Hey all,

Having similar problems past 9,000 miles -> crazy temp guage (way up, then back down) - Sometimes I get no heat at idle just after engine warms up in the morning . I have been through system flush, new heater and upper/lower radiator hoses, water pump, pressure test for leaks, and I am now on my 3rd thermostat.

The current therm is a Stant (either 190 or 195), and fixed this problem 3,000 miles ago -> although I could smell coolant I never could isolate the source.

Now its back; while driving temp guage randomly reads hot, then I turn on the heat full blast (seems to work when driving) and it drops it back after a couple of minutes. No load at all on the truck. The coolant level is always normal.

I keep up with the posts, and awhile back someone had mentioned it took SEVERAL thermostats before fixing his problem.

If it really is the therm, any high quality brand names or temp ratings anyone could suggest - or should I look elsewhere for the problem? Since the heat will sometimes not work I am assuming that that a faulty temp guage would be a result of the problem and not cause it. Its sounding to me like the therm gets stuck closed, but can 2, maybe, 3 in a row be bad??

Not sure if fan clutch is involved - seems to turn Ok, slight drag, no wobble, when engine cold.

Thanks for anything you can come up with.

-rlp

 

Go with an OEM Motorcraft thermostat. They last longer, and they
maintain a more constant temp than the 3rd party thermostats
do.......

More thermostat info:

https://www.ford-trucks.com/forums/s...hreadid=166630

 

Dude your problem is exactly the same thing im going thru. Except i've gone through 6 tstats since last november. 5 flushes, new hoses all around, new waterpump in february. Mechanic is pointing towards headgasket. But not the typical problems like white smoke, coolant in oil. Its doing the opposite and blowing air into the coolant causing bubbles and air pockets to form. I've written about this numerous times on other sites.

what year is your truck, what motor?

 

97flairside - check my sig for vehicle details.
If you (or I) are having air pocket problems, what do you think about Water Wetter. I've never tried it, but I read it will reduce the tendancy towards bubbles... and can't hurt (except for possible wasting a few bucks).

I'm thinking to give the Motorcraft brand therm a try ....

 

All my tstats have been motorcraft except for 1 that was a stant tstat for a 4.6 stang. I've thought about air bubbles and so has my mechanic. but what would cause all the bubbles to form? I've dropped my truck off at my friends speed shop. There said it has to be just the tstat also or the fan clutch. They are testing the tsta. they are drilling some small holes around the tstat to keep some coolant flowing. There theory is that the tstat is not opening at all when its cold out causing the back up of coolant then the eventual overheat. But they are worried that all the overheating it has had in the last year might have messed up the headgasket. But this is a small solution to the problem if it work. If not then the fan clutch. Which is the only piece of the cooling system that has not been replaced.

 

97flairside .. sounds like you're even more frustrated than I am.

I have read in other threads about the fan clutch - the only way I am aware to test it is the way the Haines manual describes -should turn with slight reisistance on cold engine and have no wobble.
But others have changed it out and found it fixed cooling problems.

Yo have to remove the shroud to get at the clutch - anyone know how many screws have to come out? I can see 2 at the top - wondering if there are more along sides or at bottom.

 

It should have tabs that hold the bottom in place. Remove the top screws and with the fan shaft unscrewed from the water pump pulley, pull the shroud up.

97 - Have they done a leak down test or a compression test of your motor?

 

Honestly I have no idea it there has been a leak down test. Compression test I'll say definitely not. My mechanic hated to do my tune up. Doubt he'd do that.

I had my friends speed shop work on it. They said it was either the tstat again or the fan clutch. Said the tstat just doesn't open up when its cold and I get on it. So they drilled some holes in it to allow flow. But now there is to much flow so the truck runs cool. Im getting it fixed on thursday. Will experiment. But i've spun the fan when the truck is cold and it kinda has some resistance. If you use your finger to pull up on the fan to spin it should it move at all? I mean I got it to go around about 6-8" around. I'll check to see if it wobbles tomorrow before work.

I dont get why nobody makes replacement tstats for the 4.6 f150. Ford is the only one out there. Stant only makes it for the stang. Picked me up some and will drill a small check hole like the stock one.

 

I've seen some that are so hard to turn cold that you will actually be turning the motor or slipping the pulley on the belt. The fact that it allows you to move it 6-8" has me questioning it. If you move it that far, are you just sliding past the belt that easily?

 

I never was able to tell if the pully moved or not. Is it supposed to ? I'll go and check.

 

Ok the truck wasn't exactly cold but its was pretty cool. I spun the fan but the nut/pully didn't move just the fan itself. Is that normal?

 

If you grunted while doing it, yes. I would expect a good 15 lbs of resistance or more. If it was like 3-5 lbs of resistance then I would look at the fan clutch. It should be very reluctant to move.

 

i just replaced my clutch fan. ($140 ford oem) mine spun almost totally free wheel when i knew the engine was hot. my experience with fords is a good clutch fan will cycle. when its "on" you will hear ALOT of air moving & a noticable difference in the sound of the engine.when its "off" it will spin free wheel and there wont be any air noise.they cycle alot normally when at temp. ive always been able to hear this easily with the vehicle running. my new clutch fan was pretty hard to turn by hand. just my 2 cents steve

1990 f350 460 4x4

 

Well said ssap108. Often times, you can hear it more than you can feel it.

 

well i cetainly didn't grunt when I tried to spin it. I didn't even have to exert any force. Used the tip of my index finger.

You know i haven't heard that loud fan/air noise at early in the am when i goto work. Usually you can hear the fan pulling air when the truck is brick cold. I haven't heard that at all. Im going to tell my friends shop to order/replace the fan clutch. I think we might have nailed it.......hopefully. Im also going to replace the tstat 1 more time.