1968 427 (3x2) brake problem
Thread Starter
Intermediate
Joined: Jun 2011
Posts: 31
Likes: 0
From: Ramsey, NJ
1968 427 (3x2) brake problem
1968 427 (3x2) brake problem
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1968 vette brake issue:
Had a brake pedal problem as follows.... When car sits for a few hours brake pedal goes to floor... I can pump up the brake pedal, then the pedal feels fine and stops fine ( perhaps a little grabby~).
So I replaced with New: M/C, PBB, calipers, brake lines and converted to Dot 5.... Bleed system (gravity and pump method... car seemed to be fine then reverted to the same problem.
Only other item items worth noting: I can hear a hiss (air sucking noise isolated to vacuum canister –not sure if that is normal?) located under the M/C driver side, but believe this is only the reserve for the headlights, wiper door while engine is off or while driving at low rpm’s...I also tested the PBB, (pulled off the hose/fitting- air was sucked in ( check value works fine) and M/C ( blocked off hose fittings holds pressure no problem there... I also feels like the brakes are dragging a little (won't roll back on incline, but seems to release fully after it sits.
I had spoken to more people and read more blogs then I care to mention….Starting to run out of ideas. Thoughts on problems or diagnostics I can run to narrow down?
Some of my last idea’s
• Vacuum canister issue?
• Proportioning valve issue?
• PPB Issue (internally)? - I really would like to be certain if this is a PPB issue a project to change again and can't see how a bad booster would drop teh pedal to teh floor or a vaccum canister as well?
Another (3rd one) defective new M/C?
New M/C don't like Dot 5?
Any insight or advice Greatly Appreciated - Thank you
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1968 vette brake issue:
Had a brake pedal problem as follows.... When car sits for a few hours brake pedal goes to floor... I can pump up the brake pedal, then the pedal feels fine and stops fine ( perhaps a little grabby~).
So I replaced with New: M/C, PBB, calipers, brake lines and converted to Dot 5.... Bleed system (gravity and pump method... car seemed to be fine then reverted to the same problem.
Only other item items worth noting: I can hear a hiss (air sucking noise isolated to vacuum canister –not sure if that is normal?) located under the M/C driver side, but believe this is only the reserve for the headlights, wiper door while engine is off or while driving at low rpm’s...I also tested the PBB, (pulled off the hose/fitting- air was sucked in ( check value works fine) and M/C ( blocked off hose fittings holds pressure no problem there... I also feels like the brakes are dragging a little (won't roll back on incline, but seems to release fully after it sits.
I had spoken to more people and read more blogs then I care to mention….Starting to run out of ideas. Thoughts on problems or diagnostics I can run to narrow down?
Some of my last idea’s
• Vacuum canister issue?
• Proportioning valve issue?
• PPB Issue (internally)? - I really would like to be certain if this is a PPB issue a project to change again and can't see how a bad booster would drop teh pedal to teh floor or a vaccum canister as well?
Another (3rd one) defective new M/C?
New M/C don't like Dot 5?
Any insight or advice Greatly Appreciated - Thank you
Burning Brakes
Joined: May 2008
Posts: 860
Likes: 0
From: Stratford Ontario
Looks like you have a good grasp on problem solving. I would try one more thing and that is plug all vacum lines except brake and tranny if automatic. Just to eliminate any possibility of it being vacum related. this should also eliminate the vacum leak.
Thread Starter
Intermediate
Joined: Jun 2011
Posts: 31
Likes: 0
From: Ramsey, NJ
I will try that as well... car is 4 sp, so i will block off the main line going to the vaccum canister, which i suspect is leaking....But what i have read so far this vacuum canister would have no effect on the brakes? But perhaps it does? It's worth a shot.
