just wondering if anyone knows how high is the coolant normally is in their radiator? is it supposed to be at the top of the neck, at the hole for the steam pipe or radiator reservoir tube? just trying to find out if my cap is bad, not letting the coolant back into the radiator when it cools. it seems like the coolant just goes from the radiator to the overflow tank.

 

Mine shows almost completely full all the time. The over flow bottle has extra coolant in it.

 

The ideal situation is to have no atmosphere at all in the radiator - full to the bottom of the cap. In other words, so full that when you take your cap off a little coolant comes with it.

 

In addition to being caused by a faulty cap, it can also be caused by a crack in the rubber hose that connects the radiator neck to the overflow reservoir.

 

And check under your battery ~ the rubber hose connects to an aluminum tube into the puke tank ~ if your battery leaked any acid, it will eat through it (mine did) Good fix is to put a piece of metal duct tape over the aluminum tube.

 

wouldn't you be able to spot a leak if this was the case? Mine has been doing the same thing the OP is talking about.

 

It won't leak when the radiator is pushing out the excess fluid as the engine warms up. Where is causes a problem is when the radiator cools down, creating a vacuum at the cap, and the vacuum tries to pull coolant up out of the reservoir. It can't pull it up, because air leaks into the crack in the hose, and you get air in your radiator instead of coolant. Same thing would happen if you had the hole in the aluminum tube mentioned in the other post above.