dwllama

Hi all,

This has been an issue for a while but when it was colder out it wasn't so obvious and I wondered if maybe I was even imagining it.

History is this:
Last december I got my rear brakes done (drum brakes). The mechanic changed the shoes and, because when he took the old shoes off one of the wheel cylinders popped open, he changed both wheel cylinders also. Brakes were reassembled and bled He had me helping (I was the one pumping the pedal) and his instructions were confusing at first, so it took just about forever. I think I may have let the pedal go to the floor once or twice before I knew how far down I could push it.

When everything was reassembled and after he test drove the car real quick I took it home. Trying to brake to avoid someone in heavy traffic going down a hill I found my brake response MUCH later than I expected, pedal traveled a lot farther than I thought it should, I called him and he said it just needed to adjust.

During december I partly got used to that behavior and it also improved as the brakes adjusted themselves. Throughout the winter as it was cold the brakes seemed OK although they never really stopped as well as before the brake job was done, especially with a load in the car (passengers, stuff, whatever)

Now that it's warmed up i'm definitely having trouble with it. Almost rear ended people a couple times because the car just doesn't slow down like I expect it to. Actually hit the floor with the pedal just trying to stop in normal traffic at a light.

What else I notice:
usually not too bad in the morning when I start the car. Worst in the warmer part of the day.
Pedal is soft and almost pressureless for the first 1/3 or so, doesnt seem to noticeably slow the car at all until I get past that
doesn't get really firm until (usually) the bottom 1/3, sometimes worse than that.
Edit: Parking brake is solid also.

With the car off I can pump the brake pedal a few times and get it to be solid and firm (except it still moves just a little bit first)
With the car running (in park) it does not firm up after pumping it for 30 seconds or so.
Pressure does not seem to go down, once I find where it stops and hold it, it stays there.

I also noticed when I was standing outside the car with a mechanic pumping the brakes, in park, the sound of the idle changed as he depressed the pedal.


I had two mechanics look at the car today, first the guy that did the brakes in the first place. He started the car, played with the pedal, and told me it was probably the master cylinder. (How often do brake master cylinders really go out on these cars anyway? It's got about 201k on it now)

Second a guy I met through my job that I've heard generally high opinions of, he didn't think anything was wrong when he first got in the car, but then he drove it around the block twice and told me it wasn't bled well enough and needs to be bled again.
Edit: Front brakes absolutely worked when he was test driving it - demonstrated in front of me, braked hard enough to chirp the tires, front wheels were completely stopped, rear wheels were just along for the ride.


So my question is really, if the car is still stopping, is there any way to tell between brakes that need bled and a master cylinder going bad? (FYI: there is no visible leakage under the steering column at the back of the brake pedal and the level of brake fluid in the reservoir has not changed in the slightest since december) Is there any more testing or anything else I can try to see if they just need bled or if I should actually go and spend a couple hundred to buy a new master cylinder and get it installed? Would brake booster issues possibly cause symptoms like these?

I know I wrote a book about it (I try to put all the imformation I can think of in the first post!) but I would really appreciate any help on this! I want to trust my brakes again!


By the way, this is the car listed on the side - 96 accord LX, f22b2

Thanks!!

MAD_MIKE

Even if the wheel cylinders did not pop apart you always replace the wheel cylinders when you replace the rear shoes. Simply when the shoes wear the pistons and cups move out. When you install new shoes it will push the cups and pistons back into an area the seals have not traveled on, and there can be corrosion and crud that will prevent the cups from sealing. This is important to keep note of in a moment.
Since you normally do not push the pedal that far the seals in the MC probably rode over a section of the cylinder that is rough, damaging the seals.
Drums can be adjusted if you back up and brake. But this may not work if the self adjusters are worn or seized. It is good practice to clean and lubricate the self adjusters when replacing the shoes.
Sounds like either the rear drums are way out of adjustment, or the seals in the MC are failing.
Seems like an adjustment issue with the drums. With the wheel off is it easy to spin the rear wheels with no drag on the drums? If so you want the drums to have a slight amount of drag. Don't worry, after a few miles they will self clearance, this will give the ideal amount of clearance between shoe and drum. Your brakes will feel like how they once were. Solid.
That is how the Power Assist is supposed to work
Car off, you should be able to pump the pedal 2-3 times before the assist goes away. With the engine on, the pedal should be softer. That is the assist.
An easy test.
With the car off pump the pedal til there is no more assist.
With your foot on the brake pedal start the car.
The pedal should drop about ~1"
This indicates the booster is working fine.
The booster is charged by manifold vacuum. If you pump the pedal several times in quick succession the engine will be affected by this draw. It's like a large quick vacuum leak everytime the booster needs to be charged. Pump the pedal several times and this will have the same effect as a vacuum leak.

When there are changes to the system this will have an affect.
Three things that can kill an older MC.

1. Over stroking, or flooring the pedal, will cause the seals to ride on an area of the bore that has not been used. The surface will be rough and can damage the seals. This will cause random

2. New brake fluid. When brake fluid is not changed annually the brake fluids properties change. This also affects the seals in the system. They become acclimated to the old fluid. Also old contaminated fluid can be compressed, new fluid will not be as compressible and can attain higher system pressures.

3. Killing the brake pedal. Typically the pressure that the system makes is well below 1000psi. Normal hard braking may get you around 600psi. But if after bleeding the brakes someone steps on the pedal as hard as they can, they can easily generate 1200psi. With older seals this can fail them.

