1997 ford f-150 heating issues

[x1957x]

I have a 4.6 f-150 that's a 1997. when I drive down the highway at 60mph it starts to over heat like red line on the gauge after about 5 or 6 miles. When that happens i put it in neutral and start revving it up and the gauge goes back down. Then i put it in gear and drive down the highway again and after about another mile or so it starts to heat up again and i do the same thing again cool it down Etc. Could it be a thermostat issue?, Or a clutch fan issue?, or a temp.sensor gauge issue in the intake?,or a radiator resurculation. Any thoughts or ideas will be greatly appreciated. Thanks(57

[fishing tech]

Fan clutch probably. With the truck NOT running spin the fan. If it just spins easy with no resistance the clutch is bad. Also if it wiggles front to back with your hand , it is bad. It also could be that the fins on the water pump are bad. Is the fluid level ok? Take the cap off when it is cool and make sure the reservoir is full.

[Jeremy airjer W]

The fan clutch shouldn't make any difference on the freeway?

[x1957x]

Clutch is good and the level's are good. Anyway to test the heat gauge plug? Maybe backflush unit? It only happens while driving on the highway after 5-6 miles or so then it starts.

[Jeremy airjer W]

Remove the radiator cap from the reservoir with the engine cold. Start it up and monitor the coolant level until the engine is up to operating temperature. Do you see a consistent peculation of air bubbles? if yes you may have a head gasket issue....

It sounds like its pretty consistent. When it over heats pull over (safely) and feel the upper and lower hoses. The upper should be hot and the lower should be warm but definitely not cool. The air coming through the radiator should also be hot. If the air coming out of the radiator or the lower hose is cool than there is a flow issue. either the water pump is not doing its job or the t-stat is not opening all the way.

Also when this happens turn the heater on full hot. If there is heat than you knot there is enough coolant and the water pump is circulating. If there is no heat than either it is low on coolant or there is a problem with the water pump circulating coolant.

Let us know what you find.

One last thought. look in between the radiator and the condenser. I'm willing to bet there is a lot of debris built up on the front of the radiator. Even if it doesnt solve your issue blowing that debris off the radiator will be a benefit.

[x1957x]

I chsnged the pump and the clutch fan. Seems to take a lot longer now to get up to operating temp now. Have not to it on a cruise yet just around the horn a couple times. Seems to be better at the temp gauge and if I turn on the heat it seems to get a lot warmer than before to. I could not toucb the bottom heater core hose or either of them as far as that goes and before I could hold onto it and not let go.will keep you updated as I drive it .. thanks guys

[x1957x]

Update on my 97 ford. I got a chance to drive it last night and one time it went up to the red on the heat gauge.It went back down in about 5 seconds.. I dont know why though. Maybe it is the thermostat? Not much else it could be. I felt the top hose and it was real hot and the bottom wasnt as hot but was warm to hot where I could hold my hand on it where as I couldnt on the top hose. I also look in the resivour tanks and it had no air bubbles but hot where I couldnt remove the cap. Could it be the thermostat or could it be the cap on the res. tank??

[Jeremy airjer W]

The only thing the cap on the res does is hold pressure. If it was not holding pressure than coolant would be leaking it of it.

Did you purge the cooling system after replacing the water pump. If you did not than that may have been the spike you saw.

You can not see air bubbles throughout the reservoir. Than cap needs to be removed.

[x1957x]

I guess I am old fashioned. How do you purge the system Jeremy?

[Jeremy airjer W]

Remove the cap, start the engine, let idle till fully warmed up, top off coolant as necessary, snap the throttle a couple times once hot, replace the cap. System burped.

[x1957x]

Jeremy, I purged the system a couple days ago. Was about a 1/3 of a gallon short after I was done. Dont know if it will make a differance yet but have driven it 6-8 miles down the highway so far and not ran hot yet. I will let you know after more driving is done.

