Master Cylinder

[bobss396]

Originally Posted by j cAT

I agree with bob replace master cylinder.... pedal to floor is master cylinder n/g.....why ? brake pedal pushed down too far damaging seals on master cylinder and don't forget bad,wrong or contaminated fluid... if pedal was spongy but did not go to floor I would say air.... this is bad master cylinder...

This is a common mistake made by pros too. I did a lot of brake work in one shop and we had a circle of people in the shop that we'd use to bleed brakes. Most of our work was bled with a power bleeder but we did the front calipers and the problem jobs the old fashioned way.

The person at the pedal has to be told how hard and what speed to push the pedal. The person on the bleeder does this and has to know how far to crack open the bleeder. Most of the time I just help a finger over the bleeder and left it open until that corner of the car was bled.

When you do over a few hundred brake jobs a year, you pick up on what works and gets the cars out so they don't come back!

Bob

[vgames33]

I went out this morning to try a gravity bleed, just for the hell of it. I put a clear hose on the right rear bleeder and opened it. A little fluid filled the first ince or two of hose (it was pointed up), and then nothing. I waited a few more seconds, and saw a few air bubbles escape. I tried lightly tapping on the caliper, but no more air came out. The fluid was coming out very slowly, and no air appeared to come out when I tried the other wheels. I still don't have much of a pedal, but it did feel a little bit stiffer.

I got my sister to pump the pedal for me, but I was unable to get any more results from a quick bleed of both rear wheels.

[bobss396]

Gravity bleeding gets you only so far, not very. I've never tried it in all the years I've done brakes. Bleeding brakes with a bum master cylinder only gives the person pushing the pedal a little exercise.

You also have to have a dialog going with the pedal-pumper, a simple "down" and "up" works fine. Keep the car doors open so they can hear you under the fender. Use "stay down" when you are closing the bleeder screw. You have to be in synch with each other or MORE air can be added to the system.

Good luck!

[vgames33]

Ok. I have one more trick left to try. On my '83 Toronado, I couldn't get the brakes bled for anything, and I replaced everything because I didn't know any better. I ended up using a syringe from work to pull fluid from the lines, rather than pumping. I don't know why it worked, but it did, so I'll try it. If that doesn't work, I'll put a master on it Saturday.

[j cAT]

Originally Posted by vgames33

Ok. I have one more trick left to try. On my '83 Toronado, I couldn't get the brakes bled for anything, and I replaced everything because I didn't know any better. I ended up using a syringe from work to pull fluid from the lines, rather than pumping. I don't know why it worked, but it did, so I'll try it. If that doesn't work, I'll put a master on it Saturday.

In addition to what was said here about brake bleeding I would like to add this....when replacing pads or calipers I always open bleed valve and then push caliper pistons back fully, this then removes the caliper piston fluid from system and then does not return the heat damaged fluid to master cylinder...this has always worked for me as I keep my vehicles a very long time and i have never had to replace a master cylinder or brake caliper....my first vehicle was in 1967 I am working on vehicle #4 now.....

[vgames33]

Well, I had to wait a week for the master to come in, but its been bench bled according to the Nissan FSM (hold your fingers over the ports and have someone else pump the pedal until no air comes out the reservoir) and installed. The car still has no pedal, so I'm assuming there's just more air trapped in there, although we're still getting nothing at the bleeders.

Is vacuum bleeding worth trying at this point?

Thanks for all the advice thus far.

[j cAT]

Originally Posted by vgames33

Well, I had to wait a week for the master to come in, but its been bench bled according to the Nissan FSM (hold your fingers over the ports and have someone else pump the pedal until no air comes out the reservoir) and installed. The car still has no pedal, so I'm assuming there's just more air trapped in there, although we're still getting nothing at the bleeders.

Is vacuum bleeding worth trying at this point?

Thanks for all the advice thus far.

something is wrong here ......can you describe how you installed this master cylinder? like is the master cylinder connected to the brake pedal??

[vgames33]

The FSM said to bolt the master to the brake booster, but not hook up any lines. It then said to plug the ports with my fingers while someone else pumped the pedal until air no longer came out (I went until the air bubbles coming out of the reservoir). We did have trouble with one line threading in, and I think it may be sucking in air. I'm going to disconnect it and see if anything is wrong.

If any air has been sucked in, is there any way to bleed the master without unhooking all the lines? Also, the kit that came with it did not work (the plugs didn't screw in and the hoses wouldn't fit on the plugs).

[vgames33]

Well, we got the bleed kit that came with the master to work (after a few modifications) and bled until there was no air coming from the lines. We had a good pedal after just hooking it up, but went to each wheel a few more times to make sure - no air.

