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tempature issues

low'n'go xj

low'n'go xj

NAXJA Forum User
Location
Oregon City, OR
Temp keeps going up and down while driving when giving more gas or down shifting. I have taken it in and they said tranny was ok. 4.5 inch lift, adjustable lower arms, 1 inch t case drop, 6 degree shim on axle, with a bastard pack. Some say thermostat, but before I replace it I wanted to get jeepers input first.
 
Always post basics first. Year, engine,etc. Is it full of anti-freeze? Air pockets could cause this. Also, does it run any different when the temp changes? If it seems to run a little different, such as running more rich when temp drops, it could be a bad engine coolant temp sensor.
 
94 high output 4.0, aw4 w/ np231. Doesn't run different than before. Could be low on coolant, overflow os low. Only happens when accelerate or build up speed, once I'm cruising temp goes back down.
 
You mention it could be low on coolant, so gotta resolve that and keep up with that at all times.

How old is your thermostat? If coolant is not low, I'd start there. I buy my stats directly from Jeep and also like the Stant SuperStat. Go 195 degree.
 
How old is the radiator cap? More than 3 years old it could be suspect although you would expect it to happen all of the time.

As others have posted.... I would check the thermostat.
When was the last time your radiator was flushed.

 
Before you invest too much time in testing/replacing cooling system components, renew all of your grounds with particular attention to the head-to-firewall ground. If you still have the POS braided strap replace it with 4 or 2 gauge cable, strip to bare metal, treat with anti-corrosive agent, and make the connection TIGHT.

When you see the gauge start climbing turn on your headlights and see if that makes a difference.
 
Why don't we just check the coolant ! I mean thats the most simple of things and if thats it, well great . then on to the thermostat and cap ! none of these should be considered a waste of money if they are over 3 years old ! ALWAYS start with the simple things.
 
I would put it park, get a DMM, back probe the CTS at the thermostat housing (IIRC that is where your is located), then rev the piss out of the engine to see if the reading changes.

Then switch to test the temp sensor at the rear of the head near the MAP sensor, and do the same test for it. If neither budge, it is not the cooling system or the sensors, it is a wiring or dash issue. If the one at the rear of head wanders all over the place it may be an air bubble in the head, or a bad sensor.
 
Instead of playing with it and replacing good parts, try the tests I listed in post #10.

How fast is the temp gauge number changing? If it happens in seconds, it is an electrical issue or bad sensor, if it takes 1-2 minutes to rise or fall it is not electrical. Time scale of the change is important, but missing data on your post! Are any other gauge values climbing and falling at the same time, like the voltage gauge?
 
Last edited:
low'n'go xj said:
Takes a few minutes to change, also changed temp sensor. Is the dmm tool your talking about just a voltameter? I don't notice any change in other gauges.
Click to expand...

DMM= digital multi meter, volts, ohms...

OK, so it is not electrical. A bad radiator cap can open, release too much coolant, and cause a rapid temp drop, and later higher temp peak, then repeat the cycle. Have you checked for a loose belt?

You could have a head gasket leak too!
 
3/4 play?

Most likely is rad cap, thermostat, head gasket leak, or maybe wrong pump rotation?
 
joe_peters said:
Before you invest too much time in testing/replacing cooling system components, renew all of your grounds with particular attention to the head-to-firewall ground. If you still have the POS braided strap replace it with 4 or 2 gauge cable, strip to bare metal, treat with anti-corrosive agent, and make the connection TIGHT.

When you see the gauge start climbing turn on your headlights and see if that makes a difference.
Click to expand...

Did you try this? Seen a lot of "temperature" problems that were caused by POOR grounds screwing with the gauges.
 
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