Big-Mo 500 overheating

[Anonymous-0]

I have a Big-Mo 500 that I rebuilt back in the summer. It runs fine but it will sometimes get hot when I run it. Whats confusing me is that it wont get hot every time just randomly. I thought the thermostat was sticking but after looking and seeing that it dosent have one, now I am really confused. I have tried a new radiator cap and I also tried leaving the cap loose but it still randomly gets hot and boils coolant out. Just thought I would see if some of you have ever had this problem and what else to check for. Thanks Chris

 

[Howard H.]

With no other symptoms like missing on startup or water in the oil, that is pretty odd.

I had to put a water pump on a Ford 534 truck engine one time - cranked it up (on a well) and it ran great for a few hours...

After that, I couldn't get it to keep from overheating...

Long story, short, I finally found that the impellers on the water pump shaft was loose and just would not circulate the water... Pretty surprising, especially on a new water pump...

I know HD800 engines can also have the impeller get loose on that long bolt that holds them...

Just my 2 cents...

Howard

 

[R.D.F.]

There are many possible reasons for it to overheat, how's the radiator?, has been recored lately?, has the water pump checked out?, Hoses?. We have recored radiators, NEW water pumps, hoses. Just check all the possibilites before spending money for unneeded parts. 920 295 3278, Dale and Doug

 

[ddk114]

Check that the system is indeed holding pressure. A house circulator pump will not circulate water to the upper levels unless the pressure is sufficient to get it there. Oddly enough, a massey harris combine that has the motor low and radiator high needs the pressure to make it flow. This was the same comment I gave to a neighbor that had a leaky radiator and overheat problems. Try that.

 

[J. Wondergem]

You need a thermostat to slow the flow of water through the radiator, so it can cool.

 

[glennster]

another thing to check is your distributor advance mechanism. my big mo 500 was running hot, had real high exhaust temps too. checked the advance and it was stuck. pulled the distributor and cleaned and lubed everything, runs a lot cooler now. if i remember the timing is set about 3/4 throttle and at 26-28 degrees. quick check is to pull the distrib cap, and see if the rotor will move a little , then snap back. if not, its sticky.

 

[Howard H.]

Just thinking about this today - one time also, had an old MM running fine on a well - went to check the water in the tank and the cap was stuck, tapped it lightly to get it loose and everything was fine.

Came back 3 hours later - it was dead and had overheated... Took me a while to realize, but I had knocked a big piece of scale loose inside the water tank and it had partially got sucked up against the intake of the tank, shutting off the flow.

One other thing we did was put Drano in a troublesome engine that was heating and ran it a few hours before draining and refilling. Never knew what the problem was, but that sure cured that engine, also...

Howard