It is good practice to flush the brake fluid at least every two years, and to change it with OEM fluid. Unless you have made changes and require better braking, Motul, Ford Racing, Wilwood, or Castrol LMA brake fluid.
A complete bleeding of the system should have been done, half assing it is silly if that is what happened. I suspect the drums need adjustment as well.
Keep in mind the system on FWD cars is diagonally split. Bleed; Passenger rear, Driver Front, Driver Rear, Passenger Front.
You never want the rears to lock before the fronts. If the rear wheels locked up first this would put the car into a spin. As it is most manufacturers make the cars braking front biased just to prevent the typical operator to not put the car into a spin during hard braking.
In your case there are a few factors that need to be addressed.
Verify that the rear drums are properly adjusted.
With the engine off, pump the pedal to get rid of the assist. Does the pedal feel firm or spongy? If firm the fluid is most likely fine. If spongy there is air in the system.
As for leakage, the MC can have an internal leak. The seals for the pistons inside the MC may have failed. This would allow the pedal to go to the floor with no resistance.
Boosters are very simple. They either work or they don't.
Thank you for posting as much info as you have. It makes if far easier to diagnose while arm chair quarterbacking.

zottic

Mad Mike...That was great information, I will refer to it when I do my brakes.

dwllama

I'll write a more in depth reply in the morning, but for the moment I just wanted to provide a bit of additional information (I'm SO glad the previous owners kept their service records for this vehicle!!!) in case it is relevant:

Brake master cylinder was replaced with OEM in august 2007. Brake fluid was last flushed prior to me owning the vehicle (in other words, prior to my service last december) in May of 2009.

dwllama

Solid brakes again - wouldn't that be nice! Will have to test with the brake drums when I get the chance. Is it still possible to be an adjustment issue if the parking brake seems to set well? The parking brake sets solidly pretty quickly (no more than 3 or 4 clicks up).

Do these still apply to a cylinder that's turned out to be not even 5 years old? Also, the brake fluid was flushed roughly every 2 years (at least, in 09 and '11 now) since the master cylinder was replaced (in 07).

Also, I don't think you finished your statement on #1. I'm guessing you meant something along the lines of random failures or leaks?

3: On the way home from having the brake job done I did end up hitting the brakes pretty hard once before I realized they weren't as ready as I expected them. Then again I think I'm a lot more gentle and timid about abusing my car than most people.... so "pretty hard" for me is probably not as much pressure as it is for some folks :D

I generally agree... if it was half assed I can understand WHY (given that he was having a really bad day and the whole thing took hours longer than it should have) but that doesn't mean it shouldn't have been done right. I probably will get the brakes re-bled this afternoon after work, I'm curious to see if it will change anything.

When I pumped the pedal with the engine off, it travels a little bit initially, and then is very firm. This may mean I'll be wasting my time if I get the brakes bled this afternoon but ... oh well, it still seems like the best place to start. If I do get the chance, I'll have the guy check the drum adjustment when it's off the ground also.

Sometimes it seems like people don't want to read my books when I ask for help and I get few or no useful answers Then again, sometimes I think about stuff way too much!

Thanks very much for your reply.

MAD_MIKE

I was going to mention this but did not want to flood/cascade you with too much.
http://static.ddmcdn.com/flash/master-brake.swf
Click on the red arrow.
Note how the secondary piston does not make physical contact, it's hydraulically connected, with the primary one which is in physical contact with the pedal pushrod.

Now if there was a leak or failure in the secondary piston, it would not be able to do any work. And the primary piston would have to do the work of both pistons. This GIF shows the failure of the primary, but note the pistons now make actual contact.
http://static.ddmcdn.com/flash/master-brake-leak.swf

This may account for the 1/3 travel of 'nothing', simply the pistons effective volume displacement is now halved.
If it was over stroked, and the fluid is over two years old. Yes. When it comes to brakes you cannot have presumptions about the system.
Correct. vBulletin has been screwing with my postings as of late. If the pedal is consistently low then there is most likely a failure in one of the circuits.

Perception can also be a mother****er. Although in your case I do not believe you *think* there is a difference, but that there is actually some kind of failure.
If they were bled correct the first time, even after the snafu, I think that probably the over stroking did the piston seals in on the MC.
The problem with checking brakes, is often the owner will be used to the brakes with the engine on. Normally there is no reason to depress the pedal with the engine off/car parked. So the pedal feel can be off and/or confusing when going from 'normal' to 'bleeding' to after the fact. That whole perception thing.
The more initial information, the less likely for anything to be incorrectly interpreted. Brakes are secondary to the great automotive 'mysteries' after automatic transmissions.

And check out this pdf. 3507 pdf

dwllama

I'm guessing the brakes were not bled correctly the first time. I'll give it a few days to a week to find out, but yesterday afternoon I had the brakes bled (he gravity bled them) and the drums adjusted in the back. The guy I took it to was also amazed that the mechanic that had done the brakes to begin with hadnt turned or even scuffed the inside of the drums..

Anyway, after doing that, the car actually stops again (awesome) and seems to be fixed. I'm very hopeful. As long as it doesnt start doing anything weird again..

the brakes never seemed "right" after they were done in december, it just wasn't significant enough that I was sure I wasn't imagining it, until warmer weather.


BTW, thanks for the flash links, it's always nice to have a visual demonstration!

Bad_dude

Unless the drums are too thin over time or not round and making good contact with the shoes, Honda does not recommend to turn nor scuff the drums.

dwllama

Ok - is there a reason why that you know of? They still seem to be working just fine at least

dwllama

I know this is a ridiculously ancient thread but I wanted to update in case it came up on anybody's search about any similar problems. Unfortunately I wrecked the car over a year ago 😭 tried to dodge somebody changing lanes into me at 65+ and couldn't bring the car under control before ending up face first in a concrete barrier. Anyway, the master cyclinder was completely fine, the brakes worked pretty good after that guy bled the drums but never quite as well as I expected, until I finally did a full system flush with new (Honda) fluid in 2014, after which they were perfect as long as I had the car.