First gen Ford explorer temperature gauge fluctuations

[RADIOACTIVE_TOOL_SHED___]

Ok.. so I just bought a 1993 Ford explorer xlt the temperature gauge goes up too normal after a about 2 miles of driving but then it quickly comes back down to cold but after a few more miles it gets up to almost on the red side of the gauge and comes back down to normal temperature but then quickly rises back up.. and I never see any signs that it would be overheating.. what would be causing this? Is it safe to drive?

 

[Arne13]

My first guess would be the thermostat. time to stick a new one in there. Arne.

 

[RADIOACTIVE_TOOL_SHED___]

My first guess would be the thermostat. time to stick a new one in there. Arne.

Yea I've ordered a brand new one I'm gonna put that in this weekend along with a new radiator all new hoses and water pump hopefully that fixes it

 

[JustinGibson]

Yea I've ordered a brand new one I'm gonna put that in this weekend along with a new radiator all new hoses and water pump hopefully that fixes it

That is a good place to start. While you have the cooling system apart I would also change the radiator cap, heater core, and the heater control valve if you have one. The heater core is really easy to change and if it is clogged it can cause issues like this. Make sure the small flimsy wire that is running to your coolant temp sensor to the right of your upper radiator hose on the intake isn't damaged and grounding out on anything. Are you losing any coolant?

 

[RADIOACTIVE_TOOL_SHED___]

That is a good place to start. While you have the cooling system apart I would also change the radiator cap, heater core, and the heater control valve if you have one. The heater core is really easy to change and if it is clogged it can cause issues like this. Make sure the small flimsy wire that is running to your coolant temp sensor to the right of your upper radiator hose on the intake isn't damaged and grounding out on anything. Are you losing any coolant?

Yes I am the radiator has a leak in it but it never gets low

 

[BKennedy]

I had the temp sensor go bad and it was doing exactly what you are reporting.

 

[JustinGibson]

Yes I am the radiator has a leak in it but it never gets low

That is probably your issue even if it isn't losing a lot of coolant you are lowering the pressure therefore the boiling point of the coolant and the leak is likely introducing air into the system that creates bubbles that will cause the fluctuation in temperatures you are seeing. The thermostat will open late and temperature sensor will read low when there is an air bubble around it. I chased this exact issue for a month until my radiator leak got bad and I blew a head gasket.

 

[RADIOACTIVE_TOOL_SHED___]

That is probably your issue even if it isn't losing a lot of coolant you are lowering the pressure therefore the boiling point of the coolant and the leak is likely introducing air into the system that creates bubbles that will cause the fluctuation in temperatures you are seeing. The thermostat will open late and temperature sensor will read low when there is an air bubble around it. I chased this exact issue for a month until my radiator leak got bad and I blew a head gasket.

Thank you! I definitely Won't be driving her until this weekend sure wouldn't wanna cause damage

 

[BKennedy]

I have always had high temp issues with my 1994. Its modified, but the engine is basically stock. I replaced my entire cooling system several years ago and it made it a little better. I replaced my radiator a year ago with a 3 core all-aluminum Champion unit I bought off Ebay. I closed up the gap on the bottom between the fan shroud and radiator, and resealed the gaps between the condenser and radiator. That did the trick. Temps stay between the N and R in NORMAL.

I also rerouted the transmission lines so they don't run through the radiator because I don't need a pre-heater for the trans fluid, it doesn't get that cold here. Have two trans coolers with a electric fan for the big cooler when crawling. Having the transmission and engine cooling systems completely separate seem to help as well.