Need help fast with brakes.

[nolo]

91 Honda Accord without ABS


I replaced the master cylinder in my accord. I bled the brakes with a friend. He would push on the brakes and then I would open the bleeder screw. Before he released pressure, I would tighten the screw back up. I think I'm doing the bleeding part right. I didn't see anymore air bubbles coming out of any lines, but my brake pedal is worse than when I started. I think I have air in the master cylinder still. They gave me two plastic threaded nuts and two hoses to bench bleed it. I stripped one of the plastic nuts, so I think I didn't get all the air out of the master cylinder. I'm guessing no matter how much bleeding one does you still can't get the air out of the master cylinder if you didn't bench bleed the master cylinder correctly. I already threw away those plastic nuts. Is there a way to bleed the master cylinder installed in the vehicle without those nuts? Or, where can I buy just those bench bleeding accessories?

[mpumas]

I gather the plugs that you mention screw in to where the brake lines attach to the master cylinder, correct? If so, you can just release the brake line nuts at the master cylinder and bleed off the pressure and air after you pump up the master cylinder. Do one at a time, then bleed the brake lines again.

[nolo]

Originally Posted by mpumas

I gather the plugs that you mention screw in to where the brake lines attach to the master cylinder, correct? If so, you can just release the brake line nuts at the master cylinder and bleed off the pressure and air after you pump up the master cylinder. Do one at a time, then bleed the brake lines again.

Yeah, it is the two lines feeding into the MC. Do you know what size lines they are on a Honda accord? I know it is a hair larger than 3/16in, but I need one for an import.

[nolo]

I think I'm doing something wrong with replacing the MC. I bench bled the MC without a problem, but I don't feel resistence on the brake pedal until half way down. I'm guessing I need to adjust the push rod in the MC. How can I do this without buying expensive tools? Or, is there something else I should be looking for? I need help fast. Do you guys usually adjust the push rod on the MC when you replaced them?

[jeffcoslacker]

I've worked on cars for over twenty years and have NEVER had to adjust one...and when I've heard of people doing it, it never worked right again...I would NOT mess with it, you've still got hydraulic issues.

You know you can't bottom out the piston when bleeding it, right? That can damage the seals and give you a lousy pedal.

Even though it's not normal, rather than bench bleed, I install the master cylinder, leave the lines off, then attach the bleeder kit and fill it with fluid. Then I sit in the car and slowly stroke the pedal about halfway...just keep doing it, you'll actually be able to feel the air bubbles through the pedal...and even though you don't have any hydraulic load on the cylinder, you'll feel the pedal height build and gain resistance as it bleeds. When you feel good resistance right from the top of the stroke, you're done...hook up the lines, pump it and see how it feels, then go for a drive and check it...

[nolo]

Originally Posted by jeffcoslacker

I've worked on cars for over twenty years and have NEVER had to adjust one...and when I've heard of people doing it, it never worked right again...I would NOT mess with it, you've still got hydraulic issues.

You know you can't bottom out the piston when bleeding it, right? That can damage the seals and give you a lousy pedal.

Even though it's not normal, rather than bench bleed, I install the master cylinder, leave the lines off, then attach the bleeder kit and fill it with fluid. Then I sit in the car and slowly stroke the pedal about halfway...just keep doing it, you'll actually be able to feel the air bubbles through the pedal...and even though you don't have any hydraulic load on the cylinder, you'll feel the pedal height build and gain resistance as it bleeds. When you feel good resistance right from the top of the stroke, you're done...hook up the lines, pump it and see how it feels, then go for a drive and check it...

I bought a cheap re manufactured one from Advanced Auto Parts. When you say bottom out, do you mean by pushing the rod all the way down with a screwdriver? Do you bleed your brakes with the car on or off? I have been bleeding with the engine off. I get resistance half way down and then have a friend open the bleeder screw. He then tightens it and I release the pedal. We do this for all for tires. It feels like I'm only getting half pedal through out the process. After I'm done I start the car and press the pedal. It sinks all the way to the floor with no resistance. This is probably because of the assist by the brake booster. Right??? I don't know what to do at this point. With the engine off (after bleeding), I can't get the brakes to stiffen like normal. Normally, when I press the brakes multiple times with the engine off, it will get extremely hard to push. Should I get a new MC? Can you give me something I can try? Where do you buy your MC from?

[jeffcoslacker]

Yes, that's what I meant, whether bench bleeding or bleeding the car, you never want to hit bottom, it's hard on the master cylinder because it causes the piston to overtravel it's normal stroke and get into parts of the bore that may not be as polished or could have an extreme taper, which tears at the pistons' seals.

When bleeding the car's brakes, you want to initially pump the pedal rapidly several times, then hold partway down. The person opening the bleeder should open it and close it quickly, long before the pedal travels very far...the idea being you want to have it closed BEFORE the pedal stops dropping....otherwise you'll bottom out, and if you are just sitting there with the pedal on the floor waiting for them to close the bleeder, you are inadvertantly making small movements with the pedal that are sucking small amounts of air back in, as well as smashing the piston against it's overtravel spring and hurting the seals. You want the bleeder opened and closed in a quick 1-2 movement while the pedal is still dropping, not wait until it's down and then close it.

Are you bleeding at all wheels? FWD cars use a split-diagonal brake system, this means one circuit operates the left front and right rear wheel, the other the right front and left rear. You want to bleed in the following order, right rear, left rear, right front, left front. This assures you are bleeding the longest line first, and working back towards the master cylinder. Otherwise, you could just be pushing the same air all over through the system...

