Following on from my temp gauge issue, I have just noticed another potential issue.

I just started the van (hasnt been started for 7 days) and moved it on my drive. It was running for around 2-3 minutes. I checked the heater in the cab and the air was blowing through really hot. The van doesn't normally blow hot air that quickly. Would that indicate a potential issue with the thermostat? The gauge is still not working, but if I turn the engine off then back on the gauge shows a reading but I can see it steadily rising. If I turn the engine off and on again the gauge stops working again.

If I remove the coolant sensor from the van and put it in a cup of cold water, start the van, should I see a normal temp reading on the temp gauge on the instrument cluster? Likewise, if I use a cup of hot water, should I see the temp gauge read a steady temperature?

Thanks.

The thermostat should be closed when started from cold. 2 or three minutes isn't long enough for it to start opening.
Cup of hot water won't work because sensor will cool down too quickly before you plug it in.
Was van in hot sun before you moved it?

Sounds to me like there is an air lock, bubble of air in cooling system that stops water touching sensor while engine running .

Thanks for the response.

The van wasn't in the sun as the it was shaded by the house.

Could I leave the sensor in the cup of water then start the van? I still have the old sensor to hand so I can leave that screwed in to the van to stop coolant leaking out.

Also, how would I go about trying to release an airlock in the cooling system?

Thanks again.

How many wires connect to sensor?
Are you positive you are dealing with the sensor for the temperature gauge.
It's possible there is one sensor for gauge and a different one for engine control.

This is the sensor in question. There is another brown sensor very close to where this green one is.

Take a metal paper clip, straighten it out , bend it in half, insert the ends in the plug that connects to the sensor, turn key till warning lights come on, does the temp gauge go all the way to hot?
Don't let the metal of the paper clip touch any metal of car while doing this.
Switch off , remove paper clip.
Reassemble.

You do this at your own risk.
Though it's exactly what I would do.

Thanks for the info. I'll try that in the morning.

Just out of curiosity, what will this do?

It will check that the sensor plug you are trying is for temp gauge.
Paper clip is like the sensor telling car the coolant is very very very hot.
If it is temp gauge sensor plug it also checks the gauge and the wiring to the gauge is ok, if it goes all the way hot.
If it only goes part way it shows gauge or wiring faulty.

Ah I see. Perfect. I'll let you know how I get on.

regarding the HOT air..

the thermostat is just a temperature sensitive VALVE

opening once the engine is HOT to then divert coolant through the radiator

you should be able to sense HEAT in the various hoses at stages of the warm-up,

as usual .. beware of HOT / Moving parts at any time if probing under the bonnet..
and of course beware of the cooling fan starting without warning..

I would plug in a device to see what air and water temps the ECU is seeing

Charlie

Finally got around to doing the paper clip thing.

With the clip in the temp gauge goes from cold to hot 3 times then settles outside of the temp gauge.

With the sensor plugged back in the temp gauge will start to rise slightly even though the engine is switched off. If I then turn the ignition off and back on then the gauge temp gauge goes from cold to hot 3 times then settles outside of the temp gauge. If I then turn the ignition off and back on the temp gauge will start to rise slightly even though the engine isn't running. If I start the van the gauge will just steadily increase but way quicker than it should.

Anyone got any ideas?? Does it sound like the cluster is faulty, wiring, sensor or thermostat??

Thanks.

The green sensor I've been working on is to the right of the dipstick.

That will be a temprature sensor can you replace it

Thanks for the response.

This is a new temp sensor. With the old sensor the gauge would just go from cold to hot 3 times then settle to the left of the gauge.