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Cooling system issues on 2000 Ford Ranger 4.0

I just bought a 2000 Ranger 4.0, and it runs great. There is “no check engine” light and the mpg are reasonable. My temperature gauge never gets into the normal range, its always low. I believe this is related to the water pump kicking on and off constantly. There is plenty of heat coming from the vents. Do I have a bad thermostat or coolant temperature sensor? Any and all help appreciated.

I don’t know about the water pump idea, but this sounds to me like a thermostat that is stuck partly open. If not that, then my second guess would be the coolant temp sensor or the guage is reading low.

the water pump runs constantly it does not kick on and off. since your heat gets hot to the temp you think the heater should be at then i would lean more towards a bad temp sensor. at least temp sensor and thermostat are cheap to replace but i would do the sensor first.

I think you are getting confused between the water pump and the AC compressor. The AC cuts on and off, but the water pump is always spinning when the motor is running.

Replace your thermostat with the correct one for your truck. That should work. If the temp gauge still reads low but you are getting plenty of heat all maybe good.

The sending unit for temperature might be bad, or the gauge itself could be off calibration. But, really no worries as long as you are operating at the correct temp. There are easy to use point and read temp sensors so you can tell if your are operating in correct temp range.

Probably the thermostat. If the idle isn’t more than 800 or so, it may just be the gauge being incorrect.

Here are some signs of a bad thermostat:
Takes forever to reach operating temperature
Never reaches operating temperature because it’s stuck open (or broken)
Overheating, because it never opens
Fails to regulate temperature

Like GeorgeSanJose, I believe your thermostat is stuck open.
Thermostats do get stuck open with age, and your truck’s old enough.

If your coolant temperature never gets to the normal operating range, your fuel system may stay in open loop, which will cause a fuel economy penalty.

Replace the radiator cap while you’re at it.

Do the easy stuff first: Replace the radiator cap.

That reguires no tools, no technical knowledge, no risk, and won’t get your hands dirty. But wait till the engine is cold.

There’s a potential bonus value: if changing the radiator cap replacement puts the temp gauge in the proper place, ie, higher than it has been, you KNOW that your thermostat and coolant temp sensor are good, so you save all that money, and time. Do one at a time so that you know what solved your problem.

I think its the gauge. These things are not calibrated and I really haven’t seen one with a so called “normal” range. They have cold at one end and a red zone for hot at the other, but where normal is can vary greatly from one vehicle to another, even the same model. In my experience 25-40% of scale seems to be the most common range for normal, even 50-60% on some vehicles, but most seem to be somewhat below 50%.

Keith, isn’t blaming the gauge in effect the same thing as shooting the messenger?

I agree that some of those gauges aren’t super accurate, but they’re generally accurate enough to let the operator know if the engine’s not getting to operating temperature or if it’s running too hot.
Replacing the gauge, or even testing the gauge, isn’t that easy for a DIYer. Not to mention that the gauge is almost definitely part of the instrument cluster, and possibly not available separately.

Don’t you think it’s easier and faster to replace the thermostat and the radiator cap as a first step?

Before you do anything, determine first whether you really have cooling system problem or not.Since your complaint does not involve overheating narrow down suspected causes. The fact that you said your gauge don’t move but you feel heat at the vent indicates to me that your heating system is working. First check out your gauge and/or sensor. Disconnect the terminal at the sensor. Turn on your ignition. The gauge needle should go max. Then short out the gauge wire to ground.Then Turn on your ignition. The gauge should read minimum. If you don’t either, the gauge is bad. To check out the stat, run your engine from cold. Feel the upper radiator hose. It will be cool to touch first , then after a few minutes, you should start to feel the radiator getting warmer and on to hot. Lastly check your fan clutch to make sure it runs properly. The fan clutch has a centrifugal switch and also a temperature sensor that helps control the temperature. If the fan clutch is defective, the impeller will continue to turn with the pump no matter what the system temperature is.

db4690, why just guess. How many parts would you have him replace even if there isn’t a problem. We have no way of knowing exactly where the needle is on the gauge unless maperrault tells us. The position of the needle might just be that vehicles normal, but not be considered normal by the OP.

If the OP’s previous vehicle’s normal range was at 50% of gauge scale and this one is only going to 30%, he might think that that is low when its not. If you are getting good heat, then the engine is likely getting up to temp. Its been my experience that when a thermostat starts to open too soon, the heater is the first thing to go.

Keith, I’m not arguing with you, but I’d hardly call a cap and a thermostat shotgunning it.
In my opinion, those items could probably stand to be replaced at this time, since most non-mechanics don’t have their cars properly maintained.
And since the guy’s only had the truck for a little while, we can assume the previous history is unknown (unless he got all the maintenance records, which realistically never happens).

Well lets ask the OP.

maperrault exactly where on the scale does the needle go to when the engine is warmed up?