I was out on a little test drive earlier on after fitting new top mounts, ball joints and drop links to the front of my evo 6 and on my return home i noticed the temp gauge had rocketed to max. There was no running issues with the car what so ever and no lights on the dash to indicate any further issues. Being only a mile away i took it steady and made my way home to investigate.
I turned off the car, no leaks no coolant spray or anything visible to show a lack of coolant. Left it over a hour whilst i had lunch and when i returned, i flicked the ignition on and the gauge shot right up again... I started the car and let it run with no issues at all. Still no leaks , fan kicks in and out as it should. Now what could be the cause of this? Temp gauge? Temp sensor? A thermostat issue?
Im not very mechanically minded although i do know the basics any help would be much appreciated.
Joe.

 

Anyone able to help?
I started the car this morning after a very cold night and still the gauge shot up to max. Any thoughts would be greatly appreciated

 

My guess would be the temp sensor is going wonky, I had a similar issue on my IX at one point where it would sky-rocket out of the blue but that turned out to be air in the system.
Based on the fact that you haven't been touching the system I would guess it's the sensor.

Any chance you hit the wiring while working on the other stuff, maybe knocked something loose?

Hopefully some others chime in as well!

 

After sitting all night I doubt it is hot, coolant or not. Check that the ground between the intake manifold and firewall has clean connections both ends.

 

Either the sensor is bad, or you have a short some where. Unplug the sensor, there are 2 on the evo 8/9 one for the ecu one for the gauge, i don't know if thats the case on an evo 6, and the gauge should drop to cold. If that doesn't happen you have a short, if it does you have a bad sensor.

 

This is from an evo 8, but it might be the same, you can see #6 is the sensor you would want to look at.

 

thinking about it, I haven't actually measured if the temp sensor is an NTC, or PTC type so what i said about the gauge dropping if you unplug it might be wrong. You should still do a visual inspection of the sensor try unplugging it and see if you observer a change in the gauges behavior.

 

Awesome stuff, thanks guys. There is the sensor on your diagram, number 6, it's the dash temp sender with a single wire going onto it with a spade terminal. If i unplug the wire from the sender the temp gauge in the car dies... The moment i plug it back on the gauge shoots up again. I have got a new sensor ordered and il go check the grounds now as barney said

 

Yah bad sensor then. If it was a bad ground it wouldn't behave like that, but check grounds anyway because they tend to have problems.

 

Im out checking all grounds now, all else seems ok. Must be the sensor itself and for the sake of £8 it's the first thing on the list to try. Thanks for the help lads, the new sensor should be here tomorrow so will update with the outcome once fitted

 

X2 on ground

 

Just an update lads, new sensor arrived today, had it fitted in seconds and hey presto... No more dodgy guage
Thanks again everyone. I appreciate it

Joe

 

Wooo! gotta love simple fixes

 

That happened to mine, and there was a tad bit of corrosion on the connector... cleaned it and haven't had any other issues.