Cooling system temperature gage

[elliotw]

Hi

I have a 987 Boxster S. My cooling system temperature gage on the dashboard is playing up. See item 8 on the attached picture from the Boxster manual. (Note, the gage in the attached picture is in fahrenheit whereas my Boxster is setup in celsius. Therefore the middle point, which is 175 degrees in the attached picture, is 80 degrees in my Boxster.)

When I start the engine the red warning light sometimes (but not all the time) flashes on the cooling system temperature gage, the needle stays on 40 and the on-board computer displays that the indicator has failed. Then, after say 30 seconds or so the warning light comes off and the needle goes to(wards) the middle level, before resting on the middle level. Sometimes the needle falls back to 40 and the red light flashes up once or twice more in the first couple of minutes of starting the engine. In any case, after a few minutes, the needle settles down at 80 degrees and the warning light comes off.

The good thing is my cooling system appears to be working as the needle always settles on 80, at least after a couple of minutes. While the temperature gage seems to work, at least after a few minutes, certainly some times, when the engine is started, it initially fails.

Any suggestions?

Thanks

Elliot

 

[Motorhead]

Elliot,

It sounds as though the coolant temperature sensor could be faulty ( http://www.pelicanparts.com/techarticles/Boxster_Tech/26-FUEL-Engine_Sensors/26-FUEL-Engine_Sensors.htm ).

If you can run some diagnostics (Durametric or PIWIS) you should be able to confirm this, or it will give you some other fault codes.

Jeff

 

[Glyn]

Have you checked your coolant level?, When cold the water will be lower in the expansion tank, low water is indicated with the light flashing, Once you start the car and the water starts to heat up it expands - the water level rises in the tank and this would then switch off the low coolant sensor.
The fluctuation in reading where the needle goes down then comes back up could simply be an air lock in the system, when the trapped air surrounds the temperature sensor it allows the sensor to cool - hence the needle drops, as water is circulated and the air is moved the water comes into contact with the sensor - and the gauge will rise again.
Sounds like there has been some work done on the cooling system and the system hasn't been bled properly.

I take it you do know about the bleed valve and the proper way to bleed the system

 

[elliotw]

Thanks Jeff and Glyn.

I do not know how to run the diagnostics - presumably an OPC should be able to do this (at a cost), or maybe, when I am taking my car into an independent for a totally unrelated bodywork matter, I can ask them to run the diagnostics? The procedure to change the sensor looks a little out of my depth...

Re the water level in the tank, I have checked in the boot and it is at just below the maximum level. Having said that, I did have to fill it up in the last couple of months and it may be that this coincides with the problems I have been experiencing with the gage as you suggest.

Next question...how do I bleed the system (apologies, I do not know!)?

Thanks

 

[Motorhead]

Elliot,

If you have a local Indie, they should be able to help out regarding diagnostics and bleeding the system if necessary (I agree with Glyn that this is worth doing first).

Plenty of advice on bleeding the system online. Here's a comprehensive article you may find useful if you want to DIY (see the final few paragraphs):

http://www.pelicanparts.com/techarticles/Boxster_Tech/29-WATER-Flush/29-WATER-Flush.htm

Hope that's of some help.

Jeff