Gen 1 brake question

[project 92z]

I got a 91 Z34 now. 4 gen 1 Lumina in about 12 years. Yes I like the car lol. Anyway, they've all seemed to have a soft petal. I'm used to it until i drive something else. Is that common? I recently did some brake work and tried to lock up the wheels. Only 1 did which kinda makes me think that in an emergency, my braking distance might be too great.

 

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[W30olds]

Could be a brake booster going bad

[Schurkey]

"Soft" pedal usually means air in the system.  Including air trapped in the ABS controller.

 

On a Gen 1, I'd also suspect rear calipers out-of-adjustment.  The park brake keeps the rear calipers adjusted, so if you don't use the park brake...

 

A soft brake pedal can also be caused by failing brake hoses.  Not as common, but possible.  This is typically followed by brake-hose blowout.  Given a choice, I'd go with DOT-approved steel-braid-over-Teflon liner brake hoses.  The best ones have a plastic covering over the steel braid.  The plastic outer cover prevents dirt and grit from getting between the steel braid and the Teflon liner, causing abrasion of the Teflon liner.

 

I've had failed boosters on two Gen 1 Luminas (a '92, and a '93).  In both cases, the symptom was a HARD pedal, not a soft one.  It would take two feet on the brake pedal and pushing like mad to get the anti-lock to activate on dry pavement.  I am totally distrusting of First-gen brake boosters.  I think they're ALL defective by now.  So do you have a "soft" pedal, or do you have a hard, low pedal, with piss-poor braking?

 

In my driveway, the first two things I'd do for a soft pedal is to kick and release the park brake pedal a couple-dozen times, followed by flushing the brake fluid with a pressure bleeder, including flushing the ABS.  Foot-pumping the brakes to flush fluid is entirely satisfactory, but a pain in the ass.  If approaching winter means icy roads in your area, I'd make a point of finding a deserted parking-lot somewhere and doing my best to work the bejezus out of the anti-lock, with the intention of releasing any trapped air that didn't get pushed-out the bleeder screws.

 

Gen 1 rear brake calipers have a terrible reputation.  I think this is entirely un-deserved.  Granted, my experience is with two vehicles not a hundred.  OTOH, defective boosters don't get enough publicity.

[sean1991olds]

On my 91 CSC setting the park brake really helped!! I talked to the previous owner who was also fairly religious about setting the park brake.

[White93z34]

My old Euro 3.4 never ever had a good pedal feel, 2 brake boosters 3 different ABS master cylinders, All new brake hoses, fuck that car. I could never sort it out. Guessing the Reman booster I put on was defective If I were to guess.

 

My 92' z34 on the other hand, I put a new booster on SS bake hoses, 96' brakes all around. It stops great. 

 

The rear calipers are a damn circus, I used to replace them yearly. But its likely not the source of your issues.

[Galaxie500XL]

I never was happy with the brakes on my Cutlass...they never felt dangerous, but I always felt the car took too long to stop, especially at highway speeds.  I spent quite a bit of time checking things out, changing pads, flushing the brake fluid, but never found anything out of place. 

[mfewtrail]

My old Euro 3.4 never ever had a good pedal feel, 2 brake boosters 3 different ABS master cylinders, All new brake hoses, fuck that car. I could never sort it out. Guessing the Reman booster I put on was defective If I were to guess.

 

I wouldn't be surprised. I've had defective boosters and master cylinders right out of the box for these cars.

[94 olds vert]

I never was happy with the brakes on my Cutlass...they never felt dangerous, but I always felt the car took too long to stop, especially at highway speeds. I spent quite a bit of time checking things out, changing pads, flushing the brake fluid, but never found anything out of place.

 

My 94CS stopped way better than my 91 GP, but I am still not happy with the brakes on that car. They arent bad, but they feel a bit scary on the highway when you really need them. I haven't found anything wrong, maybe that is just the way the are. Im pretty used to driving new cars now, maybe it just me not being used to old brakes. Edited January 23, 2017 by 94 olds vert

[Nas Escobar]

My 94CS stopped way better than my 91 GP, but I am still not happy with the brakes on that car. They arent bad, but they feel a bit scary on the highway when you really need them. I haven't found anything wrong, maybe that is just the way the are. Im pretty used to driving new cars now, maybe it just me not being used to old brakes.

 

 

I wonder if that has anything to do with the brake booster or ABS system. I found out 91-93 have a different booster compared to 94-96 (and 97 Cutlass)

[cutlassdude96]

later models have a larger booster

[Nas Escobar]

later models have a larger booster

 

I'm seriously considering upgrading the booster on my 93 Z34 to that of the 94 (if it's plug and play). I love the way my 94 Cutlass Supreme brakes are, perhaps not as nice and firm as a new car's brake but it's worked for me in the 4 years I've had it.

[Turbocharged3800]

the older abs modules love to have the drive gear fall off and end up with one of the circuits (or two) ending up restricted/blocked off. plenty of times I have people slam on the brake and the wheel turns by hand....every damn time I pull the lower cover off the abs unit and a gear is just laying in the bottom.

 

also, ive seen corrosion inside the proportioning valves when lack of fluid changes are involved

[cutlassdude96]

I'm seriously considering upgrading the booster on my 93 Z34 to that of the 94 (if it's plug and play). I love the way my 94 Cutlass Supreme brakes are, perhaps not as nice and firm as a new car's brake but it's worked for me in the 4 years I've had it.

as along its a n automatic its PnP

[Nas Escobar]

as along its a n automatic its PnP

 

Sweet! I asked about this in the whatever thread and got ignored. I should have just came here and hijacked the thread haha.

 

Sounds like my Z34 is about to get an upgrade!

 

Now my only question is how hard is it to get under the dash to get the bolts for the booster off?

[55trucker]

 

Now my only question is how hard is it to get under the dash to get the bolts for the booster off?

What bolts?

[l67ss]

I've found disabling abs seriously helped pedal feel and performanc

[Nas Escobar]

What bolts?

 

The 4 nuts that hold in the booster onto the firewall.

[55trucker]

Y

 

The 4 nuts that hold in the booster onto the firewall.

You're in for a surprise if you go looking for 4 nuts securing the booster to the firewall.  

[GabsOlds]

Well, how is the Booster secured to the car?

[Imp558]

Elven magic

[55trucker]

some historians believe that it was divine intervention.....a miracle of God that created the unique booster,

 

others might tell the tale of a Grimm who beheaded a Vesen who had attacked a lowly Delco-Moraine engineer & when seeing the Vesen's head on the floor the engineer came up with the idea of how to fasten the booster to the firewall. 

 

(a true story?)

[Schurkey]

Two pages of photos, all the info you could want for changing boosters on '93 and '92 W-bodies.  All you had to do was to search the forum.

http://www.w-body.com/topic/32492-hard-brake-pedal-no-stopping-power/

 

 

Here's a preview:  The Dreaded Booster Bracket With Lock Tab:

 

And the back of your booster that spins and locks into position:

 

And the tool you're going to fabricate to spin the booster off it's mount:

[Imp558]

Wow, I never knew what held them on. Could theoretically put nuts on those two studs to protect the threads and use a bar between them to spin it off.