General Coolant Flow Question

I was watching the coolant reservoir tank the other day and noticed that there is almost always some coolant coming into the tank from the top hose.

This might be a very noob question, but is that normal?

Cheers and Thanks

shinghi said:

I was watching the coolant reservoir tank the other day and noticed that there is almost always some coolant coming into the tank from the top hose.

This might be a very noob question, but is that normal?

Cheers and Thanks

Click to expand...

Yes - for a VW.

The whole system circulates. It's not just an overflow tank like a lot of cars.

Awesome. Thanks for the reply!

shinghi said:

Awesome. Thanks for the reply!

Click to expand...

Please update your profile with a useful location, perhaps including state.

Yup, that circulating coolant allows the system to easily burp out air bubbles

Hot coolant flows out of the cylinder head and goes into the radiator, the line feeding that bottle, and the heater core. The thermostat is on the outlet of the radiator, and opens to let coolant flow through when it's hot.

-J

Not just VW, all pressurised reservoir systems do it.

It's in effect just another loop in the circulation path. The coolant into the top is after the pump output, the return from the bottom is fed back somewhere before the pump inlet.
The difference is that this loop is the only one that allows air bubbles (if any) to separate out rather than be drawn back in the pump again and again.