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Hello and thanks in advance for your time and help. My brother’s truck is overheating and it’s gone past what I can diagnose by myself.
The truck is a 1994 Ford F150 with the I6 300 engine. He’s had if for about 4 months, before that it sat for a long while (not sure how long). It’s got just over 200K miles.
So the problems are it overheats, the overflow tank boils over (sometimes after the truck is turned off), and the heater has stopped working (same time).
So far I’ve replaced the thermostat and radiator cap. Patched a hole in the upper radiator hose (I believe it showed up after the overheat due to high pressure). And the coolant was filled with rust so I’ve flushed out the cooling system fairly well. Water flows through the heater core freely and drains out of the radiator drain spout pretty well. After all this I burped the system for a little over half an hour per ETCG video procedure.
The problem is still present. What I’ve now noticed is that during that 30+ minute burping with the radiator cap off the truck didn’t over heat, it got up to temperature and held there indefinitely. I replaced the cap and things started getting hotter VERY slowly. I took it for a spin after that and it went to full hot within 10 minutes. When burping I examined the level through the radiator fill neck, it stays consistent and surges up and down every now and again so the thermostat is operating properly and I’m not losing coolant. When the engine is cool the upper radiator hose has flow but not a ton of pressure (normal I think), when it’s hot the hose is bulging. After turning the engine off you can hear a lot of boiling/ movement coming from the thermostat housing.
The overflow was boiling, not releasing air bubbles, the radiator keeps a consistent level and doesn’t have air bubbles after being burped, there is no funk in the oil, and the exhaust doesn’t have any fun colors or smells. In addition to that these engines aren’t prone to head gasket failures so I think we can table that.
This is about as far as my know how can take me. I suspect a blocked radiator but don’t have a thermometer to verify. I also suspect a weak water pump but don’t know how to test that.
I’d appreciate any help you guys can give me. Thanks.
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I forgot to mention that after shutting the truck off the temperature drops like a rock and the upper hose deflates within a couple of minutes.
A ballooning radiator hose is one that is on the verge of bursting.
Best to replace it before someone gets hurt.The only substitute for using an infrared thermometer to check the radiator is to use your hand, immediately after the engine is shut off.
Feel near, not on, the radiator surface and check for cold areas.
If you have an electric fan, rather than a clutch operated fan, make sure you don’t get your hands near it after shutdown–when it may turn on.
Hopefully, you’ve already made sure that nothing is blocking the airflow across the radiator (bags, leaves, etc.)
Heater core may be also blocked due to rusty particles or there is a lack of low or there is air/exhaust gases trapped in it.
Just because head gasket failures are uncommon on this engine doesn’t mean that it wasn’t overheated enough to cause a failure or warp/crack the head.You can check the water pump by removing it from the car and inspecting it for corroded impeller fins or a loose pulley.
Of course you will need to use a new gasket to seal it up when you reinstall it.
If the water pump belt is loose this can cause overheating.Bulging may have been the wrong word, the hose is in good enough shape, but there is a visible change between when it has very little pressure in it and quite a bit. It swells a bit but doesn’t inflate or anything like that.
By hand inspection the radiator feels even from top to bottom and left to right. The lower radiator hose is pretty warm and doesn’t collapse. And as mentioned when I pull the drain plug and force water through it flows very well. Nothing is blocking the radiators air flow either, there’s a condenser and tranny cooler in front but no obstructions.
I’ve been fiddling with it some more and I can confirm that it holds temperature just fine sitting still, I’ve even held the revs up for a few minutes and the temperature stayed put. It’s only when driving it that the temperature starts to climb. It blew the upper radiator hose off last time i took it out which surprised me, I’ve pressure tested the cooling system and found no leaks and the cap functioned as it should.
I’ve burped the cooling system on a pretty significant uphill slope several times now so I’m confident no air is in there. The first time it “over heated” it didn’t completely overheat, the temperature got to the upper end of the gauge and overflow boiled over. Every time since I’ve rested and cooled the engine before it got too hot. And it’s a big, old cast iron block. I’m not saying a warped head is impossible, I just don’t think it likely. Not ruling it out though.
Do these symptoms seem in line with a failing water pump? I feel like if it was going out it would be overheating at idle as well. I’ll try to pull it off tomorrow and inspect. From playing with the fan and pulley things feel okay and it isn’t leaking.
sounds like your thermistate it stuck….. your tempture should barlly move up and down… and you said when the car is off it will drop very quickly too…
and if its not opening up fully it could cause your car to over heat… and/or your ratator or heater core is clogged,,, you can check if its clogged by feeling your upper and lower heater hoses… when your thermistat is open they should be about the same tempture and same pressure….. but I would rec replacing with a good thermistae not a really cheap oneWell the thermostat is brand new but there’s always a chance I suppose. I’ve got another one lying around, I’ll swap them out and see where we stand.
Radiator and heater core both flow water through them great. The heater core hoses feel even in temperature and pressure.
For the sake of safety, I’d replace the top rad hose anyway. A hose in good condition shouldn’t look different between hot and cold.
