Master Cylinder Brakes Problem

It should be obvious by now that your husband and son should not be working on brakes. The safety implications (death of innocent people) should be enough incentive to keep them away from safety related items and confined to changing shock absorbers and doing tune-ups.

Take the car back to the shop and pay them to replace the master cylinder. Don't have your husband buy one, have the shop do the whole job. Then if anything does go wrong, the shop carries the liability for the master cylinder, if it proves to be at fault.

Take it to the man!

I agree with lyn. I consider myself a pretty good shadetree mechanic, and I have replaced pads and shoes and bled lines successfully. But I would not attempt a master cyl replacement, not for $90 bucks.

The car is giving you a warning that something is about to go bad. Brakes have a way of failing at a very bad time.

Your number of $90.00 sounds pretty reasonable. I vote let the brake guys do it.

Sounds to me like they got the air bled out of the system and now all is well. But I would procede with caution.

Exactly. At the moment, I don't "see" any evidence of a bad master cylinder. If the brake pedal travel starts to change again, or feels spongy, or whatever, yes, maybe the master cylinder is going bad.

Take it easy for the next 1000 miles and pay attention to the brake behavior. If you have any concerns take it back to the shop.

Thank you all so much for replying to my post. My husband has changed brake pads on all our cars since day one. We have never had a brake failure. But my husband thought that the boss of the repair shop was trying to get extra money by telling him to fix the master cylinder, since the brakes worked so good after the mechanics fixed the brakes.

Right now the brakes work fine after the mechanics went over and re bled and tightened the brakes. SO Could the master cylinder be faulty if the brakes are working fine? (Apply normal amount of pressure to brakes and car stops in the right amount of distance). Thank you.

Simple answer, no. If the brakes work fine, then nothing is broken. That's like saying you need to put in new headlight bulbs because they don't seem as bright...wait...now they are, and replacing them anyway.

"SO Could the master cylinder be faulty if the brakes are working fine?"

Yes, for now the master cylinder could be applying sufficient pressure. Even if it is faulty. If it is faulty in time the master cylinder will get worst and not apply the pressure needed to stop the car properly.

I suppose that is along the same line as the tires wear down more each mile they are driven. If left long enough, they will fail. Normally, people don't swap out parts of a car until they fail. Hopefully tires are an exception to that rule. There isn't a service life replacement for master cylinders as far as I know. You swap out a part after it has failed, like alternators, water pumps, steering gear, u-joints, etc.

If you really want to be sure, I mean really sure, have your mechanics do a bench pressure test. That will cost as much or more than just having a new one put in. The labor is the same for remove and replace. The mechanic would just be putting the old one back in if it passes the bench test. The pressure test can also be done in-situ, but it is not as accurate as the bench test.

New master cylinders should be bench bled before installation anyway. Then you have to pay for the bleed down of the entire brake system after the master cylinder is replaced (new or old).

When the master cylinder is new, and put in service, it will start to wear. ..."in time the master cylinder will get worse and not apply the pressure needed to stop the car properly."

True statement.

The question is, when will it be worse, and will you notice deterioration before the car actually fails to stop properly?

Yes, you should notice the braking getting worse as this happens. Until that happens, unless a mechanic can tell you some specific problem with the master cylinder, I would not replace the master cylinder.

Modern cars have two independent braking systems. In other words, there are two "halves" to the master cylinder. One typically works the front brake on one side of the car and the rear brake on the other side of the car, while the other "half" works the brakes on the other two wheels.

It would be very unusual for both to reach anything like the point of failure at the same time.

That's a good technical point.

Thanks!

All excellent replys. Another 2 cents is when bleeding the brakes by pumping the pedal to the floor, then holding it there while your buddy cracks the line is a good way to cause a master cylinder to fail. The piston has been happy for years just working in that one section. Now when the piston is moved all the way to the other end chances are that section is dirty, corroded and the seals are pushed back forth threw that bad section and get cut. Ever rebuild an old master cylinder before? You might get lucky and they bleed up ok. Most times they do. I've bought a few master cylinders for custermers after just changing pads and not being able to get a good pedal after that I'd rather eat the master cylinder than lose the customer. If it's an old car I might suggest a new one to be safe, as it is in there best interest. I use a pressure pot now. If unavailable, I only pump the pedal half way. I hope I explained my self well enough. Good Luck

Good point. I usually bleed regularly but for those who do it on a fail-only basis, they probably would have a lot of buildup and/or corrosion at full travel. Then it ruins the seal and drags some of that crap back down the cylinder.

