BC brake booster replacement?

[brad_h1]

Hi guys, just a quick question. About 2 years ago I installed a BC brake booster kit and now the booster is loosing vacuum which is making my truck idle too high with a Holley Sniper. Does anyone know what booster this kit came with so I can buy a direct replacement? I believe it's the GM style booster. What car can I look up on Rockauto for a replacement? Thanks in advance!!!

Always chasing gremlins with this truck!

 

[broncodriver99]

Is it this kit?

https://bcbroncos.com/collections/p...er-brake-kit-all-application-for-early-bronco

Looks like they use the Mustang II booster.

https://bcbroncos.com/collections/power-brakes-valves/products/power-brake-booster-for-early-bronco

Other than that a phone call to BC is your best bet. A pic would help as well.

 

[brad_h1]

That's it, but I don't think it's the Mustang II booster. I think it's a newer style GM booster. I guess I'll have to call them, but I never seem to have much luck getting answers from them. Thanks!

 

[SteveL]

His original kits were the Mustang 2 booster but that was years ago. I'm not sure what the ones are now. I got tired of blowing boosters every year or two and went hydroboost. When I talked to a local brake vendor he said those little booster don't do well with larger tires. I'm on 35s.

 

[toddz69]

The one they use isn't an OEM piece - only available in aftermarket kits. Looks like they sell them. I would also check out MBM brakes as they sell a lot of those types of boosters (although they might be wholesale only).

Todd Z.

 

[brad_h1]

Thanks for the replies, everyone. Todd, I think you're right- which is why I've had nothing but problems with this kit ever since I bought it. It must be some cheap import low quality components. The day I installed it I had to get a new master cylinder, and I'm thinking the booster has leaked since day one too. I think I'll try and see if the Mustang II booster will fit it, as I know those are re-manned a little better than some Chinese parts. I'll update once I get a Mustang II booster to confirm it fits the bracket. Thanks again guys.

 

[SteveL]

Where are you located? Here in so cal the hot rod swap meet is this Sunday in long beach. There's a brake vendor there every month with boosters and swap kits.

 

[73azbronco]

Booster diaphragm or valve? That cheap little check valve has been known to be an issue in all brands.

 

[chuck]

The boosters should last for many years. The problems most people have is the brake rod is too long or the check valve goes bad. Run your engine a few min. then turn it off, wait a few min. and pull the check valve and you should hear vacuum leaking. If not be sure you have free play at the top of the peddle, if you do, start the engine and clamp the vacuum hose going to the check valve and the engine should slow down, if it does the booster is most likely bad. Send it back and we will replace it. When we stopped using the mustang II booster we had the new aftermarket one made to replace the mustang II booster so you should be able to install the mustang II without problems. It will be longer and the input shaft should be stamped with a mus9 mus10 or mus11. If it does not it is not a mustang booster and will cause the MC to hit the hood. The rebuilders say they are the same but they are not. Also the input rod is shaped like a J. The point of the J must point to the engine.

 

[brad_h1]

Wow. Thanks for the advice, Chuck. I'll try your method of testing hopefully tomorrow.

I did hookup a vacuum gauge to the booster and after pumping it up to 20" of vacuum, while holding the pedal down it slowly loses vacuum consistently. This would probably explain while driving, when coming up to a stop and holding the brake pedal down, my engine wants to idle about 3-400 rpms too high. I've been chasing this issue ever since I got this thing. It very well could be that I trimmed the pushrod too long... I'll keep this updated. Thanks again.

 

[brad_h1]

Hi guys. Just updating this thread. I followed Chucks test procedure and the check valve seems to work ok but when I clamp the hose while running the engine does in fact slow down. It's very slight, but definitely causing an issue. Then I hooked up my vacuum gauge again to the hose going to the check valve. I pumped it up to 20" of vacuum and stepped on the brake pedal (engine off at this point). The booster slowly loses all its vacuum while holding the pedal down.

Then to confirm this is what's causing my issue I left the hose disconnected and plugged the vacuum port on my manifold and took it for a 15 mile drive in the country so I could drive nice and slow, lol. No more high idle issues. Thanks to everyone for your suggestions. Very nice to be certain what the issue is.