Evo 2012 300.

Runs sweet after new bottom end lock down but recently I’ve been having moments where the old girl boils up. First time it’s ever started doing this. 
 

I took the water pump cover off and the plastic impeller rattles on the shaft, rocks back and forth. Still goes with the shaft but I wonder if when hot the shaft can spin in the impeller? Appears worn to me. I’m ordering up a replacement. Would this worn one be causing my overheat possibly?

I next need to check the fan switch and fan is actually working  any advice on what and how to check?

Thanks in advance 

 

To test the fan switch, an easy way to do it is to unplug the fan switch and fit an electrical bridge across the connector.

To test the fan and the bike's power supply, unplug the fan and connect 12V DC from an external source to the fan motor.

After some time the fan impellor does become loose on the shaft so it is worth replacing it on a bike your age and it is not expensive.  The connector for the thermostat/fan control system is under the left hand tank side  panel see attached document.   If the thermostat is original, it has done well to last!   

Let us know what you find.

 

Thermostst test on 2012 EVO.pdf

I picked up a new impeller today. I’ll fit it and then run it up till boiling point and see what happens. Thanks for the tips both. 

New impeller fitted. Much more snug. Feels like it’ll do a job now. Thermostat by passed and fan works. I’ll run it up to temperature on Friday. If no fan then I know it’s the thermostat. If no boiling then I know it was the impeller. 

Got out today. Sure enough it eventually got hot. I’d already set up Overdales by pass behind the left cover. And gaffa taped an Allen jey to the bike. A quick stop and a fiddle got the fan running with the motor. Successful ride after that. Well, apart from falling off and rolling down a steep hill backwards through the brambles. Skin will grow back though🙄.

 

The important bit is I need a new temp switch thingy. Looks like a pipe off job to get the rad out?

 You have to be careful. A ten year old fan can be having trouble just starting to spin.

Any warning signs? It turns smoothly, no noises, slows gradually to a stop. I’ve been seeing this as signs of that being ok?

Well, if it takes a long time to turn on. A tell tale sign the fans life is about out, spinning with the finger gets it going. I have had this happen on a couple of bikes now. A new fan is the only fix. 

Had the great joy and fun to fit the new switch today. Old part superseded by a later one with a different connection. A quick mod later and it’s all on. Old one was a complete git to get out!
 

Not heat tested yet but will do. I’ve fixed the issue regardless though as picked up to 2020 factory the other day. Well happy with it!