Is anyone around? help on brakes - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 04-11-2020, 09:14 PM Thread Starter
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Is anyone around? help on brakes

So its been a very long time since I've signed in and looked around. This place used to be hoping and was hard to keep up with everyone, looks like that no longer the case.

Any way hopping someone can help me. I replaced my master cylinder and brake booster (Master Powder Brakes) and now I've got less then about a half an inch of free play and brakes so sensitive that it will throw you through the windshield if you just think of stopping. Not joking doing less then 5mph and just touched the pedal and just about ate the steering wheel. Brakes are not too sensitive to the point that it is unsafe to drive the jeep.

Anyone with any thoughts that may shed light on this.

its a 78 CJ7 with factory power brakes and just upgraded to Vette master cylinder and dual diaphragm booster. This is due to old master leaking into old booster with both needing to be replaced. Mistake on my part was to buy parts and not install them until 18 months later

Hope there is still some of the folks I used to see on a daily basis around that can help, thank you.

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post #2 of (permalink) Old 04-12-2020, 10:48 AM
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Itís been WAY too long since there was much traffic on this board. I had to do a search to refresh my memory on the brake upgrade. I remember getting an S-10 booster for mine and doing some trial fitting. I think I remember having to make an adjustable actuation rod for the conversion. That may be your problem with lack of play.

Do you have discs front and rear? That is the reason for the corvette master cylinder, it eliminates the check valve that keeps some pressure on the rears, required with drum brakes.

Can you tell if all 4 wheels are the problem or is it only the front or rears? Have you left any skid marks and were they only the fronts or rears or all 4 wheels?

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post #3 of (permalink) Old 04-12-2020, 02:28 PM
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What Taz said.

If you can't tell whether the problem is with the front or rear try stopping on grass or gravel to see which locks up. My guess is that it's the fronts - when you're stopping there isn't enough weight on the backs to cause that violent reaction.

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post #4 of (permalink) Old 04-13-2020, 12:04 AM Thread Starter
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I believe it is the Front end that is locking up. I bought a complete brake system, master and booster pre-assembled with mounts ready to go. I think it was from Master Power Brakes but not sure, I thought it would be the easy way to do it guess that didn't work as well as I thought it would. Many years ago I did a Hydro Boost to another Jeep and sourced the parts from a GMC pickup in a junk yard and it worked great and I'm thinking I should have done the same this time around.

CJ7Taz I think you may have already pointed me in the right direction, The Vette master cylinder I needed is the older model that has a disk/drum system so maybe I've ordered the wrong system or I was sent the wrong system, As my current jeep is still a disk/drum system, will need to do some research and see if I can determine which one I have for sure. The free travel is yet still a problem, I do not remember a adjustable actuation rod, and may need to revisit this and make one as you have suggested.


Jim_Lou I believe you are correct, I can tell you that with just the weight of my foot caused the brakes to lock up and damn near put my face into the windshield. To be honest it scared the hell out of me as I almost hit my mouth on the steering wheel and forehead on the windshield, will have to test it in the back yard and see what happens.

Thank you both will try to check these things on my next days off and see what I can come up with for details. Again thank you for pointing me in the right direction, will up date you when I discover something.
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