Brake booster failure cause pedal to the floor?

BigNinjaDaddy

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Jun 6, 2021
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Brand new member and first post. I have a 2005 LLY. Was involved in a crash where the brake pedal shuddered and then dropped to the floor. The brake booster had been replaced by a shop (not an OE part, but one from Napa) a year earlier. the truck lost steering in the moment the pedal was lost as well. Thank goodness I had slowed considerably before the crash as I had braking up to that point, and then nothing. Pedal stayed on the floor with no return or pressure at all. Towed to GM dealer after crash, and part was given back to me in pieces, but master cylinder and all other components apparently fine. Has anyone ever heard of a failed or cracked booster resulting in no brakes? Thanks for your comments
 

Ron Nielson

Member
Oct 11, 2009
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Just thinking out loud, if your engine was not running, no power steering pump running, and the truck was moving downhill, your brakes would still work although they would require more foot pressure. You were still pushing on the master cylinder rod and creating braking pressure. I would think that you should have had brakes I don't understand why your braking system failed.

The only thing between the master cylinder and the braking system at the wheels is the EBCM. Maybe a problem there??
 

BigNinjaDaddy

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Jun 6, 2021
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Just thinking out loud, if your engine was not running, no power steering pump running, and the truck was moving downhill, your brakes would still work although they would require more foot pressure. You were still pushing on the master cylinder rod and creating braking pressure. I would think that you should have had brakes I don't understand why your braking system failed.

The only thing between the master cylinder and the braking system at the wheels is the EBCM. Maybe a problem there??
Hi Ron,
Truck was running at the time. Is it possible that if the hydro boost broke ( literally cracked), or the push rod broke, that I could lose connectivity with the master cylinder and therefore lose the pedal? No other components were replaced or repaired after the fact in the braking system. Also, with new OEM hydro boost replaced, no similar issues since.
 

darkness

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Jul 15, 2009
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I don’t know what the difference is between the hydro boost and a vacuum booster in function but I lost the vacuum booster on my ‘77 Chevy and the pedal went right to the floor. I thought it was the master but it wasn’t.
funny sidebar, I called my dad to come tow me home but had to do it in reverse order as to no brakes. The broken vehicle towed the functioning vehicle home and was the brakes of the whole operation 😂.
 

gmduramax

Shits broke
Jun 12, 2008
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I don’t mean to be the asshole, but it sounds like the brake fluid was trash, pedal shudder was abs, fluid got hot and pedal went to the floor.
 

BigNinjaDaddy

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Jun 6, 2021
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I don’t mean to be the asshole, but it sounds like the brake fluid was trash, pedal shudder was abs, fluid got hot and pedal went to the floor.
No offense taken. Head gasket, booster, and flush was done a year earlier. Actually was slowing down and ended up failing just as I was approaching stopped traffic. Not following too close at all, but your explanation could be correct. Steering was gone in that moment too, so not really sure. Scared the s%#t out of me though! Booster was replaced with an OEM at dealer and regular flushes with no issues since.
 

Leadfoot

Needs Bigger Tires!
Dec 27, 2006
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You said the truck lost steering at the same moment? I know my buddy lost his power steering pump (cracked shaft) and lost both steering and braking. Sounds like yours is similar. Both systems are tied together, so I guess a complete failure of the booster could cause loss of steering as well. From this diagram it looks as if the booster is first in line to receive high pressure so if it's completely/mostly lost at the booster the steering box would see minimal pressure as well....
 

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