900 Coolant Bypass

[TrailRebel]

What is the purpose of the radiator in the 900? I know to us, it looks very boneheaded, but what was the purpose of routing the system that way? Why do the newer sleds revert back to how the Edge Chassis setups(coolant into water pump, coolant out from thermostat, BYPASS to reservoir)? There has to be something from a logical standpoint why Polaris did what they did. It almost seems like the 866/755 engines were one of the only ones that never got any kind of "bypass" loop, could it be beneficial to this engine?

 

[mountainhorse]

The 900's have a beautiful thermostat controlled bypass circuit built into the motor... IMO the best bypass system yet... Probably pretty costly too.

Look at the water pump on the back of the motor.. you will see a short 1/2" hose from the pump to the back of the head... that is the bypass line... closes when the thermostat is open.

IMO...Polaris overestimated the airflow through the radiator in real-world use.... Mistakes can happen.

I have a couple of flatlander friends that I've helped...left the rad in BUT ran it in series rather than Parallel like the stock config.... Cooled much better for them... In the mountains... I have not had cooling issues with a 900 with the rad removed.

 

[Mech Engr]

rad delete

I went back and read the sticky post for rad delete and it starts off with a problem with the hose getting very close to the y-pipe. After looking at Mountainhorses great diagram I can't see why or how this could happen. It appears as though you are simply replacing a T with a Coupling but it doesn't look like you'd be changing the hose routing or strectching a hose out as was said in the sticky. What am I missing here? I definately need to do something...rode in La Porte, CA this Sunday with no grooming at all and 3+ feet of powder and unless I was actually in the powder and not on the packed trail (still real loose and powdery) I was running between 145 and 155 (too hot for me). I tried scratchers down and up with not much difference.

Big John

 

[TrailRebel]

The 900's have a beautiful thermostat controlled bypass circuit built into the motor... IMO the best bypass system yet... Probably pretty costly too.

Look at the water pump on the back of the motor.. you will see a short 1/2" hose from the pump to the back of the head... that is the bypass line... closes when the thermostat is open.

IMO...Polaris overestimated the airflow through the radiator in real-world use.... Mistakes can happen.

I have a couple of flatlander friends that I've helped...left the rad in BUT ran it in series rather than Parallel like the stock config.... Cooled much better for them... In the mountains... I have not had cooling issues with a 900 with the rad removed.

Thanks, MH. I did remove the dead loop from the system, and it made a world of difference to the coolant temperatures. In the long run, I'd like to make the upgrade to the 09 plastics, in which case there won't be any room for the front radiator. Even when off trail, unless I'm moving 15mph or slower, temps start to creep up, and when the other sleds get a little bit stuck, it's mandatory to shut the engine off, or the coolant temps will be much too warm. Sled only has 28 hours on it, with 650 miles and the radiator air dam is already starting to warp from the radiator heat. It is a constant battle to keep the snow from icing up inside the radiator cowling. On the trail only days, temps are good, and there's no ice build up in the radiator cowling.

I just purchased a used set of tunnel protectors/coolers from a Pro-X($45.00 shipped to my door so if it doesn't work out, I'm not out much), and I plan on running these underneath the tunnel, in the same location to the track, seeing how my track is studded. I plan on cutting and welding the further back hose nipples, and creating a U-shaped cooler, then just drilling two holes in front of the gas tank, and running the radiator hoses to that, instead. Hopefully, this will solve multiple problems with one solution: eliminate the radiator and all above mentioned problems associated with it, and expand the cooling system for short term stops/ better cooling, as well as eliminating a little bit of the ice chunk suitcase that builds up on the bottom side of the tunnel, in front of the rear cooler.

 

[Danbot]

I went back and read the sticky post for rad delete and it starts off with a problem with the hose getting very close to the y-pipe. After looking at Mountainhorses great diagram I can't see why or how this could happen. It appears as though you are simply replacing a T with a Coupling but it doesn't look like you'd be changing the hose routing or strectching a hose out as was said in the sticky. What am I missing here? I definately need to do something...rode in La Porte, CA this Sunday with no grooming at all and 3+ feet of powder and unless I was actually in the powder and not on the packed trail (still real loose and powdery) I was running between 145 and 155 (too hot for me). I tried scratchers down and up with not much difference.

Big John

That hose was close enough to the ypipe for me to cover it in racer tape, but your right, it never moved after replacing the T with a straight union... it was always that close.
Your symptoms sound typical for a sled that is sending most of the coolant endlessly through the radiator instead of through the heat exchanger like it should.

 

[Z-Man]

That hose was close enough to the ypipe for me to cover it in racer tape, but your right, it never moved after replacing the T with a straight union... it was always that close.
Your symptoms sound typical for a sled that is sending most of the coolant endlessly through the radiator instead of through the heat exchanger like it should.

I covered that hose with Aluminum heat tape too.