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overheating and no thermostat

fredrich_

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Joined
Apr 10, 2025
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i recently bought a second-hand 2004 yamaha rhino 660. works well, i must say and it was priced so good i forgot that this model was designed without the traditional thermostat..

here's the problem.. when i drive it for more than 40 minutes, the overheat light comes on and it will go on and off for a few minutes. has anyone encountered the same and how did you fix it?
 
Yep yep, that's a common issue with the 660, no thermostat, so the warm up is slow and that reduces the cooling efficiency, so you're probably getting heat soak after extended runs. install an inline thermostat kit and flush the radiator, then check the fan switch, to make sure the fan actually kicks on when it's supposed to, don't just ride it and hope for the best, you'll cook that engine.
 
i recently bought a second-hand 2004 yamaha rhino 660. works well, i must say and it was priced so good i forgot that this model was designed without the traditional thermostat..

here's the problem.. when i drive it for more than 40 minutes, the overheat light comes on and it will go on and off for a few minutes. has anyone encountered the same and how did you fix it?
Clean the Radiator Thoroughly,check and Burp Coolant, make sure it's at the proper level and no air pockets, also check fan Operation
 
i recently bought a second-hand 2004 yamaha rhino 660. works well, i must say and it was priced so good i forgot that this model was designed without the traditional thermostat..

here's the problem.. when i drive it for more than 40 minutes, the overheat light comes on and it will go on and off for a few minutes. has anyone encountered the same and how did you fix it?
Yeah it's kind of trickier isn't it. Well, looks to me like your Rhino's simply running hot after longer rides. So it might be a clogged radiator or low coolant flow. Give the cooling system a good flush then check the hoses. :)
 
i recently bought a second-hand 2004 yamaha rhino 660. works well, i must say and it was priced so good i forgot that this model was designed without the traditional thermostat..

here's the problem.. when i drive it for more than 40 minutes, the overheat light comes on and it will go on and off for a few minutes. has anyone encountered the same and how did you fix it?
Many owners solve this by installing an inline thermostat kit to help regulate engine temp.
 
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