Hissing brakes help please - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dave`12 · 03-15-2018, 09:47 AM

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

b454rat · 03-15-2018, 10:16 AM

Sounds like booster....

68gmsee · 03-15-2018, 10:22 AM

Yep. Booster seal may be leaking. Usually heard inside the cabin.

**truckdude239** · 03-15-2018, 10:47 AM

Needs a new brake booster

dave`12 · 03-15-2018, 12:48 PM

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

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

thanx

61K10 · 03-15-2018, 01:57 PM

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.

95 S_Trucker · 03-15-2018, 02:45 PM

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.

dave`12 · 04-17-2018, 04:32 PM

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

thanx all

03-15-2018, 09:47 AM	#1
dave`12 Registered User Join Date: Sep 2015 Location: Lake Placid florida Posts: 599	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

03-15-2018, 10:16 AM	#2
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,453	Re: Hissing brakes help please Sounds like booster.... __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 6” lift 1999 GMC Yukon 350/4L60 4" SAS

03-15-2018, 10:22 AM	#3
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Hissing brakes help please Yep. Booster seal may be leaking. Usually heard inside the cabin. __________________ 68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive...

03-15-2018, 10:47 AM	#4
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,217	Re: Hissing brakes help please Needs a new brake booster __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

03-15-2018, 12:48 PM	#5
dave`12 Registered User Join Date: Sep 2015 Location: Lake Placid florida Posts: 599	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

03-15-2018, 01:57 PM	#6
61K10 Registered User Join Date: Feb 2012 Location: pleasant valley--placerville ca Posts: 3,039	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. __________________ 1961 chevy K10 my build is------------61K10 build

03-15-2018, 02:45 PM	#7
95 S_Trucker Registered User Join Date: Oct 2009 Location: . Posts: 2,178	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.

04-17-2018, 04:32 PM	#8
dave`12 Registered User Join Date: Sep 2015 Location: Lake Placid florida Posts: 599	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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