Dual radiator caps / coolant recovery lines

[cycleguy55]

I'm using a Factory Five inline filler with provision for an overflow tube. It's mounted at the high point of the upper radiator hose.

A small expansion tank is horizontally mounted between the engine and radiator, and is connected to the radiator with heater hose tubing. This has a thermostat neck with an overflow tube as well, and is slightly lower than the inline filler.

Both overflow tubes are connected to a low-mounted tee, then to a plastic coolant recovery reservoir in the driver side wheel well.

I'd like to simplify the system by using a single recovery tube, meaning one of the two pressure caps would have to be replaced with a blanking cap that wouldn't release under pressure.

Question: Which pressure cap s/b replaced by the blanking cap - upper inline or lower? Why?

[Gaz64]

Just run a higher pressure cap on the lower point. Then at that point, cap the recovery tube.

The upper cap will then be always be the point of release into the recovery tank.

Only the upper cap needs to be removed to check your coolant level.

Gary

[cycleguy55]

Originally Posted by Gaz64

Just run a higher pressure cap on the lower point. Then at that point, cap the recovery tube.

The upper cap will then be always be the point of release into the recovery tank.

Only the upper cap needs to be removed to check your coolant level.

Gary

I have a 13 PSI cap on the upper point, and a 20 PSI on the lower. Do you feel that's sufficient pressure differential that I can safely cap the lower recovery tube?

[Gaz64]

Originally Posted by cycleguy55

I have a 13 PSI cap on the upper point, and a 20 PSI on the lower. Do you feel that's sufficient pressure differential that I can safely cap the lower recovery tube?

Can't see why not.

The only way that 20 psi cap will lift off it's seat is if the 13 psi cap jams shut.

One of my cars has two caps, the lower cap runs about 3 psi higher, (KPA caps), and says to see owners manual before removal.

Gary