Engine temperature sensor?

Hi everybody, I’ve hinted high and low on here and elsewhere and can’t find an answer.

I have the problem where my temperature gauge jumps from 3 bars to all 6 with the beeping. The cooling fan only really works intermittently but does actually work sometimes. I don’t have any EML lights or codes when this happens. This is only with a basic code reader.

I’ve changed the green coolant sensor but know that some models have another temperate sensor underneath the green one, my car doesn’t seem to have this sensor.

However looking around I have come across another plug that isn’t attached to anything, with no sensor to attach it to? The bolt that holds the capacitor looks like it could have been a sensor but I don’t know what is actually supposed to be there, can anybody put me in the right direction as to what I need please?

Many thanks

Hi

You often get plugs with nothing connected to it, so I don't think you have a problem there as yours is an intermittent fault?

Is there a coolant level sensor fitted to yours? The gauge can go to full bars and flash with a low coolant level (or faulty sensor).

Thank you for that, no there doesn’t appear to be a level sensor on the header tank, I’ve cleaned the green plug with electrical cleaner and it has run steady for half an hour at 3 bars but the cooling fan hasn’t kicked in?

Oldman wrote: ↑Thu Mar 09, 2023 5:57 pm Thank you for that, no there doesn’t appear to be a level sensor on the header tank, I’ve cleaned the green plug with electrical cleaner and it has run steady for half an hour at 3 bars but the cooling fan hasn’t kicked in?

I wouldn't expect the fan at 3 bars.

The normal running temperature is 3 bars and the fan is for over-temperature.

Oldman wrote: ↑Thu Mar 09, 2023 10:49 am However looking around I have come across another plug that isn’t attached to anything, with no sensor to attach it to? The bolt that holds the capacitor looks like it could have been a sensor but I don’t know what is actually supposed to be there, can anybody put me in the right direction as to what I need please?

I think that's the knock sensor plug. If you unravel the loom covering, are the wires twisted? There are a few plugs like that on the engine but none up that far. The knock sensor is sort of between the starter and the bottom of the inlet manifold on the back of the engine. You would only be able to see it with a mirror from the top, or, get under the car. One would have to wonder why it's been disconnected when its so difficult to get to???
The Knock sensor is not critical but if you run the engine on "cheap" fuel the engine will "ping", "pink", "knock" or "detonation" (its called a lot of things). Basically the engine will make a "clacking" noise on acceleration or heavy load. In the long run it's not good for the engine.

Oldman wrote: ↑Thu Mar 09, 2023 10:49 am
I have the problem where my temperature gauge jumps from 3 bars to all 6 with the beeping. The cooling fan only really works intermittently but does actually work sometimes. I don’t have any EML lights or codes when this happens. This is only with a basic code reader.

I’ve changed the green coolant sensor but know that some models have another temperate sensor underneath the green one, my car doesn’t seem to have this sensor.

Has it jumped up since you replaced the sensor? If yes, there might be a problem in the wiring. Or the "Low Coolant Level sensor" or associated wiring. Now the "Low Coolant Level sensor" doesn't actually sense the coolant level at all!! It should be called "The cylinder head over temperature switch"!!! It actually monitors the cylinder head temperature at the number 1 cylinder. It's under the thermostat housing behind the air filter box mounting bracket. You will need to remove the air filter box to see it. The sensor and electrical plug are blue. There is one single wire going to it. The sensor/switch works in reverse. Normally the switch is open circuit and shorts to ground when the cylinder head temperature reaches 120'C. So if the plug were to come loose...well...nothing would happen!!! That's great engineering for you!! I doubt this thing would fail in a short circuit to ground type scenario. But if you eliminate everything else.....it must be that.

If you want to test the radiator fan, run the engine and then disconnect the green coolant temperature sensor connector. The fan wont come on immediately, but it will (should) start up within 20 seconds or so.
The radiator cooling fan doesn't do much cooling of the radiator. It's mostly used for the air conditioning. The moment you turn on the air conditioning the fan will run. But without the aircon on, even in a hot climate (like here in Australia) the radiator fan only kicks in every 10-15 minutes and only runs for about a minute (when the car is stopped). So the radiator alone is doing a good job at radiating heat.

The EML light will only come on for codes that would cause the car to "pollute" or some thing that might damage the catalytic converter. The engine could tear itself apart, but the EML light doesn't have to come on!!