Brake Issue

Torchandregdoc

Well-Known Member
Cool... Hey its fixed. Stinks that you had to loose the time, but having this forum to bounce the ideas around help all of us learn something.

I'd say pops is on to something. I'll bet there is something on the cylinder wall that starts to leak as soon as the piston goes by it.
 

Ross

Goblin Guru
Woo Hoo! Finally got a fix. Sorry it was the hard way, but at least we know the solution.
I also learned that I should have broke in my brake pads and rotors better. I think I may have a warped rotor, and they are new!
 

DCMoney

Well-Known Member
False alarm on the brakes. Still not working, had a vacuum leak between the master cylinder and booster when I put the master cylinder on and couldn't tell when I was in the garage. Took it out for a drive and had manual non-vacuum assistance brakes. Fixed the leak and pedal goes to the floor again.

Had a 50+ year old mechanic come over and tell me it's air in the lines. We bled, still went to the floor, we bled again, still went to the floor. Tried a bunch of more old mechanic tricks, still to the floor.

Plugged all four lines at the caliper in the line and the pedal goes rock hard. It's a caliper issue, now to figure out which one(s).

 

George

Goblin Guru
So you have a caliper that is not square with the rotor or the pads are not seated. If the wheels are not on and torqued the rotor will be able to flop around and give a bad pedal feal.
Brad
 

Torchandregdoc

Well-Known Member
I'm still perplexed as well. From your original post, it's not clear. Are you pushing in the brake pedal and it's going all the way down, or is vac assist pulling it all the way down by itself?

If it was a caliper and it is a continuous problem, it would have to have an external leak, am I wrong? I mean, if the master is indeed pumping, the fluid has to be going somewhere.
 

DCMoney

Well-Known Member
So you have a caliper that is not square with the rotor or the pads are not seated. If the wheels are not on and torqued the rotor will be able to flop around and give a bad pedal feal.
Brad
Cant see it but the lug nuts are holding the rotor in place without the wheel on in that picture. Driving on the road wheels are torqued down, pedal slowly goes to the floor when I apply brakes, not a floppy rotor. Put roughly 60 miles on the car between yesterday and today, pads are seated against the rotors.

I'm still perplexed as well. From your original post, it's not clear. Are you pushing in the brake pedal and it's going all the way down, or is vac assist pulling it all the way down by itself?

If it was a caliper and it is a continuous problem, it would have to have an external leak, am I wrong? I mean, if the master is indeed pumping, the fluid has to be going somewhere.
With vacuum assistance, when the brakes are applied, the brakes will bite and the pedal will slowly go to the floor, brakes are still holding throughout the stroke of the pedal but the pedal goes to the floor.

Everyone I have talked to, that has helped me bleed the brakes, which are nearing the 400th time, are confused at the issue and why the pedal goes to the floor.

The calipers are all dry, none of them are leaking, fluid level does not change with relation to the travel of the pedal pass the initial push. The fluid level change when you apply the brake is tiny, you're moving the brake pads a fraction of an inch if that. With the pedal going to the floor I should see the fluid level changing. Doesn't make any sense, it points to a bad master cylinder until I plugged all the lines before the calipers and the pedal doesn't slowly drop to the floor.

If testing each caliper independently results in the pedal still going to the floor I'm going to put my vacuum regulator on, regulate the vacuum to where the assistance doesn't cause the pedal to slowly go to the floor and just be done with it.

Testing the calipers first thing tomorrow morning.
 

Joebie

Member
I've heard of people having to "bench bleed" their calipers which involves taking the calipers off the car, filling them with brake fluid on the "bench" as you might expect, and being able to shake them and gyrate them around to get any air pockets out of corners of the piston area. Then they are filled as full as you can get them on the bench and reinstalled on the car and bled in a normal way, either two-person or pressure bled.

I didn't catch it if you said it earlier, but have you been pressure bleeding or two-person pump-and-dump bleeding?

I doubt this is your problem because I dont think you'd get a pedal that slowly goes to the floor with air in the system, it'd just be spongy. Just thought I'd mention it though.
 

George

Goblin Guru
Put a pressure gauge in a brake caliper bleeder screw hole and measure the pressure. I can loan you one if needed.

Brad
 

DCMoney

Well-Known Member
I've heard of people having to "bench bleed" their calipers which involves taking the calipers off the car, filling them with brake fluid on the "bench" as you might expect, and being able to shake them and gyrate them around to get any air pockets out of corners of the piston area. Then they are filled as full as you can get them on the bench and reinstalled on the car and bled in a normal way, either two-person or pressure bled.

I didn't catch it if you said it earlier, but have you been pressure bleeding or two-person pump-and-dump bleeding?

I doubt this is your problem because I dont think you'd get a pedal that slowly goes to the floor with air in the system, it'd just be spongy. Just thought I'd mention it though.
I've done 4 methods of bleeding, 2 person pumping and dumping, vacuum, pressure at the reservoir, and I recently added a bleeder that puts fluid in through bleed screw.

Put a pressure gauge in a brake caliper bleeder screw hole and measure the pressure. I can loan you one if needed.

Brad
Thanks Brad, I might take you up on that.

Started this morning by up plugging the drivers rear brake line, hooking it back up to the caliper, bleeding it, started the car, pedal doesn't sink to the floor.

Left it hooked up move the passenger rear caliper, bleed it, started car, didn't sink to floor.

Passenger front, same process, slowly sunk to floor, recapped line.

Drivers front, same process, didn't sink to the floor.

Want to swap the passenger rear caliper (not the bracket) with the front and see if the problem goes with the caliper before I just buy another caliper. It pretty much has too be it, but I hate just throwing parts at problems without testing.
 

George

Goblin Guru
I believe the testing you done has located the problem. The issue now is the caliper leaking or is something flexing causing the issue. If there is no leakage something is flexing.

Brad
 

DCMoney

Well-Known Member
There is flexing at the caliper, tried to take video of it but it's hard to tell from the video.

 
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DCMoney

Well-Known Member
Pins are/where fine. pads are so close to the rotor not a lot of movement there.

Video shows the pins allow free movement (missing a pad), then installed with both pads, can see slight movement.


Lots of flex in the caliper that coincides with the pedal travel.


Looking for a new caliper, these don't seem to be the easiest to get in a day or so.
 

DCMoney

Well-Known Member
As frustrating this issue has been I'm calling it quits with a band aid.

Few weeks ago I tried a new caliper, same issue persist. Gave up, installed my vacuum regulator, regulated down to where the booster just started to assist then added a little more assistance till brakes felt perfect.

I get a firm pedal that provides a great feel. Brakes are capable of stopping the car at 1g+ (Gopro data). I was originally worried about the brake pedal being an on off switch, not the case with the vacuum regulator. Ill get a little tire squawk under heaving braking but haven't had a lock up with the regulator installed.

 

TravMac

Member
As frustrating this issue has been I'm calling it quits with a band aid.

Few weeks ago I tried a new caliper, same issue persist. Gave up, installed my vacuum regulator, regulated down to where the booster just started to assist then added a little more assistance till brakes felt perfect.
So you think it was just a case of being over assisted? Seeing that caliper flex just looks so off in your previous video... ha. Wonder if other cars do this but it isn't noticed.
 
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