Temp Guage Fluctuation - 98 Explorer

You'll have to pardon me if I get a bit "like that"... It's ben one of "those days" in a week full of "those days" that is actually been a month full of "those weeks"... all with no let up in sight....

I am going to assume that coolant level and condition has been checked....I can't recall if the 98 has a degas bottle system or a closed rad with reservoir system.... If it is the latter, the fluid level in the rad will need to be checked. I don't know where you live (like climate ever mattered, right?), so coolant condition and strength is important.

Your engine temp guage fluctuations are an effect of whatever the concern may be.... Faulty senders don't, as a rule, "cycle". Bad is bad and that is that.

Low coolant level IS cyclic... depending on where the air gets pushed. Bad thermostats can be (but not always) cyclic.

Word to the wise... whenever a warning device is telling us something is bad.... believe the warming device first. To assume that the warning device is bad and to continue to operate the vehicle only sets us up to spend more money than we needed to.

Jim,

Thanks so much for the input. Checked radiator coolant level (open system) and it is full. Coolant resivoir tank is low, right at fill line so I do need to add more coolant. The weather here in East Coast has been in 20's, no too cold (I lived in MN for 4 yrs so this nearly spring weather). At this point the better part of valor may be to take it in, I do not work on cars much,. I thought possibly the symptom I described was a sensor issue but as you said when sensors fail they usually fail not intermittent or cyclic.

Thanks again for the input.

VJC

One thing I did forget to mention was the thermostat... for some reason, the

4.0 (especially the cam in block or OHV design) seems to be hard on thermostats. Relatively easy for most DIYers. A 10mm swivel socket helps ease the pain and, since the bolts are small, a little care must be taken to avoid twisting them off.

While a normally functioning thermostat will "seek" a midpoint, faulty thermostats can fluctuate giving the guage a fluctuation.

HTH

I agree with Jim. My '96 OHV was notorious for needing a new thermostat every couple of years. After using the OEMs for years, I finally replaced it with a Stant "SuperStat". According to Stant, "...SuperStats are manufactured with a patented v-notch, non-linear valve design which reduces cycling, brings your car to the proper operating temperature more quickly,improves engine efficiency and fuel economy and prolongs engine life." I can attest that it does keep a more even temperature than the OEMs ever did (temp gauge usually goes to it's normal range and doesn't move much after that), but can't really confirm that it warms up any faster or not. Have had this one in going on 4 years now, and it still seems to be working fine, which is longer than any of my previous ones lasted.

Steve

I tried to buy one when I recently replaced my thermostat, but couldn't find one. I even tried a local outlet that advertised them on their national website. I finally gave up and put in what I was offered. It works great, so I'm happy.

-Paul