T-Stat for SD220


IHC in the early to mid-fifties.

Golden Jubilee
Golden Jubilee

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Post Tue Aug 13, 2019 3:38 am

Re: T-Stat for SD220

As a follow up I have been running a 180 degree thermostat all summer, my temperature gauge reading ranges between 180 to 190 degrees even on days in the low 90's.
56 S120 4x4,

Rusty Driver
Rusty Driver

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Post Tue Aug 13, 2019 8:24 am

Re: T-Stat for SD220

cornbinder89 wrote:A 'stat can provide a very necessary restriction in the flow. Without it, coolant can pass thru the radiator faster than it can transfer heat to the air. It also can raise the pressure in the block higher than the radiator cap pressure, eliminating hot spots, and cavitation damage caused by coolant boiling at the head or cyl walls. It is why Speedway and Summit sell restrictor plates for the 'stat housing when no 'stat is used. A Cummins Big Cam 4 will run 45 psi block pressure (at full governed speed) with a radiator cap pressure of 4 psi.
Low temp 'stats will NOT prevent overheating. the "stat only sets the minimum temp.
Vehicles with an oversize radiator that isn't well maintained can sometimes benefit from the increased flow when the stat is removed to "clear the tubes" but once they are clear and the system is flushed, then a 'stat should be installed.
A radiator only needs to drop the temp 10-15 degs F to keep the engine from overheating. If it can't do that, then either the system is clogged or the radiator is too small.
With a lower temp stat, all the coolant can be held at 160 where as a higher temp 'stat will keep the flow down and the coolant in the radiator will be cooler than it would be with the lower temp 'stat.
Either way, if the system can't handle the engine heat at full throttle, it isn't a question of "if it will overheat". but when.
The hotter the engine can run, the more efficient it will be.
My Truck has pulled steep grades where I have been running flat-out at 25 mph for 45min without a break, that is a test that most vehicles will never see.



I put a 160 in mine because that's what they were selling me. My original radiator was toast so I put a new 3 core aluminum one in it. I also installed a mechanical temp gauge and it consistently reads around the 160 mark even when I was driving it around in 100 degree heat the other weekend. Are you saying based on this info that I should pull the 160 and put a higher temp stat in since I'm running too cool of a temp?

Golden Jubilee
Golden Jubilee

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Post Tue Aug 13, 2019 8:03 pm

Re: T-Stat for SD220

You are running at the 'stat temp, Like I said it only controls the Minimum.
Yes, if it were mine I'd look for a 180 or 192 'stat.
Too cool running causes sludge in the crankcase and can cause the gasoline to condense out of the mixture and wash down cyl walls.

Golden Jubilee
Golden Jubilee

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Post Mon Aug 19, 2019 1:27 pm

Re: T-Stat for SD220

I should have clarified when I said I have run them without a stat, when I have done that I have used an old stat and cut the stat off the plate so I still had a restrictor plate running in the housing. When the temp is over 100 outside when the 180 degree stat opens the temp can continue to rise up to around 200 degrees before the tiny old radiators these have can start cooling the engine. I know that 200 isn't too hot but I prefer my engine to be running in the 160 to 170 range.
52 L110
61 C112
68 Cadillac Coupe DeVille

Golden Jubilee
Golden Jubilee

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Post Mon Aug 19, 2019 5:28 pm

Re: T-Stat for SD220

your engine, your choice, but 170 is too cool for best operation. Big truck diesels that use a water (coolant) aftercooler for the intake air, have to walk a fine line between engine temp and intake air temp. These run 170 deg, but they don't have to worry about fuel condensing out of the intake air.
Even heavy diesels (with air to air charge coolers) run 180 to 190 deg 'stats.
As long as the coolant isn't boiling, it isn't overheating. The only reason engines run as cool as they do is to prevent boiling of the coolant, not because it is "too hot". Deutz "oil cooled" diesels runs fine around 300 deg.
240-250 isn't too hot as long as you have 50/50 mix of coolant and a 15 lb pressure cap.
The only reason you don't want to run real close to the boil point is you can get micro-points where the coolant boils at the surface and erodes the surface. As long as you have good coolant under pressure, the temp isn't the problem.
Ideally you want oil temps to exceed the boil point of water, but in reality any temp over 180 will drive most of the moisture out, hard to do if the engine is running 160-170.

Rusty Driver
Rusty Driver

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Post Thu Aug 29, 2019 11:18 am

Re: T-Stat for SD220

So do you recommend the 180 or 192 or doesn't it matter? Does anybody have the part number for a 192?

Golden Jubilee
Golden Jubilee

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Post Thu Aug 29, 2019 4:22 pm

Re: T-Stat for SD220

I don't remember what the part number is, I have a 165* and it run 175 all the time. I have checked it with the old school thermometer.
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