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Discussion Starter #1
If so, what kind results did it yield? Did it run cooler? Take too long to warm up?
Thanks
matt
 

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Discussion Starter #4
Maybe polaris did that cuz they realized rzrs run too hot out here on the west coast? Maybe ill just have to remove mine and see what happens.
 

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TURBO'S RULE
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1,772 Posts
Why do you want to remove the t-stat ? A t-stat bypass is not the same as removing the t-stat.
Many negative things can happen when removing a closed loop cooling system t-stat.

1) Depending on the particular cooling system...
In some engine applications removing the t-stat(restriction) will dramatically increase flow, and circulate coolant in turbulent flow pattern that creates large boundary areas that cause hot spots in cooling passages. Even though the area that houses the coolant gauge sensor is cool and registers cooler you still could have hot spots in critical areas that will show up down the road as increased wear or failure.

2) Anything under 135-140 degrees for cyl head water jacket will probably not promote proper combustion.

3) depending on actual cyl water jacket temps, a new piston to cyl wall clearance might be needed for high rpm engine life. with no t-stat the water jacket temps can vary 100+ degrees. Hard to figure on a performance oriented piston to cyl wall clearance with that large temp range. In essence, it never really warms up, or keeps warmed up. A nightmare for forged pistons.

4) The electric fan set point and differential is set to compliment the t-stat engine operating temp, and should be coordinated with it for a properly working cooling system. Removing the t-stat throws a wrench in this finely tuned system, to say the least.

My opinion is to never remove a t-stat.
Highly modified engines with cooling systems heat removal capability maxed out, should get a larger radiator and maybe a higher capacity pump.
 

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Discussion Starter #6
Why do you want to remove the t-stat ? A t-stat bypass is not the same as removing the t-stat.
Many negative things can happen when removing a closed loop cooling system t-stat.

1) Depending on the particular cooling system...
In some engine applications removing the t-stat(restriction) will dramatically increase flow, and circulate coolant in turbulent flow pattern that creates large boundary areas that cause hot spots in cooling passages. Even though the area that houses the coolant gauge sensor is cool and registers cooler you still could have hot spots in critical areas that will show up down the road as increased wear or failure.

2) Anything under 135-140 degrees for cyl head water jacket will probably not promote proper combustion.

3) depending on actual cyl water jacket temps, a new piston to cyl wall clearance might be needed for high rpm engine life. with no t-stat the water jacket temps can vary 100+ degrees. Hard to figure on a performance oriented piston to cyl wall clearance with that large temp range. In essence, it never really warms up, or keeps warmed up. A nightmare for forged pistons.

4) The electric fan set point and differential is set to compliment the t-stat engine operating temp, and should be coordinated with it for a properly working cooling system. Removing the t-stat throws a wrench in this finely tuned system, to say the least.

My opinion is to never remove a t-stat.
Highly modified engines with cooling systems heat removal capability maxed out, should get a larger radiator and maybe a higher capacity pump.
Wow great reply. Thank you! I asked because mine does seem to run hot and it didn't like it, starts spitting and coughing around 210. Fan seems to kick on late, like around 205. Might just have to wire in an override switch. I think i've read on here that it helps keep the temps down.
 

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TURBO'S RULE
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...engines with cooling systems heat removal capability maxed out, should get a larger radiator...
I have been saying the exact same thing for years.
I never thought about a higher flowing waterpump.

Vince
Looks like a new radiator is in the future, or maybe an oil cooler.

Does anyone make a lower temp thermostat?
Wow great reply. Thank you! I asked because mine does seem to run hot and it didn't like it, starts spitting and coughing around 210. Fan seems to kick on late, like around 205. Might just have to wire in an override switch. I think i've read on here that it helps keep the temps down.

Hold on there... before we become a parts changer instead of a technician, lets try to troubleshoot this problem.

spitting and coughing

I am not convinced that overheating is your problem. Tell us more about your symptoms and what its doing or not doing.

Cant seem to find the fan operating temps now. But did see them in the manual before. If I remember right, those fan temps are pretty close to where they should be. You might want to search the manual for those fan operating temps specs.


Lets try the simplest things first. Good to use a logical step by step process of elimination. Since you think its overheating lets try to eliminate that first.

Do you have the manual? This note is on page 20 cooling system:

NOTE: The fan may not function or operation may
be delayed if coolant level is low or if air is trapped in
the cooling system. Be sure cooling system is full
and purged of air. Refer to Maintenance Chapter 2
for cooling system information.


Does your rzr boil over ?
 

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Discussion Starter #10
No it dosnt boil over. I have purged the system, i did this by putting the front end up in the air, opened up the bleeder screw until a steady stream of coolant was flowing out and at the same time adding more coolant at the radiator.
Preety sure i did it right but maybe i missed something?
Thanks
 

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Discussion Starter #11
No it dosnt boil over. I have purged the system, i did this by putting the front end up in the air, opened up the bleeder screw until a steady stream of coolant was flowing out and at the same time adding more coolant at the radiator.
Preety sure i did it right but maybe i missed something?
Thanks
 

