2003 2.3 xlt nearly 250k

Before my next smoke test hunting vac leaks I'm replacing the brittle plastic vac lines with rubber vac line. I haven't found any working check valves but on some of the lines there are some hard plastic thingies that appear to the eye to be nothing more than couplings to join two lines together. I can easily blow air both ways through these things. Should one of those things (or something I haven't found yet) be a working check valve for the vacuum system?

UPDATE... nevermind; turns out my reservoir has the check valve built in. I'll just leave the post in case it helps someone else.

 

Interesting, I didn't think Rangers ever had check valve in the reservoir, I have usually seen these: https://i.ebayimg.com/images/g/66UAA...fEq/s-l400.png
Used quite a bit on the reservoir line from intake to reservoir, also plumbed with EGR solenoid on the constant vacuum side

But 2.3l did change to stepper motor for EGR valve so didn't use vacuum anymore

 

Yeah, my 2001 2.3 has a check valve for HVAC control in that reservoir