Weird cooling issue on 09

Boldlygoing

Boldlygoing

New Member
Joined
Sep 5, 2019
Messages
6
Location
Atlanta
My wife's JKU has a new issue that's got me scratching my head a bit...

At low engine load ~1000 rpm or so, the engine temps climb fairly quickly.

At heavier load, the temps settle back to normal.

But what's got me confused is that when the temps climb, the air conditioning stops blowing cold. Every single time, one symptom follows the other. And every time, as soon as the rev's go up, the engine temp drops, and the AC blows cold.

I can reproduce this in the driveway.

To the best of my knowledge, the systems aren't connected mechanically except by the serpentine belt. I could absolutely be wrong about that.

I've checked coolant levels, and replaced the thermostat before I noticed the direct relationship between the two symptoms.

So, any ideas? This one's got me stumped.

'09 JKU w/3.8l
 
I should add that in the last couple weeks, I swapped the cats and doing that, was poking around a lot in the engine bay. It's entirely possible I knocked a sensor, or something else, but nothing is obvious to my eye.
 
could be something going on with the serpentine belt. Did you mess with the tensioner at all? I would check around there as well as something may have messed up. Belt on backwards kinda thing.
 
MacGuyver said:
could be something going on with the serpentine belt. Did you mess with the tensioner at all? I would check around there as well as something may have messed up. Belt on backwards kinda thing.
Click to expand...
I didn't take the belt off for the cat swap. No need. Tensioner feels good, and no noise.

I'm reading elsewhere that the AC will cut off in the event of an overheat condition. If that's true, it solves one mystery, and only leaves why it's over heating in the first place.
 
  • Like
Reactions: mrjp and Anybodyhome
Boldlygoing said:
I didn't take the belt off for the cat swap. No need. Tensioner feels good, and no noise.

I'm reading elsewhere that the AC will cut off in the event of an overheat condition. If that's true, it solves one mystery, and only leaves why it's over heating in the first place.
Click to expand...
Sounds nearly identical to the situation I had when I changed my t-stat and had some air left in the system. Do what Black mentioned above or how I solved my issue:

Once cool, remove the radiator cap and add coolant slowly (not to the reservoir- directly into the radiator). Once it settles, it'll start forcing the air back out (burping) at the cap. Continue until the coolant level is at the cap.
 
  • Like
Reactions: mrjp and BLACKJKU
Top Bottom