try changing the thermo switch, little test to see if the fan works, get a little piece of wire and put it in the connector that goes to the radiator, should see if ya fan works then, if it does then its ya thermo switch, if not then its either the fuse or the fan is scrap.

 

this is common on mk3's. try changing the expansion cap first. about £3 from rover. if that doesn't work book it in for a pressure test about £25.

my mk3 did this in all the hot weather a few weeks back.

u should be able 2 hear the fan come on cos its quite loud!

 

Can someone time how long it takes for the fan to come on from just idle-ing, to give me an idea of when it should be coming on?

 

How much would you say that you are refilling it , ie once a day, a week.

I'm having a similar problem with mine, i have to keep topping up the coolant - i did fuse the two radiator wires before but and fan came on when the temp gauge went above halfway, i was told on here it was not the right thing to do though

 

Can someone time how long it takes for the fan to come on from just idle-ing, to give me an idea of when it should be coming on?

A long time, if starting up cold from idle it will take around half an hour, maybe longer to come on, believe me, I tried it once, took feckin ages, I was gettin well pissed off.

And put some clean white paper under your car for a few hours, if it comes back with a wet patch you know its leaking then you just gotta trace the leak back to where its coming from.
As Ian said, short out the connector and check that it actually works, the thermo switches go all the time, one went on my old one

 

guys. Its a mk3, MEMS controls the fans.
Steve

 

Oooops, oh yeah, didn't even notice it said mk3, gotta learn to actually read posts before commenting, lol

 

Fans will cut in when Mems see's fit. It takes data from the coolant temp sensors and some other gubbins. If they're cutting in, then don't worry.
Steve

 

Drive it around till it has warmed up, then leave it ideling with the heater off. The fan should come on within 10 minutes. The temperature guage will rise fractionally (to exactly half way in my car) before the fan comes on. If the temperature guage gets above half way then you have a problem.
Changing the expansion tank cap is a good idea, although if it has failed, you should see water boil out through the cap.
You may have a leaking inlet manifold gasket (the water leaks into the engine and so you never see it). The water pump is also a another sorce of water leaks and thermostats fail too.
If you want a reliable K series engine, you need to replace:
The expansion tank cap
Water pump, thermostat and cam belt, before 60K
Inlet manifold gasket (only if you have a black one. New ones are green.)

If your fan is not coming on then it is probably the brown temperature sensor or yellow relay for it. I had this problem recently and replaced the sensor and relay. All is fine now.
I hope it is not, but you may also be suffering from the beginnings of Head Gasket Failure.

Most importantly, check the water level regularly and never drive the car if it is overheating or has a problem with the cooling system. It can get expensive very quickly.

 

Drive it around till it has warmed up, then leave it ideling with the heater off. The fan should come on within 10 minutes. The temperature guage will rise fractionally (to exactly half way in my car) before the fan comes on. If the temperature guage gets above half way then you have a problem.

Not true I'm afraid, my car goes upto 3/4 before the fan cuts in, apart from my water pump going (due to old age more than anything) nothing has gone wrong with my cooling system.
It stays mostly around half way but when in traffic and stuff it will creep up to 3/4 and then shoot back down to 1/2

 

bloody hell, 1/2 way normal, mine doesnt seem to go above a 1/4 now and even when the fan comes on it doesnt even touch 1/2 way

 

Not true I'm afraid, my car goes upto 3/4 before the fan cuts in, apart from my water pump going (due to old age more than anything) nothing has gone wrong with my cooling system.
It stays mostly around half way but when in traffic and stuff it will creep up to 3/4 and then shoot back down to 1/2

This probably is because you have air in the system from your leaky water pump. When an engine warmy up, water is forced out of the leak, but as it cools it can suck air in through the same leak.

bloody hell, 1/2 way normal, mine doesnt seem to go above a 1/4 now and even when the fan comes on it doesnt even touch 1/2 way

Sounds like your thermostat is stuck open.


I can only offer advice based what has happend to my car. It is the only Rover I have ever owned, so I do not have anything to compare it to. From reading other threads on here, my cooling system seems to be working correctly and I would say yours may not be. Just because it has not failed in a catastrophic way it does not mean that all is well.
I don't pretend to know everything and am happy for people to prove me wrong, but this is what I have found in my limited experience of K series engines.

 

thermostat is brand new, from rover

 

both of mine cut in whenever the hell they want.

 

This probably is because you have air in the system from your leaky water pump. When an engine warmy up, water is forced out of the leak, but as it cools it can suck air in through the same leak.

Seems you may be right here as now I've changed my pump it hasn't gone above half way, but then again, it always used to go up, even months before the leak happened, or maybe it was always slighty leaking and I just never noticed it before, ah well, its fixed now

 

Roy
so after fitting the new water pump, even in heavy traffic at a standstill it still sits at half and doesnt move?

Im just checking on this as mines never started to move above that point and above the half mark until after the new waterpump was fitted here

 

It does move again, I just hadn't tested it long enough, it did it yesterday, went upto about 3/4 then shot down.
Its ok though, still got same amount of coolant in there which mean no leaks , I'm so happy, I was adding about a litre an hour

 

mine jus goes to halfway, had my water pump done 8k miles ago.

 

how often are you having to fill it up? Keep an eye out for it, if your finding that water is disappearing quicker each time you fill up, it could be the head gasket.

But there could be other reasons, check your hoses, check the expansion tank hasn't got a hole. Try Radiator Stop Leak and see if that resolves it, its only a couple of quid from all good auto shops. Check the radiator for cracks.