rx_rotary

i need some help! when i first push my brake pedal it goes to the floor and barely brakes, but if i pump it once the pedal feels ok.
i also tried bleeding them, didnt help.
is it the master cylinder or the brake booster?

Pele

iTrader: (28)

Test your booster by doing this:

Turn the car off. Pump the brakes. The pedal should be high and hard. Start the engine while holding the pedal. The pedal should sink down a bit.

Let the pedal up. Blip the throttle a bit and shut the car off. Wait one minute. Press the brake pedal. It should feel easy, as if the car was running. Pump the brakes. The pedal should get harder and higher.

If either test fails, check the vacuum line from the booster to the engine. Also test the one way check valve in that line.

I doubt it's your booster, It's probably a seal in your master cylinder.

Take the cap off your master cylinder. Observe as you have an assistant in the car apply the brakes. (Be careful doing this. Sometimes they have to be applied hard to notice it, but fluid will splash.)

As the pedal is first hit, there should be a spurt of fluid from a port on the bottom of the resivour. Then the fluid level should drop a little. (VERY little. You probably won't notice.)

You may also want to gravity bleed the system. It's slow, but does a much better job if you have to bleed the brakes by yourself than pumping the brakes.

piston pounder

I agree the booster is not the problem!. You could have an internal leak in your master cyl. or an external leak somewhere. But also check your rear brake adjustment. If they are out of adjustment you will have a low pedal also!. If the booster was bad your brakes would feel really hard(no asist).

rx_rotary

thanx for the help!
im almost positive its the master cyl.
just in case it is the rear adj. how do i adjust them?
i have a 79.

o yeah one more ? my e-brake dosent grab.i looked under the car and had my bro pull up in down the cable is working.took the drum off the brakes expand when he pulls it. any ideas?

thanx again for the help.

piston pounder

Rear brakes are definetly out of adjustment but you could still have a leak somewhere!. Im not sure if the 79 had "star" adjusters or not so get a manual and read up!. If they do have star adjusters it very easy!.
P.s. after you adjust them your e brake will now hold!.

yayarx7

MOJO, my 80, has star adjusters.(for now anyway)

If that helps.

fastrotaries

NEVER trust a man whose car is the same color as his best friend.

yayarx7

OK you are officially NOT my best friend.

There, better?

Pele

iTrader: (28)

Take the drum off. You'll see a star wheel with a lever on it. It's usually on a pole that spans between the two shoes.

(I've never had an RX-7 with drum brakes, Can't be too specific, but this is a typical setup for any drum brake system.)

Turn the star wheel. It's threded, so it will push the shoes outwards.

After two or three turns, try to put the drum back on... If it fits easily, take it off and repeat. If it wont fit or is VERY hard to fit, turn the wheel the opposite direction One turn. Then put the drum back on.

The drum should turn somewhat freely, without the brakes dragging, but there should be some light contact when the brakes are not applied. If the drum is freewheeling, it's too loose. If the brakes are dragging, then they are too tight. You should have a hole in the backing plate where you can turn the star wheel with the drum on for final adjustment.

If the star wheel is hard to turn or if it's obviously rusted, you may want to dismantle the brake setup to clean and lubricate things. Leave one side assembled to reference if you forget how it goes together. There are many springs and some look exactly the same, but won't work if they're in the wrong position...

You may want to replace the hardware and springs. You will be looking for a hardware or "Combi" Kit and a self adjuster kit at your auto parts store. Don't be like me and have this dialogue from when I did the brakes on my Honda:

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Me: "Hey. I need some brake parts for my Honda."

Them: "What kinda Honda?"

Me: "1985 Civic Wagon, 4 wheel drive"

Them: *using computer* "Okay,sir, What do you need?"

Me: "I need some shoes, Bendix or Raybestos if ya got em, and y' know.. springs and ****."

Them: "We got Bendix shoes. 'Fraid we don't carry springs and ****..."

Me: "Okay... Just gimmie the shoes."
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I told that to other attendants in my brake systems calss, andthey all laughed their asses off... Now that I know what to call it, I'll get one when I do the brakes again.

jbontke

Here's a quick check that alot of people miss. Look under the master cylinder where it connects to the brake booster. See if there are any signs of fluid. Many master cylinders leak out here because of the seal in the rear will leak with age. If the paint on the brake booster under this spot is puffed up and comes off, then there is your leak. If you look on some cars and see this area rusted, it has happened to them also. I am going throught this now on my RX-4.

Pele

iTrader: (28)

Sometimes it leaks INTO the vacuum booster. The vacuum booster runs off intake manifold vacuum to move a diaphram and provide you with assisted force. If enought gets in there your engine will idle like crap when you hit the brakes and it will smoke like hell.