Strange temperature issue

Fozzy

Fozzy

Petrolheads
Hi folks,

I have a bit of a strange one - my temperature gauge is acting strange lately. I have always had an intermittent issue where sometimes the needle doesn?t move at all. If I tap the dash, it moves and has always stayed in the normal range after that. About 4-5 weeks back, I pulled into a petrol station after driving for 30 mins and noticed the needle really quickly went up to about three quarters, I turned off the engine and turned the ignition back on, it went immediately to the normal position. I assumed it was just the dodgy connection issue.

This morning, exact same thing happened but this time the fans stayed on for about 5 mins even when the needle was in its normal position. I?m not losing any coolant at all.

I understand that my car has two temp sensors - 1 for the ECU and 1 for the cluster. Until this morning I assumed that my cluster sensor was dodgy (or the wiring to it) but the fans coming on is leading me to believe that it might be another problem. Does anyone know how the fans are controlled - I assume it?s by the ECU?

I?ll plug it into a diagnostic and have a look at the temperature readings but in the meantime has anyone had or heard of similar issues or maybe have any suggestions or wisdom on this?

Cheers
 
As baz said sounds like air lock but if you haven't touched the coolant system only way an air lock will happen I'd imagine is not circulating for some reason or system is pressurising. Are rad hoses getting hard?
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I had a similar issue in mine and I needed a new thermostat and fresh coolant in the end.

How old is your thermostat? Maybe start by trying to burp/get rid of the air lock and then work from there?

Subaru Impreza Wrx SL Wagon 2004
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Thanks for the responses guys. Thermostat is a year old, changed it for a new OEM one when I did the belt and water pump. Haven?t gone near the coolant in 5 months hoses are not hard. Airlock is possible but as the two times it has happened are weeks apart I?m still thinking it may be related to one of the sensors/wiring/bad earth?

I?ll run it for a bit and plug it into the diagnostic and see what the ECU is reading for temperature and take it from there I guess. If it?s reading high then I?ll need to look at airlock/rad/thermostat/water pump. If it?s reading normal then I guess it?s an electrical gremlin of some sort?

Oh, the joys!!!!
 
Simple way of checking , run her until the fans come on , check the bottom rad hose , if it?s cold it more then likely an air lock .
If so you need to get the front of her up as high as you can , take the cap off the header tank (safely when hot) have some coolant ready to top up as needed .
Hold the revs at about 3500-4000rpm until the bottom rad hose is hot, the secondary fan should turn off and the primary fan should cycle in and out as usual. Top up header tank and replace the cap .
 
No harm checking temp sensor wiring and trying a different temp sensor... is your cold start staying on longer than normal?
 
KENC said:
No harm checking temp sensor wiring and trying a different temp sensor... is your cold start staying on longer than normal?
Click to expand...

Starting isn?t an issue at all - if it is a temp sensor, I think it?s the one that controls the gauge and not the one that goes to the ECU though. I?ll know a bit more and be able to rule out a few things on Saturday.

Thanks for the help and suggestions folks - much appreciated
 
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