Another hard pedal problem - Chevelle Tech
Brakes, Suspension & Steering Conversion questions & more.

 2Likes
  • 2 Post By Reelysalty
 
LinkBack Thread Tools Search this Thread Display Modes
post #1 of 11 (permalink) Old Jan 5th, 20, 1:07 PM Thread Starter
Tech Team
 
Join Date: Mar 2003
Posts: 292
Another hard pedal problem

I know that this problem has been addressed many times, but I'm not getting to the solution so I appreciate any help. I installed front discs on my 69 Chevelle in 2003 and until about 6 months ago haven't had any issues at all with them until the hard pedal showed up. Since I don't drive it more than 1-2 times/month it wasn't obvious exactly when it started. Now its hard to hold at idle and trying to power brake is practically impossible. Chevelle has about 5,000 miles since full restoration. I also have a daily driver 71 El Camino with basically the identical setup so I have an easy comparison to properly functioning brakes.

Immediately I looked at the check valve and replaced it since I had a new one that was fine - no change. So the booster was the obvious issue and I replaced it - no change. When I installed the booster I adjusted the clevis to be about the same position as the old one, but never thought this adjustment really matters. Now I'm not so sure and would like a description on how to adjust it and if it might be part of my problem.

I then tried to reset the proportional valve, although I've never heard of that before - no change. For fun, I did the standard tests on the El Camino and they were fine and I popped off the check valve after running it and for sure have vacuum stored after the engine off. Repeated it by hooking up the old booster with the same result leading me to believe it may be fine. Went to the Chevelle and did the tests but the pedal didn't drop when I started the engine, but after shutting it off I popped the check valve and had vacuum stored so no big leaks and check valve OK.

Then I saw this post and tried to space out the master with washers about 0.22" - no change but I also don't have any idea why this matters or how much to space it out. What the hell could be wrong with this brake system? Any advice would be great, I'm at my wits end on this one and would really love to drive this car again.

Ed
eduardo69chevelle is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old Jan 5th, 20, 2:55 PM
Team Member
Bill
 
Join Date: Jan 2018
Location: Boston Area
Posts: 597
Garage
Re: Another hard pedal problem

Quote:
Originally Posted by eduardo69chevelle View Post
I know that this problem has been addressed many times, but I'm not getting to the solution so I appreciate any help. I installed front discs on my 69 Chevelle in 2003 and until about 6 months ago haven't had any issues at all with them until the hard pedal showed up. Since I don't drive it more than 1-2 times/month it wasn't obvious exactly when it started. Now its hard to hold at idle and trying to power brake is practically impossible. Chevelle has about 5,000 miles since full restoration. I also have a daily driver 71 El Camino with basically the identical setup so I have an easy comparison to properly functioning brakes.

Immediately I looked at the check valve and replaced it since I had a new one that was fine - no change. So the booster was the obvious issue and I replaced it - no change. When I installed the booster I adjusted the clevis to be about the same position as the old one, but never thought this adjustment really matters. Now I'm not so sure and would like a description on how to adjust it and if it might be part of my problem.

I then tried to reset the proportional valve, although I've never heard of that before - no change. For fun, I did the standard tests on the El Camino and they were fine and I popped off the check valve after running it and for sure have vacuum stored after the engine off. Repeated it by hooking up the old booster with the same result leading me to believe it may be fine. Went to the Chevelle and did the tests but the pedal didn't drop when I started the engine, but after shutting it off I popped the check valve and had vacuum stored so no big leaks and check valve OK.

Then I saw this post and tried to space out the master with washers about 0.22" - no change but I also don't have any idea why this matters or how much to space it out. What the hell could be wrong with this brake system? Any advice would be great, I'm at my wits end on this one and would really love to drive this car again.

Ed
Have you measured how much vacuum you have at the booster? Mine fails below 14PSI. You said it was fine for 6 month so that eliminates that you didn't use the right rod for the master cylinder. It's fairly simple that a master with a recessed rod piston uses a long pin and a slightly flat with little recess uses the short. Some rods are adjustable and some if not correct require grinding. The importance is if the master cylinder piston can't be allowed return back to its normal operation position the fluid gets trapped and doesn't cycle which causes heat lock resulting with a hard peddle and poor braking. This only occurs after the fluid heats up though. I assume when you stated you did all the normal checks that included wheel cylinders actuate when the pedal is depressed. To me it sounds like you have a blockage possibly in the master cylinder itself. Good luck troubleshooting

Last edited by Billdini; Jan 5th, 20 at 3:11 PM.
Billdini is online now  
post #3 of 11 (permalink) Old Jan 5th, 20, 4:14 PM
Senior Tech Team
Steve
 
Join Date: Sep 2015
Location: Central MA
Posts: 1,421
Re: Another hard pedal problem

Since it was working, and now suddenly it isnít not, verify that you are getting good fluid flow at all 4 wheels. A frozen wheel cylinder or caliper or collapsed rubber hose could be not allowing any fluid to pass, which will give you a hard pedal too.

