design of the the TMU was changed as some had issues with the o-rings leaking.
Never knew my truck had this, or any for that matter. Damn 2022 is different vs 2001 haha
 

RodRamCar

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sounds like a one-off issue. I'd take it to a great local shop and not stress about it any longer. May save you some headache.
 

Daniel Ortiz

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Hmmm. I'll have to have a look back there. Will also check the TMU and lines going to it.

Is it just me, or is this TMU just not a well coveed topic? Can't seem to find much of any info on it...

@Jwrigh12 , you can say that again. The only reason any of us know anything about it is because some enterprising people (@caulk04 , @Wild one , @crazykid1994 , and probably some others) on this Forum have taken theirs apart and poked at it enough to mostly learn how it works. That's why I love this forum. It's full of inquisitive people willing to take a little risk to learn about their truck, and pass on their first-hand knowledge.

That Thermal Management Unit (TMU) has a thermostat in it that can overheat your transmission if it sticks. You can't buy it by itself, you have to buy a whole new TMU (ask me how I know) and extract it from within. Luckily @caulk04 fabricated a simple replacement plug that replaces that thermostat and blocks off the heated fluid. But if you want to stay stock, whole new TMU. I wonder how many people lost their 8-speed because of this little-known part.
 
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Jwrigh12

Jwrigh12

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@Daniel Ortiz yeah, I've been following that thread! I plan on making getting that bypass in the future. My trans is usually running at about 180-190. Pretty normal from what I hear... but not ideal.

Also... this project just took a turn. Followed @crash68 advice and looked higher on the block. There does indeed seem to be something leaking from the backside.

I don't have any symptoms of a cracked block/head gasket yet (no overheating, oil in the coolant or coolant in the oil, pronounced white smoke, etc).

Will most likely rent a block tester from the auto parts store asap.

Is it possibe for a head gasket to blow out the back like that and only leak coolant externally?

What other next steps would you recommend? Unfortunately, due to a recent job loss...taking it in somewhere is out of the question. As much help as y'all can give me would be incredible.
 

crash68

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Is it just me, or is this TMU just not a well coveed topic? Can't seem to find much of any info on it...
There's not much info on it because it usually just works and for the most part doesn't fail very often. One of the best thing Ram did was use the 8HP line of transmissions.
The thermal bypass built into the TMU fails on rare occasion, you'll know it has if the transmission temperature spikes well above the coolant temperature. Most of the people who want the plug for the thermal bypass usually are just paranoid about the transmission fluid temperature flirting with 200°.
 

Daniel Ortiz

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@Jwrigh12 , did you ever confirm with any certainty what the leaking fluid was? It seems to be not oil just from the picture (but only you can tell), and both transmission fluid and coolant have distinctive smells (especially if you heat them up). Determining what the fluid is is probably your next step.

@crash68 , my transmission bent 200 F over the couch and... you know. And it was being nice compared to some of the other guys it's happened to. But yeah, I know what you're saying.
 
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Jwrigh12

Jwrigh12

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@Daniel Ortiz Yeah, Im 99.9 percent sure its coolant...at least when it gets down to the area that I showed in the pictures (between the oil pan and transmission pan). The coolant I have in my truck is orange (Penzone I believe...) and the fluid that drips (again, a fairly slow drip. Came out this morning and everything was dry again) is distinctly orange. Doesnt seem to be discolored by oil in any way.
I just saw the wet top of the block this afternoon, and couldnt get up there from the ground to touch/see/smell/taste it :)
Im thinking about getting some coolant dye to confirm the exact location and that it is in fact coming from the cooling system.
 

CanuckRam1313

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Not that this is at all related, but I had a small coolant leak last year on my 19' HEMI.
Did a cooling system pressure test and the system was tight.
However, tested the original rad cap, and bam, the cap was the culprit causing the minor leak.
Replaced it with a new OEM rad cap and all has been good ever since.
 

Daniel Ortiz

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@indept that reminded me, I've been wanting to replace the coolant hoses attached to my thermostat housing since I replaced it last month. I noticed my housing had a small 90-degree offshoot from the main housing, and saw 6829763(7)AA on it.

20230106_180950.jpg20230107_105018.jpg

Turns out that Mopar part is the coolant transfer lines (rubber hose ends and metal pipe runs in between) that deliver and returns coolant to the TMU.

@Jwrigh12 I know it's only for 2017-2022 5.7L Rams, but I wonder if your 2014 has something similar. If so, could one of those end hoses (the ones on the transmission end) be leaking for some reason? If your 2014 is set up similarly, two of those rubber hoses join the metal pipes right over your transmission. You can see the pictures of the whole setup at the Mopar part link.
 
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