About one month ago my instrument panel temperature gage began behaving strangely. It would come up to normal (50% full scale) as usual but then would rapidly drop (in 4 or 5 secs) to 25% full scale and then slowly return (1-2 min) to 50% full scale. It stays at 50% for a few minutes and then repeats the cycle.

I have successively replaced the temperature sender, the engine thermostat and the coolant temperature sensor without effect. I am not losing coolant anywhere and everything else seems normal. Then is no indication of water in the oil.

This is a '96 Ford Explorer XLT with a 4.0 liter V-6 and the tow package.

Any suggestions would be appreciated. Thanks.

Dave

 

This may sound strange, but it fixed the same problem on my 91. Temp would "pulse" above and below the normal range. Problem was a stopped up heater core (I live where it seldom gets cold enough to run the heater). The heater lines allow a small amount of coolant to bypass the thermostat on a continuing basis and this seems to allow the thermostat to regulate the engine temp more easily.
You can easily prove it by taking the hoses from the engine and "looping" them back. Bypass the heater core AND any water control valve your vehicle may have (91 did not have a water flow control valve but used a blend door to seperate the airflow). If this works, then determine the actual cause, heater core or valve bypass.

Wish i had known this when the same thing was occuring on my sons 95 Mustang. We did everything imagineable and nothing helped.

Dialtone

 

I agree with dialtone. Heating units cause all sorts of issues with the coolant level, temps etc

If you get past dialtone's advice and still have a problem it may be the guage itself. Your dash cluster has four different segments (speedo, rpm, fuel/oil and battery/temp) so you don't have to replace the full cluster just the one segment. Check a wrecker and if it is cheap and your out of ideas it may be worth it (don't forget to match the dial colour).

My first thought was temp sending unit, second was the heater system and last was the guage.

 

Thanks to you both for the suggestions. I hadn't considered the heater but it makes sense. I'll give it a look as soon as I get the opportunity. Thanks again.

 

...Welcome pinehill to Ford Truck Enthusiasts!

…..See you on the boards.

 

Buy the flush connector, and you can back flush the heater core very easily.