I have a '97 F150. A few months ago, while driving I noticed my temp gauge immediately jumped to hot, not a gradual movement. I pulled over and waited for a few minutes and restarted without any problem (temp gauge went back to normal). The check engine light came on. As a result, thought it may be the thermostat going bad, so I replaced it.

Couple days ago I again noticed the temp gauge jumped to hot again while driving which triggered the Check Engine light. The truck wasn't overheating. After sitted for a moment, I restated and temp guage went back to normal again. Now it is occuring more often -- if I am driving and the temp guage jumps to hot, I put the truck in neutral, cut the engine and restart, and the guage goes back to normal.... Could it be the tempreature sensor gone bad? Any ideas what it may be??

Is the sensor easy to replace or should I have a mechanic do it -- assuming the problem is a temp sensor?

jb120

 

Hi and welcome to the forum

What size engine do you have in your truck?
The temperature gauge sender would be a good place to start.

 

It's a 5.4L. Also, I stopped by AutoZone for a reading of the Check Engine code and it responded with a P1299 code.

Any clues what it could be?

jb120

 

P1299
engine cooling system concerns
low coolant level
base engine concerns

Probably just your temp sensor failing, you can use a scan tool that has realtime readings and find out for sure.

 

thanks for the feedback!!! I thought it may be the sensor failing. Appreciate the help!

jb120

 

Hi jb120,

Did you find the source of your problem? I have a 97 5.4 liter doing the same thing. The gauge will jump to extreme hot or extreme cold, when the temp gauge jumps to cold the heater will blow cold air, when hot it will pump out hot air. This is very intermittent and usually runs normal.

Thanks

 

heptarchone is it safe to assume your coolant is full?
If it is you might have a thermostat problem. It's pretty easy to replace.

 

hi i have a98 f150 .thats been getting hot then gets cold .changed thermostats 3. times now put air vac on system took out all air .put new cap on .still goes cold then gauge goes to hot?put presure tester on system it not building up presure.so could it be a head gasket problem.

 

Geowmit,

Did you notice if the coolent level was lower than normal during any of the thermostat changes? Also, is it the guage you're using to determine that it's getting hot and cold? Could be similar to the above problem, a temp sensor gone bad.

Don't know what's going on with the pressure but a blown head gasket will show up as one or more of the following: 1) water in the oil (oil will be brown and cloudy) 2) water going into a cyclinder (usually a good size leak will produce white clouds from the exhaust) 3)water running down the block where the head meets (usually this is visible and produces steam from under the hood). In any case the coolent level drops.

Any chance the thermostat(s) were put in backwards? Pretty tough on cars today but possible.

 

Grsyhands.thanks for the reply,no water in oil,none in cyl, no leaks from heads .truck get to normal temp then goes cold.then overheats

 

From your original description, sounds like the sensor is going bad. Can't think of anything else if you say it's not really overheating.

 

Hey all.
When you replace the SENDER for the guage, the SENSOR is right next to the sender, so make sure you get the right one. DON'T over tighten the new sender or sensor either. Notice one plug will be gray, the other will be black. The SENSOR, not the SENDER is gray. The SENDER has a black plug.

Dave P.