Not usual soft brake issue.

[east302]

How would i check for an internal leak? Im guessing i would need to remove the ms right?

David is describing a way to see if the MC is holding pressure or if fluid is bypassing back into the reservoir or leaking out. There's no leak where the MC connects to the booster, right?

You can try pumping the brakes and holding it down, letting up slightly, pushing down again, letting up slightly and pushing down again to see if it starts to fall.

Or, remove the brake lines from the MC and install plugs. They sell the plastic plugs in the MC bench bleed kits, they may last long enough. See how the pedal feels. If it sinks, then there's a bad seal. If it is good, then the problem is probably downstream.

That's a pain, though, and I'm not sure just how much it will tell you since it's an intermittent issue. There may be a small defect on a seal that isn't bad enough to always allow fluid to leak.

I'd still pull the drums and double check that you don't have fluid coming from a cylinder.

Edit: make sure the calipers weren't installed backwards, the bleed screw should be at the top.




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[jiggie]

Ok so did the pump 2 times and held it and it stayed firm here is a pic of where the pedal was while holding firm. Was above the gas pedal done 5 min after driving. Pulled the rear wheels off and looked for leaks but didn't pull the drum cause I've never messed with then before. Checked front calipers and they are installed correctly. Did find out that i need new bushings in my upper control arms.

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[jiggie]

I'd still pull the drums and double check that you don't have fluid coming from a cylinder.

Edit: make sure the calipers weren't installed backwards, the bleed screw should be at the top.

Yep thats how mine look. Even all the same grease build up on my ball joints and tie rod ends lol. What control arms do you have?




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[east302]

What control arms do you have?

It's all stock. Here's a video on the drums.

You wouldn't be able to spot a small leak with the drums on. You could check the back where the line connects to the cylinder and see if it's damp, but the best way is pulling the drum. I would guess that you're ok since it's an intermittent issue.

If I was going to replace anything, I'd just swap out the master cylinder.



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[willxfs]

You can pull the drums off/on without having to tinker with anything inside. I pull mine every time I rotate the tires just to check things out.

 

[BIGFOOTDUDE1]

When i pulled the vac hose out of the booster it made a woosh sound and i had a hard pedal. Youtube videos say that means the booster is good. Is that accurate?


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normally yes

 

[jiggie]

normally yes

Well we think it might be wrong this time lol. I have a hissing noise under my dash when i press the brakes. When i let off and start driving it goes away but cant pin point exactly where its coming from so we're going to go ahead and replace the booster and ms and see what happens. Pulled off the drums this am and everything was dry. But im planning on new brakes, rear shocks, and front end bits in November so everything on the wheels will get replaced then.


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[east302]

I chased a soft pedal for over a year, never could figure it out and had to pump to get pressure. I bled the hell out of it (and the ABS unit), replaced the front and rear components, master cylinder, hoses, ABS modulating valve, combination valve...all with no improvement. I finally gave up. The booster eventually went out (you'll know when it's shot) and after replacing the booster I had a perfectly solid pedal again.

I'm not sure why.

In your case, though, I'd lean toward a master cylinder issue.


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[jiggie]

Well today i started hearing a wooshing noise when used the brakes. More like a vac leak. When i take my foot off the pedal and give it gas the noise goes away. Hit the brakes it comes back. Last time that happened it was a booster, but my booster holds good vac(if i pull the hose off it makes a loud psssh noise). So ima just save up and add the master cylinder and booster in November with everything else.


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