I've lived with this issue since I've had this truck (4 years). Want to see if someone can shed some light.

The temp gauge always stays in the cold area, even in the hottest weather. I know I know, you can't rely on the factory gauge. But along with this, it puts out very little heat from the heater core. So in the winter it sucks because of so little heat. Drive for hours, it never warms up.

I have tried 4 different stats, no change. The truck has been running for 45 minutes (right now) in the drive way. The top rad hose is ice cold. (This mean the stat is not open, but after 45 min???) The heater hoses are barley warm. The intake and valve covers are cool to the touch. This is after 45 min running time.

How can this be with a big v8? My other cars are at full heat in 15 minutes, don't dare touch the rad hoses or engine. The heater blow so hot it will knock you out.

Can anyone explain this?

 

Water pump maybe?

 

Don't think so ...bad pump would cause overheating

 

I got the same thing with a straight 6.

It was gonna freeze the other night so I drained the rad and added a gallon of antifreeze,, and let it run with the cap off...20 min later, top hose freezin' cold, 1/2 hr later, top hose just pretending to get warm so I knew the t stat was opening,

45 min later I was freezing, said, f it and came inside.

I did check the head temp with one of those laser pointer things that I trust, since I use it for my woodstove and it show head temp right by the t stat housing as 180 degrees or so,
but the top hose was not what I would call hot.


It's been a few days now and I've checked the radiator a few times, it;'s always full but I hear the sound of pouring water from the heater core from inside the dash so I KNOW there's air in there.
and it kinda looks like it's higher than the top hose etc.

I wonder 2 things
if theres air up high, and not water going thru the heat core, it can't get hot.

Maybe the same thing with the top hose.

I'm personally going to try and bleed that air out maybe by popping off the highest hose I can find, maybe top heater core hose?
or put one of those plastic flush and fill 'T' fittings in so I can open and close it.
or
park it across the driveway so the front of the truck is a couple feet higher than the back, as in
the radiator fill would be higher than the heater core.

Most normal engineering pieces make provisions for bleeding air out of fluid systems, but I digress.

The sucker runs so I'm not too pressed to be motivated.

I mean, I'm with you on the concept.
That heat has to go somewhere and even IF there's some sort of waterpump bypass the recirculates from the pump back thru the block without throwing heat thru the radiator, it's pushing the limits of physics and Boyle's law.

Next time out, I'll check heat in the BOTTOM of the radiator since the top we know will be cold, and maybe it's because there's air in the top hose/??

IDK

Might have to get some schnapps and pretend I give a darn one of these days and get out there and throw some wrenches around, fire up the other farm equipment for their mid winter exercise,
and blast around on the sleds or 3 wheelers.

and hope it fixes itself.

Let me know if you figure anything out.

 

Had the same problem on a '90 4.9L. I sold it. 2 people have bought it since then and everyone has tried ot get heat out if it wih no avail. It runs beautiful except for heat. Checked the blend door, etc, etc..3 owners and no one has pin-pointed the source of the No-heat situation.

I feel your pain.

 

If the impellor breaks to the point where it is no longer circulating fluid at all, normal thinking would be that there is zero coolant circulation resulting in overheating ??? correct ?

 

Yes that is what I ment by water pump it can still circulate enough to cool but not to keep heat. And when u hold the rpms up it should pump coolant into heater core unless just pure air locked

 

The first thing you need to do is verify that the radiator is full and the water pump is working, you should be able to see some flow in the radiator. Then try blocking the radiator completely off with some cardboard to see if the temp comes up. Do you have the original intake manifold on the truck? Maybe the thermostat has been bypassed? How warm does the oil pan get?

 

Man I just don't know....with no impellor, no circulation.

We have all had a car that had overheating problems. It generates tremendous heat. Where is all the heat going that my 351 is generating?

 

The only difference with mine is that my heater core does get hot, even with that pouring water sound running thru it. (new to me truck)

When I did the antifreeze drain refill the other night, I noticed turbulance in the rad filler neck and erroneously thought it was an open or MISSING thermostat causing it but the top hose was cold. but I also had just started the procedure so it should have been cold.
1/2 hr of idling later the top hose was STILL ccccold.

As the water level dropped in the radiator, I saw a 1/4 inch stream of water flowing into the rad neck causing that turbulence, apparently a heater core bypass that allows hot water to flow thru the heater core beFORE the engine gets hot enough to open the t stat, so the cab gets heat before the engine really warms up all the way... ok, makes sense so far. The heater core should be giving us the exact same temp of what is running thru the engine, be it cold, warm or hot.

If I had a cold heater core, I'd prob take both hoses off and blow air and then a garden hose thru it in Both directions and then maybe even fill the cooling system thru the highest top heater core hose or again, I've seen those coolant 'flush and fill' 't' fittings that have a sodabottle screw top garden hose threaded connector type things on it and situate it so that it is at the topmost elevation of the cooling system.

 

I had a 89 f150 4x4 lariat that i bought brand new in 89. it always ran on the cold side from new, the temp gauge always read in the low side. i never paid much attention to it being new and all. in the winter i always had to slide a piece of cardboard in front of radiator to get any heat in the cab. at about 155k she finally overheated one day water pump went out and boy did i get her hot. i fixed the pump and about a week later i lost oil pressure, so i shut her down let her sit a second then fired it up oil pressure came back for a mile or so then it dropped out. so i towed it, the oil pickup was so full of gunk and muck it was stupid, i opened the valve covers and it was so caked up you could not even see the rockers no kidding. after a thorough clean up i ran that truck to 205k and finally sold it. I never did the thing to warm up right. and i always figured the cool engine led to the sludge build up. sorry for rambling on but this thread reminded me of the old 89. good luck

 

yup, I know that if a waterpump belt comes off, for instance, you can hear the water boil and pop and blow a dangerous volcano of steam and coolant out of wherever it can.

Hey wait!

Is there any chance your truck has a hidden heavy duty rv towing package setup with some monsterous oil cooler somewhere?

 

2 ways to go. One put a thermostat with a hole drilled in it. Second, rig up a vacuum evacuation setup to draw a vacuum and then fill the system with collant. $20 in parts could get you going. I'm thinking that air is in the system.
Could spark plugs be a culprit?

 

ok, this is breaking the laws of physics.

If a lean running engine, lawn mower, motorcycle etc can cause cherry red glowing headers/exhaust, could the opposite be true?


Since a lot of these truck are notorius for low fuel mileage with some (allegedly) getting 2x better mileage than identical other ones and difficult to figure out.

Could they be running cooler because they are running richer?

I like the hidden tow package oil cooler idea that we may have paid for as a dealer option and don't know about it.

Whoever figures this out should get a prize or a f-t.com trophy.

 

Welcome to the forums restoman2.

We know that vacuum pumps are used all the time to purge closed systems, so that's a perfect suggestion.

Spark plugs? Let's think.

Does anyone know what a 'plug chop' test is? usually carb'd engines, bikes, atc's etc.

something like rev an engine gently and hold at a certain, perhaps cruising (where you're trying to get your best mileage) rpm.

and then kill the spark, let it die and read the plugs somehow.

I know that engines that foul plugs are suggested to run a 'hotter' plug so it doesn't foul as easily buyt that trick also comes with stern warnings of engine damage for some risky reason too.
good suggestions, rman2