I'm aware that there's a check valve in the rubber hose that connects the brake booster to the hardline on the fire wall. I have a JDM S4 TII engine, and the rubber hose running from the lower intake manifold to the hardline seems to have a check valve in it too. It also has an arrow with 'to engine' printed on it. If I blow into the hose in the direction of the arrow I get airflow, no airflow the other way.

Is there supposed to be a check valve in both hoses on each end of the hardline? Do RHD cars have just the one hose and no hardline? Can I just replace the manifold-to-hardline hose with a regular one as long as I have the check valve in the booster hose?

 

You need the check valve to prevent vacuum loss from the booster back into the intake manifold. The brake booster is vacuum assisted and is fed the required vacuum from the intake manifold. The check valve prevents pressure loss when there is no supplied engine vacuum. This would be in the event needing to stop after the engine has stalled. Typically the booster will store three pedal strokes worth of vacuum pressure.

There should be one check valve and it should be close to the booster. You can replace the booster vacuum line with a standard high quality rubber hose but keep in mind that the original hose is a molded hose. You will of course have to transfer the check valve and it will have to go in the original location it was in.

 

that is it right there. RHD car the hose just makes a ? and hooks to the booster

 

Hello all does anyone know were I can get one of these lines with the check valve in it?

 

It appears to be NLA from Mazdatrix and Atkins Rotary, but they both carry an external check valve that can be spliced into any hose. I don't know if there's anything special about the $40+ one that they sell vs a cheaper one that you could get at a regular auto parts store.
https://www.atkinsrotary.com/86-11-r...4-43-770-.html
https://mazdatrix.com/product/brake-...lve-10mm-hose/

 

does anyone know a cheaper check valve we couls use? Link