Afternoon all.

 

Back in Feb I had my cambelt and waterpump done at a main dealer. A few days later I noticed the coolant had dropped to below the min so topped it up and put a mark on the tank between the min and max to monitor the level.

 

No further issues so this was put down to the fact there was possibly an airlock in the system post maintenance.

 

Fast forward a few months, to about 3 weeks ago, I noted the level had dropped about 5mm below the mark I’d put on the tank before. I topped this up back to my marker and after the next journey checked when the level had cooled. At this point it was above the mark so left as is.

 

This afternoon I’ve been out cleaning the car and giving the engine bay a bit of a detail and noticed the level was slightly below my marker again.

 

So my question is, does the level of coolant fluctuate depending on the ambient temperature and is going off a single mark on the tank a bit silly as a result?
 

The level has never dropped below the min (other than the airlock mentioned above) so I’m talking 5mm give or take.

There is some evidence of dried coolant around the cap/overflow so I’m guessing with these extreme temps we’ve been having at some point when driving it’s dumped some. Given the cap a clean so will keep an eye on this.

Coolant will set it's own level.

 

There is a MAX & MIN mark on bottles and not a FILL TO THIS LEVEL mark.   Some will stay at MAX when at a service they are topped back to that, others will drop and should then stay pretty much where that is and where you mark with a marker. 

 

Mark where it is now as you have had hot days and up to temp running.

If it drops again you need to find out why.

I’d already topped it back up to the mark I’d put on the tank initially.

 

Will keep an eye on it and re-mark it if it drops again and do as you suggested.

So just over 2 weeks on the level is sat higher than where I’d last topped it up to (the mark I’d put on the tank initially after I’d noticed the air lock).

 

Granted the ambient temperature on the day I topped it up was a bit cooler. I’ve noticed the level sitting higher on these warmer days without the car being driven.

 

Will probably just clean the mark off I’d put on the expansion tank and periodically check to ensure it’s between the min and max.