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So I just got a 79 Vette, the old owner told me the brakes weren’t working well and it needed a vacuum pump to help. It has a cammed 355 that barely creates vacuum. I bought a bandit vacuum pump and hooked it up to a vacuum canister then to the brake booster.
One pump of the brakes and it works like a charm, brakes feel solid. However the next time I hit the brakes the pedal goes to the floor. I started thinking it may be the master cylinder, but I don’t know I feel like if that was the issue it wouldn’t feel so smooth the first press.
I then hooked the vacuum pump up directly to the brake booster and it has the same result as being hooked up to the vacuum canister.
Keep in mind the booster is strictly an assist to the brake pedal. Its design allows a little girl to lock-up all four with her little pinky toe. That was the idea on the engineer's chalk board anyway.
You have two system there. One is run by vacuum. One is run by hydraulic pressure.
The booster doesn't really care if all the DOT3 is on the ground.
The master doesn't care if the booster has no vacuum. (so to speak)
A "pedal to floor" is a leak in the hydraulic system. Or an air pocket that compresses. DOT3 can not compress.
Having said that, start looking for a wet spot near steel lines, calipers, proportional valve, fittings and rubber brake hoses.
Your long brake repair journey begins. Its a pita, but its doable.
You might as well figure on a complete flush of all six bleeders and go from there.
That was a very helpful explanation, I have somewhat of an inclination that the master cylinder is no longer good (as it appears to be the original) the fluid coming out from the bleeders appears pretty dirty (thinking it could be deteriorating master seals). I also know that the caliper seals are not the best as when I had the caliper off on the driver side today the seal was half off one piston. I already have a new master cylinder ready to go in, thinking about ordering new calipers as wel.
Use caution when ordering calipers. Lots of junk out there. Several forum members rebuild their own.
Most stores will want your core returns. So, decide which route is best for your mechanical skills: rebuild? rebuilt?
The booster seldom fails. Not much to it. Just a big metal can with a rod going through. Sometimes the vacuum fitting on the outside of the booster gets wonky.
Easy replacement
Make sure you bench bleed that new master. And check the end of it. More specifically, the piston. Make sure its the exact same design as the original.
They changed design over the yrs and are not interchangeable. The guy behind the parts counter insists: "Fits All Vettes '68 - '82. ( Nope! )
For tips on bench bleeding, click on my avatar. Look for photo album, brake bleeding. You will do well buying a Motive Tank, but a mighy vac pump will work for now if needed.
You can "pull" bubbles when just bleeding one or two corners of the vehicle. More calipers than that, push the bubbles with pressure.
Last edited by HeadsU.P.; Mar 13, 2023 at 08:44 AM.
Post some pics of your new ride and vacuum connections.
someone may see something..and check for leaks as mentioned especially inside tires etc..
is there a filter check valve in place for booster?
more pics the better..
master rebuild below… https://www.corvetteforum.com/forums...1-8-power.html
Ok so ordered new calipers and ordered the motive bleeder kit, now when it all arrives I should be good to go. Will check the plunger on the new master tomorrow and will educate myself on bench bleeding a master cylinder… Sounds like this will be fun.
Suggestion to consider. It sounds like it's too late but I would get stainless sleeved calipers if you can return those regular calipers. Stainless sleeves cost more but will last pretty much forever with new seal kits periodically. Regular steel pits and leaks, particularly when a car sits for long periods of time.
Ok so just an update in case anyone was wondering, put all 4 calipers on today backs were no problem. Fronts gave me a hassle and the hard brake lines were basically welded to the rubber lines and I was forced to cut the hard lines and then flare on new fittings.
Bench bled the master cylinder and installed then, got to final part of bleeding the brakes and lo and behold the new fittings i flares on were leaking. Just ordered new front hard brake lines, hopefully will be able to have functioning brakes next weekend….. the saga continues.
I have heard that "splicing" new lines in a brake-line run, is illegal in some states.
How ironic that the manufactures have dozens of brake line fittings, but the Gov doesn't want any more installed by us amateurs.
I have seen shops "splice" brake lines on a whim, done one myself when low on funds or just to get you to work.
Is it right? Probably not. Is it safe? Not likely.
Question: What could go wrong? Answer: Property damage or kill someone.
I am not sure which is scarier: A jealous husband / boyfriend coming at you with a gun?
