Brake help please....

[elks]

So I have a 1972 Chevy Blazer. It has been lifted running 36" tires. The brakes have always seemed a little weak. So this spring I decided it was time for new rotors, pads, drums etc. So I got all of it switched over. Got the system bled and had decent (not awesome) brakes in my inital test drive for about 4-5 good hard brakes. After the 4-5 test, the brakes were gone... Nothing. the pedal sits all the way to the floor, the lights stay on etc. There is no fluid leaking, the master is full and I even bled it before the line bleeding. I did it all in the right order etc.

Does the fact that there is no pedal mean my master cylinder went bad? It is not leaking, but I can't really even pump the brakes.

If it is a master cylinder, what up grades can I do that will makes the system better with out costing tons of money and forcing all sorts mods. Can I swap in a larger cylinder? Aftermarket upgrades? Or will a new master make all the difference. I have had the blazer for a little over 3 years, not sure how old the cylinder maybe....

I don't mind reading if you find a link.... I searched did not my situation per say.

[68 TT]

Originally Posted by elks

So I have a 1972 Chevy Blazer. It has been lifted running 36" tires. The brakes have always seemed a little weak. So this spring I decided it was time for new rotors, pads, drums etc. So I got all of it switched over. Got the system bled and had decent (not awesome) brakes in my inital test drive for about 4-5 good hard brakes. After the 4-5 test, the brakes were gone... Nothing. the pedal sits all the way to the floor, the lights stay on etc. There is no fluid leaking, the master is full and I even bled it before the line bleeding. I did it all in the right order etc.

Does the fact that there is no pedal mean my master cylinder went bad? It is not leaking, but I can't really even pump the brakes.

If it is a master cylinder, what up grades can I do that will makes the system better with out costing tons of money and forcing all sorts mods. Can I swap in a larger cylinder? Aftermarket upgrades? Or will a new master make all the difference. I have had the blazer for a little over 3 years, not sure how old the cylinder maybe....

I don't mind reading if you find a link.... I searched did not my situation per say.

I had a master cylinder piston get stuck in the bore all the way in while bleeding the brakes once. Sounds like you might have a similar problem where the piston could be stuck or damaged. A rebuilt one is cheap so I would start there.

A poor working brake booster could be causing you issues too. A vacuum leak in the booster diaphragm or just not enough vacuum coming from the engine due to a large cam will make your power brakes work worse than manual brakes and take a bunch more effort to stop the truck. How much vacuum does your engine make at idle?

[elks]

Originally Posted by 68 TT

I had a master cylinder piston get stuck in the bore all the way in while bleeding the brakes once. Sounds like you might have a similar problem where the piston could be stuck or damaged. A rebuilt one is cheap so I would start there.

A poor working brake booster could be causing you issues too. A vacuum leak in the booster diaphragm or just not enough vacuum coming from the engine due to a large cam will make your power brakes work worse than manual brakes and take a bunch more effort to stop the truck. How much vacuum does your engine make at idle?

Thanks for the pointers. I have looked and found a thread on the 1 ton master cylinder and boaster swap. I have the right bracket so I will probably go that route. I do have a pretty aggressive cam and at idle the engine is loping a bit to idel. Not like a race car, but definitely more than a stock/rv cam. I will have to dig out my vacuum gauge and see what I get for vacuum pressure. Will that be an issue if I do the 1 ton swap? I could run slightly higher rpms which should create more vacuum. Not sure what else I could do if that is an issue...

Manual brakes over power?

Thanks for the pointers. I do not want to do a disc brake swap as someday I am hoping to built another 14 bolt for it and then go to disc brakes at that point.


THanks...

[68 TT]

Originally Posted by elks

Thanks for the pointers. I have looked and found a thread on the 1 ton master cylinder and boaster swap. I have the right bracket so I will probably go that route. I do have a pretty aggressive cam and at idle the engine is loping a bit to idel. Not like a race car, but definitely more than a stock/rv cam. I will have to dig out my vacuum gauge and see what I get for vacuum pressure. Will that be an issue if I do the 1 ton swap? I could run slightly higher rpms which should create more vacuum. Not sure what else I could do if that is an issue...

Manual brakes over power?

Thanks for the pointers. I do not want to do a disc brake swap as someday I am hoping to built another 14 bolt for it and then go to disc brakes at that point.


THanks...

You can run an auxiliary vacuum canister on it if you don't build much vacuum at idle.

http://www.summitracing.com/parts/MRG-3701/

The 1-ton brakes will still have the same problem if you don't have enough vacuum to run the booster properly.

Another option is convert to hydra-boost. Power assist by hydraulic pressure off the power steering pump. Used in lots of diesel GM trucks and some Astro vans as well as a few others. This would be your best option with a big cam.

[Wrenchbender Ret]

You need a new master cyl. These are dual master cyls. No upgrade is needed. You should always replace the MC when you do extensive brake work. Like C-10 says, a reman. is not expensive.