1996 accord brake sinking

[garlicbreadman]

my friends 96 accord ex has a problem with sinking brake pedal and it only happens once in a while. quite rarely that it happens and he has to add fluid every 6 months or so.

i inspected his lines and all were bone dry and the brake master cylinder was also dry, so no external leaks. i've never had experience with brake master cylinders. could it be leaking internally in the brake master cylinder?

also, when were braking, we can hear some dook dook dook noise from the front brakes.


also how can you rule out of its the brake master cylinder or the brake booster?

 

[spasm3]

If he is adding brake fluid every 6 months, there is a leak. A sinking brake pedal usually means a serious leak. if no fluid is needed in the reservoir then the sinking pedal means an internal leak and the master cyl needs to be replaced. He may have two problems, a small leak and a bad master cyl. Check the rear brakes. if it is drum brakes , the wheel cyl are bad about leaking when they have some age on them.

 

[garlicbreadman]

Originally Posted By: spasm3
If he is adding brake fluid every 6 months, there is a leak. A sinking brake pedal usually means a serious leak. if no fluid is needed in the reservoir then the sinking pedal means an internal leak and the master cyl needs to be replaced. He may have two problems, a small leak and a bad master cyl. Check the rear brakes. if it is drum brakes , the wheel cyl are bad about leaking when they have some age on them.


car has rear disc brakes. im guessing internal brake master cylinder leak.

 

[zorobabel]

Check for leaks at the proportioning valve, they have some stupid plastic plug that fails.

 

[garlicbreadman]

Originally Posted By: zorobabel
Check for leaks at the proportioning valve, they have some stupid plastic plug that fails.

never heard of this, where is this?

 

[Mau]

It's most likely the brake master cylinder. Our 96 Accord had the same issue, replaced it and no more problems.

I replaced it with an aftermarket one from rockauto.

 

[mechtech2]

I could simply be that the pads are worn so low that the fluid got too low.

 

[SIXSPEED]

Originally Posted By: garlicbreadman
Originally Posted By: zorobabel
Check for leaks at the proportioning valve, they have some stupid plastic plug that fails.

never heard of this, where is this?

If you don't have ABS then it's located below the master cylinder in front of the fuel pump. The 2nd picture shows the black plug that sometimes goes missing and is a source of leaks. They are no fun to replace.

 

[SIXSPEED]

Originally Posted By: SIXSPEED
If you don't have ABS then it's located below the master cylinder in front of the fuel pump.

I meant fuel filter not fuel pump.

 

[garlicbreadman]

i think it has ABS, its a 96 ex 5spd with leather seats.

 

[Gasbuggy]

It's the master cylinder. My accord also had brake fluid vanish. I did mine over the summer. The hotter it gets the worse it will sink. I got around with mine going bad for about 50,000 miles. Then one day it just went and I was pumping my pedal trying to stop in time. So tell your friend to do himself a favor and replace it now.

 

[garlicbreadman]

what unit did you replace it with Shark? any aftermarket brands you guys recommend?

 

[Mau]

I went with Dorman.

 

[garlicbreadman]

Originally Posted By: Mau
I went with Dorman.

how many miles now on your unit?

 

[Gasbuggy]

Originally Posted By: garlicbreadman
what unit did you replace it with Shark? any aftermarket brands you guys recommend?



Whatever Advance Auto carries. I'm not sure at this point. I look at it like this, the stock one lasted 16 years, so the replacement will most likely provide 50% of the service life. PLENTY of time.

 

[SIXSPEED]

I replaced mine with a new Honda Master Cylinder; it wasn't that expensive by mail order. Don't forget to bench bleed the MC prior to installation to get most of the air out of it.

 

[womcat]

I have the same problem on my '94 Acura Integra. It doesn't do it all the time, but sometimes while sitting at a light or stop sign, the pedal will go slowly to the floor. Definitely does it more when it's hot out. I was thinking master cylinder too, but I also have an ABS light on. Could the ABS cause this at all? I know the ABS motor also takes brake fluid, maybe it's letting off pressure when it shouldn't?