[x1957x]

The farthest I have driven to date is about a 10 mile trip and started once to climb above half way mark and went back down and hasnt ran hot yet though!!

[x1957x]

Well. Here is what it does. I drove it 25 miles one way and stopped and got a pop. Didnt shut off.Never ran hot! I turned around and drove back 25 miles and never ran hot. I got about a mile from home and for s-h-ts and giggles I turned the air on and the temp. went up almost to the top imediately. I put in nuetral and revved it up and it cooled right down. I think just taking it off a load let it cool down though. Any ideas now. Changed the clutch fan and waterpump..

[Jeremy airjer W]

Sounds like the radiator needs to be blown out. There is likely a lot of debris accumulated in the cooling fins of the radiator. Sand and cottonwood like to build up in there. When the A/C is on the condenser is adding more heat. If there is not enough air flow through the radiator the than you can have the symptom you described.

[fishing tech]

Yep, I would blow out the radiator and condenser. Here is something you can try.

Hood closed engine running, take a rag and hold it in front of the grill. The rag should get sucked in against the grill and stay there by its self. If it doesn't there is definitely not enough air flow.

[x1957x]

Hey. Thanks fishing tech and jeremy. I will let yo know after I try it.

[chanfish]

good advise from airjer. had exact same problem last year with my wifes rendevous..too bad she spent over 500 bucks flushing etc when it just was an external radiator issue...i got ticked and went to the forum for help...airjer was spot on on this one..same symptoms as well..

[scrotec]

I have seen 6 ford 4.6 or 5.4 engines that the water pump impeller had rusted of and the edges were sharp like a knife. Easy job, worth looking at! Good luck

[Jeremy airjer W]

Changed the clutch fan and waterpump..

Looks like he pump was replaced.

[x1957x]

Still runs hot. I have blew out the condenser and radiator, put in a new clutch fan and a new water pump and it still gets hot. Is there a good radiator flush to try and see if that helps. What else can I try except maybe the system is full of crud..it has the 4.6 in it by the way and has air.

[Scott K]

Dumb question, when it is running in the red, is the cooling system boiling? Have you ever got a check engine light? I am just wondering if the gauge, or temp sensor isnt reading correct, and it isnt really over heating. If the temp gauge pegs, it should be boiling in the over flow tank, and it should be setting an over temp code in the computer. This systm should have a cylinder head temp sensor for the computer, and a engine coolant temp sensor for the temp gauge. I would hook a scan tool up to it, and see what the pcm is reading when the temp gauge is in the red, or pegged. Normal high temps would reach about 220 when hot, when it gets above 225, the temp gauge should be in the red.

Another thought, have you pressure checked the radiator cap? Water boils at 212 degrees when it isnt under pressure, but under 16 psi, it can get as hot as 240 before it boils.

Another thought, has anyone had the intake off of this thing, for any reason? This era 4.6 had two different models(vin number 6,and vin W), and one of the differences was the intake ports, and the gaskets were different between the two, and one of them would restrict the cooling, and intake ports on the intake between the head, and the intake manifold.

One more thing, is a tstat, I have ran into several bad tstats over the years, and I wouldnt rule that out just because you have replaced it already.

[x1957x]

Scott, First it has not had the intake off. 2.As soon as it starts to climb into the red i put it in nuetral and rev it up and it comes down. Could it be plugged up with crud and just have to have a cleaner run in it? I can do the termostat again and try it but maybe I should try to clean out the system first. How do test the radiator cap to??

[Scott K]

You can get an acid flush that you add to the system, then run it for a half hour, then flush it. The radiator cap, you would need a pressure tester adaptor that fits this style radiator cap. It would be cheaper to just try a new radiator cap, if you didnt have a tester for it.

[Jeremy airjer W]

Before you do anything else or spend any more money bring it to a shop that has a four gas analyzer and have the coolant sniffed for hydrocarbons. If there are hydrocarbons present than its game over, you need head gaskets. If there are no hydrocarbons than it has to be something simple that you are overlooking.