Tom Cat over heating, 1954, 40 passenger Bombaardier

Hello Tom and Ray,

I am one of the snow cat drivers at Meany Ski Lodge. It is a non profit ski lodge up in the heart of the Cascade Mountain Range some one and half hours out of Seattle Washington. The lodge and ski lifts are over 75 years old.

It is a three mile (2.7 to be exact) walk, ski or snow cat drive up to our ski lodge from the parking lot. Also a net gain of over 500 vertical feet.

Our Tom Cat is having problems over heating, what are we to do? It is a 1954 stretch Bombardier snow cat. It is 20 feet long, 10 feet wide and 10 feet tall. It holds up to 40 people inside and all there snow gear on top. Empty it weighs 10,000 pounds. Full we estimate it doubles in weights.

Some 15 or so years ago it was cut in half and stretched out an additional 67 inches. It is powered by a 1967 Chevy 282 long stroke pick up truck straight six engine. It has a manual four speed transmission. Each gear doubles in speed at 3,000 rpms. 3, 6, 12 and 24 mph in fourth. It tops out near 3,500 rpms and my guess is this is closing in on 30 mph.

In cold weather and hard snow all is well. But in soft, deep snow when above 32 degrees we have over heating problems. It can handle the load on the flats in third and up hill in second. I run the cat between 2,000 and 3,000 rpms. I can keep my foot out of the gas pedal and not be over loading the engine. But it still over heats.

We have mounted the radiator on the roof. It is a large tractor radiator with side mounted water chambers. We have a plastic electric fan on the front of the radiator pushing air thru it. It seems that even when the cat can pull the load with little trouble it over heats in the soft snow.

Jim Fahey Facilities Manager

Applied Physics Laboratory

University of Washington

206-543-3632 fax 206-543-6785

1013 NE 40th St., Sea. WA. 98105


Step One.

Replace the thermostat with a new 180 degree one. While the thermostat is out, check the coolant pumping action through the radiator. It should be vigorous with no thermostat restricting the flow. If the coolant circulation looks good, then perhaps that old '67 Chevy engine, it’s been 45 years, is badly corroded internally and the cooling passages in the head are partially blocked. Under a light load, the engine can still cool itself but when under heavy load, hot spots develop that will boil the water in the stagnant areas and make your temperature gauge climb even though the rest of the cooling system is operating normally.

If the heater works normally, that’s a good sign your water pump is at least TRYING to cool the engine…

So how come the radiator got moved to the roof?? Has that arrangement EVER worked properly?

You need to have the vehicle checked out by a good mechanic. I suspect a clogged radiator or bad water pump (broken impellers). What are the symptoms of the overheating? If you are just seeing the overheat condition on the temperature gauge then it may be a bad heat sending unit or bad gauge. We need more info. I wish I was close enough to see this vehicle. I would check it out for free.

Yeah, I’d wonder if the rad moving to the roof was ever functional too. The fan should be arranged as a puller for max cfm. The fan itself may be way too small (we don’t have a clue).

Any air in the system would end up at the rad. Do you have a recovery tank up top too? What pressure do you operate the system at? With no air in the system you’re not pushing any more vertical head since you’re also having the same water column pushing down as well.

Overheating under load can be as simple as needing a new radiator cap. Try that first.