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279 Posts
HPD makes a bypass thermostat for the 2008 to 2010 RZRs. We had problems with over heat, racing in the desert. Adding a bigger radiator did not cure the problem. At the time Polaris was having some Ranger users remove the thermostat. We tested with probes in the cylinder head and found in warm up there were parts of the head that were way to hot before the thermostat opened, and that the thermostat would not flow enough when full open. We designed a new thermostat housing that contains a larger, 2 stage thermostat, like the new Chevy V8's use. It by passes the coolent around to the water pump, for full circulation, untill the thermostat starts to open. When the thermostat starts to open the bypass starts to close. This keeps coolent an even temperature in the engine with no hot spots. When the thermostat is full open, the by pass is full closed. The thermostat flows 20 % more water than the original. Polaris got some of these from us for testing and liked them. They said it did just what I told them it would. If you look at the 2011, the thermostat is bigger and it has a permanent by pass. Making one like ours would have been more expensive than what they did. One of the reasons for the changes in the 2011 engine was for cooling. We do that with our by pass thermostat kit. We have sold a lot of them and have had no problems with over heat. It works. We have then in 170 Degree and 180 Degree. HPD Part #'s RZRTK170 or RZRTK180
 

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Discussion Starter #15
HPD makes a bypass thermostat for the 2008 to 2010 RZRs. We had problems with over heat, racing in the desert. Adding a bigger radiator did not cure the problem. At the time Polaris was having some Ranger users remove the thermostat. We tested with probes in the cylinder head and found in warm up there were parts of the head that were way to hot before the thermostat opened, and that the thermostat would not flow enough when full open. We designed a new thermostat housing that contains a larger, 2 stage thermostat, like the new Chevy V8's use. It by passes the coolent around to the water pump, for full circulation, untill the thermostat starts to open. When the thermostat starts to open the bypass starts to close. This keeps coolent an even temperature in the engine with no hot spots. When the thermostat is full open, the by pass is full closed. The thermostat flows 20 % more water than the original. Polaris got some of these from us for testing and liked them. They said it did just what I told them it would. If you look at the 2011, the thermostat is bigger and it has a permanent by pass. Making one like ours would have been more expensive than what they did. One of the reasons for the changes in the 2011 engine was for cooling. We do that with our by pass thermostat kit. We have sold a lot of them and have had no problems with over heat. It works. We have then in 170 Degree and 180 Degree. HPD Part #'s RZRTK170 or RZRTK180
What kind of operating temps should i expect to see with your bypass kit installed? Right now when running hard temps are between 200 and 215.
 

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Forgot to mention that we tried a 140 Degree thermostat and a 160 Degree thermostat in our housing. Neither one worked, too cold. It seams that the ECU thinks the engine is still cold up till about 160 Degrees. It will run rich untill then. We recommend the 180 for stock or near stock machines and the 170 for mod engines.
Powermaxx (Darrell)
 

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Discussion Starter #17
Forgot to mention that we tried a 140 Degree thermostat and a 160 Degree thermostat in our housing. Neither one worked, too cold. It seams that the ECU thinks the engine is still cold up till about 160 Degrees. It will run rich untill then. We recommend the 180 for stock or near stock machines and the 170 for mod engines.
Powermaxx (Darrell)
Thanks for you help darrell. I was looking at the 2011 set up and it looks like all they did was splice into the input line with a bypass hose that goes directly into the engine right next to the thermostat housing. Like you said, a cheap version of your set-up. So until i can afford to buy your kit what can i do to cool things down? Would drillig holes in my thermostat help?
 

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King of crash!
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Why do you want to remove the t-stat ? A t-stat bypass is not the same as removing the t-stat.
Many negative things can happen when removing a closed loop cooling system t-stat.

1) Depending on the particular cooling system...
In some engine applications removing the t-stat(restriction) will dramatically increase flow, and circulate coolant in turbulent flow pattern that creates large boundary areas that cause hot spots in cooling passages. Even though the area that houses the coolant gauge sensor is cool and registers cooler you still could have hot spots in critical areas that will show up down the road as increased wear or failure.

2) Anything under 135-140 degrees for cyl head water jacket will probably not promote proper combustion.

3) depending on actual cyl water jacket temps, a new piston to cyl wall clearance might be needed for high rpm engine life. with no t-stat the water jacket temps can vary 100+ degrees. Hard to figure on a performance oriented piston to cyl wall clearance with that large temp range. In essence, it never really warms up, or keeps warmed up. A nightmare for forged pistons.

4) The electric fan set point and differential is set to compliment the t-stat engine operating temp, and should be coordinated with it for a properly working cooling system. Removing the t-stat throws a wrench in this finely tuned system, to say the least.

My opinion is to never remove a t-stat.
Highly modified engines with cooling systems heat removal capability maxed out, should get a larger radiator and maybe a higher capacity pump.
i agree with allcools statement cool is good but cold is bad. by pass keeps water flowing and cuts down on airation ...airation causes air bubbles to form and water cools better than air.... .... also with no t stat to slow down the flow the radiator cannot rid its sellf of the heat build up in it....with high flow the heat exchange never happens....the temps are good that his fan is going on...you must have anotheir problem going on....
 

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Discussion Starter #19
Looks like ill be purging the system again this weekend just make sure i didn't miss something. Any tips here?
 

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Temps of 195 to 210 are normal with an RZR. Drilling a small hole in the thermostat disc will help NON OPEN water flow. About 1/8". If the hole is too big you will not warm up the engine in cold weather. The stock thermostat starts to open at 180 degrees and is full open about 190 to 195 degrees.
Darrell (Powermaxx)
 
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