4 wheel disc, pontiac 79' MC, soft pedal problem - Pirate4x4.Com : 4x4 and Off-Road Forum
 
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Old 05-11-2007, 07:08 PM   #1 (permalink)
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4 wheel disc, pontiac 79' MC, soft pedal problem

I'm looking for suggestion on a squishy pedal. I have wagoneer brakes up front, cadillac brakes in the rear. 79 pontiac 4 wheel disc Master cylinder & a chevy s10 dual diaghragm master cylinder. Also have a tri county bar leverage setup.

Jeep will stop fine driving, it just has a soft pedal. i can lock up all 4 tires on gravel & wet pavement, but in 4wd low (4.10 tera low, dana 300 T350 AT) it doesnt want to stop all that well down hill with the soft breaks. I'd like a firmer pedal.

I dont know if i should replace the rebuilt MC with a new one or go with my original jeep or go with an E350. It seems like i would need to move more volume to shorten my brake pedal travel, which would lead me towards the e350 MC with the bigger diameter bore. But that would decrease my line pressure.

I need a engineer to help me out here!!! so i dont start buying parts i dont need. I have no air in my lines so dont even go there,. I just had les schwab pressure bleed the brakes & there is no difference.

thanks
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Old 05-12-2007, 04:01 AM   #2 (permalink)
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check to see if the rod from your brake petal is going all the way into your MC. i had to epoxy a washer onto the MC to catch the rod now my brakes are great. i have a 95 cherokee dd booster with e350 MC.

the rod on my dd booster sits even with the booster but the single booster stuck out a couple of inches. hope this helps. i suppose you could epoxy something down in the hole of the MC also to get the feel you want.

Last edited by jeepward; 05-12-2007 at 04:22 AM. Reason: to help clairify
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Old 05-12-2007, 05:27 AM   #3 (permalink)
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Here: http://www.piratejack.net/troublesho.../trouble17.htm

Good site, lots of good information.
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Old 05-12-2007, 05:49 PM   #4 (permalink)
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thanks for the link.

when i built the brake system, i made my on mc rod, so i know its the right length.

its probably my damn caddy calipers. I'm going to put a 2psi residual pressure valve on the rear line to see if that helps in the mean time.

if that doesnt work, I'll cap the lines & do the MC test just to make sure i dont have a bad rebuilt MC to begin with.

If i dump the damn caddy calipers, what should i replace them with?
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85' CJ7, 305 TPI speed density now
350Turbo, dana 300, Tera low 4:1
dana 44 ARB 4.10, SOA YJ 6 leaf, Hi steer, wagoneer brakes
Rear dana 60 spool, 4.10,SOA YJ 6 leaf
Caddy Brakes, 79'firebird MC, chevy dual diaphram
York OBA, BEARD seats, Warn 9500ti, On Board Shower
35" goodyear MTR
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Old 05-12-2007, 09:01 PM   #5 (permalink)
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I would guess the caddy calipers. I ran them with similar issues. I went with S-10 calipers after. Basically if you've got soft pedal you're master is too small diameter wise. If you went to a bigger diameter master you'd get a harder pedal. Now I'm not sure how this relates to the wheel cylinders such as going to a bigger or smaller rear wheel cylinder and if it would make your pedal harder or softer.
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Old 05-13-2007, 02:54 AM   #6 (permalink)
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During my last go-arround with my brakes, I found removing the rear calipers (Caddy)and re-orienting the bleed screw, and tapping on the caliper while bleeding did the trick. Also, follow the procedure for parking brake lever adjustment exactly, before you ever hook up the parking brake cables and before stepping on the brake pedal. Proper set-up of the parking brake lever is critical to proper operation of the Caddy metric brakes. I can easily lock up my '33's on dry pavement (4-wheel disc MC with 1.125 bore). And don't use a residual valve in a disc/disc system, unless the MC is mounted below the calipers. You'll end up with the inner pads dragging. Also, I've read in more than one place, 4-wheel drive MC's have a longer stroke rear piston than disc/drum set-ups, and that it's important to use an MC designed for discs.
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Old 05-13-2007, 06:10 AM   #7 (permalink)
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As was noted in the site I posted, the Caddy calipers are somewhat of an issue. The writer even stated that in order to properly bleed them he had to remove them from the mounts. Good Luck.
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Old 05-13-2007, 08:00 AM   #8 (permalink)
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/forum/jeep-non-hardcore/580210-cadillac-eldorado-e-brake-spongy-pedal-fix.html

Just finished with my fix.
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