WQ Fiesta - fans always running

[Ken_AUXR8]

Hi folks

My Mrs has a WQ, but I'm wondering if its normal for the thermofans to be running virtually all the time? They start once the engine warms up, which I suppose is normal, but they're really noisy and just about drown out the engine.

Any other WQ owners notice this?
Also fuel economy is ordinary.. 9.4l per 100, its a manual. Related maybe?

[russellw]

Not something that should be happening. I suspect the default failure mode is for them to be on all the time so that would suggest the sensor is faulty or (alternatively) the engine is actually running too hot in which case there might be a cooling system failure.

The latter is reasonably easy to check if you have something to measure temperature up to 120 deg C - I use an infra-red temp sensor and aim it at the cylinder head near the water inlet as a reasonable guide.

I'd consider the former more likely and there is probably a simple test for it which i will see if I can find.

Cheers
Russ

[russellw]

Looks like the fan is controlled by the PCM using inputs from the CHT (cylinder head temp) and ECT (engine coolant temp) sensors.\

If you have a multimeter you can separate the ECT connector and read the voltage out from the sensor which should read 1.33V at 60 degrees water temp, 10.2V at 70 degrees and 0.78V at 80 degrees. Depending on which engine you have the ECT should be next to the upper water outlet.

There is also a good old fashioned bi-metallic thermostat in the thermostat housing which is obviously another potential culprit. Again it depends on model but these are generally set to open at around 88 deg C so removing it and testing it in water that you heat to 90 deg C is a simple test to perform.

Cheers
Russ

[Ken_AUXR8]

Ah Russ, fantastic info. Thankyou very much.
Yes I have a multimeter so I'll give it a go over the weekend. It's the 1.6l. Hopefully its just the thermostat.

Thanks again

[zabatron]

Easy way to check thermostat operation without removing it from car is to warm up motor to operating temperature and squeeze the cooling system hose leading to thermostat/thermostat housing,if hose is rock hard,thermostat is faulty/stuck closed,and should be replaced.