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Old 03-29-2023, 09:31 PM   #1
Wobpb377
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Stop—brake Help

Well I can’t stop since my brakes go to floor.

1986 suburban 7.4 with 13” rear so Jb7 brakes

Went for an easy job, replace rotor and pads. Did they and truck still pulled hard right when heavy braking. Replaced hard and soft line on driver side. Installed new master cylinder and bench bleed that with zero bubbles. Installed all that. Bleed/flushed entire system. Pedal is super fine. When to start it and pedal goes right to floor. Read could be brake booster—sourced and got one. Installed. Rebleed all lines and now bubbles. Pedal firm. Start truck boom pedal to the floor. Only brake components I didn’t replace was proportioning valve and rear wheel cylinders. And thoughts or tip to stop the pedal from going to floor when I start the motor?
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Old 03-30-2023, 07:44 AM   #2
kipps
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Re: Stop—brake Help

Hydroboost or vacuum booster?
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Old 03-30-2023, 10:01 AM   #3
cadillac_al
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Re: Stop—brake Help

Master cylinder still has problems. Does it ever pump up hard?
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Old 03-30-2023, 10:15 AM   #4
rick1956
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Re: Stop—brake Help

Braking systems don't provide pressure to the wheels until there is equal pressure in all the lines. In other words, if you have one wheel cylinder that is sticking, the system 'thinks' that wheel has achieved pressure that matches the other wheels. Truth is, that wheel cylinder may only be barely be pushing on the shoes because of the sticking cylinder.

ALWAYS replace wheel cylinders when doing brake jobs! Don't just check to see if they leak.

Note: This comment was addressing the original post about it pulling to one side... not the flat pedal. :-)
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Last edited by rick1956; 03-30-2023 at 04:28 PM. Reason: added clarification
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Old 03-30-2023, 11:55 AM   #5
Wobpb377
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Re: Stop—brake Help

It’s a vacuum boost.

Perhaps the propvalve Needs reset? Any tips On that?
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Old 03-30-2023, 01:46 PM   #6
bigdaddy4x4
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Re: Stop—brake Help

you need to replace both calipers and front brake hoses that should fix your problems
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Old 03-30-2023, 01:54 PM   #7
Wobpb377
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Re: Stop—brake Help

I replaced the driver side. Went to replace passenger side and the hose a got seems thinner from driver side even though it’s supposedly for my truck with the Jb7 so I didn’t replace it. Didn’t want to put a thinner line on the passenger slider before verifying it was the right line.
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Old 03-30-2023, 02:57 PM   #8
Mathew21
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Re: Stop—brake Help

Not on my Square body but on my Tahoe I just installed a new master cylinder. The new one from oreillys auto parts was bad out of the box. Warrantied it out they gave me another one it was bad out of the box also. I retuned it and ordered an AC Delco one from Rock auto and it was good. Do you still have the old Master cylinder? If you do put it on and see if it fixes the brake pedal issue.
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Old 03-30-2023, 03:17 PM   #9
Wobpb377
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Re: Stop—brake Help

It’s my daily driver and I am limited to Napa autozone oreillys. I would
Like to get Acdelco but cost to get here is around 85-100 and that is essentially the price of parts. Plus it would not get here until next weekend. I tend to stick with Napa.

I’m gonna try and swap out the new caliper I got from Napa with another one and see if it helps.
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