anders72

Brakes only work when pumped twice

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Hi!

 

After driving about 1 hour yesterday the brakes suddenly didn't work on my 73 1602. When I press the brake pedal it goes to the floor, but if I press it again it works as normal.  

 

I have been planning to replace all the brake hoses and the master cylinder since it's rusty and the rubber where the brakes lines goes appears cracked.

 

Is there anything else I need to check or replace?

 

Thanks for your help!

 

 

 

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First try adjusting your rear brakes , After that look for disappearing fluid if fluid level is stable it's the master cylinder with an internal leak,if you put your foot on the brake the 2nd pump does the pedal slowly go to the floor , if yes change the M/C . Also look for leaky rear cylinders inside the drums ( fluid will leak out of the backing plate ) Also check for wet calipers ( unlikely )

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You might also have:

 

a loose wheel bearing.  Moves around and pushes the pad back

 

a sticky caliper.  Gets hot, boils brake fluid, pushes it out of caliper.  First push moves pads back in,

second clamps the brakes on.  If it pulls a little bit to one side or another after it does this, this is kinda likely.

Easy test- after 10+ minutes of faster driving, is one (or both) sides hot?

 

t

 

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9 hours ago, TobyB said:

You might also have:

 

a loose wheel bearing.  Moves around and pushes the pad back

 

a sticky caliper.  Gets hot, boils brake fluid, pushes it out of caliper.  First push moves pads back in,

second clamps the brakes on.  If it pulls a little bit to one side or another after it does this, this is kinda likely.

Easy test- after 10+ minutes of faster driving, is one (or both) sides hot?

 

t

 

 

Thank you!

 

I did hear a squaking sound from the left wheel after this. Goes away when I brake.

 

Might be a sticky caliper then?

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Generally a sticking caliper will cause the car to pull to the left ( if the right caliper is sticking) & visa versa. Unless both are sticking of course.

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On 6/15/2016 at 2:46 AM, anders72 said:

Hi!

 

After driving about 1 hour yesterday the brakes suddenly didn't work on my 73 1602. When I press the brake pedal it goes to the floor, but if I press it again it works as normal.  

 

I have been planning to replace all the brake hoses and the master cylinder since it's rusty and the rubber where the brakes lines goes appears cracked.

 

Is there anything else I need to check or replace?

 

 

 

Last time I checked, unless the car is immobile on a pedestal, loss of brake pedal pressure - even one time - is not a good thing for you or anyone else on the road.

 

Treating this seriously, the other excellent responses implicitly suggested pulling each wheel and inspecting calipers AND wheel cylinders for evidence of leaks.  (Adjusting rear brakes does not necessarily involve removal of drum and examining wheel cylinders.  And a wheel cylinder leak often - but not always - appears on the outside of the backing plate.)    Wheel cylinders often get overlooked.  I would start there and work forward.  If you are going to check the entire brake system, start wherever you please.

 

Be safe.

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23 hours ago, TobyB said:

Easy test- after 10+ minutes of faster driving, is one (or both) sides hot?

 

t

 

 

 

Might be a sticky caliper then?

 

 

Did it pass the heat test?

 

t

 

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Lots of good advice so far.  The basics.... if the pedal went down that much in a short amount of time the system is leaking.  There's a smaller chance that its leaking internally so start out by checking the rest of the system for leaks.  You probably won't need to take the drums off since that amount of fluid will find its way outside the drum.  If its a wheel cylinder, consider replacing/rebuilding all of them.  Hydraulic system components tend to all fail around the same time, and, when you're fixing them, the second, third and fourth cylinders always go faster than the first.  ;-)

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 if the pedal went down that much in a short amount of time the system is leaking. 

 

unless fluid's boiling.  Then it'll drop immediately.  The steam's highly compressible.

 

or there's a big leak internal to the master.  It can leak around the cups if things are really shot.

 

t

 

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If you do not see any fluid leaking externally, it might be leaking inside the Master Cylinder.  It will just bypass the seals. Easy fix, but if your brakes are old and are in an unknown conditions, look over everything and at least replace the soft lines.

 

steve k.

 

p.s. i once blew out a wheel cylinder. hyper-extended it. car had an interesting reaction to it during the race :)

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I've been away for a few days visiting family and attending a classic car show.

 

Found that the brakes work normally when the car is started.  After a while they disappear. The car also now drags to the side (which it didn't use to) and the right wheel squeeks. When parked I noticed the wheel was hot.

 

Anders

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you

have 

stuck 

piston

in 

caliper.

 

Maybe

t

w

o

.

 

t

 

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On 6/22/2016 at 1:52 PM, TobyB said:

you

have 

stuck 

piston

in 

caliper.

 

Maybe

t

w

o

.

 

t

 

 

 

Caliper dysfunction?  The Tower of Brake Babel?

 

Is this response a bold move to distinguish yourself from any other VP aspirants?

 

A not-so-subtle suggestion that Viagra mixes with Dot3?

 

Beware, the other candidates may cry "overpost" ?  

 

Do not despair, you still have my unqualified endorsement for VP!

Edited by avoirdupois

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Yeah, us veep candidates tend to feel left out, so we overpost in compensation...

 

hee

 

Also, a stuck piston really can kill you- the pad's getting roasted, the fluid's being boiled, and even

the wheel bearings might be feeling the heat.  Not to mention the poor rotor....

 

Need fixin'!

 

 

t

 

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