Bad booster symptoms

[TireFryer]

What are symptoms of a bad brake booster or incorrect booster rod length? I have about 2” of dead pedal before I get any braking. It won’t even try to squeal the tires during an emergency stop (deer and idiot drivers), even though I pressed the pedal TO THE FLOOR with one foot. Yes it’s the proper vacuum brake pedal, yes I bled the brakes, yes I adjusted the drums, yes I flushed the fluid and replaced it. Wondering if it’s a bad booster/incorrect booster or the booster rod is too short maybe? Any input or replacement booster would be great.

Thanks

 

[TType85]

What are symptoms of a bad brake booster or incorrect booster rod length? I have about 2” of dead pedal before I get any braking. It won’t even try to squeal the tires during an emergency stop (deer and idiot drivers), even though I pressed the pedal TO THE FLOOR with one foot. Yes it’s the proper vacuum brake pedal, yes I bled the brakes, yes I adjusted the drums, yes I flushed the fluid and replaced it. Wondering if it’s a bad booster/incorrect booster or the booster rod is too short maybe? Any input or replacement booster would be great.

Thanks

I have been fighting that same issue for a while now. I don't have stock brakes (13.5" C6 up front 13" C6 in the rear) but my pedal has had a lot of throw before I get brakes. Correct vacuum pedal, correct booster and master. I had some others look at it and we have tried things like 2# residual valves, repeated bleeding, etc. No change.

I am currently putting a manual brake conversion on the car and hopefully that will fix it but I think I have to re-bleed the master due to a fitting that might have leaked all the fluid out. I am still getting a 1" throw before hitting a solid pedal with the outlets plugged even though the rod is adjusted to just touching the MC with no preload..

 

[TexasT]

have you done anything with the proportioning valve down on the frame? I was having probs with the rear locking up and pulled apart a rusty mess. swapped on a new brass one and magically the brakes worked again.
yrmv but if you are pedaling the original iron unit it might benefit from a clean out or replacement.

 

[TType85]

I am currently putting a manual brake conversion on the car and hopefully that will fix it but I think I have to re-bleed the master due to a fitting that might have leaked all the fluid out. I am still getting a 1" throw before hitting a solid pedal with the outlets plugged even though the rod is adjusted to just touching the MC with no preload..

Re-bled the master and got the conversion finished. There is much less dead pedal area before the brakes start applying; albeit more leg pressure is needed because they are manual brakes. Still hasn't locked them up but the pads were still cold and I have decently grippy 255 tires up front and 275 on the back so they are harder to lock up. I am going to change pads to ebc yellowstuff as recommended by Turbo6inKy.

@TireFryer I don't know what it was with the vac setup but I had the same issue yours has. Now it feels MUCH better not pushing the pedal half way down before getting braking. I tried multiple boosters (event the bigger b-body one), different check valves for the vac line, different master cylinders all without it feeling better.

 

[TireFryer]

Re-bled the master and got the conversion finished. There is much less dead pedal area before the brakes start applying; albeit more leg pressure is needed because they are manual brakes. Still hasn't locked them up but the pads were still cold and I have decently grippy 255 tires up front and 275 on the back so they are harder to lock up. I am going to change pads to ebc yellowstuff as recommended by Turbo6inKy.

@TireFryer I don't know what it was with the vac setup but I had the same issue yours has. Now it feels MUCH better not pushing the pedal half way down before getting braking. I tried multiple boosters (event the bigger b-body one), different check valves for the vac line, different master cylinders all without it feeling better.

I find this interesting as everyone swears by these vac brakes….

 

[TType85]

I find this interesting as everyone swears by these vac brakes….

That's the weird part. I had another TR with vac brakes and it was fine.

 

[KC87]

Is your vacuum booster a new one or rebuilt? A long time ago I had vacuum brakes that did the same thing,
pedal would go down quite a ways before engaging any stopping and would not locked them up for nothing.
Booster was leaking internally. Remember, always buy new boosters.

 

[TireFryer]

Is your vacuum booster a new one or rebuilt? A long time ago I had vacuum brakes that did the same thing,
pedal would go down quite a ways before engaging any stopping and would not locked them up for nothing.
Booster was leaking internally. Remember, always buy new boosters.

Do you know of a part number for a proper one? I’ll try and find one on my current one.

 

[KC87]

Do you know of a part number for a proper one? I’ll try and find one on my current one.

IIrc people get the booster for a monte carlo or one for a normal regal. Tons of stuff on here about it
Me, I'm old fashioned and like the PM.

 

[Buick Mark]

The booster has no effect on WHEN the brakes start to apply, all it does is provide assist.
The PUSHROD length WILL effect when the brakes actually start to apply.
What is happening is your pushrod is too short, you have pedal travel until the dead space is taken up, THEN the pushrod starts pushing on the M/C piston, BUT, you run out of travel before the piston can excert enough pressure to REALLY apply the friction material.

 

[TurboBob]

Swapped to vacuum last week. I used a vacuum pedal from a junk car rather than drill mine.

I used the big Caprice booster and master, Its a tight fit but works extremely well. Pedal feel is smooth and linear, pedal 'catch point' is fairly high. I have not tried a true panic stop, too much junk in the car would go flying, but heavy braking really works, and a brake torque was sliding the front tires (might swap out the rear wheel cylinders at some point).

2 thumbs up.