Another day, another fault.

[Ronin]

This is time its the coolant temperature gauge.

I got in the car today and let it run for 10 mins, and by the time i drove 2 miles temperature was bang on 90c with 22c in sunny Cardiff today.

Few minutes of driving later the gauge droppped back to 0, I stopped to fill up and put some redex in and continuted driving for further 15 mins, with the gauge showing 0.

Once i parked and switched the engine off and back on, the gauge went straight to 110 and slowly started falling back untill it settlend on 90c.

Thermostat was replaced about 500 miles ago along with timing belt etc etc.

Could this be air in the system or a bad temp sensor?

[MikkiJayne]

I'm going to go with the sensor. Its a common failure, and an airlock wouldn't read 0, since the steam in the system is usually around 90-100.

The febi part is £6.50 on Amazon

[HPsauce]

I think I once replaced mine and "once" turned into three times in quick succession due to dodgy parts.....
(Probably a boring thread here somewhere about the tricks I used to make the job easier)

Remember there are two circuits in there, though I can't recall exactly which feeds what.

[MikkiJayne]

One for the ecu and one for the cluster. Its a bit daft since the ecu sends so much data to the cluster already that it might as well send engine temperature as well and have a simpler sensor, but its a hangover from the pre-canbus days when everything was separate and needed discrete signals.

Another slightly feature is that the HVAC guesses at the engine temperature based on a load signal from the cluster and the time it's been running. Why??? Both the ECU and the cluster know exactly what temperature the engine is as they have a sensor for it, and they both talk to the HVAC via canbus! So stupid.

[HPsauce]

Originally Posted by MikkiJayne

One for the ecu and one for the cluster.

Which presumably means, depending on what has failed in the CTS unit, that all could be well but the cluster shows a suspect temperature or conversely the gauge looks good but the ECU is mismanaging the engine.

I think I've experienced both of those....

[MikkiJayne]

Yes, it can go either way - another reason having two sensors is sub-optimal.

[Ronin]

Thanks for the above responses.

Looking at the diagrams, the V6 has 2 of those, would it make sense changing both since the intake has tome come off and the part is so cheap?

[MikkiJayne]

The AMX only has #3. 3A is a 2.7 biturbo part