On a humanitarian mission in southern Louisiana that I've detailed elsewhere, and I'm having a brake issue. The issue is a longstanding one but it has gotten dangerous pulling a trailer full of heavy wet furniture, carpet etc.

Symptoms are occasional three amigos (i have done the bypass and have no codes from sensors) and the loud hissing sound when I hit the brakes. I believe the booster diaphragm is shot and has been for a long time. Basically I have no brakes until the engine gets vacuum going, and it hisses every time I hit the brake pedal. I'm not losing fluid. If it hit the brakes, vacuum is gone and hitting them a second time doesn't result in much brake.

I can find a booster and I have tools with me or I may be able to work on it at home. Now that I think about itt ill have to because there are no delivery trucks here. Or mail delivery. It is obviously a pretty big issue because I've been fine with it for years but this is a special circumstance that demands immediate attention.

The quick and dirty I need is how difficult and what are the basic steps to replace the booster. I've never done this but im reasonably mechanical and if I have a new part in front of me to look at I can generally swap it for the old part. Having a nice copy of the RAVE or taking my time just isn't an option at the moment, nor is not using the rover.

Any comments will be greatly appreciated!!!!

 

Removing and replacing the brake servo is very straightforward and easy. I had to replace mine a few years ago. I've attached the RAVE instructions.

There was someone on the forum in the last month who did it without disconnecting the brake lines from the master cylinder, which saves needing to bleed the brakes. He unclipped the lines from their supports and was able to get enough flex to get the job done.

 

Thanks mln. I guess I need to google the servo. I thought the hissing sound was in the booster, but they seem to be separate parts and the hissing is definitely in the driver footwell.. Can you attach the booster removal procedure? Or is this an "even I can do it" thing where I am going to see nuts and bolts and have it out in a jiffy?

EDIT: My bad--reading on phone. I can remove the master cylinder. I think. Then the servo/booster. Bolts and clips. Okay that is good news! I should have done it long ago.

 

Brake booster and brake servo are the same thing. The big, round, black thing mounted behind the master cylinder that looks sort of like a curling stone (you know, the Canadian ice sweeping sport akin to shuffleboard).


And yes, it's that easy.

 

Sorry, I figured it out and edited my post before I saw yours. THANK YOU SO MUCH. Clips and bolts and a vac. line. I can do that. YOU ARE A CREDIT TO THE FORUM!

 

Well I am getting conflicting info on which booster to use. I can't be picky. But http://www.autopartswarehouse.com/sk.../A1532958.html seems to be the one. Now to find it at a store within driving range.

EDIT: Well, geez, doesn't matter. I'd have better luck finding one on the side of the road than in a parts store. A RARE BIRD, I gather. FWIW, with a coupon I see it at autozone (shipped only, seven days to ship) for just under 200, including a 50 dollar refundable core charge. I am sure that is a junk brand (and reman), so I'll look for equivalents and, last ditch, find out what is involved in replacing the diaphrams, check the check valve, etc.

Found a video on how to get the master cylinder off, I presume I just wouldn't want to disconnect the lines on the bottom (so I don't have to bleed anything). Oddly ebnough, i have the master cylinder rebuild kit in my truck in the tool bin (been there for months); that will be for another day.

 

The one I installed in November 2012 is from a local boneyard truck and has been great. Based on evidence on this and other forums the failure rate for brake boosters is very low, despite your experience. I needed a replacement only because I ruined the old one by getting brake fluid into it when changing the master cylinder. Maybe Paul Grant or abran can overnight one to you.

 

Before you tear down the servo check all the vacuum hoses for splits to ensure it's maintaining a vacuum.

 

Geez! It's true what they say. No good deed goes unpunished!
I don't know if this will help or not, but for what it's worth...
I had a Volkswagen that had a similar hissing sound as what you're describing. It was the seal on the rod going into the back of the booster. However, I can't remember if it caused any trouble with the brakes themselves.
It might be worth checking out though. Maybe it's not the internal diaphragm. I'm not sure if you would hear that leaking or not. I know for sure you can hear the seal when it leaks.

 

I'm heading to the local U-pull tomorrow, was going to offer to pull one for you, but there's a whole slew of them on eBay even cheaper. You might contact some of the sellers and ask about expediting. I'd feel pretty confident with a used part in this case.... failures seem isolated.