I found out while the car was in gear but parked on ice. When I put it in gear the rear wheels would not stop spinning unless I exerted maximum pressure on the brake pedal with both feet. Even then they would come to a gradual stop only. My rear brakes were in good condition the last time I checked, which wasn't too long ago. It seems like their is not even minimal pressure getting through to the rear brakes. What could be causing this? I have heard a collapsed brake line could be the culprit but how could it block off pressure completely? I'm stumped for answers. I did a visual on the all the lines and there are no bulges or visual signs or damage anywhere. I hope it isn't the proportioning valve. Damn thing is even adjustable or serviceable.

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'88 IROC 305 TPI
Gutted airboxes
160 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel
Ram-air setup coming soon
Flowmaster muffler
Taylor SpiroPro wires
Accel cap and rotor

 

do you have drums or disc?

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86Z28, GM 350, Jet perf Q-jet & chip Dual snorkel air cleaner, Edelbrock performer intake, Edelbrock headers, Edelbrock cat-back, Off road pipe, MSD 6AL, Accel Super Coil, Taylor Spiro-pro wires, Rapid fire plugs, Jet fan switch, World class t-5, Hurst Short Throw Shifter, Ram Flywheel, Center force dual friction clutch,Aluminum drive shaft, BW disc rear 3.45's & a posi, PBR calipers, Earls braided brake lines, Polygrapite bushings all the way around, poly tranny mount & torque arm mount, Hotchkis lower control arms & panhard rod, Rancho limiter straps, KYB struts & shocks, Gm Wonderbar, Edelbrock strut tower brace, SSM sub frame connectors, Jamex lowering springs, Carbon metallic brake pads, Crossed drilled rotors, Mobil 1 Tranny fluid & motor oil, GM syntheic rear end oil, K&N, Grant stering wheel, 1,200 watt system, Jet Black Paint, 91 Z28 rims, 92 wing, Tinted windows.

 

Drums.

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'88 IROC 305 TPI
Gutted airboxes
160 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel
Ram-air setup coming soon
Flowmaster muffler
Taylor SpiroPro wires
Accel cap and rotor

 

Do you use your e-brake a lot when you park the car? That helps "adjust" the rear brakes, as does reversing for a few feet and slamming on the brakes. It could be that the shoes just aren't touching the drums.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

I've got discs and mine does the same thing. On ice it's a hazard because when I hold the brakes down my rear tires keep pushing my car no matter how hard I push. I experimented with it when the rear of my car was jacked up. On my car anyway, I couldn't lock the rear tires up when it was in gear, but when I slide into neutral I got full brake control. I'm wondering if it is set up like that for the best braking control.
Just an idea, but does anyone know if the brake system is controlled by the computer?

Any other opinions. I've been curious about this too.

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92 Formula 5.7 T-tops
Flowmaster
Other secret mods.

 

I opened up the drums and had a good look at everything. It looks perfect. Shoes are properly adjusted. I use the parking brake all the time so I know they aren't misadjusted. I know for a fact that there's very little or no pressure getting to the rear brakes because I got my roommate to press the brake pedal while the drums were off. I'm fully aware of the consequences of doing this with properly functioning brakes. Mine didn't budge even slightly. I had my Jeep's brakes blow apart like this once, but absolutely nothing on the IROC. This thing's driving me freaking nuts. A collapsed flexible brake line couldn't cause such a bad blockage could it?

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'88 IROC 305 TPI
Crappy 700R4 slushbox
Gutted airboxes
180 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel (gotta luv it)
Ram-air setup coming soon
Flowmaster muffler (puke)
Taylor SpiroPro wires
Accel cap and rotor
Kills: '94 Z28, Olds Aurora V8, bunch of Mustangs, T-birds, ricers, and others who assumed a 12 year-old car would be too slow.

 

88Iroc, as I was reading your message, I was going to suggest the body-to-axle's flex brake line. My '86 front line plugged up four years ago, your rear one is probably due since our cars are 2 years apart

It might not block off pressure completely, but it might not be allowing much pressure in.

Firechicken, unless you have ABS brakes, I don't think you're controlled by the computer. Maybe the "bushings & slides" on your rear calipers are frozen, preventing the caliper from sliding in/out on the mounting bolts? That would result in "only" the inner pad grabbing the rotor. You can buy new rear caliper mounting bolts (two per caliper) and caliper hardware kits (bushings/slides) from places like http://www.carparts.com and http://www.expressautoparts.com - the bolts are semi-expensive, they're about $8 each, and yes, they're shaped a bit differently than the front caliper bolts.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!