Manual on/off switch for rad fan??

[Cammo]

The only part of the cooling system that I haven't checked is the water pump as one of the screws has been rounded off but this has nothing to do with the fan actuating at the right temp??!!

It could, because the water won't be circulating very well there will be local hot and cooler spots.

I'm surprised at the amount of broken water pump impellers I've seen on this forum: it happens!

[Morespeedvicar]

There a fuse for the fan i'm guessing you've checked its ok? Start with simple stuff first, wiring a switch isnt that hard, but i cant remember how the nc one is wired off the top of me head.
I'll have a look tomorow after work if i get time.
Cheers
Ian

[VtypeV4]

I had an old '88 kawasaki ZX-10 which seemed to boil over before the fan kicked in. I suspected thermostat and fan problems but it was simply a poor seal on the rad/pressure cap. After i replaced it, no problems. The only thing i should note here is that the temp gauge didn't work. I didn't know at the time but the reason the cooling systems are slightly pressurised is to prevent boiling at 100c. If there's a slight leak in that seal in the rad cap, it'll boil early and froth over. Might be worth looking at?

[Neosophist]

The only part of the cooling system that I haven't checked is the water pump as one of the screws has been rounded off but this has nothing to do with the fan actuating at the right temp??!!

It could, because the water won't be circulating very well there will be local hot and cooler spots.

I'm surprised at the amount of broken water pump impellers I've seen on this forum: it happens!

Yes it does! ^_^

Firstly check your waterpumps working and the impellor blades are a-ok.. with the cover off crank the engine a few times to make sure it spins round ok.



Refil the coolant system and bleed the air out (run it with the cap off till the temp gets to 1/2 way and then snap the throttle to at least 5000rpm 3 / 4 times, allowing rpm to drop to idle between. This will purge air pockets.

Kill the engine, allow it to cool and top up with coolant, cap it and let it heat up until the fan kicks in (to test)

Easiest way to check fan works is pull wire off the switch and earth it, fan should come on.. if not check fuse / fan / wire isn't broken.

If it does suspect temperature switch (least likely but not impossible)

[Jonesy01]

I've checked the fan actually works and the fuse is fine....
The rad cap also seems in good condition

The theory of hot and cool spots in the coolant due to a broken water pump seems possible so think I'll try and whip off the water pump cover and have a look there!

I have also emailed Rick Oliver and he has suggested that the thermostat might be sticking shut until the coolant in the block boils at which point the pressure is popping it open, explosively pressurising the cooling system and dumping its contents out into the header bottle??
This also sounds like a good possibility....although I have tested the thermostat in a pan of water and it does open and close.

I really need to find the route of the problem before throwing more money at it!!

[CRM]

blocked or knackered rads. or sticking thermostat if it gets hot quickly.
a tiny hole in the thermostat can often help it open a tad earlier.

as for a fan switch, its been done to death over the years, have a quick search am sure it will come up.
it simply invloves a wire scotchlocked into the fan switch wire on the lower rad being earthed. so the switch turns it off / on when required.