Mine had this problem too. The cause was a rock jammed in my fan. It’s a tough area to clean

 

The service manual says to use a 50/50 mixture of distilled water and antifreeze. It also states "The effectiveness of coolant decreases with the accumulation of rust or if there is a change in the mixing proportion during usage. Therefore, for best performance change the coolant regularly as specified in the maintenance schedule."

The maintenance schedule says to service the cooling system at 600 miles but the footnote says to service it more frequently after riding in wet or muddy conditions.

Have you ever added tap water? If so, I would take it to a garage and have them flush the system and refill it with the proper mix.

 

Have you checked to see if the thermostat is opening? Take the cap off the radiator and start the quad. Let it idle while looking into the radiator. You should see the fliud start to flow. There is a noticable change when it opens.

There are a ton of things. Bad thermostat, bad cap, no pressure, clogged radiator (inside or out), bad water pump, etc. Do you have a service manual?

 

bobbb...I just recently changed the oil, so I don't believe that is the problem.

hiofcr...the fan is running fine, and isn't blocked.

up2snuf...the only thing that has been added to the mix is a small amount of 50/50 mix to bring it up to full level, and a couple of capfuls of coolant additive called "Water Wetter". It's supposed to help the radiator cool better. (ironic, isn't it?)

TEXmud...I'll check the thermostat. I don't have a service manual. That's why I consulted you guys.

 

My Rubi overheats too. The only solution I have found so far is a real good radiator cleaning. Make sure the water flows through the fins everywhere. Feel the back of the radiator. You may think it is getting through, but it may not be.

After one trip to the mud bath and 3 miles down the road, I need to give it a radiator cleaning. It takes way to much time. My Foreman 400 doesn't have nearly the overheating problem as the Rubicon. Do I need to give up mudding with the Rubicon or does someone have an idea on how to keep the radiator clean between mud baths?

Jeff

 

I had my header jet coated and I run the Big Gun exhaust which is already coated. I also run the HL Coolant Additive. Even with all my engine work my temp stays at 210. The thermostat is fully open at 203....so I would say my heat fighting stuff works great. As far as the radiator goes a clogged radiator will affect ANY quad that has one. I built an extra shield for mine but it got ripped this weekend so I will be redoing it. It seems to work good.