JoeB

My son has a 1997 f150 with a 4.6l. The truck overheats if not allowed to warm up at idle for at least 20 minutes. If you drive the truck before that time, it overheats. The first sign is loss of heat then the temp gauge spikes and blows antifreeze out of the overflow. As soon as you turn the truck off, open the hood and climb back in the temp gauge is reading cool, literally 2 minutes later. Once it overheats it will continue to overheat during that trip. If allowed to warm up, truck seems to run fine. Replaced the tstat and pressure tested the system at idle and it never waivered so much as 1/2 pound. We tested to see if there were any combustion gases in the antifreeze and the liquid stayed blue, no gases. The oil does not have any bubbles or milky substance. Any ideas.....

JohnnyO

mine! Came here today because I have a similar issue on a 2000 5.4L
On your son's truck, when the heater starts blowing cold, try revving the engine above 2500rpms (or if riding, turn off Over Drive, or downshift to get the rpms up). Mine at this point will start blowing scaulding hot air and the engine temp will drop back to normal. Always happens in first 3-5 miles on a COLD start. The rest of my one hour commute goes perfectly smooth once I get the t-stat to open. I've replaced upper and lower hoses, belt, waterpump, and THREE thermostats. Issue is somehow related to the pressure in the system not being adequate to open the t-stat. God help us, I know of nothing else in the system I have not replaced yet.
Since Christmas, I've just been driving the begining of the trip with the OD off for 10 miles and I can't even tell the truck has an issue!

Brakeman

Well, If this were a chevy, then I would say that you probably have a leak in your intake gasket. They have lots of problems with this, and it often behaves just as you say. Exhaust gas leaks into the coolant causing empty hot spots on the engine. When the coolant sloshes against the hot spots, it boils and steam pressure forces the coolant out the overflow. Slow Idle warming creates the hot spots but no sloshing and the small leak closes due to thermal expansion. Still not good though.. I hope that not your problem.

JohnnyO

What would be the test(s) to find out for sure?

JoeB

Well, we replaced the head gaskets and the truck is not overheating anymore. The heads are aluminum and they swell when heated. When the truck is cold the leak is present, as the heads heat up and swell the leak is sealed. The slight movement of the heads chew up the gaskets. If you do this job, make sure you use graphite gaskets as they allow for the sliding because they are slippery. I sell auto parts and had at least 10 mechanics take a look at my son's truck, including Ford dealership mechanics. Everyone said it was the head gaskets, but we couldn't get a positive combustion gas test. As a last measure we replaced the head gaskets and had the heads checked and milled. All is good so far and it's been 3 weeks.
Good luck and I hope this helps...

JohnnyO

Not what I wanted to hear. Can I have any tests done to try and be sure this is it before shelling out that kind of money?

JohnnyO

I stated this happened only when motor was first warming up, turns out if I release the pressure in the cooling system, problem will occur even with the engine hot. After leaving a shop, again within 3-5 miles heater started blowing cold and truck tried to overheat (revving again resolved problem) So is there something that draws vacuum off the cooling system in this time frame? Still have folks telling me I have air inside the system. Either pressurized or not, you can feel small bubbles in the upper heater core line as the water is moving.

JohnnyO

KISS > Keep It Simple Stupid!!!
After being advised about bubbles in the cooling system, I parked the truck on a steep incline, then drove the nose up on blocks to raise it even higher. I allowed the truck to go thru a complete warmup without the collant tank cap on it. When the temp gauge got to the point I knew the t-stat should open, I watched the coolant level rise to nearly overflowing. Several LARGE bubbles (air pockets) burped thru the hose. Once the bubbles stopped, I was nearly a half gallon low on coolant. Filled it back up and the problem has not occurred since. This makes week #3, so I'm cautiously optimistic!

A W Smith

my 98 triton 4.6 is sucking oil into the coolant system. I bought the truck at Christmas and a few weeks later noticed it suddenly lost 4 1/2 quarts of oil. No smoke, No visible leaks, Ive never seen this before. BUT I neglected to even look at the coolant reservoir. Since then it was fine. That is until today I warmed up the truck for an extended period of time more than the usual 3 minutes because I was swapping equipment onto the ladder racks and tying off scaffolding. About 20-25 minutes later I take off, all gauges normal. I get about a mile from my house and hear a whistling. No steam. just what sounds like a piccolo. Thought it was wind whistling through the scaffold plank. All gauges are normal I go another 3/4 mile and the engine stumbles and goes into limp mode. I pull into a strip mall parking lot and all hell breaks loose. The temp gauge is spiked and foam and sand colored cream it bursting out of the reservoir. This is not good. I now know where my oil went, I check the dipstick and its dry. My wife comes a half hour later with 5 quarts of oil and 5 gallons of anti freeze. It takes four quarts of oil in the crankcase and two gallons of anti freeze into the reservoir but i cant figure out how to bleed out the air pocket that is in the top hose. There is no foam on the dipstick or oil filler cap. I would expect anti freeze to get into the oil and not oil into the anti freeze. One being higher pressure than the other. Could I have a cracked oil feed galley into the water jacket? Or is this a head gasket or intake issue? It never lost oil pressure even when temp spiked. I don't have $3500 for a complete rebuilt engine. Is this common with the triton 4.6?

ericp1

i have a 1997 f-150 with the 4.6 engine mine would also overheat after first driving a few miles but once it did this it was always fine the rest of the trip but it would push water out of the cap and you could see this in your rear view mirror while driving down the road i would lose the heat in the cab the water temp gauge would peg and the enging would go into limp mode running on 4 cylinders all i had to do was stop turn the truck off and wait a min or 2 and then restart the truck and drive on and everything was fine no over heating and plenty of hot air in the cab i just got tired of fooling with it and decided to replace my head gaskets (boy that was fun) but so far that fixed the problem been a little over two years now and still no problems what i am thinking is that combustion gases get in your cooling system and thats what forces your water out and when the gases get to the water temp sensor thats what makes it go crazy just my 2 cents but i hope it helps anyone else who has this problem