fan question

[littlecat]

ok, had some 'issues ' with the cooling system on the cbr...including overheating and pretty much boiling the contents to the point you could make a cuppa each time I stopped ....but wont go into the whole long winded essay.

have replaced the rad today ( which is way better than the old one|)...kept the original fan as when tested off the bike it works fine..

whole system seems much happier today , but after leaving the bike to warm up until the needles almost off the gauge, the fans still not kicking in.

where do I start looking next ???

[Stu]

you need to know what temp the fan comes on at and make sure the sensor activates at around that temp

then you need to know how hot the water is on the bike and not just by the gauge as that could be wrong

also check the water pump is working

[littlecat]

next stupid question...how do I check the water pumps working( pretty sure water is circulating, but is there a specific way to check)

[littlecat]

and is the only way to check the sensor in the switch by taking it off ??

[Stu]

if water is circulating then chances are there is nothing wrong with the water pump

yeah taking the sensor off is usually the best way in a pan of water heating up with a thermometer in the pan and see when it switches on

if you know the values you can check it by resistance

[eastanglianbiker]

quick easy test is remove the 2 wires from sensor and connect a switch inline flick switch fan cuts in sensor might well be cattled replace or leave switch in and turn on and off manually i did on my fzr1000 for years

[Marmalade43]

When it's cold (to avoid covering yourself with boiling water) take the radiator cap off and start the bike, rev it and you'll see the water rushing about and likely the level will drop a bit when revved. This shows your pump is fine, if the pump wasn't working it wouldn't take many minutes long to boil up.

Put a meter on the terminals of the fan switch and run it to see if it switches when hot enough, problem being that the fan won't come on while you are going this, best to put a test light between the output of the switch while still connected and the battery and see if it comes on at all.

Sounds like the head gasket could be stuffed, this could show by making the hoses hard by pressurising the system when running and would likely make water exit the radiator filler swiftly when the cap is off while running.

Boiling up a bike is a swift way to a screwed head gasket so if it's not this, you need to sort it before it is.

[Tango]

Could also be an air lock in the water jacket......but, to me, it sounds like the temp switch is not operating.....test as suggested above. Also check that the thermostat is opening......could be that water is not circulating through the rad if the thermostat isn't opening.....

[cockercas]

Thermostat? Stuck open will cause temp issues.

[littlecat]

thermostats fine.

having investigated further , the fan fuse was blown....

I have continuity on the live, from connector to fuse....the neutral , from connector to switch...

but im not able to get anything from the green earth to ground.

im guessing wildly here , but looks like an earth problem, and that's about where my talent runs out.....helpppppp

[cockercas]

Run a temp earth wire and see if it works. If it dose and nothing else is effected by the bad earth just run a new wire and earth it.

[Marmalade43]

Or do a ohm test with meter to see if the earth is ok.