Engine cooling, radiator boiling overr

[William P]

After a short while of engine running the temp light comes on and the water in the radiator water is boiling., water level is ok pryer to starting engine. This is consistent. Coleman 400 bout 3yrs old

[aefron88]

Is the fan coming on? If not you likely have a failed thermo switch (drivers side of radiator towards the bottom) or a failed fan. The switch seems to be the more common failure, and relatively cheap to fix. do a search there was a post last year about troubleshooting/replacement with some good pictures.

If the fan is working, you may need to bleed coolant. these can be tricky to bleed. there is an allen setscrew style plug on the drivers side of the engine where the coolant hose goes into the block that you need to loosen to get a good bleed or there can be air stuck at the top of the engine which will reduce/stop coolant circulation.

[Joe Breaux]

look for air bubbles in coolant recovery  bottle..sure sign of head gasket  failure

[Don W]

Taking the opportunity to say I have received great help from Joe and aefron and have no doubt both know more about these machines than I do!  Both suggestions I have found to be true, while I haven't had fan problems if I ran it around 3000 RPM + in this hot FL weather (90-100 degrees) it tends to run a little warm, like me!!. Where you say "water in the radiator" I'm sure you actually mean "coolant" as a proper mix of anti-freeze, I.E. coolant will run a little cooler. Also I do not remember the name but I believe I bought in an auto parts store or maybe even AMAZON an additive that is suoposed to make it run a little cooler. Not certain if it did but it at least made me think I was helping some!! LOL  Oh, mine is a 2016 MASSIMO MSU 800, which in my mind has been a great machine. Not as nice or as many frills as say a HONDA, and I'm sure not as well built. However a funny thing, a friend had a HONDA, def a nicer machine. He had raised it up with huge tires and the gear boxes or whatever they're called on the axels. Also a snorkel, and could go in 4-5n ft of water! He brought it out to the lease a few time and I noticed if we came up to a 8-10" log across the trail he would always use 2 wheel drive to get over it! I asked why? He said with the oversized tires, wheels etc in 4 wheel drive it many times would break the axels going over logs! !Now he had over 20 grand in his, I had 10!! To each their own!!!   Good luck!

[Alien10]

Let it warm up with the radiator cap loosen so you don't let it build pressure and scald yourself when removing the cap.   When its warmed up enough so that the thermostat should be opened,  look into the radiator fill port, (not the over flow jug) does the coolant appear to be moving or circulating in any way?  If it is just sitting there, chances are you either have a failed thermostat or a failed water pump.   Also carefully observe to confirm that there are no steady gases or steam being emitted out of the radiator fill.  That would  indicate a head gasket fail.  Further, the coolant should be clean, not discolored or frothy. 

Others may have more and better thoughts on this. 

[Joe Breaux]

Giant wheels put enormous strain on driveline not designed for them. I ll bet his brakes don't work well either

[Joe Breaux]

My Massimo does pretty well in mud but you cannot exceed about 18 inches of water or slipping belt occurs. But it will keep up with more expensive rigs in mud.