Brake nightmare!

Kustomvida90

Not-quite-so-new-guy
Feb 14, 2019
7
1
3
Richmond ca
Hi guys , I recently did a full brake restoration on my 1986 v8 Montecarlo, after the job was finished I have next to nothing braking power!… also I noticed that there’s bubbling inside the MC when brake is pressed in the rear chamber that holds the fluid for the front! At first I thought it was a defective MC so I changed it and it did the same thing .. I changed out the master cylinder 4 times already
There’s no break fluid leaks at all anywhere In the car ….

I bled the crap out of the system !
The pedal goes to the floor when car is on
It feels like there’s no pressure whatsoever going to the brakes ..
I replaced the following
•Brake booster
•master cylinder (4 times because the past 3 were defective)
•rotors
•calipers
•brake pads
• wheel cylinders
•drum brakes and all the springs
•rear hard brake line
•Russell braided line for the rear
•Russell braided lines for the front
I properly bench bled the MC
And also properly bled all 4 wheels . I’m stumped you guys I could really use some help
Thanks in advance
-Santana
 
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1KWIKSIX

Greasemonkey
Jun 26, 2017
235
341
63
Mississauga , Ontario, Canada
Hi guys , I recently did a full brake restoration on my 1986 v8 Montecarlo, after the job was finished I have next to nothing braking power!… also I noticed that there’s bubbling inside the MC when brake is pressed in the rear chamber that holds the fluid for the front! At first I thought it was a defective MC so I changed it and it did the same thing .. I changed out the master cylinder 4 times already
There’s no break fluid leaks at all anywhere In the car ….

I bled the crap out of the system !
The pedal goes to the floor when car is on
It feels like there’s no pressure whatsoever going to the brakes ..
I replaced the following
•Brake booster
•master cylinder (4 times because the past 3 were defective)
•rotors
•calipers
•brake pads
• wheel cylinders
•drum brakes and all the springs
•rear hard brake line
•Russell braided line for the rear
•Russell braided lines for the front
I properly bench bled the MC
And also properly bled all 4 wheels . I’m stumped you guys I could really use some help
Thanks in advance
-Santana
Try this after reading this article

 
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Reactions: 3 users

64nailhead

Goat Herder
Dec 1, 2014
5,767
1
12,368
113
Upstate NY
There is an excellent chance that you have the proportioning valve (combination valve) not centered. Or you have air in the system - if it's in the master cylinder, then you will never get that out bleeding conventionally. Lastly, you could have a minor leak at a fitting that is allowing air to be sucked back in which leads to a continual issue like you're having.

Regarding a leaky fitting. If you used stainless steel lines and/or fittings at any location, then they need to be very tight to get the metal to conform to seal. It requires force on the fittings that doesn't seem like they should need. One of the reasons that NiCopp brake line has taken off is because it much more pliable and conforms much easier leading to less leaks and issues.

Bleed the master cylinder with plugs in the outlet ports rather than a hose fed back into the reservoir. With the ports plugged you will know immediately when the air has been removed from the master.

If you have managed to get your prop valve uncentered, then there are a couple f things that can be done to get it centered. The easiest way that I've found is to open up all the bleeders and let it gravity bleed for 8-12 hours. This is easy, but boring. You can't let the master cylinder run dry, so you have to monitor it regularly. Open all of the bleeders with the master cylinder filled to the brim. Until you start seeing a drip from each bleeder every second, it's not bled sufficiently. As you see a wheel end start dripping quickly, close that particular bleeder. Once all of them are bled sufficiently you should have a brake pedal on the 1st or 2nd pump. Once this achieved, run back around the wheel ends starting farthest away and re-bleed conventionally. Again, this, nor anything else, will work if your master cylinder is not bled completely.

I've been where you are before I started with the gravity bleeding method. I've had a car take more than 3 hours before I got a single drip. Patience is a virtue with this method and DON'T let the master cylinder run dry. It's a nice 6 pack job over the course of a day.
 
