Coolant Loss Explained?

[mpboxer]

I was out this past weekend in the dirt pushing the truck, but I didn’t think that hard. Ambient temperature was mid 70s, in 4hi through some single track desert trail. Coolant temps hovered between 200F and 220F. Don’t remember trans and oil temps but nothing concerning. When we got to our destination I smelled coolant and realized it was leaking from the bottom of the reservoir near the fitting. The coolant was also bubbling in the reservoir (). No check engine lights or warnings.

Returning back to camp I babied it and kept engine about 190F. No more coolant loss. I drove it home the next morning 300 miles keeping it under 200F on the highway and side streets with no coolant loss or bubbling.

I bought a new elbow fitting (actually entire hose assembly because Jeep doesn’t just sell the fitting) and new reservoir w/cap (these are on back order and very hard to get). I disassembled the coolant bottle from the fitting to find the bottle was fine and the fitting wasn’t cracked.

Here’s the interesting part. There’s a weep hole near the threaded portion of the bottle where cap screws in and goes down to the bottom of the bottle. This would make it appear as if the fitting was cracked, when in reality, if coolant was making it past the cap it would leak from under the bottle. Needless to say, I just installed a new cap and reinstalled the old bottle on the old elbow fitting because I didn’t want to introduce more variables and other parts looked fine. Not sure if this logic makes sense but if the cap is not holding the correct pressure (21psi) I would get the boiling over in the reservoir sooner. I haven’t had a chance to run it up to 220F and test my theory or if the cap fixed it yet, but I am curious what others think?

Also, could this little weep hole be a reason for coolant loss over a long period of time, evaporation? Also, could this be why some think the fitting is cracked underneath the bottle when actually it isn’t?

Thanks,
Mike

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[westrollamo]

Thanks for sharing! I'm seeing some loss as well in my 2023 and I've been keeping an eye on it. Temps have stayed steady in the 190-220 range depending on ambient temps and loads so I'm not terrified yet. But any explanation besides it getting eaten by the engine would be good.

 

[Charles 236]

It would be good to pressure test the cap. I have seen several caps fail to hold pressure in the past year on these systems.

 

[Minty JL]

I have had mine to the dealer for this same reason and they said they could not find anything wrong LOL.

Well thank you to the OP, I will check this later today. My runs in the normal temp range and no over heating what so ever

 

[ShadowsPapa]

I've seen more than one person post about a small leak from that bottom fitting area, and it leaks down onto hot stuff, leading to the smell.

It would be good to pressure test the cap. I have seen several caps fail to hold pressure in the past year on these systems.

As with any other vehicle, such as my nephew's 69 Javelin - a weak cap can lead to excessive "fluid expansion", and in really bad cases, excessive heating as coolant at the hot spots could boil. Caps can cause, or resolve, a few issues.

I run mine right at the tank seam and it stays there - in fact, I've only added just a bit of coolant one time since I bought the thing July 2022. That way if things do get hot, it's not forcing out the reservoir, and there's enough in there to handle small leaks (I keep watch on fluids as a matter of habit anyway - used to "fill the gas tank, add oil and check all fluids" days when I was a mechanic in the 70s. Thankfully those days are done!)

 

[BourbonRunner]

Hmmm. By the power of deduction I believe your Jeep's motor was made by BMW.

 

[Minty JL]

Hmmm. By the power of deduction I believe your Jeep's motor was made by BMW.

Yeah BMWs stupid plastic expansion tanks, plastic pipes and waterpumps

 

[BourbonRunner]

Yeah BMWs stupid plastic expansion tanks, plastic pipes and waterpumps

***laughs in 75,000 mile increments***

 

[Hootbro]

Interesting. Would explain reports of people losing coolant but system pressure checks fine.

 

[Rusty PW]

Now, I'm going to have to feel around that area to find that hole. Just wondering if I could jam a piece of hose up in that hole to redirect the overflow.

 

[Charles 236]

Now, I'm going to have to feel around that area to find that hole. Just wondering if I could jam a piece of hose up in that hole to redirect the overflow.

Redirecting the flow would work, but you will need to make an opening in the metal bracket that supports the coolant reservoir. But if there is coolant coming out of the overflow opening, there is a bigger problem. At the very least the pressure cap isn't holding pressure (not as rare as it should be, I have tested a fair number of caps that failed well below the 21 PSI rating), at worst, a failure internal to the engine causing pressure to overload the pressure cap. Just my experience.

 

[Minty JL]

I just looked at my invoice from the dealer. They pressure tested and reported no leak found.

 

[mpboxer]

Now, I'm going to have to feel around that area to find that hole. Just wondering if I could jam a piece of hose up in that hole to redirect the overflow.

There ya go. It should be towards the driver side.

 

[Freems]

Yep, it’s been driving me nuts…

 

[ShadowsPapa]

Redirecting the flow would work, but you will need to make an opening in the metal bracket that supports the coolant reservoir. But if there is coolant coming out of the overflow opening, there is a bigger problem. At the very least the pressure cap isn't holding pressure (not as rare as it should be, I have tested a fair number of caps that failed well below the 21 PSI rating), at worst, a failure internal to the engine causing pressure to overload the pressure cap. Just my experience.

Exactly - fix the reason for the overflow. Don't just ignore it and band-aid it.

Caps do go bad. It's not all that uncommon in older types of systems, either - it just gets ignored more because of different "overflow tanks". It's easier to not realize the cap is bad.

My Stant tester won't do these caps..........unfortunately.

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