loseing power temp in red

Well I am in a process of a limitation bled cooling system maybe it is a sensor as it corrects itself soon after I lose power.it happend today on a hill but soon resumed power.if this is a sensor where will I find the offending one to clean check.already been advised that there is a sensor that will send a message to ecu to cut power if it sences the engine is hot.that advice was from on here my thanks for that.dont see how it would cool quikly if engine was to hot.

From your description of what's happening, it sounds to me like you still have air in the system, which will confuse the hell out of the temperature sensor because the air will be significantly cooler than the coolant.

The coolant temperature sensor is mounted into the adaptor where the top hose connects to the engine block - between the block and where the pipe branches off to the heater and about 6" from the bleed screw. It's the only sensor in that area so can't be confused with anything else

When the ECU detects over-temp it goes into limp home mode, limiting engine revs and causing very rapid cooling as it also turns on the electric fan in front of the radiator. If the engine is really getting that hot then you may well have blown the head gasket, which may also explain why you're getting air into the system all the time. I had this on my first Td5.

Hope this helps

Thanks it helps but I dont like the sound of it.ive located the sensor in the manual would your explanation explain why it cools and regains power and would it drive ok with a blown head gasket. Also how much would that cost?I have just drove back from surrey to rugby I drove there on fri car only lost power on a steep hill in surrey.would this be possible if head gasket had blown.and wouldnt sensor removal and clean be worth a go.

Mine drove fine for a couple of months with the head gasket blown. The only sign that it had blown was the constant need to bleed the coolant system and the ocassional very high temperatures, after towing or thrashing along country roads, which very quickly returned to normal once limp home mode had cut in.

After a while the coolant system started to pressurise all the time resulting in coolant being blown out of the header tank overflow and the radiator blowing up like a balloon. Both these symptoms took time to develop.

There is certainly nothing to be lost by removing the sensor and giving it a clean.

Good luck

Thanks sounds like I better get someone to look at it as Im a novice and don't have anywhere I can make a noise or time for it to be off the road.

dmjb said:

Well I am in a process of a limitation bled cooling system maybe it is a sensor as it corrects itself soon after I lose power.it happend today on a hill but soon resumed power.if this is a sensor where will I find the offending one to clean check.already been advised that there is a sensor that will send a message to ecu to cut power if it sences the engine is hot.that advice was from on here my thanks for that.dont see how it would cool quikly if engine was to hot.

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it's somehow the other way around as the sensor is sending constantly the engine temperature to ECU and if the temp is above the admited limit the ECU cuts the fueling...it's the coolant temp sensor, quite cheap so you better put a new one to rule it out(unless you find some visible problems with the wiring/plug), or you can check resistances with a multimeter but then you need a thermometer too for comparison with the values in the table

see attachment...and the quoted part is the next page in the book after the attached part

The ECT sensor can fail the following ways or supply incorrect signal:
l Sensor open circuit.
l Short circuit to vehicle supply.
l Short circuit to earth.
l Incorrect mechanical fitting.
l Signal fixed above 40 °C (104 °F) not detected.
l Signal fixed below 40 °C (104 °F) not detected.
In the event of an ECT sensor signal failure any of the following symptoms may be observed:
l Difficult cold start.
l Difficult hot start.
l Driveability concerns.
l Instrument pack temperature warning illuminated.
l Temperature gauge reads excessively hot.
l Temperature gauge reads excessively cold.
In the event of component failure the ECM calculates coolant temperature from the fuel temperature sensor signal. If
this occurs, the limit engine operation if coolant temperature is too high becomes inoperative.
The MIL will not illuminate in an ECT sensor failure.

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