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Old 09-27-2020, 01:08 PM   #1
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Red face Brakes locking 89 Fleetwood P30 Chevy rear disks

Going crazy here Have replaced the hydroboost twice believe I have the correct one looks like the one we replaced leaking originally actually looked like it was getting fluid into master cylinder.
Changed master cylinder twice. Can drive around parking lot apply brakes 50 times no problems get out on the highway without apply brakes much. All the brakes lock up pedal rock hard steering seems stiff? Brakes seem to release within about 30 minutes Any ideas Seem to have lost power steering fluid odd though I do not see a leak PLLLeeease
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Old 09-27-2020, 01:18 PM   #2
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Hydro boost fluid getting into the brake fluid system is a bad thing for brake system seals. If your correct and this happened the hydro fluid may have gone past the master cylinder and attacked seals. Is there a proportioning valve in the system .

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Old 09-27-2020, 01:19 PM   #3
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The master cylinder is not returning fully, blocking the brake fluid from returning out of the calipers. That causes a slight drag that overheats the pads cause them to expand and squeeze the rotors.

Step on and the let up on the oedal and look in the master cylinder. You should see a bit of movement in the the fluid as it returns.

Next time it locks up, open a blessed and see if fluid shoots out.

Some of the pedals use a bellcrank to turn the brake cluster sideways. If its sticking, it will hold the pedal down a bit. When the brakes lock up, pick the pedal up with your toe and see if they reliese.

Flex hoses can block fluid return but on both front and rear would be rare.
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Old 09-27-2020, 01:23 PM   #4
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brakes

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Originally Posted by Kevin1955 View Post
Going crazy here Have replaced the hydroboost twice believe I have the correct one looks like the one we replaced leaking orinally actually looked like it was getting fluid into master cylinder.
Changed master cylinder twice. Can drive around parking lot apply brakes 50 times no problems get out on the highway without apply brakes much. All the brakes lock up pedal rock hard steering seems stiff? Brakes seem to release within about 30 minutes Any ideas PLLLeeease
CHeck the rubber hoses, they swell up inside and stepping on the peddle has enough pressure to push the fluid into the caliper but the caliper only uses the o-ring that it seals with to return, not much pressure. I had this problem and figured it out by jacking up a wheel applying brakes and wheel was locked. Loosened the hose fitting and it released. Hope this helps.
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Old 09-27-2020, 01:57 PM   #5
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Originally Posted by clifford j View Post
Hydro boost fluid getting into the brake fluid system is a bad thing for brake system seals. If your correct and this happened the hydro fluid may have gone past the master cylinder and attacked seals. Is there a proportioning valve in the system .

CLIFFORD
Not sure about the valve or know where it is ?
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Old 09-27-2020, 02:18 PM   #6
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Actuator rod between the booster and master is likely slightly too long. This can prevent the master cylinder piston from fully retracting, so brakes will drag. Reach out to the hydroboost manufacturer regarding proper adjustment of this rod, or bellcrank if you have one of those in between the pedal and hydroboost.
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Old 09-27-2020, 02:38 PM   #7
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If it is a 1989 and the rubber hoses are original, I would bet on Jim being right about the hoses. I have replaced a bunch of hoses for swelling on the P32 chassis.
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Old 09-27-2020, 03:57 PM   #8
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If it is a 1989 and the rubber hoses are original, I would bet on Jim being right about the hoses. I have replaced a bunch of hoses for swelling on the P32 chassis.
These normally fail one at a time. But certainly if they are original, they are far, far past their "best by" date.
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Old 09-27-2020, 09:09 PM   #9
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There's a weep hole between the hydroboost and master cylinder to prevent fluid exchange.

Stiff steering indicates a hydraulic pump or power steering problem; if you're not getting enough pressure you'll feel a hard, unboosted pedal.
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Old 09-28-2020, 04:50 AM   #10
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Let's recap what the OP said: changed leaking brake booster, changed M/C twice , pedal ok in parking lot test, brakes lock up on highway , brakes release after 30 minutes. Pedal is rock hard when brakes locked up, steering felt stiff.
OP didn't tell us if brakes were normal before the booster was replaced, did the OP confirm it was a booster fluid leak and not M/C dirty fluid leaking. Did the OP top off brake fluid to the M/C prior to the problem (correct fluid ? )
More information from OP would be helpful

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Old 09-28-2020, 05:08 AM   #11
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So if the bellcrank is sticking ( if equipped ), that would account for the brakes staying on and the change in steering.

When the brakes are applied, some PS pressure is diverted to the hydroboost.

Toe pulling up, under the pedal is the first test.
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Old 09-28-2020, 09:59 AM   #12
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Quote:
Originally Posted by clifford j View Post
Let's recap what the OP said: changed leaking brake booster, changed M/C twice , pedal ok in parking lot test, brakes lock up on highway , brakes release after 30 minutes. Pedal is rock hard when brakes locked up, steering felt stiff.
OP didn't tell us if brakes were normal before the booster was replaced, did the OP confirm it was a booster fluid leak and not M/C dirty fluid leaking. Did the OP top off brake fluid to the M/C prior to the problem (correct fluid ? )
More information from OP would be helpful

CLIFFORD
Bought this mh and when I first drove it home the ps made a little noise and first application of brake pedal went way down near floor. Pumped the brake at stop next application pedal up and braking started sooner just didn't feel like brakes were stoppiing that well. Added ps fluid and used mh 1st stop same thing pedal near floor. On road for a couple days babyied it pedal up farther stopped but still did not feel that good. Climbed under saw fluid leaking weep hole checked level front part mc looked like it had dark fluid needed ps fluid assummed booster leaking. Bought booster such a pain changed mc also. bled brakes pedal up brakeing greatly improved. Drove in storage parking lot worked great testing brakes etc for about 1 mile. Went to drive home got about 3 miles away brakes locked Let sit for about 2 hours brakes released drove back to storage minimal braking. Changed Power booster again same thing replace mc again same thing. One thing of note Chevy told me these had JB8 brakes? At the supply hose the specs on the mc said this fit this unit rear discs mh etc but did mention JB9 brakes. Also at rebuild used dot4 fluid which supposedly is compatible with dot 3. Any way changeing hoses going back to dot 3 today. Hoping this works
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