Could use some help... - Team Camaro Tech
Brakes, Suspension & Steering Conversion questions, Steering & Handling

 
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post #1 of 10 (permalink) Old Nov 12th, 11, 07:23 PM Thread Starter
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Andy
 
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Could use some help...

Hey guys -

Been having trouble getting a firm pedal with my brakes. The car is new to me (about 2 months) and I'm not sure what is stock versus what is original. First of all, it's a 68 that has the stock four piston calipers up front and drums in the rear. When I got the car, the left front caliper was leaking so I rebuilt it with the aftermarket o-ring kit and all seems to be good. When I took the wheels off, I noticed that everything on the left front of the car should have been on the right and side and vice versa. Didn't exactly give me too much confidence in the previous owners skills.

Anyway, rebuilt the calipers, replaced the front hoses with the proper hoses, replaced the master cylinder (it was leaking slightly), replaced both rear wheel cylinders (one of those was leaking) and a clogged rear brake line. After all of that, no matter how much I bleed the brakes, the pedal is very very soft and the car does not want to stop.

I'm wondering if perhaps the power brake push rod is the wrong length?? Also, would like to know if the power brake setup uses the same clevis that the manual brakes do. Curious if things are hooked up wrong. If anybody else has any other ideas, I'd love to hear them. Thanks!

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post #2 of 10 (permalink) Old Nov 13th, 11, 03:23 AM
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Kevin
 
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Re: Could use some help...

Andy...does the car have a adjustable proportional valve? That may be preventing a good bleed along with the lack of a hard pedal. Seeing the guy fubbed up the front brakes, check to be sure the bleeders are on TOP!! I have seen them on wrong when a friend could not get a good pedal.

Go to you local auto store and buy a pump oil can..rinse with brake fluid then put a rubber hose on the end and attach to the furthest rear wheel bleeder valve. Remove the cover from the master cylinder and then pump slowly about ten times. You may want to place rags around the master cylinder to catch any overflow..if its too full.

Repeat the same process on the drivers side rear, the passenger side front then the drivers side front. It should get all the air out and give you a nice pedal ! Be sure to keep checking the brake fluid in the oil can..you don't want to pump air into the system.

Kev
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post #3 of 10 (permalink) Old Nov 13th, 11, 09:00 AM
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Re: Could use some help...

Quote:
check to be sure the bleeders are on TOP!!
Yep, seen that one.

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post #4 of 10 (permalink) Old Nov 13th, 11, 09:39 AM
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Re: Could use some help...

Years ago I had the same problem with my manual disc brake equipped ’67. No matter how much I bleed them I could never get a firm pedal. My front calipers had been upgraded with stainless steel bores and everything was new or rebuilt. The only part I hadn’t replaced was the brake hold off valve.

Then one day I removed the hold off valve and temporarily bypassed it with a piece of steel brake line. I bled the brakes and had a great pedal for the first time since I bought the car. The hold off valve was the problem. The valve has a push button on the back side which was sucking air into the system. The funny thing is it wasn’t leaking any brake fluid. My plan is to someday rebuild the old valve and reinstall it. I am not in a big hurry because the brakes work great without the valve in the system.




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post #5 of 10 (permalink) Old Nov 13th, 11, 11:21 AM Thread Starter
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Andy
 
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Re: Could use some help...

Kev and Steve - I will try both of your suggestions. And yes, the bleeders are on TOP! I will report back soon.

Any chance you can do something about the cold weather in Chicago please? not too many more times this year I'll get to drive it!

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post #6 of 10 (permalink) Old Nov 13th, 11, 11:23 AM Thread Starter
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Andy
 
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Re: Could use some help...

Just for my own sanity, do you guys know the answer to the question I had above? I've ready about the push rod being different depending on the set-up. Could this cause any problems? Or which clevis I'm supposed to use? Given what this guy did, I want to make sure that everything is solid even after I get a firm pedal!

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post #7 of 10 (permalink) Old Nov 13th, 11, 03:32 PM
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Re: Could use some help...

Soft pedal= air in the lines.
I all ways gravity bled brakes, open the R/R bleeder let the brake fluid come out for a min and while the bleeder is open have some one step on the brake ones all the way to the floor and tell them NOT to let it go till you close the bleeder. do that to all the wheels.
Nick
ps make sure your master cylinder has fluid while you doing that.

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post #8 of 10 (permalink) Old Nov 13th, 11, 05:34 PM
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Re: Could use some help...

Quote:
power brake push rod is the wrong length??
The normal post is is .."my brakes dont release"....
Basicaly u press on the pedal and with a short pin it takes a bit to take up the slack, before moving the MC piston...and then when the MC piston starts to move there is not enough pedal movement to full actuate the the brakes....pumping will sort of help, but not completely....And u will find u have harder and a little more brakes without the booster connected...
Im assuming since u found left on right right on left, blockage in pipes, the sence to replace slaves with a new MC..u basically know a bit more than the basics..
What u describe is a actuating pin a little sort....and your logic is coming back to the actuating pin etc.

Check the depth of the old MC and new

Its easy to feel when a pin is too long by backing off the booster/MC mounting bolts
use a depth gauge and do tthe maths, and/or drop a couple small washers in....covered in grease to take up the slack.
Grease...well that makes the washers stick in place and not fall out while trying to put it back together.

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post #9 of 10 (permalink) Old Nov 14th, 11, 06:23 PM Thread Starter
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Andy
 
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Re: Could use some help...

Quote:
Originally Posted by Steptoe View Post
The normal post is is .."my brakes dont release"....
Basicaly u press on the pedal and with a short pin it takes a bit to take up the slack, before moving the MC piston...and then when the MC piston starts to move there is not enough pedal movement to full actuate the the brakes....pumping will sort of help, but not completely....And u will find u have harder and a little more brakes without the booster connected...
Im assuming since u found left on right right on left, blockage in pipes, the sence to replace slaves with a new MC..u basically know a bit more than the basics..
What u describe is a actuating pin a little sort....and your logic is coming back to the actuating pin etc.

Check the depth of the old MC and new

Its easy to feel when a pin is too long by backing off the booster/MC mounting bolts
use a depth gauge and do tthe maths, and/or drop a couple small washers in....covered in grease to take up the slack.
Grease...well that makes the washers stick in place and not fall out while trying to put it back together.
Perfect. Thanks for the explanation!

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post #10 of 10 (permalink) Old Nov 14th, 11, 06:25 PM Thread Starter
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Andy
 
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Re: Could use some help...

Quote:
Originally Posted by MRCOOL_RSSS350 View Post
Soft pedal= air in the lines.
I all ways gravity bled brakes, open the R/R bleeder let the brake fluid come out for a min and while the bleeder is open have some one step on the brake ones all the way to the floor and tell them NOT to let it go till you close the bleeder. do that to all the wheels.
Nick
ps make sure your master cylinder has fluid while you doing that.
I would normally agree with you but here is the problem. I sat in the car while my father bled the brakes. We first gravity bled them and got the pedal to firm up a bit and then bled them some more with my pedal assist. The problem is that once I started the car, the pedal went back to being very soft. This is what is confusing me as the pedal really shouldn't change much with the car running.

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