wer steering spraying fluid

[gpa]

Maybe you guys can help with a question on a Chevy farm truck.
It's a '76 with a slightly larger pump than a passenger vehical.
When you shut off the engine, it sprays fluid from the cap, even if the fluid level is down quite a bit.
I am looking for possible sources of air in the system but a web search has not yielded much yet. Looks like new lines for a start?
Thanks for your thoughts.

[fredsterra]

Could it be a check valve leaking back to the reservor? When the engine is running it builds enough pressue. But when you turn the eninge off the pressure in the system is leaking back.

[gpa]

So here is were we are.
We supposed the overflow was due to air in the system & decided that the lines to the factory cooler should be replaced due to cracking & swelling.
Because it would be tough to pull sheetmetal for that job, we just bypassed the cooler for now. The water pump & valve cover gaskets are also new.
Let's see what happens after a spin in the morning.