Wow, did you ever leave yourself open with that one!

Someone who wasn't paying attention to the subject, might think you're talking about something other than brakes.

_{It is Friday, after all.}

That's what she said.

Oh. So the mechanic could have inadvertently broke the master cylinder. By pressing all the way down on the brake when bleeding the brake lines. They didn't charge us for bleeding and adjusting the brakes even though it took 1 1/2 hr. Maybe they felt bad about inadvertently breaking the master cylinder.

Boy, I never realized how difficult it was to be a car mechanic. Almost like being a Doctor with all this difficult diagnosing. Nothing is certain. You go to a Dr. he gives you a diagnosis. It may or may not be right. He gives you a medication. It may or may not help. You just keep going and hope someday he figures out your problem. I never go to Dr.'s although I respect them immensely

in time,the master seal will fail, and the car will dissolve into tiny particles. This statement is insufficient to guide any kind of safety program.

Master cylinders fail like an overloaded bridge does, which is very rarely catastrophically. They almost always leak, because a seal has failed. ABS complicates bleeding. I'm a shadetree mechanic, air in the lines is almost always the problem with mushy brakes. You could have a failing caliper, which generally causes pulling to one side, and again, often leaks.

If you read my previous post #5 there are examples of signs of wear, when I suggest that the master cylinder be changed.

Replacing the master cylinder, and following expert advice in general, would be prudent. One problem that might arise (not that I know anything about '94 Hondas) is the master cylinder seal failing because the bore gets out of round when hot. If you can avoid replacing it with an aluminum master cylinder (aluminum has a higher coefficient of expansion than steel) you might be better off.

I hope the $200.00 we will have to spend to get the master cylinder fixed will fix the problem. There doesn't seem to be a problem with the brakes now. But I hope the $200.00 we spend won't cause contaminants to get in the brake line or lead to another brake problem that we will be liable for. My husband and I don't like going to regular mechanics because our bills are always so high and then the problem doesn't get fixed. We did have a very excellent mechanic beforehand, a relative of a friend. He always got things 100%+++++ right, even the most difficult fixes like leaking gas tanks. But, alas, he is much in demand and can't work out of his home at this time. I of course don't know anything about cars but try to do the research.

We did successfully solve the carbon buildup in the 2004 honda after we spent $100.00 at the honda repair and went back twice with no help with the acceleration of the vehicle. The problem was solved by using the next higher up grade of gas. That helpful tip was a recommendation of a mechanic. Thank you so much for all the expertise and excellent advise. I am showing the comments to my husband so he can utilize them. Thank you very much.

Not to belabor the point but we have spent $600.00 on a sticky gas pedal with the mechanics not being able to fix the problem. and $500.00 on an air conditioning problem in two different cars, without the money resolving the problem. I really hope the $200.00 resolves our apprehension about the brakes. It was only supposed to cost $30.00 to get the brakes tightened and re bled. The brakes seem to be great after the aforementioned service was done, but since the shop didn't charge us, we also feel a sense of trust and gratitude towards the shop and we don't want our son to get into an accident.

If you are going to, in my mind, waste money on replacing parts that are working perfectly fine at this point in time, you might as well replace all of the slave cylinders for each wheel as well. May as well replace all of the brake lines, too. Throw in the booster and proportioning valve and you'll have a whole new hydraulic system.

The question is: Are we smarter than the boss at the repair shop who told us we need a master cylinder? Question 2: Would we want to jeopardize our son's safety if we knowingly don't replace the master cylinder after the repair shop told us to?

My husband says that there is no way to tell if the master cylinder is bad by looking at it, and the tests suggested by the persons commenting to this master cylinder problem on this forum don't seem to indicate that there is a fool proof way to tell if the master cylinder is bad by any tests.

It just seems fishy to me that you go to get the brakes re bled and tightened for $30.00 AND then there just happens to be an additional problem related to the brakes. And the brakes seem fine to me. The boss of the shop just came over after the work was done and applied the brakes and said you need a master cylinder. It just seems coincidental. Especially when I read on this site another person with a honda had a brake problem(brakes going to floor) AND he went from replacing the brake pads, bleeding and re bleeding the brake lines, checking the brake fluid etc. as the 1st plan of attack against the brakes not working. He seemed to indicate in his post that if the brakes were fixed he would not have to search any further for a problem with the brakes. His brakes WEREN'T FIXED. So then he addressed the issue of the possibility of the master cylinder or brake booster being bad.

