Honda Civic brake pressure

Tiny
SUM2
  • 1994 HONDA CIVIC
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 227,000 MILES

1994 Honda Civic ABS, Lx. I have all disc brakes. I just installed new brake pads on all four. I bled all four brake systems the proper way, starting from rear right, front left, rear left, then front right. The brake pedal still has little to no pressure. When I apply pressure on the pedal when the engine is off, it starts with no pressure (goes all the way to the floor) then after a pump or two it has some pressure but never maintains the pressure, pedal goes to the ground slowly. I turn the car on and there is never pressure, it goes to the floor all the time basically. What suggestions do you have to solving this pressure problem? Would flushing the brake system help at all?

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Monday, April 11th, 2011 AT 2:41 AM

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Tiny
CARADIODOC
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Sounds like internal leakage inside the master cylinder. That is commonly caused by running the pedal all the way to the floor during bleeding. Crud and corrosion build up in the bottom halves of the bores where the pistons don't normally travel. When the pedal goes all the way down, the lip seals get ripped on the corrosion. It's okay to go all the way down with a new or rebuilt master cylinder, but with an old one, pretend there is a block of wood under it and never go more than half way to the floor.

The clue to determining if this is what happened is to pump the pedal rapidly to see if it will build pressure, then hold it but if necessary, ease up on the pressure a little then push harder again. If the pedal suddenly falls away and there's no external leaks or loss of fluid in the reservoir, suspect the master cylinder needs to be replaced.

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Monday, April 11th, 2011 AT 3:30 AM
Tiny
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I suspect it is the master cylinder also. I'll look into getting it replaced and update afterward. Thank you so much for the quick and thorough answer!

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Monday, April 11th, 2011 AT 3:59 AM
Tiny
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I forgot to mention the motor revs up slightly when I apply the brakes right now. Any clue what is going on?

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Monday, April 11th, 2011 AT 4:10 AM
Tiny
CARADIODOC
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I wouldn't worry about that just yet. If the brake pedal is moving with little pressure, there might be a lot of vacuum being lost in the power booster with each stroke. The engine will respond just like if it had a vacuum leak but the engine speed should come back down in a few seconds if you hold the pedal down.

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Monday, April 11th, 2011 AT 4:17 AM
Tiny
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Do you think I would need a new brake booster also? Or only the master cylinder?

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Monday, April 11th, 2011 AT 4:21 AM
Tiny
CARADIODOC
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Just the master cylinder. I never heard of a bad booster in all my years of mechanicing and teaching, ... Until a few years ago. GM owners have their own set of problems, but for the rest of us, about the only thing that can happen is the diaphragm develops a leak. You will hear the hiss when you press the brake pedal. That opens a valve to let atmospheric pressure in so the engine vacuum can pull on it.

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Monday, April 11th, 2011 AT 6:32 AM
Tiny
KHLOW2008
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When replacing/repairing the master cylinder, before reinstallation, ensure the seal between the master cylinder and booster is in good condition. The seal tends to fail resulting in vacuum leakages.

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Monday, April 11th, 2011 AT 1:47 PM
Tiny
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Thank you cardadiodoc and KHlow2008 for the helpful advice. I'm now going to work on the car. I'll update when I can. Thanks again. This forum has been very helpful in troubleshooting this frustrating problem!

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Monday, April 11th, 2011 AT 7:17 PM
Tiny
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So I changed the master cylinder today and the problem is still the same. I bled all four brakes and the brake pedal still goes to the floor when the car is turned on. Any ideas?

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Tuesday, April 12th, 2011 AT 3:20 AM
Tiny
CARADIODOC
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If you have the parking brake built into the rear calipers, it's possible they aren't adjusted up yet. I'm not real familiar with Honda's rear disc design, but for some other brands, the rear pistons will not self-adjust out from just pumping the brake pedal like in front calipers. The rear pistons will move out like normal when you press the pedal, but they will go back in when you release the pedal. What you may have to do is work the parking brake multiple times to walk the rear pistons out until the pads contact the rotors. If the cables are rusted tight or you don't trust them, you can use a pliers to work the levers on the calipers back and forth until the pistons come out.

If you have this design, you wouldn't have been able to just push the pistons back into the calipers to fit the new thicker pads in. You would have had to use a special tool to screw the pistons in.

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Tuesday, April 12th, 2011 AT 3:35 AM
Tiny
KHLOW2008
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Ensure you have sufficient free play for the handbrake lever. Without sufficient cable free travel, the rear calipers would not self.