The pedal was nice and stiff until the engine was started, then it went straight to the floor again. After shutting it off, it feels like there is a little less pedal than before, but its still nice and stiff. I see no leaks, nor do I hear any hissing.

[j cAT]

Originally Posted by vgames33

Well, we got the bleed kit that came with the master to work (after a few modifications) and bled until there was no air coming from the lines. We had a good pedal after just hooking it up, but went to each wheel a few more times to make sure - no air.

The pedal was nice and stiff until the engine was started, then it went straight to the floor again. After shutting it off, it feels like there is a little less pedal than before, but its still nice and stiff. I see no leaks, nor do I hear any hissing.

after bleeding it is not unusual for pedal to go to floor as the vacuum that was in booster needs to build up..... next check booster vacuum lines for any leaks....

[MobileMom]

Originally Posted by vgames33

After changing both rear calipers, pads, and rotors, I cannot get the pedal on my sister's Maxima to stay up. I can bleed everything, get a good pedal, let it sit, and then the pedal is low again. I've been told to change the master cylinder, but I'd like a second opinion since its not my money.

The car is a '92 Maxima SE with 4 wheel disk brakes and no ABS. The fluid is new in the entire system, and it has been through about 3 quarts of fluid since I started bleeding. The pedal is high but spongey with the car off. With the car running, the pedal is about 2/3 of the way to the floor and still spongey. It will sink after only a few minutes of sitting.

Hey there. I am hoping I might be able to give you a slighty more indepth reply to your question. After reading the replies between you and the others, I think I have enough information. lol. As far as the master cylinder goes, it very well could be that. The most obvious symptom of a blown master cylinder, is that the pedal goes all the way down. Now, I'm and not saying it goes most of the way down, it goes ALL the way down, till its just about touching the floor of the car. Your car will most likely still have drum brakes in the rear. Have you noticed any fluid leaking out of it? Either when the car has sat a while, or when it has been running? A blown master cylinder usually just lets in air, and you a losing fluid. That fluid is going somewhere. Can you find it? Even for as much as you are losing, it could only be a small leak, so you might have to watch for it. Park the car on dry concrete, try letting it sit without running for a couple hours, than try letting it sit for a while when its running, preferrably warmed up.

Now, if I am right about the car having rear drum brakes, it sounds to me like you have a bad Wheel Cylinder. And you might have to go as far as pulling the drum brakes off to fully see the leak.

If you do not have rear drum brakes, than in that case I would agree with others suggestions of a master cylinder.

Another thing that would be wise to look for, is a brake in any of the lines. You have brake lines that start at the master cylinder, and follow down under the car to each of the brakes on your car. Get out a flash light and follow the brake lines as best you can. You might need to jack up the car to get a true look at them. But look them over thoroughly.

It is wise to seek a second opinion on any pricey car repairs. A lot of mechanics will give you a "quick" quote to sell you on the repair. If they did not look at it for at least an hour, then they did not look thoroughly enough.

You can easily get an idea of the correct diagnosis for your car by going through a process of elimination (POE), which is what most experienced mechanics go through, and it usually doesnt include a computer or any tools to do that.

If your looking for anymore information, this web site is an awesome help
http://www.troubleshooters.com/tautomot.htm
and so it this one
http://www1.autozone.com/UseCase,S00...tInTheZone.htm

They both have great easy trouble shooting guides.

If you'd like anymore information from me, check out my page at
http://www.myspace.com/acceleratedautomotive

Good Luck!

[72chevelleOhio]

This is wrong, and I'm a bad person. However, I am going to he'll anyway so.... ....

Originally Posted by MobileMom

If you'd like anymore information from me

NO!

[mrbreezeet1]

know this is an old(er) thread, but what did you come up with? I just found/joined this forum.
Question, was the pedal OK before you replaced the rear parts?
I wanted to comment that on these type calipers, where the e-brake acts on the piston, and when replacing the rear pads, that require you to wind in the piston, sometimes the piston needs to be wound out to where there is minimal clearance between the piston and the pad/rotor.
Sometimes the piston is wound too far in, and this will give you your low pedal.

Another thing I have ran into, and you would not think it was an issue, but are the front caliper sliders nice and free?
Sometimes this can give you a low/spongy pedal.
Tony

[mrbreezeet1]

Originally Posted by bobss396

Gravity bleeding gets you only so far, not very. I've never tried it in all the years I've done brakes. Good luck!

YMMV, but having to work alone at home a lot of times, I have got a 100% full brake pedal from gravity bleeding.
A few times have then found a "helper" but have not gotten any more air from the system.
Tony

[vgames33]

Sorry, I never posted when I found out what the problem was. The drivers side rear caliper was defective. It started visibly leaking after a while.