If $200 gives you piece of mind, by all minds do it. Be aware that you can still have brake problems (I'm thinking of things like a hose or line breaking, or whatever).

Ask the mechanic why he thinks the master cylinder needs to be replaced.

The boss of the repair shop said the brakes went to the floor, but they don't. My husband and I are really killing the brakes of our other vehicle trying to ascertain whether there is a difference. I tend to be a person that just keeps trouble shooting and doesn't know when to stop. But I have saved a more easy going family from some dangers such as a leaking gas tank in another vehicle that no one would believe me when I kept telling them I smell gas!!!!!!!

Maybe the guy was pushing the clutch...just joking...or am I?

had EXACTLY the same problem with my VW Golf many years ago.. nothing to do with the brakes.. its the front brake discs.. they are worn. I have a VERY long story behind this which is WAY to boring.. but it cost the VW dealership THOUSANDS as they could not get it right even after 12 visits and 8 months of investigation by the dealership...

Replace the discs!!

I've seen that before. The thickness of the rotor (turned beyond specs) would not stop the pads before they reached their excursion limit giving a soft pedal. The calipers would retract to the set point, only to go through the next cycle the same way.

Interesting. But, for this poster, iiuc, the brakes were bled and there is no more soft pedal.

I just drove my husbands much newer honda around and stopped at about 10 stop signs or intersections. What a difference. You only have to tap on his brakes to get the vehicle to stop.

I thought you had to press harder on my son's brakes just because it was an older vehicle or just ?different. My son's 1994 honda brakes are not soft brakes (by that I mean the brakes are much improved since the mechanics re bled the brakes and adjusted the brakes) (one doesn't have to apply as much pressure as before), BUT they do not in any way have the fast reaction time my husband's brakes have. You barely tap the brakes and the car stops.

Does that mean the boss at the repair shop was right, and he just happened to coincidentally catch the bad master cylinder because he had to help pump the brakes while the other mechanic bled the brakes because the other mechanic pumping the brakes was needed elsewhere??? Or could there be another problem causing my son's brakes to not have the fast reaction time that my husband's much newer honda has, and then we will have to get something else fixed when the new master cylinder doesn't fix the problem. Thank you very much for all your help.

My husband says that there is no way to tell if the master cylinder is bad by looking at it, and the tests suggested by the persons commenting to this master cylinder problem on this forum don't seem to indicate that there is a fool proof way to tell if the master cylinder is bad by any tests.

Ozzb gave you some of the ways to test for a master cylinder that is starting to go bad. Another way is to back up slowly for a long stretch of road. The prolonged light applications of brake pressure followed by release, but not all the way released will usually show up a master cylinder that is only sealing when pressure is high.

My first reaction to the statements you have given us is that your family may have disconnected the vacuum line to the booster. Or in some other way limited the vacuum to the booster. That is the usual culprit when a pedal is high and hard, accompanied by poor breaking performance. If you hired mechanics and they did not spot this in 1.5 hours, what would you tell your customer? 1) They were too stupid to notice it. 2) The six times that you bled the brakes was wrong, but we did it correctly for free. 3) The tooth fairy left pixie dust on the brake pads.

Weather or not the master is starting to go is for you to test and decide. Good luck.

Hi there:

The Honda is nearly 10 yrs. old, and 90.00 is a good price for insurance. Brake fluid attracts and holds moisture, usually visually confirmed by a discoloration (turns dark). The higher the humidity in your area the quicker the fluid will deteriorate. Often when replacing brakes a tech will recommend flushing the system which replaces all the fluid and removes any air. Damage to Hydraulic components can occur due to contaminated fluid so a quick visual inspection (internally) of the rear cylinders and front calipers should be done. This can be done by a chemical test of the old fluid for Iron oxide contamination (most home mechanics don't have this capability.) The mileage (and humidity) is a good way to get a rough idea. Over 100k miles and average humidity above 50% will cause deterioration in all but very high tech brake systems. A Honda has a very basic system that is easy to maintain but subject to all the problems caused by contamination. I agree with some of the other posts on this topic about bleeding the air out of the system. Air will cause a soft pedal and longer pedal travel. It sounds like your problem has been cured, but once again replacing the master cylinder is cheap insurance.

∑undog, Automotive systems engineer (retired).