Water temperature gage

37 chief · Dec 13, 2021

What would make my water temp gage peg to past hot on my JD 401 B? Water is not boiling. Then back to normal temp. It's not hot outside today, in fact itis rather cold. Stan

rustred · Dec 13, 2021

i would say the thermostat might be slow opening and once it opens all is good.

Steve@Advance · Dec 13, 2021

My first guess would be low coolant, but I'm sure you checked that.

Possibly a failing thermostat, but even that is mechanically unlikely. Usually they fail once and done, or stick open.

If you replace it, be sure it has a small vent hole or a notch in the disc. If not, drill a 1/16 inch hole in the flat of the top to let some water circulate while it is coming up to temp.

I assume this has a mechanical gauge. If electric suspect a shorted sensor wire or the sensor is failing.

For it to have really gotten that hot, something should have been steaming and blowing!

sotxbill · Dec 13, 2021

no bleed hole as others have said... and/or... an air pocket trapped so that the thermostat did not see the temp come up till much later.. or binding due to crud/rust, or thermostat fixing to go bad. Some models must have the weep hole or bleed hole on the edge of the thermostat to stop this. Others not so much. The ford 2000 gas tractor will do this horrible bad with no weep hole where the diesel version will not. But the thermostats are in much different locations.

SVcummins · Dec 13, 2021

Sticking or stuck thermostat or an air bubble in the system

MARK ROBKE · Dec 13, 2021

I am going to go the other way and say gauge issue. I would see if grounding the sender wire at the sender makes the gauge peg. Then follow the wire back to the gauge and see if it is shorting to ground somewhere (rubbing on something). If is not overheating, then I bet sender or wire issue. Mark.

37 chief · Dec 13, 2021

The tractor has been working all year with no heating problems. The radiator is new along with the thermostat. I use JD Cool-Guard II Coolant. The motor didn't overhear. There was no pressure at the cap. I have until next April to figure it out. I did one of my last my last mowing jobs today. Stan

37 chief · Dec 13, 2021

I should have mentioned, it's a mechanical gage. Stan

showcrop · Dec 14, 2021

With the additional info of new radiator and T-stat, I would be checking to see if it will burp anymore air. My recently restored '67 roadster, on first heat up will go to 230 then come down to 210 and stay there. I attribute it to difference in temp between where the sensor is and the T-stat bulb. It is on my list for this winter to replace the T-stat with a lower temp one, and put a 1/16 hole in it.

MARK ROBKE · Dec 14, 2021

You can use an infra-red thermometer to check against the dash gauge. Aim the red dot next to the sender and see how close they are. Infra -red thermometers are pretty cheap to buy-very handy for a lot of things-like checking bearing temps. Mark

37 chief · Dec 14, 2021

Good idea. I am going to see what amazon has. Stan

Water temperature gage

37 chief

Well-known Member

rustred

Well-known Member

Steve@Advance

Well-known Member

sotxbill

Well-known Member

SVcummins

Well-known Member

MARK ROBKE

Well-known Member

37 chief

Well-known Member

37 chief

Well-known Member

showcrop

Well-known Member

MARK ROBKE

Well-known Member

37 chief

Well-known Member

Similar threads