Looking and shopping around to replace a cracked loose brake booster vacuum line.
But every where is out of stock. For S5 TII

Wondering if the FD part will work?
It needs a check valve in the line.

 

The hard part will be finding the check valve, the hose is generic. On my S5T2, I replaced the hose with a length of silicone vacuum hose, ID of the hose was 8mm if I recall. But I still had the original hose, so I just removed & reused its check valve in the new hose. Make sure you install it in the new hose with the same orientation it had in the old hose or it won't work.

 

There is special brake booster hose that is rigid enough to not collapse under use. It can be expensive, but I found a Mopar part on eBay that had the bends I needed. I too just used the old check valve...don't know how to advise you there.

 

Atkins sells an external check valve that they claim will work. Here their webpage: https://www.atkinsrotary.com/store/8...tegory_id=2196

If I recall, this issue was discussed before, and the poster recommended buying the FD booster hose and cutting it to length.

 

That Is what I though of doing is getting the FD version and adapting it

 

Any one way check valve will work, junkyards are littered with versions from zillions of Japanese cars.
You don't need to overthink this.

 

every car that has a vacuum booster will also have the check valve....

 

Check valve I used.

 

no. every car has a check valve. in the case of the engine failing, you still need brakes

 

Hmm. I'm fairly certain my old NA FCs didnt have them on there... could be wrong I suppose.

To your engine failure point, i dont want to get into an arguement, but if the engine did fail, there wouldnt be enough vacuum to sustain brake booster function. If you dont believe me, shut your engine off while youre driving and try to use your brakes.

 

try it in the driveway. you should have enough vacuum for 2-4 applications of the brake pedal.

 

You are.
Mazda liked to use an in-hose valve...kinda like a suppository, so it wasn't immediately obvious, but if you had a vac booster, you had a check valve.

TGood thing you don't want to argue because you'd lose.
The point is not to sustain brake function, it's to maintain it long enough to stop. A non running engine doesn't stress the brakes much.

 

The more you know...

After some google searching I've found that the main function of the check valve is to keep air out of the system.

I'm just speaking from personal experience; I have shut my engine off while rolling and I didnt get 2-4 more pumps out of the brake. The brake pedal instantly hardened.

 

Your booster may not be working optimally.

 

Brand new car... I dunno.

 

Yup, and if air can get in, you can't retain a vacuum for very long, And for turbo/supercharged cars, you need the check valve to prevent the power brake's vacuum chamber from going from vacuum to pressure during normal driving.

Getting more than 2~4 assisted pumps sounds about normal for a non-running engine... Just from personal experience on my driveway (which is a hill) I've often had to roll one for the cars down the hill (non-running) in neutral and hit the brakes in order to make room for another car to pull out of the garage, Doesn't seem to matter which car, but 2 good assisted pumps of the brake pedal with a non-running engine is about all I'll get and it's manual brakes from there..