When to add coolant to fill it to MAX level?

[Escape08]

Is it when the engine is cold or when the engine is hot? Which is ideal. Thanks

 

[pbm]

I don't think it really matters but I do it when cold. The half inch that it goes above the full line when 'hot' isn't significant IMO.

 

[Warstud]

Doesn't matter there's different levels for hot and cold

 

[doitmyself]

With my non-pressurized overflow tank I keep it at the max line when it is cold. It rarely rises more than a half inch when hot.

Are pressurized coolant tanks different?

 

[brianl703]

Are pressurized coolant tanks different?

Not as far as how much the coolant rises that I've ever noticed, but you really don't want to fill a pressurized coolant tank when it's hot..

 

[UNC032]

I just do it when it's cold. My reserve tank has a "Cold" line on it.

 

[The_Jeff]

The worst case scenario is you'll vent a little coolant. I overfill mine a bit as well.

 

[mclasser]

I fill halfway b/w min and max when cold to allow for some expansion room. But like others said, a little overfill is no big deal.

 

[Greasymechtech]

All my cars are filled to the full coolant/antifreeze level when cold, as it says in the owners manuals and factory service manuals...

I haven't seen the difference among degassing pressurized bottles and traditional overflow/recovery bottles when it comes to level checking.... all are to the full line when cold.

 

[GON]

I fill and maintain the coolant overflow reservoir at the max line, while cold. This allows me to know if there is a change in coolant levels. Any other fill point reduces the ability for one to notice a loss in coolant, even if small.

I am also a big proponent of having the coolant reservoir easy to read- which equates to replacing the reservoir when it becomes discolored. Below is a pic of the just replaced reservoir in my Navigator, both the old and the replacement. What a difference. Also, is a before and after picture of the coolant reservoir replacement on my 2002 F350.

replacement on my 2002 F350.