1972 Chevelle, 454, 200-4r non-lockup, 12 bolt 3.73
1981 Camaro Z28, 355, TH350, 3.73
lucifershammer is offline  
 
post #4 of 11 (permalink) Old Jan 5th, 20, 6:34 PM Thread Starter
Tech Team
 
Join Date: Mar 2003
Posts: 292
Re: Another hard pedal problem

Yes, it was perfectly fine for 16 years and only the last 6 months has been acting up. I measured the depth of the hole for the rod in the MC at around 1-3/4" so it must be the longer rod just like the one that was in there for 16 years. Nothing changed in the engine during that time that would impact the vacuum but it is probably low due to the cam but I'll check it.

Forgot to mention that I jacked up front and rear and checked that all the brakes were working, but that is only enough to stop it rotating with my hands so not necessarily a good test.

I'll say I never thought the MC could be the problem and hate the idea of changing it unless its bad. The collapsed rubber hose is also a new idea that I'll have to check and get back to everyone on it. Probably will be next weekend before I find time now but thanks for the ideas. Does this rule out the proportional valve?

Ed
eduardo69chevelle is offline  
post #5 of 11 (permalink) Old Jan 7th, 20, 5:00 PM Thread Starter
Tech Team
 
Join Date: Mar 2003
Posts: 292
Re: Another hard pedal problem

Just did a vacuum check, both the El Camino and Chevelle are idling right at 15 inches and pretty solid. Given that the El Camino is working fine there is no way in my mind that the vacuum is the problem. In a few days I'll get to checking the rubber hoses and report that back.

Suggestions on how to verify I have good flow at each wheel? All I did was rotate the wheel and have someone push the brake to verify it locked the wheel - is that good enough?
eduardo69chevelle is offline  
post #6 of 11 (permalink) Old Jan 7th, 20, 11:43 PM
Lifetime Premium Member
leo
 
Join Date: Oct 2003
Location: Southwest Florida
Posts: 13,317
Re: Another hard pedal problem

Your problem isn't at the wheels, it lies at the booster. Maybe the vacuum hose to the booster has collapsed internally, Good luck!!

Leo Paugh
Maryland Chevelle Club #017
A.C.E.S.#3731
progress has little to do with speed, but lots to do with direction

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
LeoP is online now  
post #7 of 11 (permalink) Old Jan 11th, 20, 12:25 PM Thread Starter
Tech Team
 
Join Date: Mar 2003
Posts: 292
Re: Another hard pedal problem

I also think its at the booster given the symptoms. But, just to be thorough I inspected all the flexible lines and they seem fine - only about 4 or 5k miles on the cars since resto but 18 years. Anyway, no cracks, collapsed, or leaks anywhere in the system under the car.

Back to the booster/master cylinder/prop valve. Can someone offer opinion about whether hard pedal could be ANYTHING other than the booster or vacuum?? I just redid my vacuum check by removing the check valve at the booster to rule out anything else and see around 14" (had 15" on the line to the distributor). The hose seems fine and I know the check valve is fine.

I'm back to the booster itself. If the booster holds vacuum does that means its OK or not necessarily? I did a test where I ran the engine for a minute, shut it off, and after a few minutes pulled the check valve and there was strong vacuum and seemed the same as the El Camino. Also, the old booster I removed acts the same way.

But the damn pedal doesn't move at all when I start the engine (El Camino moves 1/2 - 3/4") and if I drive with or without the vacuum connected there is NO difference. Gotta be a 2nd bad booster, right?
eduardo69chevelle is offline  
post #8 of 11 (permalink) Old Jan 18th, 20, 1:59 PM Thread Starter
Tech Team
 
Join Date: Mar 2003
Posts: 292
Re: Another hard pedal problem

Anyone? I'm going to put in a 3rd booster today because I can't imagine anything else causing this. Is there something else I should be looking at?

Like I asked on the last one - can someone offer opinion about whether hard pedal could be ANYTHING other than the booster or vacuum?

Thx, Ed
eduardo69chevelle is offline  
post #9 of 11 (permalink) Old Jan 18th, 20, 11:13 PM
Tech Team
 
Join Date: Aug 2018
Posts: 853
I had a blocked hard line over rear axle cause hard pedal.
67_LS1 and lucifershammer like this.
Reelysalty is offline  
post #10 of 11 (permalink) Old Jan 19th, 20, 12:07 AM
Team Member
Tony
 
Join Date: Apr 2006
Location: Cleveland, OH
Posts: 3,256
Garage
Re: Another hard pedal problem

What brand Power Booster are you using?

'69 Malibu 383/TCI TH350/8.2 3.36 Eaton Posi. Street Edge 10" 2800, E-Tec 170s, Custom Mike Jones HR Cam, RPM Air-Gap, StreetAvenger 770, Pertronix HEI, Hedman 1 5/8" Headers, Moser Axles, PMT 1320R Kit. [email protected] 111 MPH, 1.6865 60 ft, Nitto 555
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
blue_69_malibu is online now  
post #11 of 11 (permalink) Old Jan 19th, 20, 11:27 PM
Tech Team
Ben
 
Join Date: Apr 2017
Location: Seattle
Posts: 159
Re: Another hard pedal problem

Howís the pedal not running? Still hard? If they are comparable, Iíd swap the el Camino booster to the chevelle and see what happened. Thatíd rule in or out the booster.

No car yet; currently looking for 66-69 project/driver.
skreddy is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome