We finally got some summer heat and humidity here at my place. 100 degrees and 40% humidity. I feel for you southerners! ANyway, I just noticed the coolant level in the reservoir is lower than normal parked on level and shut down a few minutes after getting home. My question is, when its hot will the motor suck coolant out and put it into the system or should it be Higher in the reservoir when hot because of coolant expansion? I guess you could look at it several ways. Thanks!

 

Guessing that after shutdown and before it has a chance to cool the fluid should expand filling the tank, should be higher

 

I agree, should be new the full line with engine hot.

 

It will expand when hot and may fill the bottle some. When it cools down it will suck the resivoir down. This will not happen if you have an air bubble/pocket in the system or a good size leak. It will only fill the bottle then and will not suck it back to the radiator.

 

Cool thanks everyone! I think its just fine. I had my coolant flushed couple months ago with a new thermostat and water pump. I hadn't paid a lot of attention to it since.

 

i would keep a close eye on the coolant level for a while.

the level would slowly go down in my old chevy 3/4 ton, never saw a leak so did not worry about it,

but would add some coolant to tank every 3 to 4 months.

head gasket was leaking, coolant was being sucked into motor and was going out tail pipe.

was a 350 gas motor,

do not know if a diesel could do the same, but answered the question of where the coolant was going.
head gasket job fixed the problem.