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Discussion Starter #1
After replacing the vacuum booster, master cylinder, brake fluid and front calipers, the brake pedal still goes to the floor.

What else can I try?

Thanks for your ideas.
Patrick
 

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2008 TBSS Red Jewel RWD
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Just to confirm ... you replaced all those items because the brake pedal goes to the floor? Was there anything that happened to the vehicle like an accident before the pedal went to the floor or did this just happen out of the blue? Maybe an ex that cut the brake lines?

Sent from my moto z3 using Tapatalk
 

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Discussion Starter #3
Just to confirm ... you replaced all those items because the brake pedal goes to the floor?
Nothing was wrong with the brakes until I replaced the rear wheel bearings. Somehow, 1 of the rear calipers locked up, so I just replaced it.

I was surprised how simple it was, so I decided to replace the front calipers as well. After bleeding all of the calipers, I went for a quick test drive. At the first intersection, the pedal went to the floor.

My fear/hunch is that my assistant may have used too much leg pressure when we were bleeding the brakes.

I assumed it was the master cylinder that broke, but after replacing it, the pedal still went to the floor.

The vacuum booster just made a hissing sound, so I replaced it. Still no luck.

There might be a trouble code, so I’ll check that tomorrow.
 

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'08 Silver TBSS
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After replacing the master cylinder, you most likely have air trapped in the ABS unit, so you'll need to bleed that first. To do that you'll need to activate it using a Tech 2 which only GM has or find a dirt road and lock up the brakes to activate the ABS. Afterwards bleed the brakes like normal.
 

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Discussion Starter #5
Thx; I’m going to bleed everything 1 more time.

I think the only part that I haven’t replaced is the ABS module (available on Rock Auto for cheap).
 

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After replacing the vacuum booster, master cylinder, brake fluid and front calipers, the brake pedal still goes to the floor.

What else can I try?

Thanks for your ideas.
Patrick
After replacing the vacuum booster, master cylinder, brake fluid and front calipers, the brake pedal still goes to the floor.

What else can I try?

Thanks for your ideas.
Patrick
When you replaced the master, was it bench bled or bled on the TB to purge the air? If not, bleed the master first, then go to the passenger rear and bleed again, then the drivers rear, then pass front and drivers front. You may need to bleed the ABS if this doesn't work. Not sure how long your lines were open or if pedal was depressed with no calipers on which would suck the air up into the lines. A Mighty Vac tool (about $36) may help to bleed the lines also.
 

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Discussion Starter #7
After replacing the vacuum booster, master cylinder, brake fluid and front calipers, the brake pedal still goes to the floor.

What else can I try?

Thanks for your ideas.
Patrick
It ended up being the rear ABS speed sensors. When I replaced the rear wheel bearings, I removed the ABS sensors to check inside the axle tube. When I reinstalled them, they didn’t go all the way back in. I bought a Tech2 which immediately indicated the rear wheel sensors were having troubles.
It seemed like the new bearing was in the way.
So using a dremel, I made some clearance and was able to fully insert the wheel sensor.
No problems since!
 
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