Motor heating
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Cross-Country
Joined: Sep 2020
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Motor heating
1987 f150 4.9 I've rebuilt the motor new water pump new hoses and new tstat. The motor runs great it warms up and the temp is normal. But if you raise the rpms to about 2000 and hold it for a couple minutes the temp rises let off and let idle temp continues to rise. It will go pass the l on normal and gets very close to the hot line. I backed flushed heater core and have burped the engine put it on jack stands and let it set over night. I had a extra radiator so swapped them and still same result. Whether t stat is in or not it does this. Ignition timing is set. None of the radiator hoses are collapsing and they are new. The only thing I've not replaced is fan clutch. It seems ok but I'm out of ideas. The truck originally had a fan with 5 blades and I choose to put on on that has seven blades. Any ideas of something I've not tried. It is not air in the system I've tried burping many times and it's not the tstat also I checked the direction the water was moving and that is correct so the water pump is correct also new radiator cap.
There is no oil in antifreeze or any antifreeze in oil. Truck runs smooth And no smoke out of exhaust. Compression checks are good and even on all cylinders
There is no oil in antifreeze or any antifreeze in oil. Truck runs smooth And no smoke out of exhaust. Compression checks are good and even on all cylinders
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Cross-Country
Joined: Sep 2020
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I have a fan shroud the heater blows hot air and yes the fan blows air on the engine its sucking air through the raidiator
I have not reaplaced the temp sensor but the motor gets very hot i believe it is correct. You can't touch the radiator hoses they are so hot
I have not reaplaced the temp sensor but the motor gets very hot i believe it is correct. You can't touch the radiator hoses they are so hot
Lead Driver
Joined: Oct 2016
Posts: 6,185
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From: Houston/Sugar Land
The fan clutch should be replaced when a new water pump is installed. A bad fan clutch can be a cause of overheating. Don't know it this applies to you but I would try to diagnose the clutch. Sandy
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Cross-Country
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I can do that i have a infered thermometer. But i atill believe its getting hot. It gets so hot you cant lay your hand on the hoses. Also when you shut it off you can hear the water boiling
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Elder User
Joined: Sep 2018
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From: NC
13 psi radiator cap? engine while running sound like a jet from under the hood? and it never quiets down? probably fan clutch. 13 psi is what the cap should be. Not losing coolant? puke tank level staying within normal range? Check that FIRST.
I had a Chevy that exhibited the same symptoms, drove me insane, turned out it was blowing exhaust gasses into the cooling system, so no oil in the water, no water in the oil, you may want to get a tester to see if there is combustion gasses in the cooling system. I kept having to fill the cooling system is how I figured it out.. short runs, no worries, til after a while.... longer runs... where was my coolant going....exhaust gasses were forcing it out and pressurizing the cooling system and forcing the fluid out.
I had a Chevy that exhibited the same symptoms, drove me insane, turned out it was blowing exhaust gasses into the cooling system, so no oil in the water, no water in the oil, you may want to get a tester to see if there is combustion gasses in the cooling system. I kept having to fill the cooling system is how I figured it out.. short runs, no worries, til after a while.... longer runs... where was my coolant going....exhaust gasses were forcing it out and pressurizing the cooling system and forcing the fluid out.
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Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
Yes it can. Get a Motorcraft Radiator cap. Its worth it. Maybe 10-15$.
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Cross-Country
Joined: Sep 2020
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I put the 13 psi cap on it made it worse. Shot the radiator hoses with a infred gun engine got up to 225 fahrenheit the over tank was bubbling over bad. I shut the engine off. The only things left to replace is the fan clutch and radiator
Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
2 things to check.
Is the lower radiator hose warm or cool?
When you installed the t-stat, did you check it in a pot of boiling water to see if it was opening? What brand of t-stat did you install? I have posted about the junk Stant t-stats and other 5$ t-stats from the parts store.
All of my trucks have Motorcraft t-stats. Never once had a problem with them. Only one has a Mishimotor 180°F t-stat and I use it strictly for fun and towing throughout the spring and summer. It cost double the Motorcraft t-stat.
There's a reason OEM parts cost more. I have personal experience with Stant t-stats failing. When they fail to open and then the hose blows sending boiling antifreeze all over the engine, wiring, everything. This is the best case scenario, hoping that the engine wasn't so far overheated that the heads aren't warped, or blown a headgasket.
Or when the customer puts in a fail safe 8$ Stant t-stat and it fails in January, 12°F outside, and your stuck buying another OEM Mopar/Chrysler t-stat @ 30$, and the Mopar coolant for $15.
If the truck is overheating just sitting at idle, I agree that it's either fan clutch, radiator, or t-stat.
Is the lower radiator hose warm or cool?
When you installed the t-stat, did you check it in a pot of boiling water to see if it was opening? What brand of t-stat did you install? I have posted about the junk Stant t-stats and other 5$ t-stats from the parts store.
All of my trucks have Motorcraft t-stats. Never once had a problem with them. Only one has a Mishimotor 180°F t-stat and I use it strictly for fun and towing throughout the spring and summer. It cost double the Motorcraft t-stat.
There's a reason OEM parts cost more. I have personal experience with Stant t-stats failing. When they fail to open and then the hose blows sending boiling antifreeze all over the engine, wiring, everything. This is the best case scenario, hoping that the engine wasn't so far overheated that the heads aren't warped, or blown a headgasket.
Or when the customer puts in a fail safe 8$ Stant t-stat and it fails in January, 12°F outside, and your stuck buying another OEM Mopar/Chrysler t-stat @ 30$, and the Mopar coolant for $15.
If the truck is overheating just sitting at idle, I agree that it's either fan clutch, radiator, or t-stat.