I changed the sidelight bulbs on Monday and noticed the expansion tank was at a level beneath the minimum. I topped it up and it didn't take much to bring it back to sit between Max and Min. I didn't bleed the system or run it up with the top off. I just topped it up (maybe my mistake). Anyway I used the car for the first time today and noticed the coolant temp gauge rise as normal and settle in the normal position. I then noticed it would fluctuate ever so slightly about this position. it wouldn't go above it but would drop a little then after some acceleration it would rise again to the normal position. We are only talking about 2-3mm within the graduated markings. This could be normal and I've never noticed it before. It could be that I should haven't bled the system after adding the little amount of coolant I did. Air bubbles are passing the sensor? Or, it could be that the HG is gone and the lack of coolant is due to that and now any extra welly from my right foot is superheating the coolant. Or I could be just driving myself insane thinking about it. No contamination present anywhere. I'll check the level tonight when I get home. I guess I'm asking if anyone has had any similar observations of the gauge?
Mega late reply - but I've not seen this on mine. You might want to check the coolant temp using some kind of OBD device - mine fluctuates between 84° & 87° C with no noticeable difference on the dial. When I got it, it only warmed up to 66° C so I've had to change the thermostat. The standard thermostat is rated to open at 89° C (mine was broken) and for me that's just under the third bar when you include the larger first bar. I know on some cars (not sure about ours) deliberate smoothing is applied to stop it fluctuating - on my last car anything between 75-105°C produced no movement on the gauge to stop people worrying about a fluctuating temperature within normal limits. Lastly, remember the coolant is considered a service item - 72k / 6 years.
Hi Yeah I flushed and changed the coolant when I changed the EGR cooler. I've grown to live with the needle position. RS 175 Lux
