1975 Ford 4100 overheating

[rustred]

Sounds like the radiator shop ripped you off, no surprise.

Hard to say , but they should show the customer where his problem is. But all kinds out there .

 

[used red MN]

I am just thinking if a head gasket is blown, would it pressurize the water jackets and prevent water from circulating? How would i check for that? Bubbles in radiator?

In my opinion this is you next step. May need to intentionally overfill the radiator to do this. The air will come into the radiator at the top point of the neck for the top hose. You have to have it full enough to see those bubbles coming in. In your OP you talked about rusty coolant and plugged external fins. Those have been addressed and your problem still exists. So now I will ask what is telling you it is over heating? Does it boil and push coolant out or is the gauge just telling you it is hot?

 

[DavidTT]

What's telling me its hot.? First thing is the gauge, second thing is touching the engine block and head. One thing that surprised me was that the top of the radiator and even the coolant in the top was touchable; warm but not hot, and no coolant was blowing out. Once engine got to almost the red, or barely touching red on the gauge, i shut it down. I had the thermostat in spring towards the block..

 

[Destroked 450]

If the gauge is showing higher temps but coolant in the top of the radiator is just warm you either don’t have coolant circulating, or your gauge is off and the engine isn’t hot enough to open the thermostat
Before I did anything else I get a cheap temperature gun and see what the actual temps are
I have two tractors (4000, 6600) that the temps gauge will move over next two the red line within 5-10 minutes after start up, but they never go into the red unless they are actually getting hot. The gauge on my 4000SU will barely move but when it gets 3/4 up the gauge it’ll start pushing coolant out the overflow because it’s getting hot
The temperature gauges on these old Fords were never real reliable and ones in aftermarket clusters are even less reliable for accuracy
Again use a temperature gun and get some actual temperature numbers, you could be throwing money at a inaccurate gauge reading

 

[used red MN]

First thing is the gauge, second thing is touching the engine block anad head.

Your hand will jerk back when it touches a 120F surface. Engines run at almost 200F, judging the temp by you touch is worthless. If it is not boiling it’s not that hot. You need an hard help IR temp gun to help you diagnose this. Your gauge might have just started reading wrong.

 

[scootergmc]

Maybe I missed it, but if you haven't replaced the gauge and/or sender (at minimum) that's the first thing I would do, either that or find another port and plumb in another for comparison.

 

[rustred]

What's telling me it’s hot.? First thing is the gauge, second thing is touching the engine block and head. One thing that surprised me was that the top of the radiator and even the coolant in the top was touchable; warm but not hot, and no coolant was blowing out. Once engine got to almost the red, or barely touching red on the gauge, i shut it down. I had the thermostat in spring towards the block.did u feel the lower rad hose ?

 

[rustred]

Did u feel the lower rad hose. ? Cool means the coolant is not circulating. I don’t see how the engine can run hot with a new rad core and thermostat and water pump. You have something not correct there. Take the thermostats out as I’m sure I said. Then look at the coolant in the rad. It will be circulating fast. Like gotta start someplace by elimination. Plus them temp guns work good for checking temps. For 25.00 u can have one.

 

[DavidTT]

Ok, i will do that. I also have new radiator hoses coming, and i will use the laser infared thermometer on the block and head and see if the gauge may be bad

 

[DavidTT]

UPDATE. I changed the upper and lower radiator hoses, reinstalled the thermostat with the peep hole at the top. I ran ran it and it didn't get hot hot according to the gauge.... I bush hogged about 4 acres of 4 to 7 foot tall fields with a 6' bush hog. Worked it hard. It didn't over heat. It did run a little above the middle of the gauge , where it used to run a little under the half way on the gauge. My new thermostat is a 168 which is what is read it calls for, and maybe my old one was of lesser degrees... ?? I checked it with my laser thermometer and it read somewhere between 180 and 135 on the block, head, thermostat housing, and radiator. The gauge did start to register a little on the hot side a couple of times, but never got into the red. So i might have a gauge acting up a little. But my guess is the hoses fixed the problem??? They looked ok, but maybe it was like somebody said, they can go bad and look ok....

Thank you for all the responses.

 

[rustred]

UPDATE. I changed the upper and lower radiator hoses, reinstalled the thermostat with the peep hole at the top. I ran ran it and it didn't get hot hot according to the gauge.... I bush hogged about 4 acres of 4 to 7 foot tall fields with a 6' bush hog. Worked it hard. It didn't over heat. It did run a little above the middle of the gauge , where it used to run a little under the half way on the gauge. My new thermostat is a 168 which is what is read it calls for, and maybe my old one was of lesser degrees... ?? I checked it with my laser thermometer and it read somewhere between 180 and 135 on the block, head, thermostat housing, and radiator. The gauge did start to register a little on the hot side a couple of times, but never got into the red. So i might have a gauge acting up a little. But my guess is the hoses fixed the problem??? They looked ok, but maybe it was like somebody said, they can go bad and look ok....

Thank you for all the responses.

Most important check temp of top hose then bottom hose. Or top of rad tank and bottom tank. Bottom should be cooler. And the hotter the thermostat the hotter the engine runs. Years ago on them old vehicles it was common practice to put in a cooler stat for summer, 160-180. 190 was for winter. The head will be hotter than the block temp. You got to follow the circulation path and record the temps. If the bottom hose is like an old rubber boot and soft mushy then it can collapse. Top hose no, as it’s more pressurized and the lower hose is on a suction.