soft brake pedal

[EsperHamid]

Hey guys it's been a while.

Front driver side, brake fluid splashed all over the tire.

1 - Brake booster not leaking under the dash.
2 - All bolts are well tightened and not leaking.
3 - Bled the brakes and well tightened the bleeder valve no leaks from there.
4 - Brake lines look fine !! no cracks !! no evidence of leak.
5 - Brake pads have 7mm left on them without the back plate.
6 - no cracks in brake booster vacuum hose.

Leak evidence coming from the opening in the caliper bracket. could the piston be leaking ?! where from ... it is becoming dangerous.

[H311RA151N]

Hey guys it's been a while.

Front driver side, brake fluid splashed all over the tire.

1 - Brake booster not leaking under the dash.
2 - All bolts are well tightened and not leaking.
3 - Bled the brakes and well tightened the bleeder valve no leaks from there.
4 - Brake lines look fine !! no cracks !! no evidence of leak.
5 - Brake pads have 7mm left on them without the back plate.
6 - no cracks in brake booster vacuum hose.

Leak evidence coming from the opening in the caliper bracket. could the piston be leaking ?! where from ... it is becoming dangerous.

Pull the caliper off and have a look. It's likely leaking from around the piston.

[C91BLX7]

Replace the caliper.. inspect the brake line as well.

[EsperHamid]

thx for replying guys, here's what I did, I removed the piston by pumping the brakes and it made a mess, the fluid that came out was a lot, I didn't bother me at the time because I said I'll easily fill the cylinder and do the redneck braking.

so I replaced the seal and installed the piston back, took it for redneck braking to get air out but the pedal seemed super soft now.

My CB wouldn't stop unless I floor it !! even with the hand brake, it rolls a little before it stops.

Do I need to bleed only the front driver side where I replaced the seal or all 4 tires ?
HELP !! MY CB is too dangerous to drive now.

[wildBill83]

Bleed all four, start at the furthest from the reservoir.

[EsperHamid]

will do wildbill thx

[johnl]

because I said I'll easily fill the cylinder and do the redneck braking.

"redneck braking"???

Whatever, you've let a lot of air into the system, it's not surprising the car won't stop. Complete brake bleed needed.

[EsperHamid]

Would someone plz know the correct size of the seal cause I got an after market one ( maybe chinese very cheap) and it didnt seem to have solved the problem, still leaking

[wildBill83]

Did you hone the bore?

[johnl]

Did you hone the bore?

There's no need to hone caliper bores, the seal doesn't seal on the bore (other than where it contacts the groove in which the seal sits, which isn't subject to wear). The seal seals on the outside of the piston, which needs to have a good surface. The only thing needed for the caliper casting itself is to make sure it's clean and remove any rusty accretions (including in the groove, especially in the groove).

Master cylinders and slave cylinders are a different thing, the seals do seal against the bore wall.

[EsperHamid]

What is the size of the seal please, coz i got the wrong one, the contact where the seal sits and meet the piston doesnt have any rust on it

[johnl]

What is the size of the seal please, coz i got the wrong one,

I've just measured a CB7 front caliper piston for you, the OD is 57mm. My verniers won't reach far enough into the caliper bore to get an ID measurement, but it's only a bit bigger (maybe about 0.5mm or so). The piston OD is the measurement you need.

[EsperHamid]

Thank you Johnl, I already bought an entire caliper from the junkyard, but will keep your info for reference because I think my problem isn't over yet.

alright, after changing the whole front left caliper, no leaking anymore, I bled the brakes for the 4th time now, my brakes are still weak, eventhough the pads are still good.

The brakes are not floored but not as they should be. Here's what I am noticing.

Knocking sound from my front right caliper whenever I press on the pedal. I have to press many times to stop my car. Though there's no leak to be noticed from that caliper.

Also, when my car is off and I push the brake pedal many times, it hardens and while doing so, I hear some hissing from under the dash each time I pump the pedal .

There's no leak from under the dash

Seriously help me guys, I got tired of bleeding my brakes many times, its painful too.

[Kev1990]

Hello I see you've been dealing with this for a while. Here's what I just went through with my brakes when it was cooler out brakes felt fine sometimes rarely had to pump them but when it got 70-80+ outside they would sink/get soft every stop I would have to pump my brakes just to barely stop no visible leaks but it turned out I had a very slow internal leak on the master cylinder nothing visible though put on a new master cylinder everythings fine now and I'm not lossing any brake fluid like I was. I was lossing very little though and the bad master cylinder was causing my front right caliper to seize up from uneven pressure from what I believe is due to the internal leak. So here's what I would do if I were you.

Post how much you got your caliper at the junkyard for one as you can go right to Pepboys get a fully rebuilt caliper for our cars for like 39.99 I think it is as I replaced both of my calipers thinking it could of been the problem.

If it were me I'd put the car up on jack stands if you only have one jack/lift do it at each wheel very important to make sure you have no leaks closely inspect all wheels. Did you use two new crush washers on the brake line to your junk yard caliper? If not I would go out and get a set of washers to ensure no leaking. Pump your brakes hard when the car is off look around on each inner tire for leaks. Also try pumping your brakes when the car is off in general pump it til it gets hard and see if it sinks any just slightly sinks you have a leak/bad master cylinder.

Do you have drum brakes? If so jack the car up check both rear drum bakes take the drum off check the pad thickness and inspect it for leaks/wear in general. See if your back wheels spin freely if they spin too freely you have to adjust what I believe is the star nut adjuster on the drum brake so it doesn't spin so freely get it to where it has some resistance when spinning the back wheels you will also feel your emergency brake get tighter you want it to be 4-6 clicks to full potential. Do some research on how to adjust the starnut on drum brakes as I've heard posts on here in the past that unadjusted drum brakes can cause soft/sinking brake problems

If you haven't already I would just throw in a new master cylinder in my case though my sinking brakes I bled them after not doing it for 2+ years before changing the calipers and got very minimal air/bubbles so I know it wasn't a leak. If I can think of anything else to help you with ill post it but please do what I said and post back to me as I see you've been dealing with this for a while witch I know it is not fun. BTW make sure your bleeding them in the correct order. Forgot to mention I let my master cylinder go for so long that it was putting so much extra pressure on the right brake it actually worn down the pad a lot faster then the left and actually caused my right brake pad to fall off while driving then gouged the router at the time I drove to my mechanics shop with the emergency brake the whole time LOL!

[EsperHamid]

alright to isolate the problem after bleeding so many times.
I did the following in a parking lot, I un-plugged the vacuum hose of the brake booster that goes to the IM

Plugged the IM and turned on the car, the brake pedal would harden-off but the car took some time to stop which is normal without brake booster.

However, I concluded that the bleeding procedure was successful since the brake pedal became hard.

the problem is that the fluid level in the master cylinder is still the same and I notice each time I open the reservoir cap, 2 or 3 bubbles appear.

I think the problem could be the master cylinder is plugged or something ?!

please advise