Classic Temperature Reading

[LFB531]

I noticed a couple of days ago that the reading on the dash needle reading was off, it dipped down to low, then back to normal and back again. There were no signs of anything nasty going on but when I had a quick poke around later, the fan wasn't cutting in even after a prolonged tickover in the drive. Plenty of heat from the heater though. I did notice the coolant overflow reservoir was empty it seemed.

I've not had a close look yet but I can't see a leak anywhere and no water under the car. No suggestion of HG symptoms that I've noticed either.

As the needle movement was very fast, I'm inclined to think sensor. I'm new to Subaru so just wondered if there's a combined one or two separate senders (ECU and dash?), I had a quick look online and there seems to be conflicting info.

Its a 2001 turbo wagon, GC8. Any pointers before I start getting dirty much appreciated.

[vxr2010]

I would change the temperature sensor first , fill up the reservoir and the expansion tank and see over a few days if you are loosing coolant , if you are getting a lot of bubbles into the expansion reservoir it could be hg , some bubbles are normal , with hg when they go it has a tendency to over fill the plastic reservoir and in the process off empty out the contents of the expansion tank , or just empty out part of the cooling system into the engine , but I would try sensor first I think there easy to get too and see what happens , post again or pm when you have done that and I will see if I can further advise , other issues can be rad caps or thermostats but I have never had an issue with those before

[stanton_a]

The temp gauge is almost as useless as the dummy oil pressure light, down load the torque android app or similar iPhone software, get a cheap dongle from the bay and at least you'll be able to have real time info on the Temps only works on odb2 cars though, you'll should be OK on my01 onwards.


The middle of the water temperature gauge is about 85-90° by the time it hit the red there's a good chance you'll have cooked everything,

If it's a duff sensor it's a bit fiddly to get at as it's sits under the intake, it's located on the water cross over pipe on top of the block,
If you remove the alternator you should be able to see & get it if you have small hands

Could be an airlock as it's quite common problem, fill the overflow (left of rad) half full make sure the header tank is full run the car with the header tank cap off and burp your hoses & top up as necessary,

Edited by stanton_a on Monday 2nd May 18:20

[LFB531]

Thanks for the advice. I'm just waiting for a sensor to arrive and will give that a go.

Main reservoir at normal level for cold and I've not touched anything coolant wise so I'd be a bit surprised if an airlock had appeared.

Used the opportunity to strip the seats out and attack the interior with a Rug Doctor carpet/upholstery machine. It's a bit scary to see what crud comes out but suspect this has never been done in 15 years so understandable. Well worth the effort and £30 odd hire charge. The seats in particular look amazing.

[vxr2010]

So you are not loosing any coolant ? The plastic tank on the rad is the level the same and its filling up a bit more when warm and going back to normal levels when cold , and no other symptoms like bubbling in it , if that's the case then maybe just the sensor ?

[LFB531]

Just swapped the sensor for a genuine Subaru one (£ouch!), it's the three pin version and thanks for the access advice. Alternator swung out of the way and an offset 19mm ring spanner soon had the sensor changed. Cleaned up the plug as I had it free, put back nice and shiny.

Unfortunately, nothing has changed. Temp guage still moving up and down very fast between 1/4 and 1/2 marks. I'm still a bit concerned I've no fan coming on, I left it idling for long enough I would think.

I'm fairly new to Subaru but not a complete novice with spanners. Is there a decent on-line source of wiring schematics somewhere that I can have a look at how they put this thing together?

Thanks again.

[vxr2010]

Could it be a battery issue getting too old ? or a poor connection or found the actual dash gauge be the problem , are you getting any actual engine symtoms or just a guage going mad ?

[LFB531]

The battery seems fine. As I've no symptoms of overheating, I think the next step is to pop out the dash pod, I can't believe that two senders have an identical fault. Out of interest, I'll also pop some volts over the fan to make sure that actually works!

[TEKNOPUG]

Is the thermostat working properly?

[vxr2010]

If you definitely have no engine heating issues it must be the sender or the guage , has the car done much mileage and how old is it , if it's thermostat then I would expect engine problems , it could be trapped air , I've always taken the pressures expansion tank cap off when it's cold and started it if it's got air the level goes down on start up just top it up , but unless you have done a coolant change why is there air there ?

[stanton_a]

For parts I'd use www.importcarparts.co.uk genuine parts but half the price

Www.opposedforces.com has various diagrams and parts numbers,

[LFB531]

Sorry chaps, I'm not going at this very fast, sat here now with my arm in a sling!

It's a 90,000 mile classic, bog standard from 2001, one of the last ones I guess. Nothing done to cooling system, no obvious leaks, runs just fine. If the temp gauge was taped over you wouldn't know there was an issue.

The needle moves around to fast for it to be the thermostat in my opinion.

So with the new sender in and no change to symptoms, I don't think there's any option but to pull the dial.

I'll keep you posted!

[stanton_a]

I was speaking to a mate who said there's actually two temp senders in the cross over pipe one for the ecu and the other for the dash display, bit of a pita but could you have pulled the wrong one ?