Hard Pedal

[Gospel Runner]

I would like to get some help with my brake problem. I have a 70 Road Runner with a high lift cam, which means I have no vacuum for my brakes. I have a new rebuilt power booster, SSBC front disc brakes, new MC from SSBC, new electric air pump and new vacuum canister. All of this and still I have a hard peddle and no brakes. What am I missing here? I keep throwing money at this problem and there is no more money to throw at it. Someone has had this problem before and solved it. I just need you to tell me what you did so I can do the same thing. Any help would be greatly appreciated.

 

[Swampdog]

I had to install a vacuum pump plumbed into the brake booster.

It is an electric one. You can feel some vibration when is running but soon kicks off. Hope this helps.

 

[Gospel Runner]

I have an electric pump that I paid over $250 for. The pump is connected to the vacuum canister and the canister is connected to the power booster.

 

[Zeppelin264]

Master needs better bleeding

 

[Car Nut]

What size is your master?

 

[Gospel Runner]

I bench bled the master until there were no are bubbles present. When I bled the brakes (several times BTW) I have great fluid flow. That is why I do not understand why this system is not working. I do not know the size of the MC. I suppose I can llok it up on the SSBC website.

 

[Car Nut]

Check your vacuum pressure. If master is bigger than 15/16" with power brakes, your pedal will be hard. 1" master would be better with 4 disc brake set up. 1-1/8" or bigger is best for manual.

 

[Yatzee]

Check your vacuum pressure. If master is bigger than 15/16" with power brakes, your pedal will be hard. 1" master would be better with 4 disc brake set up. 1-1/8" or bigger is best for manual.

You've got this "bass assward", smaller bore for manual, larger for power.

 

[Yatzee]

I would like to get some help with my brake problem. I have a 70 Road Runner with a high lift cam, which means I have no vacuum for my brakes. I have a new rebuilt power booster, SSBC front disc brakes, new MC from SSBC, new electric air pump and new vacuum canister. All of this and still I have a hard peddle and no brakes. What am I missing here? I keep throwing money at this problem and there is no more money to throw at it. Someone has had this problem before and solved it. I just need you to tell me what you did so I can do the same thing. Any help would be greatly appreciated.

Had the same issue and I think the SSBC master that comes with the kit is inadequet. I went to a hydro boost system that I got at the recyclers for $100. Problem solved! I only had 10" of vacuum and needed serious brakes for my ride.

 

[Billccm]

I have a 70 Road Runner with a high lift cam, which means I have no vacuum for my brakes.

Just out of curiosity, have you measured vacuum? I was told with power brakes vacuum required was greater than 14 inches.

 

[Sixpactogo]

I'm curious as to whether you have a dual ballast booster or single. For front discs, you need the dual ballast. No matter how much vacuum you have, the single ballast will not be enough boost.

 

[PurpleBeeper]

Just out of curiosity, have you measured vacuum? I was told with power brakes vacuum required was greater than 14 inches.

I like this idea. Can you tap in a vacuum gage to see just how much vacuum you have from your vacuum pump going to the brake booster? If you have good vacuum, then the problem is something else.... like the master cylinder.

How sure are you that you have good fluid flow.... I mean gushing out flow..... at all 4 wheels? I chased a similar problem for MONTHS and turned out both of the reproduction brass proportioning/hold off valves I got from Inline tube (I think everyone is selling those same parts....not picking on Inline in particular) were BOTH bad. I hit another car because of them....no lie.

 

[Yatzee]

I would like to get some help with my brake problem. I have a 70 Road Runner with a high lift cam, which means I have no vacuum for my brakes. I have a new rebuilt power booster, SSBC front disc brakes, new MC from SSBC, new electric air pump and new vacuum canister. All of this and still I have a hard peddle and no brakes. What am I missing here? I keep throwing money at this problem and there is no more money to throw at it. Someone has had this problem before and solved it. I just need you to tell me what you did so I can do the same thing. Any help would be greatly appreciated.

You need no less than 18 inches of vacuum for reliable operation of a power booster, it doesn't matter if it's a single or dual. You also need a good volume of vacuum to evacuate the booster cavity and maintain operation. Vacuum pumps do produce good vacuum but take time to evacuate a large void, hence the canister, but now you have to evacuate the volume for the canister and the booster. That's a big job to ask a small pump to do. It may be able to produce 21 inches of vacuum but if it's connected to a two gallon container how long would it take to reach that vacuum level. Does the manufacturer actually rate the pump for your purpose and guarantee it's operation? Do you have check valves between the pump and canister or canister and booster? A hard pedal is indicative of low vacuum. If you press the pedal and then start the car, does the pedal drop, it should if you can make enough vacuum. If you can't resolve this issue your cheapest route is a good manual setup, either that or an electric assisted master cylinder. As far as master cylinders go, you need only look at the recall of Wilwood 7/8 bore masters, and this a company well known on international markets. $hit happens and when there's three components involved, it's hard to tell which ones at fault. With only 12 inches of vacuum with my motor you can see why I went hydro boost. May as well use the power steering pump for more than just steering.

 

[Gospel Runner]

Thank you for all of your advice. There is so much here I almost don't know where to start. My car is at the shop at the High School where I teach. The maintenance group was refinishing the floors in my wing so I was not able to get to the car the past two days. Monday morning I will check the vacuum pressure. I have no idea if the booster is single or dual. How can I determine that? I am going to look over my paperwork and see if I can determine the MC bore? I will check back with you as I get some answers to your questions. Again, thank you for your help. I feel the hope you have infused in me about getting to the bottom of this problem. God bless each of you for taking the time to help me!

 

[Gospel Runner]

The MC is 1-1/32" bore. I have only the front disc brake set up.

 

[Gospel Runner]

Yatzee what is a hydro boost system? Who makes it and what is the cost? I am just enquiring for now until I get the information needed on Monday.

 

[Billccm]

Hydro boost uses the power steering pressures for power brake boost. Many GM trucks and SUV have hydro boost.

 

[Gospel Runner]

The pump I have is rated for 20 inches of vacuum. The canister is 5" diameter and 6-3/4" long.

 

[Sixpactogo]

Thank you for all of your advice. There is so much here I almost don't know where to start. My car is at the shop at the High School where I teach. The maintenance group was refinishing the floors in my wing so I was not able to get to the car the past two days. Monday morning I will check the vacuum pressure. I have no idea if the booster is single or dual. How can I determine that? I am going to look over my paperwork and see if I can determine the MC bore? I will check back with you as I get some answers to your questions. Again, thank you for your help. I feel the hope you have infused in me about getting to the bottom of this problem. God bless each of you for taking the time to help me!

Take a picture of your booster for us. I used the stock single ballast booster for drum brakes in my car when I put it back together with front disc brakes. I had 20" of vacuum with a hard pedal and with the brakes on, the car would walk away with slight acceleration. I had to upgrade to the dual ballast booster.

 

[Gospel Runner]

I am going to take a picture of my set up on Monday when I get into the shop. Thank you!