Temp Indicator Spikes and Engine Revs

[dacdog]

Have a strange issue. 2007 Explorer V6, 120K miles, While driving the engine suddenly starts Revving and the temp Indicator Spikes to max with the temp warning light displaying. I slow to the side of the road, everything starts sounding normal again the temp goes back to center of gauge, instantly, not slowly like it was really hot. Drive off and all is good for rest of trip. Checked coolant and all is good. My first thought was fan clutch. Any suggestions?

 

[Flag Gibby]

I would say, change the temperature sending unit first before you do anything else since it is a $12 part and a 10 minute job to change it. If the unit is acting up then it can give an erratic temperature reading causing the vehicle to modify engine parameters based on that reading which is not correct. Also, if you have never changed the coolant on the vehicle a flush and fill wouldn't hurt with that many miles on it.

 

[dacdog]

Thanks Flag,
I have ordered the thermostat housing and the sending unit. Decided to replace all as I noticed a leak around the housing. My wife indicated she has had the issue a few days before telling me! I added coolant, drove it and it happened to me. The coolant had just been topped off, hence my thought it was OK. Thermostat probably hadn't opened since topping off. Once opened, enough coolant got into the engine and radiator to cool things down. Had to add more coolant. Haven't had the problem since. The leak around the housing doesn't leave fluid on the ground, apparently it evaporates on the hot engine before making it to the bottom!

 

[ZO6_Vette]

It is the Thermostat mine did this just be fore it failed, run don't walk as it could cost u a head gasket job.

 

[Flag Gibby]

Dacdog, Your new information makes much more sense now. You were seeing an air pocket pass through the housing and across the sensor making it spike like that so there may be nothing wrong with the temperature sending unit. Since you are going to replace the housing take the time to replace the thermostat + o-ring too (not much more of an expense for those items).

Z06 Vette - the motorcraft thermostats fail open so I am not sure what you are getting at.

 

[ZO6_Vette]

Dacdog, Your new information makes much more sense now. You were seeing an air pocket pass through the housing and across the sensor making it spike like that so there may be nothing wrong with the temperature sending unit. Since you are going to replace the housing take the time to replace the thermostat + o-ring too (not much more of an expense for those items).

Z06 Vette - the motorcraft thermostats fail open so I am not sure what you are getting at.

Except for the one in my 06 that stuck closed.

 

[dacdog]

Follow up,
Replaced the thermostat housing assembly, very simple task. Leak is gone and all is good! just glad she didn't cook the head gasket. Thanks for the inputs! Used the Dorman aftermarket assembly, Amazon $60, includes thermostat in completely assembled housing. We'll see if it lasts another 120K.