Been chasing down a soft brake pedal issue. Guy I got it from changed booster and I thought he said mc so I bled and bled and bled with no change. So I changed the mc thinking if he did change the mc he must of left air in it. So I bench bled it and bled the system a few times and still same issue. So I checked the brake pads and shoes and wheel cylinders. They look good. Then I tried smacking the calipers to release any stuck air and bled them again. Issue seemed to have fixed let car down with tired back on started car and to the floor again... I'm at a loss with this.

 

No one?

 

Okay can you see anything stamped on the brake master cylinder like "7/8" or anything? I'd be curious to know of the guy used the correct booster and/or master cylinder combo for your car.

Seeing as how brakes are 100% safety I'd probably buy a new master cylinder first, then try bleeding again. You will want two people to properly bleed your brakes. One will pump the brakes and then hold the pedal down with pressure while the other cracks open the bleeder. Repeat this process at each corner until there's only solid fluid coming out from each corner. Do so in a criss-crossing pattern where you start with the wheel farthest from the master cylinder in this order:

I found an old Super Street article that gives a pretty good write-up on how to do this:

http://www.superstreetonline.com/how-to/additional-tech/htup-0807-honda-brake-bleeding-tutorial-guide-and-tips-with-pictures/

If you still have a soft pedal after the master cylinder replacement, then you might have a bad booster. Typically though, a bad booster will cause a rock-hard pedal more than it will a soft pedal. It can definitely cause a LOW pedal though.

 

Yes I've already changed the master cylinder and bled the brakes. Still have a soft/low pedal. As soon has I push the brakes it fall to the floor then brakes work way at the floor.

 

Chain parts store master cylinders suck. Very possible your new one is no good.

Also check that the rear drum brakes are properly adjusted.

 

It's a Honda mc. The drums are adjusted fine

 

When you push to the floor and hold it down, will the car stay stopped, or does the pressure go away and the brakes release by themselves?

Is there ABS or just standard brakes?

 

Car will stay stopped yes. It will throw you forward in the car at the very end of travel. I can hold it and it not move. Car does not have abs

 

Ok update. Changed booster.... issue is still present.

 

Ok so this is a 97 lx. It's has new master cylinder, new booster. Changed them because it has a soft pedal or a lot of pedal travel before brakes are applied. Bled and bled and bled. Checked pads and shoes, wheel cylinder and looked at the flex lines while pumping the pedal didn't see any collapsing. When bleeding the front it has a lot of pressure so when I crack it open to bleed it shoots out across the parking spots. Rear have lower pressure because the obvious drum brakes. Can't fine the issue. Brakes don't come on till the floor but car will not lock them up but will throw the car forward. Lost at this moment.

 

If you didn't use the special master cylinder rod adjustment tool you very likely have a sizable gap between the push rod and the booster.

The tool is ridiculously expensive but is required to set the push rod clearance.

 

The special tool is not required as the service manual gives you a measurement with the booster out of the car.

 

I think you are mistaking things. Step 1-8 uses the special tool and then finally step 9 has an adjustment if the booster is out of the car. Step 9 I believe is for pedal free play pre-setup. Regardless, you still have to set the clearance of the MC to the booster regardless if it's in or out of the car using vacuum and the special tool.




You can't just skip to step 9 if you removed the booster.

 

Very well that's stupid. Never had to do it for my teg. Should include in the instruction to follow steps 1-8 after doing step 9 or in conjunction with.

 

You probably got lucky on your teg.

I don't understand how you think you can skip steps 1-8 and think it's just fine and dandy.

Also, if you pay attention to the steps, step 9 has you adjust the clevis locknut which doesn't have anything to do with the pushrod clearance in the master cylinder.

The push rod clearance locknut is the starnut on the other part of the rod in that section, two totally different lock nuts for two totally different parts of the job.

The other part that comes to mind, what order did you bleed the brakes?

 

Ya I know they are 2 different things. Just irritating to have to get a tool that isn't cheap to use just once.

 

I hear ya. It's why I just pulled the whole booster and MC from the salvage yard. Once seperated, you have to "calibrate" the pushrod. Definitely annoying and a pita due to the stealership pricing.

I thought I would get crafty with some plastigauge but after looking at the setup, I realized it would be a total crap shoot if the plastigauge would stay on the rod or stick in the tube and cause even more grief.

So yeah, the tool is 348 CDN here in BC so I feel your pain.

 

Theres a certain sequence to bleed the lines... Its NOT furthest to closest, but for the life of me i cant remember the proper sequence. Ive said it in countless threads on here in the past


If not done in this sequence, you will still have a soft pedal

 

Update had the booster adjusted and pedal would only get hard but brake activation would still be near the floor, so being at a loss I changed the hoses up front and wheel cylinders in the back and still the same issue if I hit them fast and hard it'll be like normal then drop to floor. If I rip on it in a parking lot and try to lock em up it throws forward and the rear locked at least one and the front had one lock

 

Re-bleed after finding brake sequence


EDIT: Found it

Bleed the brakes:
Right Rear, Left Front, Left Rear, Right Front.
You do not go farthest to closest with Hondas.

Always bench bleed the Master cylinder when replacing the master cylinder, ABS unit, or proportioning valve.

 

That's how I've bled it and I have bench bled the master cylinder

 

So I had a similar issue happen on a different vehicle, bled and bled and bled the lines, what worked was a vacuum bleeder. I was using the usual "have someone push the pedal down while I open the bleeder valve" method and the brakes stayed soft no matter how much I bled them. Used a vacuum bleeder and that fixed it. Sometimes the air is stubborn.

 

The shop has tried to vaccume bleed it. Still the same. I can smash the pedal to the floor and it locked up 2 tires but still drops to the floor.

 

I worked at a Chevy dealership and had a similar problem on a customers cruze. I eventually figured out 1 caliper was replaced with the wrong side, so the bleed screw for the caliper was on the bottom of the cylinder instead of the top allowing air to be trapped in the caliper cylinder. Might be worth checking.

 

Has correct calipers bleeder are on top