Coolant leak and slow speed fan not working

[Mr Toad]

Hi All,

When I last posted about the coolant leak it was suggested that I bypass the oil cooler which I have done but there has been no difference still loosing a small quantity of coolant. The thermostat has been replaced the inlet manifold gaskets have been replaced with a coating of Hylomar there is no leak at the water pump or in the V.

I tried a test suggested on here, i.e. take off expansion tank cap run the car cold for about 10 seconds at idle and then accelerate up to the red line, if coolant shoots out of expansion tank this confirms HGF. I did this but no coolant shot out of the expansion tank. Is such a test conclusive or not?

I discovered today that the slow speed of the coolant fan is not working, could this cause coolant loss and do I need a new fan?

Any assistance will be gratefully received. I should mention that the car is a 2003 MG ZTT KV6 with 60,000 approx miles.

Martin

[SD1too]

Originally Posted by Mr Toad

I discovered today that the slow speed of the coolant fan is not working, could this cause coolant loss ..

Yes.

... and do I need a new fan?

No. You can repair it. Is it a 2 or 3 speed motor?

Simon

[Mr Toad]

Thanks Simon. I don't know whether it is a 2 or 3 speed fan. I can't see a resistor therefore I suppose it is 3 speed in that case wouldn't I be better off replacing the whole fan with a new 2 speed one. On the V8 you have to cut the shroud to clear the aircon pipes I know this because I have just fitted one. I assume it is the same for the KV6 or can you just swing the shroud out of the way to get to the fan motor?

Martin

[SD1too]

Originally Posted by Mr Toad

... I suppose it is 3 speed in that case wouldn't I be better off replacing the whole fan with a new 2 speed one.

In my view, no you wouldn't. My reasons for saying that are:

• A new 2 speed system is expensive. A set of brushes for your 3 speed cost £20.
• You don't have an unreliable resistor to worry about with the 3 speed.
• The 2 speed is noisier than the 3 speed.

On the V8 you have to cut the shroud to clear the aircon pipes ... I assume it is the same for the KV6 ...

You will read posts which say that it is, but with a bit of ingenuity and by taking my time I managed to re-brush my 3 speed fan motor without cutting the shroud.

If you do decide to replace rather than repair, perhaps you'd consider offering your removed 3 speed to Arctic.

Simon

[Mr Toad]

Hi Simon,

On closer inspection it is in fact a 2 speed fan with a resistor. The high speed is working therefore I suppose it is either the relay or the resistor that is faulty. What do you think please?

You said previously that if the low speed fan is not working this is responsible for the coolant loss. Where do you think the coolant is going?

Martin

[SD1too]

Originally Posted by Mr Toad

I suppose it is either the relay or the resistor that is faulty. What do you think please?

Hi Martin. Is it a silver coloured resistor? If so, it will be that.

You said previously that if the low speed fan is not working this is responsible for the coolant loss. Where do you think the coolant is going?

On a 2 speed system with a failed resistor the fan will not start running until the coolant has reached 112 degrees. Not only is that much too hot, it is only three degrees below the temperature at which the temperature gauge rapidly swings to the red line and you're officially overheating. You also run the risk of the expansion tank cap venting to relieve the pressure with consequent coolant loss which will probably leave little or no trace.

But don't get bogged down in theory Martin. You have identified a fault with the cooling system and it needs to be repaired immediately. You can then reassess the situation.

When the thermostat was replaced, who did the work? If you did it yourself, did you refill and bleed the system afterwards by raising the expansion tank and by following the MGR procedure exactly? If not, this can cause problems with coolant level.

Simon