Radiator (coolant overflow) cap is "loose?"

[Maverickxeo]

On my 2023 3.6L Overland, I had a bit of a situation today - I parked the vehicle, and coolant started POURING out from the coolant overflow tank. I initially thought that the bottom fitting or tank had cracked, but it turned out (after some investigating) that the cap was "loose."

I've noticed this before where I'd check the coolant and the cap does not take much force to actually remove it (when cold, of course) - is that normal?

It seems to be fine 99.9% of the time, but it seemed to loosen itself off - I'm wondering if either the tank or the cap are actually a little "warped" and the cap vibrates off (if that makes sense?).

Sponsored

 

[MT1]

It seems to be fine 99.9% of the time, but it seemed to loosen itself off - I'm wondering if either the tank or the cap are actually a little "warped" and the cap vibrates off (if that makes sense?).

The cap is really, really, easy to cross-thread. It feels like it is on tight, and looks it correct, but it ain't right. The only clue that it is on incorrectly to me is that there are more turns to "tight" when it is cross-threaded.

 

[g2020]

I parked the vehicle, and coolant started POURING out from the coolant overflow tank. I initially thought that the bottom fitting or tank had cracked, but it turned out (after some investigating) that the cap was "loose."

I've noticed this before where I'd check the coolant and the cap does not take much force to actually remove it (when cold, of course) - is that normal?

Update on November 7, 2025:

New Coolant Recovery Bottle (68283565AB) delivered today.

1. Includes both Coolant Recovery Bottle and Coolant Recovery Bottle Cap (68442532AA)
2. The cap turns smoothly, and the lock after the final twist is secure
3. The cap makes up 60% of the price of the bottle + cap (68283565AB)
4. Although the capacity of the bottle, to a level just below the MAX line, is one quart (I measured it), the amount of coolant that can be removed, with a siphon, is slightly less than one quart because the bottle is chambered

Original reply:

Try replacing the Coolant Recovery Bottle Cap (68442532AA). If it does not stay fastened / locked in place, you may need to replace the Coolant Recovery Bottle (68283565AB) as well. Please confirm these part numbers for your vehicle before buying.

When refilling the coolant recovery bottle, use the same 50/50 prediluted coolant that is already installed. The part number, for MOPAR 50/50 Prediluted Antifreeze / Coolant (OAT, MS-12106), is 68163849AC.

In my case, the cap required several turns before the final twist securely locked the cap in place. That is, until I had a coolant flush & fill done at a shop. They replaced the correct cap with a Wrangler cap (part number written on the cap) by mistake, and the threads on the coolant recovery bottle were slightly deformed. I replaced the Wrangler cap with a new correct cap because I didn't want to deal with the !@#$% at the shop. The new cap doesn't lock like it used to, but it is secure enough that I haven't had any overflow issues. I bought a coolant recovery bottle to keep in reserve in case the pressure seal fails.

The tolerance between the new bottle & cap might not be as tight as it used to be. When I bought the new cap at a dealership in August, I asked one of the salesmen if I could try the cap on a brand new Gladiator on the lot. The final "lock" that usually occurs, on the final twist, was not as secure. I don't know the reason for this, but the slightly looser cap and/or bottle might have been reengineered to prevent cross-threading.

 

[Maverickxeo]

The cap is really, really, easy to cross-thread. It feels like it is on tight, and looks it correct, but it ain't right. The only clue that it is on incorrectly to me is that there are more turns to "tight" when it is cross-threaded.

I double checked - and it, nor the neck, are cross threaded. They do thread together well, but they just don't feel "tight" when it's threaded all the way. There's a little "pop" or "click" when it is almost tight (maybe 1/8 of turn before it is on all the way) if that makes sense, though.

 

[MT1]

I double checked - and it, nor the neck, are cross threaded. They do thread together well, but they just don't feel "tight" when it's threaded all the way. There's a little "pop" or "click" when it is almost tight (maybe 1/8 of turn before it is on all the way) if that makes sense, though.

That sounds very much like the situation I had. "Cross threaded" might not the correct wording. Maybe the cause is something with how the cap is placed on the bottle before tightening, that results in it not "locking" as described by @g2020.

The bad/loose seal happened the second time I used the cap, and needed 4-5 half turns before it felt tight. Coolant only leaked/boiled out around 230F, in slow traffic. The good seal happened something like 2-3 half turns.

Sponsored