Coolant Levels in Radiators

[William2]

I thought I would start a new thread on this. If you have an overflow bottle connected to the rad filler cap should you top up the radiator when cold to the bottom of the filler cap or should you have the coolant level lower to allow for expansion?

[ericbushby]

Fill it to the top.
As the coolant expands it overflows into the bottle and is sucked back as it contracts.
Make sure you have the correct filler cap on the radiator with the return valve built in and that there is some coolant left in the bottle when cold.
I think that is all there is to it.
Eric in Burnley
1967 S3SE DHc

[john.p.clegg]

..and the end of the pipe in the bottle is near the bottom , not at the bottom.

John

[Robbie693]

Just fill the rad as usual but the level is not critical - the coolant in the expansion bottle will top up the rad if it's working correctly. You may notice the level drops a bit after the first few heat cycles as the system is replenished and any air is expelled. Any topping up should be done in the expansion bottle. I hardly ever remove my rad cap...

Robbie