The brake booster started to make a hissing sound when the pedal is depressed. I ordered a new aftermarket booster from Amazon, but it will take some time to get it here. Do you think it would be safe to drive the vehicle meanwhile? The brakes work OK right now; I just started to hear the sound a couple of days before. Should I also order the master cylinder? I understood that when the brake booster fails, the pedal sometimes goes to the floor, and at this point the master cylinder could be damaged.
Bad brake booster
- Thread starter santon
- Start date
Also, I found this discussion: https://www.trailvoy.com/threads/front-brake-woes-too-much-whoahs.213315/. I don't understand what the issue is with this "relay pin" (a rod that presses on the plunger of the master cylinder). I already replaced a brake booster on the Trailblazer of my friend; it was pretty straightforward. We just put the new aftermarket booster on without swapping that "relay pin" and without adjusting anything, and it was just fine. It is written in that thread that "Typically you never get a rod in a new/reman/rebuilt booster. " However, I remember that the aftermarket booster had everything, including the part that presses on the master cylinder (the "relay pin"). What am I missing here?
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I remember somebody having an issue with that rod once. Either they replaced the master cylinder or the booster and it would continually depress the piston in the MC because the rod was either too long or the MC piston was closer to the rod. I can't remember how they fixed it but I think they wound up shimming with washers between the MC and the booster. You should be able to put the MC back on without feeling like you're depressing the piston. The MC should sit flush with the booster without resistance.
It should be fine to drive except you might be losing vacuum and making the engine run lean. Sounds like it leaks only when depressing the pedal. At worse, if you lose the booster completely, the brakes will be hard to depress but still functional.
It should be fine to drive except you might be losing vacuum and making the engine run lean. Sounds like it leaks only when depressing the pedal. At worse, if you lose the booster completely, the brakes will be hard to depress but still functional.
Check Out Post #14 in this Thread where @xavierny25 found (and SOLVED) a problem with the Phenolic Disk Brake Piston Units going Bad, locking up, and perhaps *Hissing* as the result of constant pressure against the Brake Disk Platter:
Also... another Diagnostic Angle can be examined via a FLIR Camera to pinpoint a Non-Returning Disk Brake Pad issue via the Excessive Friction and Heat it generates:
Also... another Diagnostic Angle can be examined via a FLIR Camera to pinpoint a Non-Returning Disk Brake Pad issue via the Excessive Friction and Heat it generates:
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