eightTfourTA

iTrader: (3)

I've got that awesome disc brake rear on my '84 T/A. It seems, sometimes they work well. Most other times though, the pedal sinks a little lower and it takes more effort to slow the car, but if I give it a quick pump they're fine again It's already got a new booster and master cylinder, replaced a few months ago. The pads aren't worn much, rotors appear ok. Calipers out back are about a year old, not sure of the fronts though. Any suggestions?


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D.R. Stevens
1984 Trans Am 305HO L69
original engine
Dual snorkel AND hood
louver induction, K&N
CK rods/B hanger
Accel HEI super coil
timing bumped to 8*
700R4 built up with Superior shift kit
3" Pace Setter exhaust
(Heddman Hedders soon)
3.42's out back
other superficial stuff
1991 Firebird 305 L03
Removed silencer ring
bypassed Thermac
K&N filter
otherwise stock

TomP

I think you're having the exact damn problem I'm having... the first press of the brake pedal sinks right to the floor? And then, if you release the pedal, and push it back down quickly, you get nice, firm brakes?

I'm going to order the recall kit today for the back calipers. I think the "no brakes on first pump" has to do with the calipers' problem of the pad not being against the rotor. I think the first pump uses all the brake fluid to extend the rear pistons to press the pads against the rotor.

I think the quick second pump doesn't allow "time" for the rear pistons to retract, and, since the rear pistons are against the rear rotor, all the brake fluid is distributed equally to all four corners, instead of "just" to the rear.

Apeiron's been "the man" with info regarding the recall info, and even got us a service bulletin regarding master cylinders (for guys like me that swapped to a pre-89 rear disc setup, in my case, an '84 T/a's 3.73/posi/disc axle).

Look on this board for a message I just resurrected about "rebuilding the screw-in style calipers", and check out https://www.thirdgen.org/messgboard/...ML/002027.html .


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-Tom P (Hot rodded 1986 Firebird 2.8l)

Ward

iTrader: (1)

Could it possible be air in the lines?

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1983 Firebird
TH700R4 Auto
Small Block 400
LG4 ECM, Intake, Carb, Distributor, etc.
Soon to be non-computer.
Clarion Head Unit 45X4
2 Pioneer 400W 12" Subs
Third Gen Performance
"A four cylinder is half an engine."
"Ponies can run, but birds can fly..."

TomP

I've bled the ever-loving-hell out of mine; can't find air anywhere, but it might be worth checking for you, eightTfourTA...


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-Tom P (Hot rodded 1986 Firebird 2.8l)

eightTfourTA

iTrader: (3)

Thanks, TomP. Yeah, I bled the living chit out of mine, too, no improvment. I'll look into that recall thing, that's probably what it needs. The rear calipers got replaced with stock replacements, but that alone probably isn't good enough to make it all work right.
Tom, or anyone who's reading with this same disc setup, after your car's sat for awhile, like overnight, do you get a moan from the rears under light application? I do, and even the Haynes manual mentions this.

TomP

When I swapped the rear, I rebuilt one caliper, and bought a rebuilt stock one for the other side. That one I bought doesn't work at all... while the one I rebuilt seems to work (and probably had the recall work done).

The recall kit is on special-order... looks like I won't be doing the job this weekend.

Hey- since you bled your brakes as much as I did... say you've got the m/c cap on, and the car's shut off. If you pump your brakes, say, 8 times in a row, and then pop the m/c cap off- do you see foamy fluid? I never get air in the lines, thru bench-bleeding and "press-the-pedal" bleeding; but I'll always get foamy fluid if I pump the heck out of the brakes.


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-Tom P (Hot rodded 1986 Firebird 2.8l)

TomP

Oh, and I thought that "rear brake moan" was for rear drums? I'll go back and re-read that section tonight... I do get a moan, but it's at random times, and I usually associated it with the rear calipers "trying" to work.


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-Tom P (Hot rodded 1986 Firebird 2.8l)