If I were you, I'd open the master cylinder lid, and fill to the top. Leave the cap off. Take the rear bleeder screws completely out of the wheel cylinders. Watch the fluid coming from them as it gravity bleeds....and keep the master full of fluid. When they begin draining a solid stream of clean fluid with no air, put the bleeders back in tight, then move to the front and do the same, remove the bleeders, let it flow, keep it topped off, replace the bleeders when you have a good stream of clean fluid without air. Sometimes if there is a large amount of air in there, this will get it moving...air is compressible, unlike fluid, so when you pump on it with the pedal, it just squeezes up and then expands when you release, without moving much. But if you allow for a slow flow, it will work it's way either out to a bleeder or back through the line and out the open MC port (because the pedal is up).

Once you have seen good fluid at all four wheels, and all the bleeders are back in and tight, you should have a pretty good pedal...I'll usually tap each caliper/wheel cylinder lightly with a mallet to dislodge any air bubbles that may be clinging to insde surfaces and make them float to the bleeder, and open one more time, there may be a small bubble or two, or nothing at all, depending. then just for good measure, I'd open the lines slightly at the master cylinder and see if any bubbles escape there....if not, it should be ready to drive now.

I worked alone in a shop at night for 12 years with nobody to help me bleed brakes, and this has always worked...I haven't left on on the rack yet for lack of brakes...

If you just simply can't get a good pedal, just take that MC back to Advance...they'll defect it out and give you another, just tell them you bled it correctly but it won't build pedal height...and start over, doing it like I said, install it first, leave the lines off, and put the bench bleed tubes on it, then bleed it with the pedal, taking care not to bottom, and feeling what the air feels like as it purges and also being able to feel the pedal stroke firm up so you know it's happening. Then put the lines on, and assuming you already did the gravity bleed at the wheels, you should have all hella brake pedal now...

Yes the pedal feels different with the car running, the booster's assist negates the little bit of pedal you have, making it hit the floor and feel like there's nothing there.....I don't bleed with the motor running...like I said, the harder you push air in a hydraulic system, the more it wants to just compress rather than move....

An old trick to tell if you still had air in the system was to rapidly pump the pedal several times, then hold, and have someone watch the resevoir when you release the pedal abruptly...doing that compresses any air very tightly, and when you release the pedal, the compressed air rebounds back to original uncompressed volume so violently, it shoots a large forceful shot of fluid back through the return port into the resevoir....instead of the gentle rippling disturbance you see when fluid returns under normal fluid pressures...but the design of the Honda's MC makes this difficult to see...

[jeffcoslacker]

PS...

I have gone through as many as three rebuilt MC's from discount auto parts stores before getting one that worked correctly...it's not that uncommon...that's why we don't use discount auto parts at the shop...too much time wasted in problems like this or comebacks later for defect parts...

[jeffcoslacker]

Just for reference, in case you are wondering about the split-diagonal layout...

In RWD cars, the brake load was something like 65/35 bias to the front, front did most of the work, but the rear also had to brake the drive wheels and there was additional weight of a differential and axle back there, which requires extra effort...

In FWD cars, the split is more like 90/10 front bias, because all the wieght of the engine and tranny resides over the front wheels, and it's stopping the drive wheels as well...the rear brakes actually have very little to do on a FWD car...

So with a front/rear split like the old cars, if you lost the front circuit to hydraulic failure, you still had a reasonable amount of stopping power in the rear....but in a FWD car, if you lost the front circuit, you are left with 10% in the rear, very dangerous situation. So by implementing the split diagonal layout, a loss of one circuit still leaves you with one front and one rear brake, a safer alternative...you'd think the car would turn in circles when braking in this scenario, but it doesn't, the rear wheel's grab offsets the front wheel pull pretty well, and the driver is aware something is wrong, but still has nominal stopping power, and can be safely driven to a repair shop...

[jgr7]

One more trick if you have someone with you that you aren't sure is going to push the pedal slowly and not to the bottom (wife-girlfriend) put a large book on the floor boards under the pedal and just have them push down to the book slow and hard and hold tight until you get the bleed screw closed.
Jeff

[nolo]

OK... I went and returned the other MC and got a new one. Well, I was reading the instructions and it says that if the rod is too short the booster will make a groaning noise. That is what I was getting with the last MC. I'm guessing I need to adjust the rod to make it a little longer???? I'm going to do my regular process right now, but if it doesn't work, I think I need to either buy a higher quality MC or adjust the rod. What do you think?

[nolo]

I think I will have to adjust the push rod to get this to work. I want to just buy an OEM instead, but the dealerships do not have them in stock in my area. What is a good brand MC that would be OEM specs from a local parts house?

[n8zdogg]

Your autozone part is probably a reman part, brake master cylinders are pretty specific. I've had two of them come from autozone that were bad right out of the box. I've been getting the my brake parts at NAPA since and haven't had a problem. Note, if you bottom the piston when bence bleeding the master cylinder, you may have torn the seal and the cylinder is now bad, I have always bench bled at about half stroke if that makes sense.

[nolo]

Originally Posted by n8zdogg

Your autozone part is probably a reman part, brake master cylinders are pretty specific. I've had two of them come from autozone that were bad right out of the box. I've been getting the my brake parts at NAPA since and haven't had a problem. Note, if you bottom the piston when bence bleeding the master cylinder, you may have torn the seal and the cylinder is now bad, I have always bench bled at about half stroke if that makes sense.

Is adler the company that makes the master cylinder for Honda?

[jeffcoslacker]

I think OE supplier to Honda is Aisin, but I can't swear to it.

I still don't see why you'd have to adjust the pushrod, but if you do and you get it working, beware of symptoms of brake drag from overlength rod adjustment, will burn the linings and even cause hydraulic failure in extreme cases...