Hello,
I have a strange brake issue happening:

The brakes are weak (not stoping very well, getting worse). When I am driving, the faster I go, and I hit the brake just like in panic stop, it's like I hit a hard wall with the brake pedal and the car doesn't stop very well.

In the winter I had a frozen caliper that ate the pads and put a groove on the rotor. I freed it up and now I just replaced the calipers front and I have pads and rotors on order.

I also have a set of stainless braided lines (4) on order which I will replace soon as possible. So when I do that, I will replace all the fluid in the system.

The question is, do I might have a master cylinder on it's way out and I should replace that too?

The clue here is that as i drive faster I stop worse. Now that could be because the speed is faster and the stopping distance is worse, or vacuum related though if I had highr rpm I should have a better vacuum and it should help me stop using the brake booster so that's unlikly.

I don't think it is the proportioning valve since I don't have lock ups and the rear brake only doing 20% of the work anyway.

My pedal is pretty low and squooshy, the low part is probably the front pads needs to be replaced since the rotor is scored too.

Any thoughts?

Thanks in advance!

 

So I went back and bleed the entire system again. When the engine is off, the brake pedal is very stiff and can not go down to floor.

When engine is on (not driving), if I press the brake pedal hard, it will slowly sink to the floor. Also, if I press it hard and quick, I feel resistance and then the pedal will slowly go down all the way to the floor.

I also check the vacuum hose with the check valve in it and it is not cloged and the check valve works in one way when blowing/ sucking air into it.

The brake pedal sinks (A little more then I would like to see it) when engine comes on and my foot on the pedal.

Needless to say, the car is in the driveway and it will stay there until it is fixed.

Is my master cylinder in need of replacement?

Any Clues are WELCOME!

Thanks

 

The pedal slowly sinking is CLASSIC for a bad master cylinder.

The pedal sinking too much when you start the engine may be related, but not sure. Make sure you check the length of the MC pushrod, old against new. They have to be exactly the same or you'll need Honda's special measuring tool so you can adjust the brake pedal pushrod.

 

I'd wait until you've flushed out the old fluid to rule out air, water, or just old ass fluid being the cause. Otherwise, if you've got relatively new fluid in the lines and are confident the system is properly bled of air - if under any circumstances your brake pedal ever goes all the way to the floor (most likely in hot temps.) then it's almost certainly the MC unless it's leaking fluid somewhere (level would have changed on MC reservoir).

Just having a low or squishy brake pedal isn't necessarily a sign of a problem (better safe than sorry though) depending on the car. My low (compared with some cars) brake pedal didn't change with new pads but changing the fluid made it much firmer and, as of yet, has prevented the pedal from traveling to the floor in hot temps. However, I wouldn't be surprised if I eventually have to get a new MC since the fluid hadn't been changed on a reg. basis by previous owners.

 

Thanks for the replies.

Old fluid flashed away. Pedal is hard.

Problem still exist, quick press of the brake pedal is kicking back .

Replaced master cylinder thinking it had an internal leak. That turns out not to be the case.

So next is replacing the proportioning valve. I think it is stuck. That's the only device that engages when a panic brake occurs unless you slide and then the ABS starts distributing pressure to the different calipers.

Any thought are welcomed.

 

I changed the proportioning valve but the same issue still exist.

Slam the brake and the pedal kick back and the car doesn't stop until the pedal start giving up to me pressing it.

If I slowly press the brake pedal the car stops fine.

So far I have replaced 2 front calipers, serviced the rear calipers and greased the caliper bolts. Changed the 2 rear flexible brake hoses to stainless braided.

Also changed the Master Cylinder, and proportioning valve. The only two components left are the ABS modulator and the brake booster.

When I replaced the MC, I noticed that the gasket between the MC and the booster is slightly worn. I also noticed that some paint is missing under the booster.

What do you think? Change the booster first?

Thanks

 

So I have also replaced the brake booster.

Problem still exist.

The few things that are left are the ABS modulator, rear calipers and brake lines.

The rear calipers looked good. The lines I doubt if they clogged. So only thing left is the ABS modulator.

There are no codes. And the ABS system does an initialization when engine starts. Although I have not heard it come on. It should buzz.

Anyone have other ideas?

 

It seems like it was after all the brake booster.

I thought I still had a problem with the ABS so I came up with a way to isolate parts of the hydraulic circuit.

On my ABS modulator there are 6 ports. 2 from master cylinder and then 4 for the diagonal front and rear.

I bought 2 brake lines 8" from autozone and I bent the tubes to so that they closed front brakes on the modulator and rear brakes. Then of course I have no control of the brakes anymore but since I knew and tested the emergency brake I can turn the car on and see how the pedal feel.

Since the pedal now felt VERY firm I knew that the problem is not the ABS modulator. I wanted to hook back the rear brake and then the front brakes one at a time. So I did.

So I hooked up the rear and they felt fine. I noticed that the pedal only sink 1/4" when the engine turns on. That's good.

When I hooked up the front brakes the pedal became very spongy so I went and bleed the two fronts again and the pedal become harder.

I took the car for a spin and problem solved!


What I have learned from this are a few things:
1) Always use flare fitting wrench!

2)PB blaster works great with putting it on and waiting a few minutes. Then take a hammer and GENTLY tap the fittings to release the tension. Then you can use the flare nut wrench to open the fittings.

3)I saved my self a bundle of money for a new ABS modulator that was not needed. Good thing that I performed these tests first.

4)I can extend my ABS modulator test to test the individual circuits (2) inside the modulator. This is if one circuit is not working correctly and the self ABS diagnostics didn't catch it.

5)Speed bleeders ROCK! They have them at Autozone and also online.

It is ALWAYS importent not to drive the car while you have brake problems.

 

Nice to know it's fixed, thanks for telling us the results. Strange behavior, but interesting to know for future problems.

I liked the Speed Bleeders too. But after a couple winters with road salt, they didn't work any more. Try as best as you can to protect them from corrosion.

 

Thanks JimBlake, I will definitly put the rubber boots on the bleeders.

I think because I open the entire brake system, I will have to use the car a bit, excersize the ABS and then go and rebleed the brake system again.