Weird Cooling Problem

[drwambo]

Hi,
I'v got a 96 EB 4.0 and have recently had some strange cooling issues. Not sure what to replace.

Started in cold weather, truck would get HOT, for a second or two then I guess the thermostat opened and it dropped to normal. Heat started working, so I assumed thermostat (I have not replaced it yet, as it doesn't happen all the time.)

When driving for about 1 hour on the highway recently,
The temp gauge started going up and down - never really hot, but up there. Then the Idler pulley blew apart, and the serpentine belt went. Limped the last 3 miles home.

Replaced pulley and belt. However, now when driving, the temp gauge will climb to about half way up then drop back down to what I think of as "normal" for my truck. Happens constantly.


So, my question is, wht do I replace?
Heat works, truck doesn't run hot, but temp goes up and down.

Not leaking coolant, but I do get a whiff of it now and then.

Waterpump?
Thermostat?
Temp sensor?
Explorer???

Thanks,

Douglas

 

[TPLYNCH]

Start w/ the radiator cap. Cheapest fix for the cycling temp gauge.

 

[Arizona EX]

I had the same thing happen to me. After several radiator caps (some of them leaking, dont use the ones with the lever type locks on top) my problem was solved. Later it started up again and I realized something was up when i smelled coolant inside. My heater core had a minute leak causing the same problem. I have had nothing but problems with radiator caps and thermostats. I have had 2 sticking thermostats, one causing my intake manifold gasket to blow. Good luck

 

[mrboyle]

Have you checked the coolant level?

 

[93exploder]

I think it is either the waterpump or the rad cap.

I recently had this happening, radiator had a leak, so I replaced that, used the same cap because i had just recently replaced and flushed. But the temp guage still likes to dance around on me. I am hoping its just the radiator cap.

 

[drwambo]

Coolant level is fine. I'm off to get a radiator cap today. We'll see if that works - as well as "burping" the system as some archive threads suggest. At first I thought it might be the water pump, but after driving around town for about 1/2 hour at 65 degrees outside it never got warmer than halfway up the gauge.

I'll try the above and see what happens.