With the engine cold, grab the bottom rad hose and squeeze it firmly in a few spots along its length. You shouldn’t be able to collapse it. If you can pinch it shut, replace it. It’s a sign that the internal stiffener has corroded away, and the hose will collapse when the engine is running, restrict coolant flow and cause an overheat.
So I’ve put in a new, verified working, thermostat today. Burped it some more. Will do it a few more times.
After more research I’ve discovered something… weird. On level ground and when pointed up hill the temperature is fine. When I go downhill the gauge starts climbing almost instantly. Around 15 seconds of significant downhill will bring the gauge from normal almost all of the way to hot. Go back up hill or level out and it stops climbing. Park it up hill and leave it running and the temperature starts falling within a minute or so.
I have zero clue why going downhill would be causing an overheat? Air pockets maybe, I’ve burped it again and again and I’ll do it some more. Any one have some ideas, I’m stumped?
This is a long shot but did anyone mess with the serpentine belt?
I got rid of a E150 with the 300 that kept overheating, I found out later it had a reverse-flow water pump on it and someone altered the belt’s routing so it would turn opposite from normal. When I put the belt back to the proper route I unknowingly caused my pump to not work any more.
Like I said it’s a long shot that you have the same reverse pump problem, BUT you might want to verify the belt routing, might be turning the pump the wrong way. Also, if there’s rust in the coolant the impeller fins may have deteriorated on the pump and it’s not pumping much.
[quote=”crazyapple92″ post=175264]
After more research I’ve discovered something… weird. On level ground and when pointed up hill the temperature is fine. When I go downhill the gauge starts climbing almost instantly. Around 15 seconds of significant downhill will bring the gauge from normal almost all of the way to hot. Go back up hill or level out and it stops climbing. Park it up hill and leave it running and the temperature starts falling within a minute or so.I have zero clue why going downhill would be causing an overheat? Air pockets maybe, I’ve burped it again and again and I’ll do it some more. Any one have some ideas, I’m stumped?[/quote]
Sounds like an air pocket, if I remember right the temp sensor is on the back end of the head so when you’re facing downhill any air will rise up to the sensor and it will peg out as hot very fast. If it does happen to have a failing water pump it would make it very hard to ever get the air bled out properly.
I did a quick search online and it sounds like some guys like to run the engine while parked on a hill facing upwards to help purge the air out faster.Nodak, There was tons of rust in the coolant to be honest. I’ve flushed it out several times and there’s still a bit in there. I suspected the impeller may have rusted out as well. But the pulley on it feels tight, there’s no leaks from it, and from what I can tell I seem to have good pressure and flow. I tried pulling the water pump to inspect it but ran into some snags, I need specialty tools and more patience than I have left I think.
Interesting thought on the reversed belt set up, I’ll pull up a diagram and double check it in the morning but no one has touched the truck since we bought it and it’s ran fine until now. Still, never hurts to rule out something easy.
I’ve been burping it on my terrible Mt. Everest style driveway so I’ve got the uphill aspect covered. Must have been an air pocket though as after some more burping and driving it’s gone. And it doesn’t seem to be overheating now, it will keep a fine temperature while it’s in the driveway idling, but now when I take it out it warms up to about %75 of the gauge and just stays there the whole time.
[quote=”Rob781″ post=175186]sounds like your thermistate it stuck….. your tempture should barlly move up and down… and you said when the car is off it will drop very quickly too…
and if its not opening up fully it could cause your car to over heat… and/or your ratator or heater core is clogged,,, you can check if its clogged by feeling your upper and lower heater hoses… when your thermistat is open they should be about the same tempture and same pressure….. but I would rec replacing with a good thermistae not a really cheap one[/quote]The lower rad hose should be noticably cooler to the touch which would rule out a blocked rad and bad fans
Alright, I’m heavily suspecting the water pump at this point, I just want to see if you guys can confirm.
So the truck is running hot but not overheating now. It stays around the middle of the gauge at idle, then gets to and stays about halfway between normal and hot when driving. It moves around a bit depending on how hard I’m driving as well. Also after it’s warmed up the heat will work for a few seconds when I turn it on then it blows cool. If I turn it back off and wait a minute or two it’ll do the same thing.
So I’m thinking the impeller is corroded, at idle it works okay, but when the engine spins it faster it’s not able to move as much water as needed. Opening the heater core circuit just adds to the problem. This would, to me at least, explain why it was overheating so slowly before and why it’s usually okay at idle.
I should mention that I recently put in a 160 degree thermostat, this is probably why it’s running warm instead of overheating now. It’s a band-aid fix and will be corrected once I have the real issue fixed.
Let me know if this makes sense. Thanks.
I am not as smart as some of these other guys so listen to them 1st. Based off your last post, if coolant is not low and air is bled out, I would suspect pump with intermitant heating and your over heat problem. If I read it right., your overheating uphill also which your engine has to work harder than going down hill or in idle and would probably appreciated the normal flow of coolant instead of diminished.
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