Brake pressure
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
Brake pressure
hello, 1982 owner, brakes losing strength. About 1 month ago, push brake pedal all the way down and the car wouldn't stop immediently. Did a bleed, felt amazing after. Then slowly, every day since then, Ive felt the brakes gradually losing strength until now where its basically at what it was before. New rotors calipers and pads. Checking fluid levels, the left bank might have lost a little, cant confirm. Checking the wheels, the front drive side wheel has some fluid behind it, but cant confirm if thats brake fluid or its source. Visual inspection of the lines themselves doesn't reveal much. Suggestions for troubleshooting? I might be ok with shooting the parts cannon, so long as we put it on semi auto not full auto.
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,573
Likes: 7,015
From: New Or-leens Loo-z-anna
Power brakes? Test the one-way vacuum valve to make sure it isnt losing vacuum while pressing the brake pedal.
If possible, change the rubber brake lines if you end up rebuilding a caliper...they age and swell.
Try to locate the leaks and correct them.
If possible, change the rubber brake lines if you end up rebuilding a caliper...they age and swell.
Try to locate the leaks and correct them.
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
Ok thank you. Whats the process for the rubber lines? is it just compression fittings on both ends? The calipers are new, should be good. Also how do I locate leaks?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Your Master Cylinder reservoir will tell you a lot and narrow it down to front or back brake fluid issues.
Don't know what you mean by "left bank". Its either front rez or back rez that is losing fluid.
You already did rotors, calipers & pads. So, it's safe to assume the rubber hoses could be original or very-very old.
You can purchase a set of four rubber lines. Shop around but insist on American made for brake parts.
The front hoses only, must come with a copper crush washer. If you intend to replace the hoses, start soaking all eight end-fittings NOW with PB Blaster and again the next day.
You will also need a set of "line wrenches".
YouTube will have a video showing the procedure for swapping out hoses. Not too bad a job if all the fitting release w/o issues. And of course, the entire system will need to be bled again.
Also, possibility the Master itself is going south. But that's another story another day.
Don't know what you mean by "left bank". Its either front rez or back rez that is losing fluid.
You already did rotors, calipers & pads. So, it's safe to assume the rubber hoses could be original or very-very old.
You can purchase a set of four rubber lines. Shop around but insist on American made for brake parts.
The front hoses only, must come with a copper crush washer. If you intend to replace the hoses, start soaking all eight end-fittings NOW with PB Blaster and again the next day.
You will also need a set of "line wrenches".
YouTube will have a video showing the procedure for swapping out hoses. Not too bad a job if all the fitting release w/o issues. And of course, the entire system will need to be bled again.
Also, possibility the Master itself is going south. But that's another story another day.
Pro
Joined: Mar 2007
Posts: 553
Likes: 97
All C3 vettes suffer from this. The pistons have lip seals, the spindles get old and the rear bearings are easily out of spec. A common issues with C3 brakes is residual pressure where you have to step on the brakes once a week or they will leak. Once they leak it's pretty much game over and need a rebuild. It's actually not that bad but is a reality. Your calipers may just need honed and rebuilt. Depends how often the car was driven before the problem started. Could also be lines as has been said, those can be upgraded with modern braided lines rather than just rubber hoses. Also, once the pads are damaged by fluid, they will have a tendency to fade, no fix there either, need new pads. Another issue is worn spindles and rear bearings. If the front spindles might developed grooves, that will cause fade and leakage under hard braking, destroying the pads. If the problem is in the rear only, it's probably bearings or u-joints but again, brakes will need replaced and rebuilt.
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
All C3 vettes suffer from this. The pistons have lip seals, the spindles get old and the rear bearings are easily out of spec. A common issues with C3 brakes is residual pressure where you have to step on the brakes once a week or they will leak. Once they leak it's pretty much game over and need a rebuild. It's actually not that bad but is a reality. Your calipers may just need honed and rebuilt. Depends how often the car was driven before the problem started. Could also be lines as has been said, those can be upgraded with modern braided lines rather than just rubber hoses. Also, once the pads are damaged by fluid, they will have a tendency to fade, no fix there either, need new pads. Another issue is worn spindles and rear bearings. If the front spindles might developed grooves, that will cause fade and leakage under hard braking, destroying the pads. If the problem is in the rear only, it's probably bearings or u-joints but again, brakes will need replaced and rebuilt.
while I’m here, how strong are the factory ebrakes? I just adjusted mine, they are engaging but they aren’t nearly as strong as I thought they would be, and I’ve got new shoes.
Safety Car
Joined: Jul 2005
Posts: 3,691
Likes: 833
From: WI
What's the condition of your rear rotors: Old, new, rusty? Generally rust builds up on the inside surface where the emergency brake shoes rub if the emergency brakes aren't applied much (esp when moving slightly to scrub the rotors clean). Then they don't stop or hold very well till the rust wears off ...which can take a while depending how bad the rust was. But overall, in good condition they should hold the car pretty well. Of course, like most cars, parking brakes (or emergency brakes) are not that effective slowing a car down as it's moving ..like front/rear brakes. They should be considered parking brakes more than emergency brakes.
That leak resulted in air getting into your system. Was it leaking at the O-ring?
That leak resulted in air getting into your system. Was it leaking at the O-ring?
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
What's the condition of your rear rotors: Old, new, rusty? Generally rust builds up on the inside surface where the emergency brake shoes rub if the emergency brakes aren't applied much (esp when moving slightly to scrub the rotors clean). Then they don't stop or hold very well till the rust wears off ...which can take a while depending how bad the rust was. But overall, in good condition they should hold the car pretty well. Of course, like most cars, parking brakes (or emergency brakes) are not that effective slowing a car down as it's moving ..like front/rear brakes. They should be considered parking brakes more than emergency brakes.
That leak resulted in air getting into your system. Was it leaking at the O-ring?
That leak resulted in air getting into your system. Was it leaking at the O-ring?
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Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
Did a hose replacement everywhere. Bled, and now it feels a bit better. Idk if its full strength tho, part of me thinks it isnt but I dont have a reference point to go off of. Any Techniques to diagnose?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Of the five Brake Bleeding Methods, which one did you conduct?
1. Gravity method.
2. Pressure method.
3. Vacuum method.
4. Pedal method.
5. Let somebody else do it method.
And, did the front rubber hoses get a copper crush washer installed?
1. Gravity method.
2. Pressure method.
3. Vacuum method.
4. Pedal method.
5. Let somebody else do it method.
And, did the front rubber hoses get a copper crush washer installed?