Or an unexpected brake pedal to the floor !
I am not sure which is scarier: A jealous husband / boyfriend coming at you with a gun?
Or an unexpected brake pedal to the floor ![/QUOTE]
i can speak to that..
OP…while waiting look and check carefully on a 79 at brake clevis so this does not happen in link below… shocking how that was designed. https://www.corvetteforum.com/forums...ying-79-a.html
i also had to replace my front line, they leak if you remove and install many times.
A chance to clean up when replacing brake line. I got steel from vendor zip..great fit with coils too.
I am not sure which is scarier: A jealous husband / boyfriend coming at you with a gun?
Or an unexpected brake pedal to the floor !
i can speak to that..
OP…while waiting look and check carefully on a 79 at brake clevis so this does not happen in link below… shocking how that was designed. https://www.corvetteforum.com/forums...ying-79-a.html
i also had to replace my front line, they leak if you remove and install many times.
A chance to clean up when replacing brake line. I got steel from vendor zip..great fit with coils too.[/QUOTE]
Holy crap that’s nuts!!!! I will check my clevis pin while I wait lol.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
If you need brake parts in the future I like CSSBinc. https://www.cssbinc.com/
Good prices and great parts. Never had issues with their equipement. Also inline tube. Used their stainless brakelines lines and they fit perfectly. https://www.inlinetube.com/pages/catalogs
I have heard that "splicing" new lines in a brake-line run, is illegal in some states.
How ironic that the manufactures have dozens of brake line fittings, but the Gov doesn't want any more installed by us amateurs.
I have seen shops "splice" brake lines on a whim, done one myself when low on funds or just to get you to work.
Is it right? Probably not. Is it safe? Not likely.
Question: What could go wrong? Answer: Property damage or kill someone.
I am not sure which is scarier: A jealous husband / boyfriend coming at you with a gun?
Or an unexpected brake pedal to the floor !
Sorry, but this is incorrect. Brake lines get spliced all the time, and properly done it's perfectly safe. The problem arises, and probably the illegality as well, when Johnny Shouldn't-Own-Tools goes to the hardware store and buys compression fittings to fix his brakes. That is a recipe for disaster. But properly done double flares with a correct coupler is perfectly fine.
In fact GM has a splice on the rear brakes on my truck right from the factory. Probably because of the length of tubing required.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Originally Posted by Kilobuck84
Sorry, but this is incorrect. Brake lines get spliced all the time, and properly done it's perfectly safe. The problem arises, and probably the illegality as well, when Johnny Shouldn't-Own-Tools goes to the hardware store and buys compression fittings to fix his brakes. That is a recipe for disaster. But properly done double flares with a correct coupler is perfectly fine.
In fact GM has a splice on the rear brakes on my truck right from the factory. Probably because of the length of tubing required.
There was a whole to Do on this subject a couple of years back. Any joint, any tee, any fitting in a brake line can be considered a splice if you look at it that way. I had a 66 mustang with factory splices, a 62 F100 with the same. Some folks get an opportunity to say something and they just go off on some tangent rather than thinking about it logically.
Plenty of tools and parts out there to double flare a brake line.
If you need brake parts in the future I like CSSBinc. https://www.cssbinc.com/
Good prices and great parts. Never had issues with their equipement. Also inline tube. Used their stainless brakelines lines and they fit perfectly. https://www.inlinetube.com/pages/catalogs
I actually bought the lines from inline tube, they messed up at first and shipped the wrong ones but their customer service was great and shipped me the correct ones very fast.
Sorry, but this is incorrect. Brake lines get spliced all the time, and properly done it's perfectly safe. The problem arises, and probably the illegality as well, when Johnny Shouldn't-Own-Tools goes to the hardware store and buys compression fittings to fix his brakes. That is a recipe for disaster. But properly done double flares with a correct coupler is perfectly fine.
In fact GM has a splice on the rear brakes on my truck right from the factory. Probably because of the length of tubing required.
Sorry, but you are incorrect. Research it. Several states do not allow splicing of brake lines. It's very dangerous because its the most likely place to fail.
Just because somebody splices all the time does not make it legal.
The brake system in our vehicles is susceptible to over 400 lbs pressure. Because of that, the proper repair is to replace the entire brake line w/o splices.
Vacuum issue/Brake problems
