Overheating Bombardier SkiDozer SV200

I want to help groom a snowmobile trail with my 1973 SkiDozer, but it runs up to about 210 or 220 degrees when pulling the 6 foot wide groomer. I've checked coolant and fan belt and I've got a shroud around the fan. The automatic transmission cooler is mounted in front of the radiator. The engine is the standard Ford 6-cylinder gas. Any suggestions?

If it dose ok when running normal with no heating problems try droping down a gear and see if that takes care of it

Also check you timing and be sure it is properly timed....vacume advance unhooked...This can make a 6 cylinder heat up real fast. Maybe pull a plug and see the color. if it is white, it is too lean and this wil cause overheating as well.

When was the last time the themostat was changed? Could be hanging up.

As was said, lugging the engine in heavy snow can cause this as well.

Good luck, Kirk

if the thermostat was removed than you could have too much coolant flow and cause overheating under load also you could also have sediment in the bottom of the raidator i would look at timing and look at the pluggs to see that the carb is jetted right for your aplication first than run a can of fast flush through the system than than replace the thermostat and see how it works

Thanks Don and others. I've got a new thermostat and had the radiator boiled this summer. (It runs OK at 195 degrees without a load). Right now I'm suspecting timing (dwell angle). Too cold right now to test those, but I'll try to get it into my heated shop (I know, a luxury) ASAP. One factor might have been the overheating occured when air temp was about 32, so today it maybe wouldn't even overheat.

don't discount a defective t- stat my jeep did the same thing replaced the t-stat the second time and now it works great also look for steady bubbles indicating a leaky head gasket or a hairline crack in the head also don't discount a the carb may be jetted too lean for your conditions but start with timing and dwell first

Pretty good ideas all, but always revisit the last fix. Thermostat manufacture has changed and they no longer respond the way originals did. They tend to be more all or nothing these days. The Jeep folks (Willys) fix that by drilling 1-3 holes about 1/8" diameter in the rim. This will not slow your warmup, but will ensure some amount of continuous flow. The rapid open-close cycle reveals itself in "mild" overheats. Usually the system will blurt some fluid and settle down a quart low or so. Only a good gauge catches the smallest of swings in temp. I bet the harder you run it the more stable the temps. Before you do anything drastic like rebuild your distributor gears, try poking some holes in the thermostat.

My $0.02.

PS, the differences in thermostats has to do with metallurgy and the EPA in the 21st century.

195 at "no load" is a little warm IMO. That machine should run fine in much warmer temps than 32. Verify your temp gage is indicating the correct temperature also

I agree with all the above.

Has the water pump been replaced?I have seen the impeller blades erode away enough to cause flow loss and over heating.
Has the antifreeze to water ratio been checked?Too much antifreeze can cause the coolant mix to hold more heat.
Has the radiator and cooling system been flushed?Radiators can get scale in them from minerals found in water,especially if the water came from a well or heavily treated city water.Are the radiator fins clear so air can flow through?
Has the engine been tuned up recently?Timing and a lean mix has already been covered above.
Has the valve lash and timing chain been checked?I know that engine has hydraulic lifters but parts do wear causing timing and valve lash issues.
Has the muffler or exhaust tubing been damaged?This can cause over heating due to exhaust flow restriction.

Alaska Snow Cat said:

195 at "no load" is a little warm IMO. That machine should run fine in much warmer temps than 32. Verify your temp gage is indicating the correct temperature also

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I agree.No load should be 160F* to 180F*.

Our club has a 1969 SV200. This summer the radiator was re-cored with a 3 tube core. That made a difference but prior to that the orginal fan drive bearings failed years ago and the guys just bolted a standard 4 blade fan to the water pump and added two small electric fans to the radiator to help. One inside and one outside. That outside one would fail from time to time.

We have since converted the ignition to an electronic unit from Pertronix, we run ported advance, and we replaced the carb with one from a 300 6cyl which has a slightly richer fuel map.
The final change was to run a LoBoy fan on the back side of the radiator with a temp switch to turn it on and off (we also have a manual override in case of failure) and to change out the transmission oil cooler with a B&M one that has it's own fan (automatic switch with manual override).

We found that when grooming the engine wasn't tunring fast enough to pull enough air through the radiator. We'd run 250* on the trans oil and that just preheats the radiator and it can't cool well enough.

Our unit will now run at 185* and you hear the booster fan cycle on and off from time to time. Trans oil is never higher than 180* which will make the tranny last longer.

We changed out the head two years ago with one from a 1982 Cougar. Ported it a little, Added the port divider and decked it an extra 0.050" to bump the compression up a bit. The last two years we've used an average of 2.4 gallons per hour grooming. Not bad for a 250 Ford. Hope this helps.
Speedy

Thanks for all the suggestions. I finally tried a new temperature guage and found that was the problem. I've yet to test it on a long grooming run, but on short test runs it seems OK.