My temp is goin up and down

[BigBOB]

I have a 99 XLT 4x4 and was wondering if any one has experienced the temp to rise and fall while driving. When I start it in the morn, the temp climbs like usual then reaches almost to the red and goes back to the middle of the gauge where it normally stays when it's warmed up. A few minutes later it may or may not repeat the cycle. The radiator and overflow tank are both full, it's got plenty of oil, and it's not leaking any fluids. The only thing I can think of is the thermostat. Any help would be greatly appreciated!

 

[Okrazie1]

Welcome to the site!

Your thought about the thermostat is probably right. The factory thermostat is not known for its longevity (I had to replace mine at about 22,000 miles). Replace it with an aftermarket t-stat like a Stant and you should be good to go.

 

[BigBOB]

Thanks, any idea on the best temperature? I've got the Haynes manual, but I know that sometimes what they recommend isn't always what's best.

 

[Okrazie1]

You'll want to stick with the stock temperature, which is 195 degrees.

 

[BigBOB]

Thanks a lot I really appreciate it!

 

[P51DTUG]

My '92 does the same thing... changed the t-stat and it sill does this..? Could this be the temp sensor? Just about ready to let it go....BOOM! My patience with this issue is wearing very thin...

Jim

 

[Opera House]

If it is in backwards

It will also do that. pellet goes to engine. Any of your other gauges act funny? Did the new thermostat have a burp hole? I buy the cheap ones and just drill a 1/16" hole in them. Any bubbles from the overflow tank? Maybe you just got a bad one.

 

[liquid217]

checked the fan clutch? i had a 93' aerostar that was doing the same thing. (I replaced the thermostat also). After all was said and done, it was the fan clutch.

 

[Blee1099]

Just do preventive maintance and it should go away. Every two years on all my vehicles, I like to flush the system, changing hoses, change thermostat, cap, etc.. About $30 of parts and fluids is alot better than a cracked block.