New Mj Owner, Gauge Cluster Swap Question

[dacanadaguy]

Hey everyone, I just picked up an '86 MJ longbed with a 2.5 4cyl (not the original motor but i'm sure it's still a renix)

 

anyways i have a quick question, the previous owner swapped out the original "idiot light" cluster for a cluster with actual gauges from a 4.0L XJ (i believe)

 

and he mentioned that the temp gauge doesn't display correctly, saying that it reads much lower than it should, he also said that it might just be a simple sensor swap, something like running the temp sensor from a 4.0L vs the sensor from the 2.5L? (it would make sense to me, i imagine the sensors would have different voltage readouts)

 

does anyone have any input on this? would switching out the sensor make it read correctly? or is there another way to rectify that? because i don't want to have the gauge reading normal temp if it's actually about to warp the head

 

thanks in advance guys.

[Eagle]

The 2.5L and the 4.0L used the same temperature sensor, so that's not the problem.

 

First question: What does your gauge actually read once the engine is fully warmed up, and what do you think it should read?

[dacanadaguy]

i haven't had it up to operating tempurature since i bought it, but i'm told it reads around 1/4 to 1/3 of the way, and if it's anything like the 4.0L i would imagine it should be reading slightly over half way at normal operating temp?

 

i'll probably give the thing a boost tomorrow and let it run for a while so i can see for myself what it reads

[Eagle]

The needle should be straight up at operating temperature. That said, the nedle in my '88 Cherokee has read low for at least five years. I probably need to refresh the grounds to get it accurate again, but I haven't had time.

 

I don't think it's wise to start trying to diagnose a problem without even knowing if there is a problem.

[Keyav8r]

Check the actual temperature by "shooting" the thermostat housing with an infrared thermometer gun. You may be able to borrow one from one of the auto parts chains that loan tools (or just drive it there and let them do it). Then you'll know if the gauge is reading near the actual temperature and will have a starting place for diagnosing the problem.

Could just be a stuck or missing thermostat.