Brake HELP
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3rd Gear
Joined: Sep 2022
Posts: 3
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Brake HELP
84 Bronco 351W c6
I have no pedal when truck is running.
here's what ive done so far.
New wheel cylinders 1.5 yrs ago (just inspected-still good no leaks)
New booster 1.5 yrs ago
New rear lines 1.5 yrs ago (from "T" to wheel cylinders)
new calipers, rotors, pads, master cylinder (bench bled well), all 3 rubber lines, and brake line from proportioning valve to rear.
i bled the brakes a ton. I get pressure built up until the truck is started, then the pedal goes to the floor soft.
im stumped. No leaks anywhere. I triple checked all the connections. The only way i get pressure in the pedal while the truck is running, is if i unhook the booster vac line.
I kicked the pedal hard in an attempt to potentially unstick the proportioning valve if that was the problem but yo no avail.
any ideas?
I have no pedal when truck is running.
here's what ive done so far.
New wheel cylinders 1.5 yrs ago (just inspected-still good no leaks)
New booster 1.5 yrs ago
New rear lines 1.5 yrs ago (from "T" to wheel cylinders)
new calipers, rotors, pads, master cylinder (bench bled well), all 3 rubber lines, and brake line from proportioning valve to rear.
i bled the brakes a ton. I get pressure built up until the truck is started, then the pedal goes to the floor soft.
im stumped. No leaks anywhere. I triple checked all the connections. The only way i get pressure in the pedal while the truck is running, is if i unhook the booster vac line.
I kicked the pedal hard in an attempt to potentially unstick the proportioning valve if that was the problem but yo no avail.
any ideas?
Last edited by Jonmerrill87; Sep 7, 2022 at 07:22 AM.
Logistics Pro
Joined: Jun 2009
Posts: 4,818
Likes: 83
From: Cedar Rapids, IA
Did you replace all these items, including the brake booster, in an attempt to fix the soft pedal issue? Do the brakes work to stop the truck, or is the braking effectiveness as crappy as you'd expect it to be with a soft pedal? Are you vacuum bleeding, 2-person bleeding, pressure bleeding, or using some other method to bleed? Somewhere is there a section of clear tubing to confirm no air bubbles are in the fluid during the bleeding process?
-Rod
-Rod
Fleet Owner
Joined: Oct 2005
Posts: 20,789
Likes: 1,753
From: Kentucky
I have seen vacuum brake boosters cause the soft/no brakes issue. Since you claim to have good brake pressure/feel with the engine off or engine on/no vacuum to the brake booster that is pointing to a bad booster even though it is only 1.5 years old.
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3rd Gear
Joined: Sep 2022
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Did you replace all these items, including the brake booster, in an attempt to fix the soft pedal issue? Do the brakes work to stop the truck, or is the braking effectiveness as crappy as you'd expect it to be with a soft pedal? Are you vacuum bleeding, 2-person bleeding, pressure bleeding, or using some other method to bleed? Somewhere is there a section of clear tubing to confirm no air bubbles are in the fluid during the bleeding process?
-Rod
-Rod
Fleet Mechanic
Joined: Apr 2012
Posts: 1,275
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When you replaced the pads did you compress the calipers with the bleeder open, or just push the fluid back into the MC? If you pushed it back into the MC, you could've messed up a valve.
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Logistics Pro
Joined: Jun 2009
Posts: 4,818
Likes: 83
From: Cedar Rapids, IA
On and '84 there's probably no real valve to mess up since there's no ABS. I'm leaning towards the brake booster being the issue based on your description of the symptoms and since that wasn't just replaced in an attempt to solve this issue. I can't really draw a correlation to it failing right after you replaced the front brake pads and rotors. But there's not much chance of causing the issue you describe just from changing the brake pads and rotors either, unless you opened the bleeders to compress the calipers and let some air in. Can you borrow the time of someone to confirm whether the front brakes are locking up when pumping the brake pedal with the engine off, then confirm the calipers release when the brake pedal is released? Have you performed a careful visual inspection of the brake work to make sure you don't have a twisted hose or signs of an old/worn brake hose?
-Rod
-Rod
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Sounds like normal operation of the brake booster to me
There may be no problem at all with the truck
If you slam on the brakes it will put your nose on the glass is my guess
It's a common occurrence, your issue, where after a brake repair you think yours are spongy
Go road test the brakes and do not worry too much about the pedal feel in a Bronco
It's supposed to be light or smooth / spongy
Fought your complaint at the dealer 2k times
A road test to convince the owner he is going thru the windshield without a seatbelt usually does it
There may be no problem at all with the truck
If you slam on the brakes it will put your nose on the glass is my guess
It's a common occurrence, your issue, where after a brake repair you think yours are spongy
Go road test the brakes and do not worry too much about the pedal feel in a Bronco
It's supposed to be light or smooth / spongy
Fought your complaint at the dealer 2k times
A road test to convince the owner he is going thru the windshield without a seatbelt usually does it
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