Massimo 500UTV cooling fan doesn't come on

[Tebo]

I don't use my 2012 500UTV a lot. Occasional yard work and plowing snow. I noticed cooling fan was not cycling as normal, wasn't coming on at all. Overflow reservoir was dry so I added. Pulled the connector at the sensor on the rad and jumped a wire across the terminals, turned on key and fan working, so I figured bad sensor. Replaced sensor and fan still doesn't come on. Radiator is full to the top. I started it cold and let it idle so I could monitor. The coolant hoses get hard from pressure and radiator gets hot. It gets too hot to touch for more than a few seconds so (I assume) coolant has to be circulating, but no fan. I have no problem replacing parts but I have no idea where to go next. When I do use it I can tell from the heat coming through the cover that it's getting hot so after a short while of use I park it. I'm considering running the fan with a toggle switch but that's rigging, not fixing. Don't know if this is related but even with a perfect battery it labors on the starter. On and off the starter a few times and it fires up. Any advice I can get will be appreciated. 

[T-boss 410]

Did you check the fan relay?

[TapBoss]

There are a  lot of Massimo owners on here that have hard wired the fans to run constantly due to the overheating problem.  I have also read a few posts about relays corroding.

[Tebo]

I jumped the connector at the temp sensor on the rad. Fan came on so wiring is good to this point. Maybe I replaced a bad sensor with another bad one. Made in China after all. I'm going to dig the old one out of the garbage can and check resistance with some heat from a lighter. Should have done this first... If the switch in the sensor is good then I see no reason why it's not working. To be continued. 

[ElbowRoom]

I had this problem with an Odes UTV. There was too much air in the rad. The rad sensor can't read the temperature of air. To remove the air, I lifted the front wheels 20" (or more) higher than the rear (as on a trailer ramp), idled with rad cap off, and kept adding coolant to keep it full until all air bubbles came out which took about half an hour.  The fan came on as soon as enough air came out. But if at first, the fan  doesn't come on, turn engine off and let it cool BEFORE it overheats, then continue idling and removing air bubbles until the fan does come on. If this problem, keeps coming back, there's a leak that needs fixing.

[Tebo]

On 9/20/2021 at 7:55 PM, T-boss 410 said:

Did you check the fan relay?

Not sure where the fan relay is. But I have power at the temp sensor, screwed into rad on passenger side, so assuming all wiring is good.

[Tebo]

On 9/21/2021 at 11:19 AM, TapBoss said:

There are a  lot of Massimo owners on here that have hard wired the fans to run constantly due to the overheating problem.  I have also read a few posts about relays corroding.

Thanks for the reply TapBoss. I'm considering running the fan on a toggle but as a last resort. 

[Tebo]

On 9/24/2021 at 9:23 PM, ElbowRoom said:

I had this problem with an Odes UTV. There was too much air in the rad. The rad sensor can't read the temperature of air. To remove the air, I lifted the front wheels 20" (or more) higher than the rear (as on a trailer ramp), idled with rad cap off, and kept adding coolant to keep it full until all air bubbles came out which took about half an hour.  The fan came on as soon as enough air came out. But if at first, the fan  doesn't come on, turn engine off and let it cool BEFORE it overheats, then continue idling and removing air bubbles until the fan does come on. If this problem, keeps coming back, there's a leak that needs fixing.

Thanks ElbowRoom. When I pulled the cap the rad is full to the top. I ran it with the cap off (sitting level) to see if coolant was circulating. I didn't see it moving but as it warmed the coolant started moving up. So I put the cap back on to keep it from overflowing. It built pressure (hoses got hard) and radiator got hot to the touch. But no fan... I have a shop crane so I will definitely try this trick. I've seen lots of posts about air in system. I've never had it opened so if there is air then there must be a leak, somewhere. I expect I will lose a bunch of coolant before it burps. What type of coolant should I use? I've looked through the manual and didn't see anything listed. 

[ElbowRoom]

Tebo, I don't know if Massimo needs a special coolant, but I use regular green colored coolant. To prevent losing coolant while it idles, I stick a small funnel in the rad (after sanding off the funnel seam) and keep it about 1/4 full of coolant. This way, I don't lose coolant while the coolant expands and shrinks during idle, and it makes it easier to see the air bubbles come out.