Ford 961 Powermaster Overheating

[Dalton0914]

I have a gas Ford 961 Powermaster and I had a problem with it overheating super quick. I first replaced the thermostat and that didn’t change anything. Compression in all cylinders are perfect. However, if I leave the radiator cap off, it doesn’t build pressure in the radiator and circulates coolant as it should. The second I put the radiator cap on, it builds pressure in the radiator and stops circulating immediately. I’m leaning towards weak water pump or cracked head but wanted to see if anyone has experienced this before I spent a lot of money or pulled the head. Thanks

 

[bc]

I have a Ford 1500 with the 2 cylinder Shibaura diesel engine. It was running hot on me. Ended up with a cracked head by a valve. Took it to a shop in Wichita 2 years ago to get it welded. Got it back about 2 months ago. Been too busy on other projects to reinstall it.

You might be better off posting this over at the Ford forum and those Fix Or Repair Daily guys can help you trouble shoot it.

 

[old]

I have a gas Ford 961 Powermaster and I had a problem with it overheating super quick. I first replaced the thermostat and that didn’t change anything. Compression in all cylinders are perfect. However, if I leave the radiator cap off, it doesn’t build pressure in the radiator and circulates coolant as it should. The second I put the radiator cap on, it builds pressure in the radiator and stops circulating immediately. I’m leaning towards weak water pump or cracked head but wanted to see if anyone has experienced this before I spent a lot of money or pulled the head. Thanks

Drain the cooling system and fill with vinegar and run it till it get hot. Shut it down and let it cool. Rig a way to use a garden hose into the block drain so you can back flush it at the block drain. Drain it by way of the block drain and then drain it at the radiator drain. Close the radiator drain and hook up your rigged hose to the block drain and back flush with the garden hose with the cap off. Then fill with water and see if it still over heats. If it does flush a 2nd time with vinegar and repeat all the steps

 

[leroy in ne]

Possibles: Fan belt slipping. Radiator full of dirt, grass clippings, seeds, ect. on outside. As old said above, backflush after vinegar soak. lower radiator hose collapsing. As you said bad pump, head gasket or head. Quicky test of gasket and head is to take fan belt off, fill radiator to top, start engine and look for bubbles in radiator, you may have to have a helper open throttle when doing this check. Also is it possible the thermostat was put in backwards, it has happened by accident with distractions.

 

[grandpa Love]

Could be running really lean..... timing? Carb?

 

[DaveBN]

I would think you could run it for several minutes with no coolant in radiator before it gets hot. If I gets hot sooner than that it's something besides radiator type problem. Curious how you know coolant stops circulating with radiator cap on.
Dave

 

[showcrop]

I have a gas Ford 961 Powermaster and I had a problem with it overheating super quick. I first replaced the thermostat and that didn’t change anything. Compression in all cylinders are perfect. However, if I leave the radiator cap off, it doesn’t build pressure in the radiator and circulates coolant as it should. The second I put the radiator cap on, it builds pressure in the radiator and stops circulating immediately. I’m leaning towards weak water pump or cracked head but wanted to see if anyone has experienced this before I spent a lot of money or pulled the head. Thanks

I also wonder how you know that it stops circulating. The only way that I know is with an infrared thermo.

 

[Blackhole49]

I also wonder how you know that it stops circulating. The only way that I know is with an infrared thermo.

That makes 3 of us. Why do you feel it is overheating? How long does it run under a working load before it over heats with the cap off?

 

[used red MN]

Hello Dalton, welcome to YT! You mention “the compression in all cylinders is perfect” In my opinion this may be more of a problem of getting compression into the cooling system. Just a small amount of compression leaking off into the cooling system would not drop the compression reading in a cylinder. Fill the radiator to where the top neck coming out of the engine is covered with coolant. With the tractor at a lower temp so the thermostat is not opening start the tractor and look it the radiator for bubbles. If you see them compression is leaking into the cooling system.

 

[Dalton0914]

Possibles: Fan belt slipping. Radiator full of dirt, grass clippings, seeds, ect. on outside. As old said above, backflush after vinegar soak. lower radiator hose collapsing. As you said bad pump, head gasket or head. Quicky test of gasket and head is to take fan belt off, fill radiator to top, start engine and look for bubbles in radiator, you may have to have a helper open throttle when doing this check. Also is it possible the thermostat was put in backwards, it has happened by accident with distractions.

Thanks for the info, the thermostat wasn’t backwards. That was the first thing I checked.

 

[Dalton0914]

That makes 3 of us. Why do you feel it is overheating? How long does it run under a working load before it over heats with the cap off?

Never had it overheat with the cap off. I feel it’s overheating because of the lack of power, the way it would run, the fact it was hard to stay in the seat because of all the heat coming back in my face, and the new temp gauge displaying it’s hot

 

[Dalton0914]

I would think you could run it for several minutes with no coolant in radiator before it gets hot. If I gets hot sooner than that it's something besides radiator type problem. Curious how you know coolant stops circulating with radiator cap on.
Dave

Dave,

Just a guess it’s not circulating with the cap. The second I put the cap on, it builds pressure in the radiator, wants to blow the cap off, pushes coolant out the overflow, and the temp gauge rises.

 

[old]

Dave,

Just a guess it’s not circulating with the cap. The second I put the cap on, it builds pressure in the radiator, wants to blow the cap off, pushes coolant out the overflow, and the temp gauge rises.

Cap could be bad. All pressurized radiator systems have a pressure cap that opens from 4-8psi and if it doesn't open then it causes problem or your over fill or both

 

[Dalton0914]

Cap could be bad. All pressurized radiator systems have a pressure cap that opens from 4-8psi and if it doesn't open then it causes problem or your over fill or both

I started with that cap and I’ve bought 2 new ones and still have the same issues.

 

[Blackhole49]

Never had it overheat with the cap off. I feel it’s overheating because of the lack of power, the way it would run, the fact it was hard to stay in the seat because of all the heat coming back in my face, and the new temp gauge displaying it’s hot

What used red said. From what your saying, everything is working fine with the cap off, witch doesn't make sense with your symptoms. Have you tried running it for an extended period (mowing or plowing) with the cap loose (don't let it build pressure)?

 

[Dalton0914]

What used red said. From what your saying, everything is working fine with the cap off, witch doesn't make sense with your symptoms. Have you tried running it for an extended period (mowing or plowing) with the cap loose (don't let it build pressure)?

Believe me, I know it doesn’t make sense. I’ve talked to a lot of mechanics I know and they all say the same. I haven’t tried it with a loose cap. When the cap is on, it overheats. The longest I’ve ran it without the cap on was about 30-45 minutes but it was just top dressing corn. I think I’ll try the vinegar flush a guy mentioned earlier in this thread.

 

[MARK ROBKE]

Your problem sounds like compression leaking into the water jacket. IE, blown head gasket or cracked head or block. I believe the is a kit with test strips you can but that test for combustion gases (leaked compression) in the coolant. I doubt coolant stops circulating, the compression just builds in the coolant.
I don't think checking compression in the cylinders will tell you anything, it probably would leak enough to cause a problem, but not show up as a big compression loss. Mark.