Overcooling??

[Airborne Ranger]

I have a 98 Ranger with a 2.5L 4banger. It takes me about 5mins to get to work so the engine sometimes doesn't get a chance to fully warm up. I usually let it sit for about 5 mins at idle before I take off to let it warm up alittle. When the engine gets warmed up, I turn on the heater and the temprature guage just immedietly goes back to "C" It's been doing this for about couple weeks now and I suspect it maybe the thermostat??? My Rangers temp guage usually runs between C and H on the guage right smack in the center where it belongs. Turn on the heater and it falls back to C real quick. Why does it do this???? 91

[LouisanaJeeper]

Your thermostat is probably stuck open.

[rusty bumper]

I agree...Try changing the thermostat.

On cars nowadays, the engine needs to run at the proper temperature so the computer sensors can fine tune the engine.

[Lost Pup]

Is the cooling system full ?

[bretfraz]

While you're changing the thermostat, install a new radiator cap. Maintaining full pressure in the cooling system is important. Plus a new cap is only a few bucks.

[Lowejackson]

Or it could be faulty wiring or sender. Before buying a new thermostat, take out the old one and test it in some gradually heated water.

[Airborne Ranger]

Originally posted by Lost Pup
Is the cooling system full ?

Lost Pup,

Yes my cooling system is full. The coolant is not green so on top of everything a good flush and refill should be in order soon. Tks to everyone for the help ,,,,,,91

[BradE]

Originally posted by bretfraz
While you're changing the thermostat, install a new radiator cap. Maintaining full pressure in the cooling system is important. Plus a new cap is only a few bucks.

Werd.

Don't get another Motorcraft thermostat, they SUCK. I had 3 die in my Explorer. Get a Stant, Robert Shaw or something of that nature. NAPA house brand is Stant, and costs about $5 for the thermostat and 25 cents for the gasket. I've been running the Stant for 15K miles so far and no problems.