1982 brakes acting up
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1st Gear
Joined: Apr 2019
Posts: 1
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1982 brakes acting up
i have a 1982 corvette collectors edition that's having brake issues. it randomly started having this problem last summer after driving it for a couple months. prior to me getting the car it had been sitting for quite some time
when i apply the brake the pedal sinks to the floor and the brake light on the dash comes on and the brakes will barely work. i can pump the pedal and get some pressure back and the light to go off but then as soon as i let off and drive and have to stop again the same thing happens. i have checked the reservoir level and the whole system for leaks and didn't see any. There is no fluid in the booster and it seems as though the booster is getting pressure (although not sure) it makes a sucking noise when i pull the check valve out of the booster. i don't think there is any air in the system as i haven't opened the system at all but i'm thinking its the master cylinder but i don't want to just throw parts at it and i am horrible with diagnosis. any advice would be greatly appreciated
when i apply the brake the pedal sinks to the floor and the brake light on the dash comes on and the brakes will barely work. i can pump the pedal and get some pressure back and the light to go off but then as soon as i let off and drive and have to stop again the same thing happens. i have checked the reservoir level and the whole system for leaks and didn't see any. There is no fluid in the booster and it seems as though the booster is getting pressure (although not sure) it makes a sucking noise when i pull the check valve out of the booster. i don't think there is any air in the system as i haven't opened the system at all but i'm thinking its the master cylinder but i don't want to just throw parts at it and i am horrible with diagnosis. any advice would be greatly appreciated
Le Mans Master
Joined: Aug 2006
Posts: 7,431
Likes: 1,561
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Hi and welcome!
Start by bleeding all the calipers and look closely for any leaks.
NOTE: there are two bleeders in the rear, bleed the inners first then the outers.
Drive carefully after this and if the problem returns check the run-out.
NOTE: there are two bleeders in the rear, bleed the inners first then the outers.
Drive carefully after this and if the problem returns check the run-out.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
I would suspect the master. Even if the fluid level does not drop, the piston seals could be allowing fluid to slip past, or in laymans terms, pedal to the floor, no pressure but no leakage anywhere. The booster is just an assist for your foot pressure. Its really not involved with the pedal sinking to the floor.
A great test to determine if the MC is faulty is to isolate the MC from the rest of the system. To do that, you need to remove the front & rear brakelines and plug the MC ports with suitable plugs. Do not use a hardware bolt and do not damage the flare inside the port. You can however use a piece of pre-made brakeline with a fitting on one end. (Your MC has to different port sizes) The other end can be pinched off. With both ports blocked, you should be able to actually stand on the brake pedal.
If the MC is ok.
Keep in mind that after this test, you have introduced air and that a complete bleed off will have to be done starting at right rear inner.
A great test to determine if the MC is faulty is to isolate the MC from the rest of the system. To do that, you need to remove the front & rear brakelines and plug the MC ports with suitable plugs. Do not use a hardware bolt and do not damage the flare inside the port. You can however use a piece of pre-made brakeline with a fitting on one end. (Your MC has to different port sizes) The other end can be pinched off. With both ports blocked, you should be able to actually stand on the brake pedal.
If the MC is ok.
Keep in mind that after this test, you have introduced air and that a complete bleed off will have to be done starting at right rear inner.
Last edited by HeadsU.P.; Apr 20, 2019 at 05:11 PM.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Pretty broad statement. Could be caliper seals, pin hole in steel line, faulty rubber hose, distribution block fittings, Proportional Valve, etc, etc, etc.
Any loss of pressure anywhere will result in a pedal to the floor.
What the fluid level is doing in the MC reservoirs will determine where to look next.
Any loss of pressure anywhere will result in a pedal to the floor.
What the fluid level is doing in the MC reservoirs will determine where to look next.
Pro
Joined: Jun 2014
Posts: 706
Likes: 294
From: New Jersey
Pretty broad statement. Could be caliper seals, pin hole in steel line, faulty rubber hose, distribution block fittings, Proportional Valve, etc, etc, etc.
Any loss of pressure anywhere will result in a pedal to the floor.
What the fluid level is doing in the MC reservoirs will determine where to look next.
Any loss of pressure anywhere will result in a pedal to the floor.
What the fluid level is doing in the MC reservoirs will determine where to look next.
If it was anything else, there would be a puddle of brake fluid somewhere.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
That's what someone wrote in post #3. Just want the O.P. to know that one should never jump to conclusions and start throwing expensive parts at an issue.
Sometimes calipers will leak and never or seldom leave a tale-tell sign. No wet tire, no wet lines, no wet pads. Nothing.
This diagnostic issue goes back to "what the fluid level is doing" in the MC.
Up? Down? No change?
Sometimes calipers will leak and never or seldom leave a tale-tell sign. No wet tire, no wet lines, no wet pads. Nothing.
This diagnostic issue goes back to "what the fluid level is doing" in the MC.
Up? Down? No change?
Last edited by HeadsU.P.; Apr 22, 2019 at 09:14 AM.
Safety Car
Joined: Jul 2010
Posts: 4,018
Likes: 388
From: Chandler AZ
i have a 1982 corvette collectors edition that's having brake issues. it randomly started having this problem last summer after driving it for a couple months. prior to me getting the car it had been sitting for quite some time
when i apply the brake the pedal sinks to the floor and the brake light on the dash comes on and the brakes will barely work. i can pump the pedal and get some pressure back and the light to go off but then as soon as i let off and drive and have to stop again the same thing happens. i have checked the reservoir level and the whole system for leaks and didn't see any. There is no fluid in the booster and it seems as though the booster is getting pressure (although not sure) it makes a sucking noise when i pull the check valve out of the booster. i don't think there is any air in the system as i haven't opened the system at all but i'm thinking its the master cylinder but i don't want to just throw parts at it and i am horrible with diagnosis. any advice would be greatly appreciated
when i apply the brake the pedal sinks to the floor and the brake light on the dash comes on and the brakes will barely work. i can pump the pedal and get some pressure back and the light to go off but then as soon as i let off and drive and have to stop again the same thing happens. i have checked the reservoir level and the whole system for leaks and didn't see any. There is no fluid in the booster and it seems as though the booster is getting pressure (although not sure) it makes a sucking noise when i pull the check valve out of the booster. i don't think there is any air in the system as i haven't opened the system at all but i'm thinking its the master cylinder but i don't want to just throw parts at it and i am horrible with diagnosis. any advice would be greatly appreciated
Possible the previous owner didn't bleed it properly?
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