68 brake pedal low - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 11 (permalink) Old Nov 11th, 01, 09:17 AM Thread Starter
 
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Specs:
68 Camaro, 327, 350TH AT, Power brakes, drums all around

Recently replaced:
front wheel brake cylinders and rubber hydraulic lines (runs from cylinder to metal hydraulic line in wheel well), master cylinder, power booster.

Problem:
brake pedal goes all the way to the floor before getting any type of braking action. I tried bleeding the brakes myself and it didn't seem to be making any difference, so I took it into a shop and they flushed/bled the brakes. However, the problem remains. The guy at the shop said it might be the rear cylinders, but I am sceptical. Any ideas??

Note: this vehicle has been garaged for several years.

TIA
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post #2 of 11 (permalink) Old Nov 11th, 01, 09:55 AM
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did you replace the rear brake hose? Also, was this car an original P. Brake car or did you add it?
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post #3 of 11 (permalink) Old Nov 11th, 01, 03:37 PM Thread Starter
 
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No, neither the rear cylinders or brake hoses/lines were replaced. The power brakes are original; no conversion has been done.
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post #4 of 11 (permalink) Old Nov 11th, 01, 03:41 PM
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John
 
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Is the master cylinder pushrod clevis pin in the correct (lower) hole in the pedal?

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JohnZ
'69 Z28 Fathom Green
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post #5 of 11 (permalink) Old Nov 11th, 01, 04:29 PM
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Make sure you're getting a good fluid flow out of the rear wheel clyinders.It must spary out with pressure applied to the master cyl. Rear hoses deteriorate internally and when you replace the master cly, you get air trapped between the master nad rear brake hose.

-Gary
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post #6 of 11 (permalink) Old Nov 11th, 01, 05:50 PM
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The 2 main reasons for a low pedal is air in the lines or rear brakes out of adjustment.....If the master was bad you would get a low pedal but the brakes would pump up then fade again....
post #7 of 11 (permalink) Old Nov 12th, 01, 03:44 AM
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If it has been sitting in a garage for several years the first thing I would look into is who put the car there in the first place?? Ask them if there was a brake problem at the time it was parked.
If no problem thenb it sounds like you have a problem with the master cylinder, replace it,
for the little extra cost replace the rear cylinders as well, Now you know that the hydraulics are in good SAFE operating condition, Look at the shoes and drums, are the drums rusted, has the brake shoe material deteriated?? Last but maybe the first thing is adjust and clean ( or replace ) the brake shoes, free up and lubricate the adjusters, free up the park brake cables, adjust them to the proper tension, Do the job right and complete the first time, its not worth penny pinching when it comes to brakes, I would also consider a new mechanic, If he had done a complete inspection, He would not be guessing at what the problem MIGHT BE!!!!
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post #8 of 11 (permalink) Old Nov 12th, 01, 10:53 AM
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Make a series of firm stops in reverse, that is what makes the self adjusters work.
They might be stuck.
David

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post #9 of 11 (permalink) Old Nov 12th, 01, 02:00 PM
 
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check out system completely agian
pedal goes to floor on application
no leaks seen/bleeds ok.
---------------------------------------------
check brake booster leaks internally while
vacuum applied.to check it start motor ,
pump up brakes hard ,turn motor off
push on brake pedel should fall and stop
about 1.5 inch.
---------------------------------------------
to check master out/may leak internally.
block all 4 flex hoses off and start motor.
pump up pedal .
should be hard as rock,and hold
if it drops to the floor thats your problem.
--------------------------------------------
now to isolate the problem when the master is ok.leave all 4 flex hoses blocked ,pump
up pedal motor running,it will be like rock.
release ,one by one,
the hose pliers and note if one of the 4
brakes / clys drop to the floor .
you can leave the good ones pinched off.....
---------------------------------------------
other note problems associated to low brakes
or soft brakes /no leaks are: worn brake
pads/shoes,bad caliper ,or whl cly, sticks,sucks air,stuck,binding.
brake hoses or brake lines ,pinched or
blocked with gunk.oversized drums or
undersized rotors , brake fade ,hard shiney rotor or drum surfaces ,rear brake adjustment,
air in system ,bleed properly in sequence.
proportioning valve ,sticks, stuck .
brake fliud deteriorated.

these are some pointers that you can use to
to find your problem,start again /don`t
throw parts at the car
--------------------------------------------



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post #10 of 11 (permalink) Old Nov 19th, 01, 05:03 PM Thread Starter
 
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I've been in the midst of a move, so I haven't had time to work on the Camaro. You guys have responded with a lot of good info, thanks!

In response to some of the posts:
- the pushrod pin is in the lower hole on
the brake pedal. (the upper one has a
threaded bolt in it. does that seem
right?)
- brake fluid flows readily out of the rear
cylinder nipples. it doesn't appear to be
impeded in any way.
- there are no leaks evident anywhere in the
brake system, neither brake fluid or
vacuum.
- the brake pedal does not "pump up". The
pedal goes all the way to the floor no
matter how many times it is pumped. The
brakes _do_ work at that point. That is,
with the car moving, when you step on the
pedal it goes to the floor but the car
stops.
- I put the car in the garage. Originally,
because it had a cracked gas tank and rot
under the vinyl top, amongst other things.
The brakes at the time were OK, but a tad
spongey.
- The shoes, drums, etc. look fine. Nothing
is "sticking". The auto-adjusters seem to
work OK. I've tried backing up and then
stopping hard several times, without any
change in the pedal action.

rennycal, I like your methodical approach. Unfortunately, the pedal doesn't pump up at all so I can't follow it. I've got the feeling that there's some simple reason for why the brakes are doing this, but I'm not much of a mechanic and it's beyond me!
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post #11 of 11 (permalink) Old Nov 20th, 01, 09:09 AM
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Eric
 
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I had this exact same problem and concluded that the "self-adjusters" did not "self adjust" no matter how many times I stepped on the brakes when moving backwards.

I fixed my problem by manually adjusting the self adjusters. Never found out why they did not self adjust though.

I have also heard that the wrong master cylinder (one for disc brakes) will not work with the drum brakes. The reason is that the two different master cylinders pump different volumes of fluid when you push the pedal.
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