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78Delta88

Royal Smart Person
Supporting Member
May 23, 2022
1,306
1
1,100
113
SW Arizona
New and rebuilt masters are a big problem. Take one apart fresh from the box and you will see what I mean. Buy high quality New. I learned the hard way too, never again will I buy rebuilt or some of the "New" from parts suppliers. If after bench bleed and you are getting bubbles?? Yeah something is not right. Bad cup or seal that is picking up air and putting back in the MC. If your foot is going right to the floor... You are not building pressure. No pressure equals no brakes and there is nothing there to bleed.

The tool will help with centering the valve, but sounds like your not even having pressure to that point. You need to analyse what you have and why it's not working. Stop throwing money at it and replacing everything. This is what bad brake shops do. Drain your wallet and car still not right.
 

mikester

Comic Book Super Hero
Mar 10, 2010
2,964
3,852
113
Small town NY
I had trouble bleeding the brakes on my wagon. Kept sucking air and I couldnt figure out from where. Turned out it was one of the fittings on the proportioning valve. I had to look at the top fitting with an inspection mirror to see it leaking. I hate using SS lines.
 
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scoti

Royal Smart Person
Sep 5, 2019
2,007
3,464
113
Texas
Were these 'bad' master cylinders each 'bench bled' before installing into the car? Four in a row suggests the issue is possibly elsewhere.
 
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78Delta88

Royal Smart Person
Supporting Member
May 23, 2022
1,306
1
1,100
113
SW Arizona
I had same thing several years ago on GF's Malibu. Bench bled, then at wheels, everything was fine, yet less than a week later... MC failed.

Then a few years later 98 Sebring. Three absolute bad ones sequentially. Same issues ... Would not bleed, or push fluid to 1/2 car at a time.

Finally got good one, all issues went away. Bled normally, worked normally.
 
Last edited:

69hurstolds

Geezer
Supporting Member
Jan 2, 2006
8,352
18,071
113
The unfortunate issue is most new GM/Delco masters are now or have long been defunct. So it's either Chinesium or a rebuilt unit, or NOS GM. And that's only as good as the manufacturer/rebuilder. Cheap components and process mean cheap quality. Never mind the price isn't so cheap anymore for anything.

Even if you did find an NOS master cylinder, it's been on the shelf so long, it MAY not work, either. From my eperience, they're not dry when they put them in the box, but over the years, how long could it sit there without ever being used? It might be ok, or it may not.

Either way, when bleeding, I advise using that center pin tool.
 
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scoti

Royal Smart Person
Sep 5, 2019
2,007
3,464
113
Texas
The unfortunate issue is most new GM/Delco masters are now or have long been defunct. So it's either Chinesium or a rebuilt unit, or NOS GM. And that's only as good as the manufacturer/rebuilder. Cheap components and process mean cheap quality. Never mind the price isn't so cheap anymore for anything.

Even if you did find an NOS master cylinder, it's been on the shelf so long, it MAY not work, either. From my eperience, they're not dry when they put them in the box, but over the years, how long could it sit there without ever being used? It might be ok, or it may not.

Either way, when bleeding, I advise using that center pin tool.
I just use a nut-driver. Convenient handle & small enough blunt tip.....
 
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Kustomvida90

Not-quite-so-new-guy
Feb 14, 2019
7
1
3
Richmond ca
Hi guys , thank you all for sharing your knowledge .. 64nailhead I did all the steps that you suggested and noticed an improvement in the brakes .. the car now gushes a hefty stream of brake fluid on all 4 tires when bleeding . I bled the master cylinder until all the air was gone… also I used the prop valve tool .
The pedal still feels soft
And it’s still bubbling at the master cylinder ..
I also checked and tightened the hell out of all my ss lines .. the mechanic i had hired left them a lil loose .
I double checked the calipers to make sure none were sticking or leaking , everything checked out .. drum brakes got adjusted also
 

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