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Darren Cook
Hello, new here.

Thought this would be a good place to ask,

I have a Focus 1.6 Zetec (mk1) that has a issue i cant seem to fix.

The cooling/Radiator fans wont engage, engine gets to 95*C and starts misfiring, not sure how accurate this is as im using the ECU reading that stated engine was -4*C at starting (actually around 11*C)

Seems to cool down a lot (95c to around 82c) with the heater engaged to max. so temp sensor seems to be working...

Anyway, i've checked the fuses, and hot wired (by passed) the relays. both relay fan 1 and relay fan 2 come on when bypassed with wire.

no fans engage when AC is on, no fans engage when engine heats up... im kinda lost?.. ideas?
Dan62
Are the pipes to and from the radiator hot when its up to temperature ?
It could be a stuck thermostat so the coolant not flowing thorough the rad, seeing that your heater is working your water pump is ok.

Did you check or change the relays ?
Darren Cook
[quote name='Dan62' timestamp='1320599569' post='151506']
Are the pipes to and from the radiator hot when its up to temperature ?
It could be a stuck thermostat so the coolant not flowing thorough the rad, seeing that your heater is working your water pump is ok.

Did you check or change the relays ?
[/quote]

Hoses seem warm but not checked the relays as my multimeter went to heaven. waiting on a new one to arrive.

correct me if im wrong but isnt there just one thermostat in this car? between plug 2 and 3?
Dan62
The thermostat is located inside the thermostat housing exiting the side of the cylinder head, it is a mechanical valve which opens and closes regulating the engine temperature, it opens to pass coolant to the radiator.
As for the temperature sensor, yes there is only 1 but the ECU looks at other inputs to decide whether it signals the fan(s) to come on, I think for A/C models there is a second sensor on the rad which controls the second or high speed fan.

If you suspect the thermostat you can remove it and the engine should never reach normal operating temperature. You can test the thermostat by placing it in a cup of HOT water, you will see it open and then close again when it cools down.... Just make a note of which way round it is fitted when you remove it as it is a directional thing !
artscot79
[quote name='Dan62' timestamp='1320602613' post='151519']
The thermostat is located inside the thermostat housing exiting the side of the cylinder head, it is a mechanical valve which opens and closes regulating the engine temperature, it opens to pass coolant to the radiator.
As for the temperature sensor, yes there is only 1 but the ECU looks at other inputs to decide whether it signals the fan(s) to come on, I think for A/C models there is a second sensor on the rad which controls the second or high speed fan.

If you suspect the thermostat you can remove it and the engine should never reach normal operating temperature. You can test the thermostat by placing it in a cup of HOT water, you will see it open and then close again when it cools down.... Just make a note of which way round it is fitted when you remove it as it is a directional thing !
[/quote]

if the engines 95 the hoses will be bloomin hot not warm and the rad should be hot top to bottom if not either the temp sensors faulty or the thermostat i recon the sensor which is between plugs 2 and 3
Darren Cook
[quote name='artscot79' timestamp='1320612528' post='151557']
if the engines 95 the hoses will be bloomin hot not warm and the rad should be hot top to bottom if not either the temp sensors faulty or the thermostat i recon the sensor which is between plugs 2 and 3
[/quote]

The ECU dash display (diagnostics) shows the temp sensor betwen plug 2 and 3 is picking up temp changes and reporting 95*C so surely this is working? or is this readout different?

Also is there any way to check the thermostat without removing the housing and draining the whole cooling system? seems a lot of effort if it is not at fault?.

Forgot to say all this started when whilst i found another fault (rocker box gasket died and spark plug area was filled with 1-2cm of oil). ever since this it has seemed to be doing this.

My first idea was indeed that temp sensor but as the ECU was seemingly getting the temp i figured it would be okay to rule that out?

On another note, why isnt the AC switching on both fans regardless of the sensors? different fault or joined?
Dan62
There is a very easy way to fix this, unplug the coolant temp sensor which should be located at the side of the engine by the thermostat housing. There is a fail safe for this sensor so it will turn the fans on.

The sensor on the cylinder head is the cylinder head temp sensor.

You don't need to drain the entire coolant system to do the thermostat, undo the top rad hose and drain the coolant into a container, do the thermostat and refill the expansion bottle with the saved coolant.
Darren Cook
[quote name='Dan62' timestamp='1320627039' post='151588']
There is a very easy way to fix this, unplug the coolant temp sensor which should be located at the side of the engine by the thermostat housing. There is a fail safe for this sensor so it will turn the fans on.

The sensor on the cylinder head is the cylinder head temp sensor.

You don't need to drain the entire coolant system to do the thermostat, undo the top rad hose and drain the coolant into a container, do the thermostat and refill the expansion bottle with the saved coolant.
[/quote]

When I looked the SE engine only had the head sensor?? Not a coolant sensor?
Darren Cook
Just had a long drive out. car was been a **** so pulled up and checked. radiator was cold. reserve was warm ish. engine was HOT (reporting 92*C) bottom right hose was hot. top small to reserve was warm. others cold.

Im thinking thermostat? any input?
artscot79
[quote name='Darren Cook' timestamp='1320945146' post='152086']
Just had a long drive out. car was been a **** so pulled up and checked. radiator was cold. reserve was warm ish. engine was HOT (reporting 92*C) bottom right hose was hot. top small to reserve was warm. others cold.

Im thinking thermostat? any input?
[/quote]

thermostat would just be opening so rad will be cold given its cold outside the engine wont get that warm and the thermostat opens and closes depending on temp only way to check is take it out for ten minutes then park it on the drive interior fan off and bonnet shut and let it idle it could take up to 20 minutes then check the rad and the hoses you may be pleasantly surprises to find they are hot if not then yes it will be a thermostat
Darren Cook
[quote name='artscot79' timestamp='1320952258' post='152103']
thermostat would just be opening so rad will be cold given its cold outside the engine wont get that warm and the thermostat opens and closes depending on temp only way to check is take it out for ten minutes then park it on the drive interior fan off and bonnet shut and let it idle it could take up to 20 minutes then check the rad and the hoses you may be pleasantly surprises to find they are hot if not then yes it will be a thermostat
[/quote]


This was after around hour and half driving. car was misfiring. and as above. radiator was cold.
artscot79
[quote name='Darren Cook' timestamp='1320953186' post='152106']
This was after around hour and half driving. car was misfiring. and as above. radiator was cold.
[/quote]

it needs live diagnostics then as theres too many things it could be and it could be a multitude of things engine temp is either wrong or it is correct therefore the thermostat would have to be stuck open so the engine temp isnt getting up to what it should if the thermostat was stuck closed the expansion tank i would have expected to be hot as all the engine heat would be running through there without diagnostics you will spend a fortune replacing bits in the hope it fixes the issue if it were mine ide book it in
Darren Cook
It has already been in for dignostics when all this started. Garage claimed it was fine...


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