ECT Drops 50° When Lifting Throttle

f22beaver

f22beaver

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Joined
Sep 24, 2022
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35
Location
Indianapolis
2008 JKU w/ 3.8

Had a broken ECT sensor. It then wicked coolant into the connector. So I changed the connector and replaced with an OEM ect sensor.

Now when I let off the throttle this is what my ECT reports.

I know I need to burp it just to make sure I don't have air, but have you guys seen this before?

If it was a thermostat failed open wouldn't it just be cold all the time?

Screenshot_20240930-190447.png
 
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You would eventually get a code for a failed or failing t-stat. It's not unheard of for a t-stat to act up like this. I'd start with burping the system to rule out air causing this issue.
 
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I'm very familiar with an open t-stat. Easiest issue on a Jeep to rule out.

An open t-stat will throw a code on JScan that says something like the engine is not operating up to the minimum temperature. Best way to confirm an open t-stat is to cold-start the Jeep and wrap your hand around the upper radiator hose. If you feel coolant immediately flowing on start-up, it's an open t-stat. A properly operating t-stat will prevent coolant from flowing out of the rad via the top hose until the engine reaches around 200 degrees.

The other thing you may notice with an open t-stat is the temp gauge sitting just below halfway, and it doesn't fluctuate. When this happened to me, I replaced the t-stat, didn't completely burp the air and took it out for a short drive. The temp gauge was all over the place, didn't need the JScan to tell me that! I got home, jacked it up a little higher and properly burped it.
 
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Burping didn't do anything. In fact.....

My P2181 - Cooling System Performance is back along with this reported temp. And just to be obvious, it's not 44 degrees here. 70 air temp and the 90 degrees the coolant started at feels right because I drove it two hours ago. The code sets immediately when it drops to 44 degrees.

I checked grounds and cleaned a few but they were fine, still came back.

Can someone tell me where the ECT plug wires go? Which connector and pins? I can't help but wonder if I still have coolant in a wire.

I'm all ears for any ideas.
Screenshot_20241001-194755.png
 
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