So the master cylinder went in my 85GT and I swapped it out. I didn't bench blead it, but I have bled the brakes twice as the problem continues. The brake peddle is hard and the light on the console shows I have no brake lights (which I have confirmed) so what is happening? Everything worked (aside from the peddle going to the floor) before I swapped out the MC. I was told I may need to adjust the pushrod, but wanted to confirm before I do anything else that makes the issue worse. Thank you for the help in advance!
Please Help With Brake Issue
- Thread starter Capricious85
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No brake lights may be the switch on the pedal where it connects to the booster linkage. Did you check this area to see if the switch is seated properly, or if it became dislodged and possibly binding up the brake pedal slightly?
When installing an MC, it should be bench bled. The angle of the MC when mounted tends to trap air at the very tip of the MC, and it's difficult to get it out. If you jack the rear end up high enough, you may be able to bleed it out, but the best way to do it is level in a vise.
The vac line to the booster was reconnected correct? If you rest your foot on the pedal and start the engine, does it sink slightly?
When installing an MC, it should be bench bled. The angle of the MC when mounted tends to trap air at the very tip of the MC, and it's difficult to get it out. If you jack the rear end up high enough, you may be able to bleed it out, but the best way to do it is level in a vise.
The vac line to the booster was reconnected correct? If you rest your foot on the pedal and start the engine, does it sink slightly?
mikestang63
SN Certified Technician
How did you isolate the problem was the MC
did you dislodge the brake booster hose by accident
you should not have to adjust the pushrod for swapping MC
you can bleed the MC by loosening up the two lines coming off the MC just until air and some fluid starts to come out and pump the pedal until all of the air is out, while checking filling up the MC
There is also a connection off the bottom of the pedal for the brake light switch- did you mess with it
did you dislodge the brake booster hose by accident
you should not have to adjust the pushrod for swapping MC
you can bleed the MC by loosening up the two lines coming off the MC just until air and some fluid starts to come out and pump the pedal until all of the air is out, while checking filling up the MC
There is also a connection off the bottom of the pedal for the brake light switch- did you mess with it
Hey guys, my apologies for the late reply. So after reading your advice, I took the master cylinder off to bench bleed it and did so. Before reinstalling the master cylinder I checked to ensure the pushrod from the brake booster was operational. It pushed with firm force when I tested it. I reinstalled it and bled the brakes again. When I bleed the brakes there is no air or spurts, just straight brake fluid, but the problem remains. Right after I re-installed the master cylinder there was a little bit of movement in the brake pedal,in terms of actual break feel, but now it's gone again and the brakes are solid. The brakes do work but they are completely manual. I forgot to mention originally that I do have a line lock on the car. Does anyone have any thoughts?
Hey guys, my apologies for the late reply. So after reading your advice, I took the master cylinder off to bench bleed it and did so. Before reinstalling the master cylinder I checked to ensure the pushrod from the brake booster was operational. It pushed with firm force when I tested it. I reinstalled it and bled the brakes again. When I bleed the brakes there is no air or spurts, just straight brake fluid, but the problem remains. Right after I re-installed the master cylinder there was a little bit of movement in the brake pedal, in terms of actual break feel, but now it's gone again and the brakes are solid. The brakes do work but they are completely manual. I forgot to mention originally that I do have a line lock on the car. Does anyone have any thoughts?
I am not up on line locks but I understand the concept, I don't think air in the lines is the problem, start the car and pull the vacuum line off the booster to see if you have vacuum to the booster, if you have good vacuum then the booster is suspect.
Can you delete the linelock to take it out of the equation?
Can you delete the linelock to take it out of the equation?
Hey guys, my apologies for the late reply. So after reading your advice, I took the master cylinder off to bench bleed it and did so. Before reinstalling the master cylinder I checked to ensure the pushrod from the brake booster was operational. It pushed with firm force when I tested it. I reinstalled it and bled the brakes again. When I bleed the brakes there is no air or spurts, just straight brake fluid, but the problem remains. Right after I re-installed the master cylinder there was a little bit of movement in the brake pedal, in terms of actual break feel, but now it's gone again and the brakes are solid. The brakes do work but they are completely manual. I forgot to mention originally that I do have a line lock on the car. Does anyone have any thoughts?
i did put a vacuum gauge on at the t and confirmed vacuum. I guess I'm confused at the fact that there is vacuum and the pushrod actuates with no issue, with enough force (in my opinion) to engage the master cylinder. I can eliminate the line lock to make sure that isn't the issue. Just kind of baffles at this point. I even purchased and tried another master cylinder to ensure there wasn't a problem with the one that was on the car (I had just replaced it and thats what started these issues)
The booster can still malfunction with vacuum, there usually is a wooosshhing noise you hear when depressing the peddle means the diaphragm is cracked but yours is a hard peddle.
Rockauto has cardone and acdelco booster under 70 bucks they are a vender here so: 5% Discount Code: 973B31C0B06FBB
There is lmr too but they are higher priced, some ebay stuff too for between 65 and 100 bucks
don't know way this changed to bold type, I feel like I'm scolding a child
GET OFF MY LAWN YOU BRAT!
Rockauto has cardone and acdelco booster under 70 bucks they are a vender here so: 5% Discount Code: 973B31C0B06FBB
There is lmr too but they are higher priced, some ebay stuff too for between 65 and 100 bucks
don't know way this changed to bold type, I feel like I'm scolding a childGET OFF MY LAWN YOU BRAT!
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