probs with brakes

[driftmunky]

my pedal goes almost all the way to the floor before it starts to work. i don't think anything is leaking cuz i always check the brake fluid level and it never goes down. i brought my car to the local z shop and he took it for a drive and said that's it's probably my brake booster. he swapped it out with a used one , and he said it brakes way better now. i kinda disagree, it is slightly different but pretty much the same. now i'm no mechanic but isn't there some way the mechanic could've inspected the brake booster, master cylinder, or calipers to see what the problem was before he changed my brake booster? he just assumed it was the brake booster and changed it. anyways, i wasn't too happy with that cuz i spent money and now it's still the same.

i was thinking it was the master cylinder. i was thinking of buying a master cylinder off ebay for my car(71 240z) but the mechanic said it's not good cuz it may not be the right one and i should buy a new master cylinder from nissan. the one from nissan costs $600CDN i think. if i buy one off ebay is there anything i should check or look for to make sure it fits my car?

[2ManyZs]

You can get a new master cylinder for your 71 from MSA for a little under 200 bucks (142.95 US in their new catalog). The 70-71 master is different from the later ones in that the reservoirs are reversed. Should be a few other suppliers that can supply one, might possibly try Napa or one of the chain auto stores, might save a few bucks. Or if you are so inclined, you could buy the cheaper 72-on master and then reverse the lines, little more work that way but with a tubing bender and some care it's possible.

For a couple other things to check, first verify you have no leaks. One of the main areas for leaks is in the rear wheel cylinders. The only good way to check them is to pull the rear drums, could be a pain to do, but it's the only sure way to check them.

Second, check your pads and shoes to see if they might be worn to the point where they really ought to be replaced. One trick is to pull up on the emergency brake one click at a time and see if the brake pedal becomes "harder", if it does, it's time to replace shoes for sure, and possibly pads.....

Third, if it hasn't been done in a while, you could try a proper bleeding, starting with the master cylinder, then moving to the wheel the furthest from the master cylinder and working your way to the left front as the last one (RR-LR-RF-LF).

I would try all these things first, and then if it doesn't help, then change the master cylinder as it would be one of the only things left that could cause your problem.

[driftmunky]

i'm pretty sure nothings leaking as i check the brake fluid and it's always the same...thanks for the info..:classic:

[Daniel]

2mz's could you please explain the logic of step #2 "trick" so my little brain can understand it? Thanks Daniel

[St.stephen]

In addition to what 2manyZ's said, please check the condition of all the rubber lines on the brakes. A collapsing rubber line under pressure will cause the same condition.

daniel, the technique 2 many is describing is that by slowly utilizing the e brake what you are doing is spreading the shoes closer to the drum. When you apply the brakes, the shoes have less distance to travel therefore giving you more pedal "pressure".

Honestly, i don;t think it was your vaccum booster. I agree with 2many...put the car up on stands and start getting dirty. Give the rear wheel cylindars a good once over and try bleeding the system before getting into renewal.

When was the last time your entire brake system was serviced??

[2ManyZs]

Well Daniel, St. Stephen has already explained it. It was a trick we used when racing, as the fluid got hot and the pedal started getting a bit soft, pulling on the e-brake would tighten the rear brakes and give you a stiffer pedal. Hard to heel and toe when the brake pedal was going almost all the way to the floor. Didn't really give you any better brakes, but it made you "think" you did....:cross-eye

[St.stephen]

driftmunky.... one other thing, you said you were considering purchasing a master cylindar off ebay....

I can be rest-assured that you are looking for a new one correct??

[driftmunky]

yes i was looking at a new one on ebay, but i will bleed the brakes first and check the brake lines. hopefully that will solve the problem.

thanks for the help guys

[billcapp]

I don't know why you wouldn't consider a rebuild kit for the master. They are available at a very reasonable cost ($10) US. When the master begins giving problems, it is usually the rubber seals becoming worn. Not too likely the inside walls of the master wearing very much (even at 30 years old).

Hope this opens another avenue to repair.

[hmsports]

I tried to rebuild my 71's master cylinder and ended up buying a '72 and swapping my lines. I couldn't get the rear shaft out of the cylinder. Worked on it for quite a long time -- over several days. Here's the picture of the line swap...

I used the original lines, just swapped them and carefully adjusted their fit by hand.

[Daniel]

I must be missing something.I would expect the brake pedal to get become harder when the e-brake was pulled.How does the fact that it does mean you have worn shoes?2mz's post reads if it gets pedal gets harder you need shoes.huh?? Daniel

[2ManyZs]

Daniel, it could mean two things in respect to the rear brakes. Either the shoes are well worn and/or your brake adjuster wheels are not working on the rear cylinder....Having to manually adjust the rear brakes with the E-brake is not the solution to the problem, only an easy way to see if you need to check the brakes, easy to do while driving, but it won't solve the problem....

Sorry to misleading, it's only used as a means to see if the brakes work better after a manual "adjustment". If the pedal gets harder when you ratchet the E-brake up a notch or two while driving only indicates that you need to remove the drums and check your shoes and/or brake cylinders.

When racing, and the fluid is getting hot and the pedal is getting soft, it will help bring the pedal back up some, but if you continue to run the car like that, it will burn up the rear shoes as they will be adjusted too tight.