ok vaccum brakes how should they feel?

[blackgn231]

They seem a little spongy not sure if that normal, I bleed the master cylinder before ,I installed it, fluid was coming up out the back port when it was pushed in is that normal, and should they be hard when pushed in? Since I have not had any its hard to know how they should feel anyone , bleed all the wheels also not much air.

 

[Junior Samples]

They seem a little spongy QUOTE]

yup..mine too, bled em, bled em and bled em some more. dont feel like powermaster or hydroboost.

I just deal with it

 

[twodafloor]

vac brakes feel

Mine feel good, but I have steel braided flex hoses and S-10 rear cylinders. good luck guys

 

[DailyDrifter]

Did you push the button in on the prop valve?

 

[GNasty]

If the entire braking system is working properly, vacuum brakes should feel great just like on any other car with vacuum you've driven.

I have the braided steel lines, but my brakes went from feeling 'good' to 'great' after I adjusted the back brakes.

 

[blackgn231]

Moved vaccum line

Moved the line to top of throttle body that helped some and am going to put new back brake shoes on with S-10 wheel cylinders.what yr wheel cylinders do I get?

 

[GN owner]

"and should they be hard when pushed in? " My brakes are the same and I've been trying to find out the cause since this is not normal. I've felt the brakes on my friend's GN and his brakes felt like a normal vacuum brakes. I've even swapped out the MC and vacuum booster with his car and the results were the same!!! I've replaced the MC and vacuum booster along with new brake shoes, rotors, rear wheel cylinders and front calipers. Still no change!!! I've had an 85 Olds Cutlass so I know what the brakes should feel like and mine definitely does not feel the same!!!

 

[GNasty]

"and should they be hard when pushed in? " My brakes are the same and I've been trying to find out the cause since this is not normal. I've felt the brakes on my friend's GN and his brakes felt like a normal vacuum brakes. I've even swapped out the MC and vacuum booster with his car and the results were the same!!! I've replaced the MC and vacuum booster along with new brake shoes, rotors, rear wheel cylinders and front calipers. Still no change!!! I've had an 85 Olds Cutlass so I know what the brakes should feel like and mine definitely does not feel the same!!!

Are you getting your vacuum from the top of the throttle body billet like the turbo TAs, and NOT tapped into the PCV line?

Have you replaced the rubber brake lines (two in the front, one in the rear)? I've heard that they can degrade over time and expand internally when pressing the brakes, causing a softer pedal.

 

[GN owner]

My vacuum source is from the top of the TB. I bought the vacuum block with the fitting for the vacuum booster from Kirbans. My pedal is not soft but gets harder the more you depress the brake pedal.
On a car that comes from the factory with vacuum brakes normally when the brake pedal is depressed and the car comes to a stop you can depress the brake pedal some more and it will sort of feel like you are pressing against a semii-hard rubber stop as the pedal has some give to it. Mine feels hard at that same point when the car is stopped and does not have more give to it! I've changed boosters, front calipers, rear brake cylinders, brake shoes and disc pads and even the proportioning valve. Only things not changed are the brake lines themselves.

 

[TurboBuRick]

My vacuum source is from the top of the TB. I bought the vacuum block with the fitting for the vacuum booster from Kirbans. My pedal is not soft but gets harder the more you depress the brake pedal.
On a car that comes from the factory with vacuum brakes normally when the brake pedal is depressed and the car comes to a stop you can depress the brake pedal some more and it will sort of feel like you are pressing against a semii-hard rubber stop as the pedal has some give to it. Mine feels hard at that same point when the car is stopped and does not have more give to it! I've changed boosters, front calipers, rear brake cylinders, brake shoes and disc pads and even the proportioning valve. Only things not changed are the brake lines themselves.

Had the same issues here. Put a new brake line from the prop valve to the rear brakes and all is good.

 

[GN owner]

Rick,

Did you replace all of the brake lines (steel and flexible lines) or just the flexible brake hose between the chassis and the rear axle? I hope this will fix my problem also.

 

[TurboBuRick]

Ended up replacing the entire system. All new ss lines, prop valve, rebuilt calipers and new rear cylinders. I also installed a hydratech hydroboost brake booster. Brakes are toe toucher's now.


Where did you get the calipers from? Are they new or rebuilt? One thing that improved the feel of the pedal was when I rebuilt my front calipers. The slider bushing were seized up restricting the caliper from moving. They have rebuild kits for this. They come with new bushings and orings. Used a little anti seize on them now they were like money. Before this I had the same condition you describe. I did change allot of things so it's hard to say exactly what fixed but I would thinks something or some things are binding up restricting movement.

If the pedal is hard it's one of 2 things. Either not enough power assist or the brake components are stiff.

Hope this helps.......

 

[GN owner]

Rick,

The front calipers and rear wheel cylinders are rebuilt units. From your description it appears that the hydroboost made the biggest difference with the brakes. Did you have vacuum brakes to begin with before you made the change to hydroboost? Must be night and day compared to vacuum brakes. My vacuum is around 15-16 inches at idle so I would think that should be good enough for the vacuum brake booster to operate with. I will continue to pursue this when I get time to work on the car again.