1. Was the master cylinder bench bled before installing?
2. Is the master cylinder of the correct size?
3. Is there sufficient/excessive brake pedal to booster free travel?
4. While bleeding the system, was there a lot of air in system?
5. Is the ABS system working correctly?
6. Did you perform bleeding of the ABS master pump? System is under high pressure so be careful when working on it.
7. Does pumping the pedal brings it up and does it sink when pedal is held?
8. Did you check all the caliper slider bolts for smooth movements?
9. Was any caliper pistons difficult to retract while replacing the pads?

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Tuesday, April 12th, 2011 AT 3:35 PM
Tiny
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1. Yes.
2. Yes.
3.I don't know what this means?
4. No.
5.I haven't taken the car off jack stands yet. I've been turning the car on and pressing the brake pedal in. Should I put the car down and test the brakes? Will this make a difference?
6. I did not bleed the ABS master pump. Will I have to do this?

Cardio - I did have to use a tool to push the rear caliper pistons in. I'm not clear about working the parking brake. However I did pull it up at first and it felt like nothing was happening and I kept pulling it and then it went to normal. I think this is what you mean by working the parking brake.

I'm going to do another rebleeding. Hopefully I'm just bleeding it incorrectly.

Here goes.

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Tuesday, April 12th, 2011 AT 7:33 PM
Tiny
CARADIODOC
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Yup. You got what I meant by "working the lever". When you started to feel resistance is when the pistons came out far enough to contact the pads and rotors.

You might consider KHLow2008's suggestion about bleeding the ABS unit. Some vehicles require a scanner to activate some of the valves so the air can escape. This is particularly important if the master cylinder ran dry, or in your case, you replaced it. Here are a couple of tricks you might find useful in the future:

When the hydraulic system is opened, as in when replacing a caliper or brake line, fluid will drain out of the reservoir. If allowed to occur, you will have to bleed the system to the wheel you were working on and you may have to bleed other wheels too. To stop the fluid from draining out, use a stick from the seat to the brake pedal to hold the pedal down a couple of inches. The lip seals in the master cylinder will block the fluid from flowing while you do the work. When you're ready to bleed what you worked on, remove the stick, keep the reservoir at least half full, and gravity-bleed as necessary. Don't fill the reservoir to the top unless you have all new disc brake pads installed. If there are worn pads, you're going to have to push the pistons back in when you install new pads in the future and the fluid behind the pistons will go up to the reservoir and overflow creating a mess.

The second trick applies to replacing the master cylinder but only those that have two steel lines coming out, not four. Crack the soft metal nuts loose so you don't have to struggle with them after the master cylinder is unbolted from the booster. When it is off, use it as a lever to bend the steel lines upward just enough so the fluid doesn't run out. Do your normal bench-bleeding on the new one, then screw the two lines onto it. Finger tight is sufficient. Use the master cylinder to bend the lines back down, then install it to the booster. Loosen the nuts just a little, then have a helper press the brake pedal very slowly so it takes about 10 seconds to go half way to the floor. You'll see air bubbles come out by the line nuts. Snug them up before your helper releases the brake pedal. The pedal should be allowed to pop back quickly. By pressing it slowly, any air bubbles in the lines will tend to stay where they are or they will float back up. By releasing the pedal quickly, the fluid rushing back up will wash the air bubbles up into the reservoir. This will prevent you from having to bleed at the wheels.

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Tuesday, April 12th, 2011 AT 8:39 PM
Tiny
KHLOW2008
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For the ABS pump, remove the pump relay and use a fused wire to jump the terminals and make the pump work momentarily. You would know when the pressure has built up sufficiently when the pump noise slows down. Give that a try and see if the pedal increses in height.

For item #3, if the booster push rod had been adjusted out of specs, it can result in the brake pedal being too low.

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Tuesday, April 12th, 2011 AT 9:00 PM
Tiny
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Success! I had to buy a one man bleeder kit from the store. I bled the brake system 5 times then turned the car on and bled the system one more time. I drove it around the neighborhood and the brake systems work perfectly! I started the job thinking I just needed to get pads all around, but then found out the master cylinder needed to be replaced from this wonderful forum. Thank you for your help cardio and KHLow! The entire job ran about $150. I saved so much money doing it myself. Now I have thick pads all around and a strong braking system. Peace of mind!

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Wednesday, April 13th, 2011 AT 3:01 AM
Tiny
CARADIODOC
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All right. One in a row! Happy to hear you can safely buzz off into the sunset. I mean "sail off", not buzz off!

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Wednesday, April 13th, 2011 AT 3:04 AM
Tiny
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My muffler was broken from the previous owner, so I removed it while doing this job. So it does sound more like a buzz when i'm driving without a muffler! Thanks for the help!

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Wednesday, April 13th, 2011 AT 3:08 AM

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