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Old 03-15-2018, 09:47 AM   #1
dave`12
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Hissing brakes help please

Not sure where to put this. My daughters 2002 S10:

when you push the brakes light (but enough to stop truck) all is normal.
brakes hiss when you push medium hard. the hissing noise is in the cabin, the plunger going into the power booster. Brakes still work, and feel like power brakes.

Never experienced this. Could it just be that something suppressing the noise has deteriorated?

Hoping that I don't have to replace the brake booster. It's quite tight there. If I do, could someone point me to instructions? I only see 2 bolts on the booster to the master cylinder, nothing else holding all this together. Not sure if removing them will allow me to pull the master cylinder away and pull out the booster?

Any advice appreciated!

Dave
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Old 03-15-2018, 10:16 AM   #2
b454rat
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Re: Hissing brakes help please

Sounds like booster....
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Old 03-15-2018, 10:22 AM   #3
68gmsee
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Re: Hissing brakes help please

Yep. Booster seal may be leaking. Usually heard inside the cabin.
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Old 03-15-2018, 10:47 AM   #4
truckdude239
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Re: Hissing brakes help please

Needs a new brake booster
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Old 03-15-2018, 12:48 PM   #5
dave`12
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Re: Hissing brakes help please

Well, i figured as much, now it's unanimous.

Time to stretch before bending myself into a pretzel to get it out.

thanx
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Old 03-15-2018, 01:57 PM   #6
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Re: Hissing brakes help please

I have had 2 new boosters on my 61 tk both new. first on a 9" made noise in cab when pedal was applied. Second one is a duel diafram and it makes the same swish noise. no rubber or plastic boot inside at the firewall. Brakes work great just have that little noise.
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Old 03-15-2018, 02:45 PM   #7
95 S_Trucker
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Re: Hissing brakes help please

There is a pin hole in the diapram. Unbolt the master cylinder. You can leave the brake lines hooked up. Make sure there isn't a brake fluid leak at the rear of the master cylinder. Thats the biggest cause of failed boosters. Then there are 4 nuts holding the booster to the firewall. The clip that holds the booster to the pedal rod is kinda a pita. Id have a new one handy. I usually break them upon removal.
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Old 04-17-2018, 04:32 PM   #8
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Re: Hissing brakes help please

that was it. fixed it. they made it about as tough as possible to get to the bolts.

thanx all
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