Good Morning wise ones
Not really retro but could apply to retrofit engines, so hopefully the mods will let me get away with this!
Car is a 52 plate Focus 1.6 zetec S 1.6. In normal driving the temperature gauge will suddenly shoot up to the maximum, red zone, far too fast for it to actually be registering an accurate temperature increase. Soon after this it will drop back down to the middle, and then if allowed to continue the needle will 'bounce' around the gauge, which will continue until the EML comes on, and the car goes into limp home mode, not fun on the M1!
So far I have replaced the thermostat, flushed the cooling system, checked wiring and replaced the Cylinder head temperature sensor, (CHT) which is not a water jacket unit, but sits in a blind drilling in the centre of the head, between plugs no 2 and 3. apparently the reason for this is that if there is no coolant left, the CHT sensor will still get a reading, and lets the car run indefinitely on two cylinders, swapping pairs as each pair becomes too hot, with no coolant in the system (OOOOERRR!)
According to the web, many people have this problem, but repairs seem to be varied, both in diagnosis and success. So far I have found it could be the Expansion tank cap, or the radiator fan resistor (unlikely since it doesn't actually overheat, just thinks it is), a modification by Ford comprising of a replacement header tank, bypass hose and 72 deg thermostat ( again unlikely since the car has now done 155k with no faults) or a faulty ECU.
The most stupid part of this is that I temporarily 'cured' it by undoing the CHT sensor 1/4 or a turn, which the engineer in me was screaming couldn't be right, and it was OK for a week, but then started again. I checked the sensor but it isn't bottoming in the hile, or making contact with any part of teh head apart from the screwthreads.
So the false reading is fooling the ECU into thinking its overheating which is why it goes into limp home.
I knew there was a reason i prefer older cars! HELP! Thanks very much
Not really retro but could apply to retrofit engines, so hopefully the mods will let me get away with this!
Car is a 52 plate Focus 1.6 zetec S 1.6. In normal driving the temperature gauge will suddenly shoot up to the maximum, red zone, far too fast for it to actually be registering an accurate temperature increase. Soon after this it will drop back down to the middle, and then if allowed to continue the needle will 'bounce' around the gauge, which will continue until the EML comes on, and the car goes into limp home mode, not fun on the M1!
So far I have replaced the thermostat, flushed the cooling system, checked wiring and replaced the Cylinder head temperature sensor, (CHT) which is not a water jacket unit, but sits in a blind drilling in the centre of the head, between plugs no 2 and 3. apparently the reason for this is that if there is no coolant left, the CHT sensor will still get a reading, and lets the car run indefinitely on two cylinders, swapping pairs as each pair becomes too hot, with no coolant in the system (OOOOERRR!)
According to the web, many people have this problem, but repairs seem to be varied, both in diagnosis and success. So far I have found it could be the Expansion tank cap, or the radiator fan resistor (unlikely since it doesn't actually overheat, just thinks it is), a modification by Ford comprising of a replacement header tank, bypass hose and 72 deg thermostat ( again unlikely since the car has now done 155k with no faults) or a faulty ECU.
The most stupid part of this is that I temporarily 'cured' it by undoing the CHT sensor 1/4 or a turn, which the engineer in me was screaming couldn't be right, and it was OK for a week, but then started again. I checked the sensor but it isn't bottoming in the hile, or making contact with any part of teh head apart from the screwthreads.
So the false reading is fooling the ECU into thinking its overheating which is why it goes into limp home.
I knew there was a reason i prefer older cars! HELP! Thanks very much
