Brake Power Booster ID and Replacement

[win32exe]

Hello, yesterday i started feeling that the brake pedal is going too low before i feel any braking, i check the master cylinder and it was low so i filled it up, that didn't help, when i started it up i can hear a vacuum leak from under the dash at the back of the power booster, so i figure the booster needs replacing, pretty sure i have an odd setup, so i need some identification help and which new part to order.

i also have a power booster i pulled from another Eagle SX/4 i had years ago, i don't think i can use any of it but will add the pics.

the booster in the car is bolted to the bracket, not riveted.

can i swap the booster without removing the bracket from the firewall?

master cylinder has outlets on the passenger side.

the spare booster\master are on the other side(1980\81 i think) bracket is smaller too

Henry

[89 MJ]

I believe some of the AMC vendors rebuild them, but that takes time. Somewhere on here is a thread about swapping to hydroboost if that's a route that interests you. Otherwise, I would check out Master Power Brakes and find one that is close in dimensions.
https://mpbrakes.com/?srsltid=AfmBOorJk9jGINeeEVCnlxJIbHYPKmWsw8nfR94KQNvmD_kDobpPZHl_

[Ludworks]

It all looks pretty standard to me.

You probably won't be able to remove the booster with the bracket in place. To get mine out I removed the nuts holding the booster to the bracket, then removed the nuts holding the bracket to the firewall (they're up under the pedals, not too hard to get to, just annoying). Only with both sets of nuts removed was I able to wiggle the booster out past the shock tower.

You probably lost the poppet seal, possibly the diaphragm. They're not particularly special, they're just difficult to get at. A good old-school mechanic would be able to help, otherwise a rebuilt unit from a vendor like 89 MJ suggested would be your easiest option. You'd have to be pretty careful on your measurements for a universal booster to fit, but certainly possible as well.

[AMC of Houston]

There are a number of companies out there that'll rebuild your unit to as-new condition.   I've used https://www.brakeboosters.com/ in CA in the past for AMC's and one of my Jensen Interceptors.  Did a fine job.

[win32exe]

so it is a regular 83 power booster? do all the 83 and older power boosters bolt on to the bracket?

Thank you

[Ludworks]

As far as I'm aware. Looks like a regular 83+ 8.5" Bendix. Only the first few years had the different style.

[win32exe]

Ludworks, is there a rebuild kit? you mentioned a poppet valve or diaphragm replacement...

Thank you

Henry

[win32exe]

hey, with a vacuum leak, should the pedal be harder to press? mine is easier to press up top and starts to break when the pedal gets to the bottom of its travel, but i do hear a loud vacuum sound coming from the booster under the dash, i don't have 4 WD actuators on vacuum anymore, there's no vacuum to the 2/4WD switch.

Thank you for any input!

Henry

[89 MJ]

A rebuild kit would be a good option for people that don't want to wait for a service to rebuild theirs. I'd be interested in that too.

[89 MJ]

hey, with a vacuum leak, should the pedal be harder to press? mine is easier to press up top and starts to break when the pedal gets to the bottom of its travel, but i do hear a loud vacuum sound coming from the booster under the dash, i don't have 4 WD actuators on vacuum anymore, there's no vacuum to the 2/4WD switch.

Thank you for any input!

Henry

You might want to try pulling the vacuum line off of the booster and see if that makes a difference in pedal feel. Make sure the engine is running when you test it, but you might want to plug the vacuum line so the idle isn't super high. I think that would be the best way to see if the booster is bad.

[Ludworks]

Loud vacuum noise at rest is usually a pretty good indicator of a bad seal, but still try pulling and plugging the vacuum hose to the booster first just in case, you never know. Pedal feel can vary depending on the nature of the leak. When you step on the pedal of a correctly functioning booster there should be some air noise, you're letting atmospheric pressure in to part of the chamber, but it should be silent when not in use.

Try this simple test: "With the car turned off, pump the brake pedal four or five times until you get a hard brake pedal. Continue to hold the brake pedal down with moderate pressure and start the vehicle. The brake pedal should drop. If this brake pedal remains hard, there is a problem with the brake booster."

I think, but cannot confirm, that this kit would have most everything needed for a rebuild:
https://www.powerbrakebooster.com/product-page/bendix-gen-2-rebuild-kit-8-5-double

In your shoes I would open up the booster and take a look at what's going on. The diaphragms are probably good and wouldn't need to be replaced, it's probably just one of the air valve seals. Many Bendix seals have a part number on them so if you find one torn up it's probably something you could locate online pretty quickly.

It's also possible that some of the metal parts are rusty and the seal(s) are hung up or malfunctioning because of it and some emery cloth or scotchbrite might be all you would really need.

You need to be very careful working in a brake booster though, one little scratch or chip on the wrong piece and you're done.

I'm going to tear my Eagle booster apart in the near future. Considering the availability issues I might be inclined to put together a rebuild kit if the one I linked isn't right.