Author Topic: 68 Camaro brakes disc/drum  (Read 794 times)

monaroman

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68 Camaro brakes disc/drum
« on: June 19, 2017, 10:54:27 PM »

Hi,

Had the power assist unit repaired and a new check valve. Still having hard brake pedal issues. 18" of vacuum present. No other work performed on the braking system.

Any suggestions please?

arocars

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Re: 68 Camaro brakes disc/drum
« Reply #1 on: June 21, 2017, 01:18:31 AM »
I dont know the answer to your question, but I clicked into this post to see what others answered. Seeing that no one did, I did a google search on '68 camaro hard brake pedal.' I came up with several plausible causes. Seems like the most common cause was low vacuum (not your problem), the prop valve doesn't open, and the ball in the check valve gets stuck.

monaroman

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Re: 68 Camaro brakes disc/drum
« Reply #2 on: June 21, 2017, 09:35:40 PM »
Hi arocars,

Thank you for taking the time out to do a little reseach. John Z has a good article of disk brake set up and how the components function. It's on this web site.

Hopefully have a play this weekend.

Cheers.

monaroman

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Re: 68 Camaro brakes disc/drum
« Reply #3 on: July 10, 2017, 10:44:15 PM »
Hi,

I replaced the hose fFrom the manifold to check valve still hard brake pedal at idle. 18"inhg at idle.i removed the master cyclinder and started the engine. The booster piston moved freely once brake pedal was pressed.

I manually moved the booster piston out once the car was running and it returned to normal position in the booster once I released it.

I noticed the metering valve/hold off valve at the rear of the body has a silver plug type shape. Does that require resetting in the out position?

Any help would be appreciated.

Thank you.

68Zproject

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Re: 68 Camaro brakes disc/drum
« Reply #4 on: July 12, 2017, 08:58:11 PM »
That valve functions to hold off pressure to the front brakes and send more to the rear so the front doesn't skid or visa versa.  When you bleed brakes you have to push the button in or just the front will bleed and not the rear.  If it works it should be in the out position.  I guess it could have crud in it or be frozen and not work, but I think the biggest problem I've seen with what you're describing is the pushrod length.  Search on here or at TC on hard brake pedal.
68Z28

monaroman

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Re: 68 Camaro brakes disc/drum
« Reply #5 on: July 25, 2017, 10:14:22 PM »
Hi 68Zproject,

I think your on the right path with push rod length. I can't loacte a solution but I'm thinking extend the thread on the push rod and trim push rod length to suit?

Hopefully this weekend I shall a have a play if weather is good.

Thank you.

z28z11

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Re: 68 Camaro brakes disc/drum
« Reply #6 on: July 26, 2017, 01:44:31 AM »
The '68 and '9 master cylinders have different rod length depths, as you probably have known or understood. If you look at Delco master cylinder rebuild kits (that are the right part numbers for the applications), you can readily see the difference. I think the '8 is a longer rod if I remember correctly, a lot of rebuilt cylinders and likely services probably use the '69 and up shallow piston, so ergo the problem.

Just my opinion -

Regards,
Steve
1968 Z28 M21/U17 BRG/W
1969 Z28 X77/M20/VE3 LeMans/W
1969 L78 X66/N66 Cortez/BVT
1969 Z11 L48/M35/C60/C06

monaroman

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Re: 68 Camaro brakes disc/drum
« Reply #7 on: August 09, 2017, 09:21:39 PM »
Hi,

Thank you z28z11 and other members.

Found a very small intermittent small leak on the new rubber seal which holds the check valve. Replaced and bench tested. This was done at the rebuilders workshop. Installed and started softish pedal on start up. A long cruise and the brakes performed really well. A little firm but perhaps some final adjustments may improve that. Enjoyed the learning curve.

Cheers.