There were 2 things I was going to replace on my 04 F150 when I realised maybe only one is the culprit. The truck rarely reaches standard operating temperature, I assumed the thermostat was stuck open.
But I have a second problem, I am sure fan clutch is shot because most of the time it roars like a semi tractor off the line. Could my engine not be warming up because the fan is contantly pulling too much air? (due to the clutch sticking) To determine if my fan clutch is indeed shot, I am wondering how freely the fan is supposed to spin by hand when the truck is off, if I give it a push should it keep spinning, or will there be more resistance than that? I can move mine, but it will definitely not keep freewheeling.

 

It's more likely the thermostat - if the thermostat is closed, the coolant is recycling within the engine and it doesn't matter how cold the radiator is.

 

If the thermostat was closed wouldnt the engine run hot?

 

sounds like the heromstat is stuck open did you try taking the radiator cap off and seeing if you can see coolant flowing constantly? also the clutch fan could be the problem too, i have seen a stuck fan clutch cause low operating temp. it should have little resistance you should be able to spin it and for it to rotate 1/2- 1 turn before stopping, if you really have to push it, its not operating correctly.

 

If it's STUCK closed, of course. The function of a thermostat is to open and close to keep the coolant temperature as close to the rating as it can. When it's closed, the coolant recirculates in the block, when it opens, it circulates through the radiator.

 

Even when a thermostat is fully closed, even stuck closed, some fluid still circulates through the radiator...rough guess about 10%. When it's really cold or you have a really efficient system, this can very well be enough circulation to keep the engine at a perfectly normal temp with the thermo closed. Does happen. I have a F250 radiator in my truck and this time of the year especially on the freeway, I see engine temps hanging around 185*, and that's with a 195* thermo.

How are you verifying the water is not reaching a normal temp? Do you have an aftermarket gauge or is the stock gauge not reaching a position that you normally see?

So most likely, if it's not reaching temp for sure, then the thermo is stuck open. Even if the fan were cooling constantly, it would not fully overpower a normal working thermo and keep the engine too cool.

The fan should turn by hand when cold relatively easy, but you shouldn't be able to swing it around. I've never had one that would make a whole bother revolution on it's own.

 

The stock guage is not reaching the half way point, (not even close) and the heater is only blowing warm air when the engine finally does warm up (which is taking longer than normal.)

As for the fan, I think the clutch must be shot then, because, yes I can move it but it seems to have more resistance than what it should, according to the results I have found. It stops as soon as I let go after giving it a push.
It must be a combination of both the thermostat being stuck open and the fan clutch then.

 

I'm still going thermostat. I don't think you're getting what most of us have said...even if the fan is bad, if the thermostat was working normally it WOULD NOT run that cool.

Before I ran out and bought a new fan, go compare yours to a new one or someone with an old one to make some comparisons.

You've also got to keep in mind, that fan still works when it's cold. Even though it doesn't bite as much air when cold, that suckers pretty efficient and still draws quite a bit of air. I personally think your fan is fine.

 

The 192's work best IMO. Stay away from the 195's . I tried them all and even replaced the clutch fan. Same problem. Went with a 192, -problem gone.

BUT - I did this with a 98 model.

 

192 / 195...what ever. I was referring to what ever stock is. Since you introduced it though, I don't possibly see what difference three degrees can make. I'd bet those things aren't even contstructed / calbrated to a three degree tolerance.

 

Clutch Fans very rarely go out. When they do, it's because they loose their seal. Signs of bearing fluid leakage is a sign.

 

No logical reason why a 195 would not work right where a 192 would, but stranger things have happened. Brew got a bit upset about what Galaxy said but he thought it over and fixed it.

 

Alright.

 

Thought it over

 

The fan clutch in my 2002 5.4 liter was bad...evidenced by roaring fan at all RPM levels. Temperature never seemed to run any cooler however...which makes sense since during 90% of driving, even with a stuck clutch, the fan wouldn't be turning that fast.

If your truck is roaring though...best to replace the clutch. Easy job for the most part. I side with the others and say do thermostat too.