Vacuum question

[four-eyed stang]

What are the little cylinders that run inline with some of the vacuum hoses? I have an 81 and all the hoses were toast. My brother replaced them but left them off saying that I didn't need them. Is this true?

[87 STEPPER]

If there what im thinking of there a check valve and you do need them!

Usually there on the line that runs to a vacuum reservoir for your a/c & heat slector. so that when you turn on the a/c or heat you don't have a large demand on the vacuum system and it will come on and stay on!

Meaning with out the ck valve installed when you have the a/c on and your @ a stop light its blowing and when you take off your eng uses all the vacuum and the a/c quits blowing untill enough vacuum is produced by the eng. to restore the vacuum demand.

And sometimes there will be one on the vac line for the cruise control reservoir that supplys the vacuum servo for the same reasons only you need it at cruise instead of at take off cuz you can't have cruise control enguage at a dead stop.

So basiclly there installed to keep a constant vacuum supply on your accessories that require large vacuum demands.

You need to reinstall them in the proper lines and heve them facing the right direction when you look at the ck valve theres gonna be a flat side and the other is gonna have a slight angle to it the angle side is the direction of flow and needs to point to the vacuum reservoir.