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Discussion Starter #1
Hey there Polaris fans,

First time I’ve started a discussion, so forgive me if this has been covered, and please direct me to the conversation.

Stupidly, I lent my 2002 Magnum RMK 500 to a colleague for the weekend, whilst I was away.
When I returned he informed me that coolant was jetting out of the reservoir and it was pretty much empty by the time he got back. Also the temp indicator was on. I also noticed a heap of mud under and around the bike (thanks for cleaning it mate), which may be a factor in the problem. He has been pretty vague about how he was riding the bike. I’m assuming like it was a racer.

I inspected the radiator and hosing and there doesn’t seem to be any leaks. I topped up both reservoir and radiator with coolant and let the bike idle for a good time. I came back to the bike spitting coolant again. Fan was not working.

So let it cool, cleaned it up a bit and repeated steps and it seemed to work great, fan was doing its job (turning on and off), temp indicator stayed off and coolant stayed in. Thought it was fixed. Took it out for a ride and the problem happened again, nearly lost all coolant out of reservoir. Towed it back to avoid cooking it. Also noticed fan wasn’t working again.

I’m a rookie with the mechanical side of things, kind of learn as a problem arises. What do you think?
Is this a thermostat problem? Hope it’s nothing serious. Inspected coolant and oil and no bubbles, etc, so I’m guessing head is ok, no leaks.
In my own rookie opinion, if the thermostat controls the fan, then that may be what is causing the fan to sometimes work. I may be completely wrong.
Tonight I am going to carefully pressure wash the radiator in case of mud build up, but looks pretty good from the outside.

Any assistance explained for a non mechanic would be greatly appreciated.

Also, I am keen to buy a service manual for my bike. Any links?

Cheers,

Mo from the Kimberly, WA, Australia.

P.S I live in a remote community with no mechanic/shops. I usually mail order parts.
 

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I had very similar issues with a 2001 Magnum 500HDS. It turned out to be an intermittent power supply problem which I couldn't eliminate. I ended up finding another spare powered plug below the headlight which was switched through the key. I cut off the old supply to the fan and spliced in the new supply. Never had an issue since.
 

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On the left side of engine there is a sensor with a wire out of it, if you unplug the wire with the key on, fan should come on, if not temp sensor is bad.
 

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Discussion Starter #8
First up, just like to thank all for the support over the last few days- first time on a forum, should've joined earlier!
In regards to the cooling system, while I had next to no coolent, thought Id check pump and thermostat. No damage/tested well.
Russ I am having a bit of trouble locating the sensor wire plug to test the temp sensor. Would love to try with a but more 'rookie' help.
Pduff I found the extra power socket and did what you said. The fan switched on straight away. So I guess it will keep it cool. Will test. Problem is, I think the fan is constantly on/won't switch off: turns on as soon as I switch to accessories, before even starting engine, and remains on till I turn engine and key fully off.
Did this happen to you?
And is this bad for the fan? If not, it's a great fix and I'll be happy with it.
Cheers guys-
 

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Moharic

If the fan is coming as soon as you turn on the key then you have spliced in at the wrong point. The thermo switch is on the bottom of the radiator on the right hand side. Your new power supply should still run through the thermo switch to activate the fan.

One positive, you know the fan works, you now just ave to see if the thermo switch is at fault. Trace back from the thermo switch and make are your new power supply is running through the switch and not directly to the fan

Cheers

Phil
 

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Discussion Starter #10
Cheers Phil, will do this arvo.
Took it out with the fan running constant and the temp light still came on. Didn't hear boiling coolant though. Checked reservour when i got home and it was empty. Was dark though, will test out again today.
Could be air pocket in system too. I did burp it, on incline. Used bleeder on water pump housing too.
I'm going to remove radiator to give a thorough cleaning. Have been reading through forum and it seems to be one of the easier fixes before buying parts.
Also heard that this 'vintage' of Polaris model is known for being hard to remove air pockets.

Obvious question: could anyone explain/show me what i should be looking for to ensure coolent is moving around system? Had engine running, took out bleeder out again and it squirted out coolant. I guess that shows movement?
Am thinking maybe the thermostat is a litte sticky even though it did open when tested in boiling water, OR, pump is not working, even though impeller looked in good shape.

First things first: give radiator a good cleaning (i heard white vinegar works well), and try to get all the air out of the system.

Am beginning to wonder whether the bloke I lent it too (who got stuck in mud) did the damage, or it was just bad timing and in need of some TLC...

Cheers, Mo.
 

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Discussion Starter #11
Don't think I have any movement in the system. Burped it as much as I could, kept topping it up slowly till full (in top radiator cap), started her up with cap off and coolent just sat there and got hotter and hotter till it started to slowly overflow.

Water pump?
 

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Discussion Starter #12
Just took it for a spin, as the fan started whilst I was idling, so I'm guessing temp sensor may be ok. Took it for a few k's, light came on, looked underneath and the little hole under the water pump was leaking coolent. Any ideas?
 

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Discussion Starter #16
Sorted!

Figured out the problem. I hope this can assist anyone with a similar cooling system problem.

The water pump impeller ended up being loose on the shaft that drives it. I found this out by opening the cover and turning on the bike. It didn't rotate. Checked the lock nut and it was able to be tightened (in fact the first time, i took impeller off, i left it loose on the shaft so it could spin when i gave it a tap. Wrong!) Turned her on again and bingo, around it went.
Gave it a bit of a clean, flushed the system, refilled, burped and everthing is going great. Fan comes on when it's meant to and most importantly, no overheating.
I'm guessing some sediment got into the pump over time; that and some heavy riding knocked the lock nut around a bit. Am going to get a new one, just in case. As you can see from pics, the nut and pump housing have experienced a bit of wear and tear. I'm sure this is pretty normal. They're resilient machines!
Cheers for the advice guys. I hope this helps others-
 

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