I’m fine, luckily. But my brake assist just disappeared on the highway. Cruising along, doing some pulls, music playing all amazing and a great pay-off for all the work that’s gone into this car in the last few years.

And then.

Hard pedal. Very little brakes.

Stood on them hard, pulled over and now the car is on a flatbed because I’m not foolish enough to drive without power assist.

I’m guessing it’s the brake booster. Everything else has been rebuilt recently and that’s definitely what it feels like. Could be the check valve. Either way, I’ll be putting in a rebuilt booster, new check valve and all new soft lines around the booster.

So this is just a little PSA: brake booster diaphragms are rubber, rubber degrades. You can’t see inside the booster, don’t assume it’s in good shape. I put RZ brakes on this car, spent cash on a big turbo, and left the old original booster. Don’t be like me. I could have easily written off this car and put me and others in serious danger.

 

I haven't research availability of boosters for FD's but I know with older Nissan's like 240sx and 300ZX they can be very hard to come by these days even aftermarket.

 

Turns out it was just the check valve. Same effect, no boost for the brakes. Check your ****! Replace it!

 

Yeah I haven't heard of too many boosters failing, but I have had that check valve fail. You still have brakes you just don't have the vacuum assist so initially it feels like you have no brakes but you just have to put a ton of leg into it.

 

Yup. Scared me for sure. FD brakes with no assist are pretty bad!

 

Chase Bays makes a Brake Booster delete. It changes the size of the Master Cylinder to keep the pedal pushable while still providing braking power. Also cleans up the engine bay nicely!

 

Looks like the RHD booster is still available, I guess if one needs it it can be used with a longer hose for the different nipple location. What I couldn't find was the check valve, what's a good replacement for it?

RHD Booster Part# F10043800A

 

A70 supra check valve or any brake booster check valve from any car that doesn't have it integrated into the hose

 

It's embedded in the hose, so you're looking for the hose not a valve per se. Check with Ray Crowe.

 

RHD part number for the hose with valve
F10043640B