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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: 76_Scottsdale on January 31, 2008, 12:06:47 am

Title: Here's a weird one
Post by: 76_Scottsdale on January 31, 2008, 12:06:47 am: About 5 minutes ago I was parking my pickup and and brake pedal went to the floor ( I already have the new master cylinder, I'm installing it tomorrow) As my brake pedal went ALL the way to the floor, my Red BRAKE light came on in the bottom left corner of my dash. Now I've seen this light come on maybe once randomly since i've owned the pickup, and it never comes on when the emergency brake is engaged. Now this red light is illuminated and won't go off. I have no idea what could of caused this does anyone else?
Title: Re: Here's a weird one
Post by: Redneckchevy on January 31, 2008, 12:15:59 am: Red light comes on during brake failure ....Fix the problem light goes off
Title: Re: Here's a weird one
Post by: 76_Scottsdale on January 31, 2008, 12:50:07 am: that makes sense i thought it was an indicating light to tell when the e brake was on
Title: Re: Here's a weird one
Post by: VileZambonie on January 31, 2008, 04:47:43 am: A loss of brake pressure will cause the differential pressure valve in the combination valve to ground the wire to the brake lamp. You can verify it by simply pulling the wire off of the combination valve. Before you just replace the m/c check your wheel cylinders for leaks. Make sure you bench bleed the mc before you install it also.
Title: Re: Here's a weird one
Post by: autorepr on January 31, 2008, 06:20:53 am: It could be a ruptured rusty brakeline on something as mature as a 76. If it's a rear line you'd still have a little pedal towards the floor. If it's a front line the pedal pretty much drops like a rock. If the red light doesn't come on with the park brake, the switch on the p. brake assembly may be unplugged, but the light lights up for both.
Title: Re: Here's a weird one
Post by: RSBAD454 on January 31, 2008, 07:00:54 am: One area people fail to check is the brakes. I agree with above, pull rear tires and drums off and check wheel cylinders, then check front calipers and rubber lines. You can also check behind the master cylinder where is mounts to brake booster for leaks. Bleed the system real good either way, especially if the fluid is black.
Title: Re: Here's a weird one
Post by: 76_Scottsdale on January 31, 2008, 02:25:56 pm: I'll make sure to check the wheel cylinders because that's the only place it could be leaking, I've checked everywhere else, but then again the fluid would eventually go down in the M/C and it hasn't. If there's any problems with a wheel cylinder then I'm going to just swap to disc brakes instead of wasting money on the drums.
Title: Re: Here's a weird one
Post by: Bowtie Bomber on January 31, 2008, 07:11:52 pm: My friends truck did that. Rolled the rubber seal around the piston in the master cylinder. I put on his new master and it worked great after that.