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Discussion Starter · #1 ·
I've driven alot of older cars and I'm used to haveing to double pump the brakes to get the car to stop. but on my lil Z it's gotten alot worse lately.

When you apply the brakes properly it sinks to the floor and you have to pump it 4 or 5 times before preasure builds up. but if you stomp on the brakes preasure is there already.

I've looked for leaks and havent found any, and I've bleed the system so many times now I've lost count. Does anyone have any ideas of what I should be focussing on? anyone have this prob before?
 

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If you are sure you have no leaks then it should be your break booster that has gone bad. When mine went south, I could hear the air leaking past the seals in the booster when I would apply the brakes. Make sure you have bleed the breaks correctly. I usually attach a hose to the bleeder valve and submerge the other end into a cup of brake fluid. When you pump the brakes to bleed the lines it sucks back break fluid instead of air and makes a tremendous difference. If it is your master cylinder you should notice a leak where it has penetrated the seals.
 

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Discussion Starter · #3 ·
> If you are sure you have no leaks then it
> should be your break booster that has gone
> bad. When mine went south, I could hear the
> air leaking past the seals in the booster
> when I would apply the brakes. Make sure you
> have bleed the breaks correctly. I usually
> attach a hose to the bleeder valve and
> submerge the other end into a cup of brake
> fluid. When you pump the brakes to bleed the
> lines it sucks back break fluid instead of
> air and makes a tremendous difference. If it
> is your master cylinder you should notice a
> leak where it has penetrated the seals.

Unfortunately i dont think i will be able to hear any air leaks over my pacesetter exhaust. =P but how hard is it to rebuild the booster. ive seen the rebuild kits in vic brit and i think M/S. a new or even rebuilt booster is way out of my budget at the moment, and i visited the local pick a parts last weekend but there were no 240s only 280s and their boosters looked to be in worse shape that mines does.

i was thinking of picking up a brake booster vacuum can from Summit, would this be a waste of money???
 

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I remember reading in my Haynes manual about this - they put in a caution that while it is 'possible' to rebuild the booster yourself it is highly discouraged! It's $150 or less for a rebuilt booster, if you can't afford that right now you can go without it for a while and you'll just have to push on the brake pedal harder which takes a little getting used to! I've been doing that for a few months and just ordered a new booster.

Try disconnecting the booster - unhook the vacuum line from the engine to the check valve and plug that up with a bolt or something so you don't have a vacuum leak from the engine. Now, you will have to push fairly hard on the brakes to stop the car but there shouldn't be any 'pumping' involved - it should be very consistent. If this isn't the case, you likely have a problem somewhere else.

-Brian

> Unfortunately i dont think i will be able to
> hear any air leaks over my pacesetter
> exhaust. =P but how hard is it to rebuild
> the booster. ive seen the rebuild kits in
> vic brit and i think M/S. a new or even
> rebuilt booster is way out of my budget at
> the moment, and i visited the local pick a
> parts last weekend but there were no 240s
> only 280s and their boosters looked to be in
> worse shape that mines does.

> i was thinking of picking up a brake booster
> vacuum can from Summit, would this be a
> waste of money???
 

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Discussion Starter · #5 ·
hmmm...

> Try disconnecting the booster - unhook the
> vacuum line from the engine to the check
> valve and plug that up with a bolt or
> something so you don't have a vacuum leak
> from the engine. Now, you will have to push
> fairly hard on the brakes to stop the car
> but there shouldn't be any 'pumping'
> involved - it should be very consistent. If
> this isn't the case, you likely have a
> problem somewhere else.

> -Brian

hmmm.. that sound simple... so just plug up the hoses right? and if the sinking persists, its not the booster. cool, ill try that, thank brain.
 

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>I've read all the other responses you've gotten on this subject and I agree with all of them; It's your master-vac.
I don't agree that it's too difficult. I have done two of them and it's not hard at all. Just take your time and follow the instructions TO THE LETTER! The best price on an OEM rebuild kit are out of Cherry Hill Nissian in Chery Hill, New York (if they have any left).
As to your question about a can from Summit: Unless you have a big cam, the most this will do is put a band-aid on the problem. Fix it right the first time.
 

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Re: definitely the master

the only thing the brake booster does is help you push the pedal down. that's it. it doesn't help build more brake pressure or anything like that. there is a simple test to see if your brake booster is working. you just shut the motor off and then pump the brake pedal until the booster fills with air and the assist is gone. then hold the pedal down and start the motor. if you feel the booster pull the pedal down, it is working properly. the master cylinder on the other hand will develop an internal leak. you can't see it leaking, because it all happens inside. the master will leak under light pressure and seal under heavy pressure. this is especially noticeable when you are sitting at a light and the pedal slowly drops to the floor while you have light pressure on the pedal. but jam on the brakes and they work fine. replace the master and your brakes will work fine.

-casper
 

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Listen to Casper - It's the Master!! n/c

> the only thing the brake booster does is
> help you push the pedal down. that's it. it
> doesn't help build more brake pressure or
> anything like that. there is a simple test
> to see if your brake booster is working. you
> just shut the motor off and then pump the
> brake pedal until the booster fills with air
> and the assist is gone. then hold the pedal
> down and start the motor. if you feel the
> booster pull the pedal down, it is working
> properly. the master cylinder on the other
> hand will develop an internal leak. you
> can't see it leaking, because it all happens
> inside. the master will leak under light
> pressure and seal under heavy pressure. this
> is especially noticeable when you are
> sitting at a light and the pedal slowly
> drops to the floor while you have light
> pressure on the pedal. but jam on the brakes
> and they work fine. replace the master and
> your brakes will work fine.

> -casper
n/c
 

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Not the Booster (Master Vac)

> I've driven alot of older cars and I'm used
> to haveing to double pump the brakes to get
> the car to stop. but on my lil Z it's gotten
> alot worse lately.

> When you apply the brakes properly it sinks
> to the floor and you have to pump it 4 or 5
> times before preasure builds up. but if you
> stomp on the brakes preasure is there
> already.

> I've looked for leaks and havent found any,
> and I've bleed the system so many times now
> I've lost count. Does anyone have any ideas
> of what I should be focussing on? anyone
> have this prob before?
If it were, you would have a hard pedal
 
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