Head Water Sensor.

[blue flash]

Hi everyone. I seam to be using quite a bit of fuel when the engine is cold and it takes a good 15 miles for the gauge to move even in good weather. there's a new thermostat on it. my question is:does anyone think the head water sensor is playing up and the computer is thinking the water is colder than it actually is. thanks in advance.

[artscot79]

first off if you mean the dash gauge that is the coolant temperature not the head temp the engine will be warming up just not the coolant howeve after 15 miles you should have some reading on the gauge however if you have the heater on hot and max speed or 3 yopull struggle as the heater is taking all the heat away from the engine as its meant to do start with getting the car up to temp see if theres coolant flowing into the expansion tank then see if the top hose opens

[blue flash]

Thanks Ascot.my mistake,coolant temp.No don't have the heater on at all.I'll give your idea a go tomorrow when stopped raining? lol.thanks.

[artscot79]

after say 10 miles youll find the coolant tank is slightly warm you can leave it to idle but it takes a bit till the top hose warms up if you put the dash trick on the head sensor temp should start around 40 if its showing a minus its faulty the head temp is 40 degrees higher so 93 when the thermostat should be open will show as a head temp of 133 there should be coolant flowing to the expansion tank if all of that is okay then all seems fine

you have to remember the dash dial is the coolant temp not engine temp if the air going through the car is overcooling the thermostat will keep closing and diverting the coolant through the head to the expansion tank back out the expansion tank and round the head thats how the system works if you have the heater on that draws hot air from the engine so in coldish weather the thermostat on a short journey may never actually open

[stef123]

what engine is this on? I know my old 2001 mk1 1.6 petrol only had the one temp sensor and that was in the cylinder head.

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Well I took it for a spin artscot. did 10 mls with the blower off and indeed the gauge did move sooner. The tank was warm and the top hose by the time I got home.I had an engine temp of 118. also,the gauge seams to dip every time I throttle hard, is that normal?? thanks for your help as always. MK 2 2005 1.8 diesel stef.