if anyone could help me i would so appriciate it. my dad bought me a 1995 f150 4wd 4.9L . for the first 3 years i had the truck i rarely drove because i worked or was on call 24/7. the first problem i noticed with over heating was imediatly when i would have the air conditioning on the truck would heat up. so i just never ran the AC and had no problem. here lately though i have been having some problems as i have had to drive the truck more. when it first started to over heat i figured it was the thermostate so i replaced it about a week later started overheating agian so i put on a new water pump ran fine for a week or 2 and started overheating agian and i noticed my fan was not turning so i put on a new fan clutch. worked fine for a couple days now i have a new problem. my truck is heating up then the temp will drop real low then heat up and drop sometimes it will run fine other times. when it heats up it is making the coolant back up and out of the overflow. making me have to refill the radiator and at $15 per gallon an anti freeze its starting to get expensive. i was hearing a sound from the glove box area which i believe is the heat coil sounded almost like a fan spining agianst something was told there was air so i put a T in with a cap so i could get the air out seem to help with the sound but truck still heats up then goes down. every day is different it seems. sometimes i can just get in and go not have a single problem other days it overheatsand the watter all backs out of the radiator not a little but all takes almost 2 gallons to refill. can anyone please help me figure this out. it seems like the thermostate all over agian to me but it hasnt been but 2 months since i replaced it. thinking about taking the thermostate out completely but i would like heat

 

Watch your coolant level closely, the truck probably has a leak and you are finding air pockets due to the low fluid level, hence temp goes up. Have the system pressure tested to locate the leak. Your problem is not the t-stat unless you installed it backwards.

If the truck overheats only at high speeds, then the radiator is plugged up.

 

it over heats at any speed. for an example yesterday i put antifreeze in but it kept heating up and going down antifreeze then came out of the overflow. tonight i put another gallon of anti freeze in and my truck heated up a little then temp droped but ran just about fine except for small moves in temp.

 

i have looked for leakes never see any the only time i c any kind of a leak is when collant comes out of the overflow and its boiling hot. both hoses comming from heat coil are hot also so i just dont know il see if mabey i can get a presure test tomorrow who knows mabey that will tell me something im just at a loss

 

I have been having similar problems with my 94 off and on for the better part of a year. Do you have bubbles in your radiator when your engine is running? I had several leaks that where detected with a pressure test. Then i noticed a very strong smell of fuel and an oily sheen in my coolant, blown head gasket. Spent 100+$ on thermagasket from rxauto, it did not help!!!!! The efi 5.0 ecm manages a lot of drivability according to engine temperature. I ran mine w/o tstat and fuel milage was very crappy , bout 11 mpg . I live in se texas and it is not usual to have freezing temps for more than a few hours, so i only run water for now. I just put in a barrs product and am no longer loosing water and temp is steady for 4 days now. I still have little or no heat from heater but atleast it is NOT ovr heating for now. I will flush and fill this wknd and see if it holds on. I love this truck and it is a very clean ride w only 118000 miles I'm 2nd owner. I'm shopping a head job or engine swap at this point. The barrs is only a temporary fix but it gets me to work and back for now. Could b worse. Always check those tstats in the kitchen b4u install them. 2 of 4 i have purchased over the past few years did not open all the way, it could save u thousands in repairs. I think you r going to find the tstat to be the least of your problems if it is any.

 

I would also check your fan clutch to see how hard or easy it turns.

 

Could also be a bad Thermostat.

 

Thermostat, blown head gasket, or air pockets.

I'll repeat these tips for clarification.

Thermostat can be tested in the kitchen. Put t-stat in a sauce pan with water. Heat up and see if it opens. Best to test alongside a new one to compare operation. You can always return new one if you end up not needing it, since it was never installed.

The head gasket's condition can be determined by taking off the cap and watching if there are bubbles coming out as the engine is running. Do this with a cool engine.

As far as air pockets, you'll need to bleed the system and get all the bubbles out. Bubbles can stop your coolant flow, if they're trapped somewhere. Not sure how your system is set up. Can anyone can chime in on this? Some systems are as easy as filling up with engine off, then squeezing the hoses. Some require the engine to run to push the bubbles out. Others require the engine to heat up and build pressure to get all the bubble out.

Also, for better cooling, check the condition of your radiator. Maybe it's time for a new one. Might be okay for the winter, but come summer...

 

Thermostat, blown head gasket, or air pockets.

I'll repeat these tips for clarification.

Thermostat can be tested in the kitchen. Put t-stat in a sauce pan with water. Heat up and see if it opens. Best to test alongside a new one to compare operation. You can always return new one if you end up not needing it, since it was never installed.

If you go to the trouble of removing the thermostat, just replace it.

The head gasket's condition can be determined by taking off the cap and watching if there are bubbles coming out as the engine is running. Do this with a cool engine.

As far as air pockets, you'll need to bleed the system and get all the bubbles out. Bubbles can stop your coolant flow, if they're trapped somewhere. Not sure how your system is set up. Can anyone can chime in on this? Some systems are as easy as filling up with engine off, then squeezing the hoses. Some require the engine to run to push the bubbles out. Others require the engine to heat up and build pressure to get all the bubble out.

Start the engine cold w/ radiator cap removed. Allow to reach normal operating temperature, topping off the radiator during the process. replace cap when air is no longer apparent in system.

 

the first thing I would look at is the radiator cap. a worn cap will not allow the pressure / heat to open the thermostat. simple solution .
next .. do you usually use tap water / the sediment in tap water may have settled over time despite using antifreeze clogging the tiny radiator tubules .
have the radiator cleaned professionally . I've seen allot of stuff come out of a radiator that reduces its capacity and flow. I 've come to make a habit of using only distilled water in the radiator . no problems other than leaky water pump in time which will happen anyway.

good luck let us know ,