Brakes

[Canadian1968CoronetR/T]

Ok, I am on my way to have my newly rebuilt brake booster taken off and go to standard brakes. Have not been able to get enough vacuum, have had two mechanics work with booster, it has small cam, but they really don't know what to do ,that will last, plus it would be time consuming which means a large cost with no guaranties. What do you guys think good move or not.

 

[krowbar]

Ok, I am on my way to have my newly rebuilt brake booster taken off and go to standard brakes. Have not been able to get enough vacuum, have had two mechanics work with booster, it has small cam, but they really don't know what to do ,that will last, plus it would be time consuming which means a large cost with no guaranties. What do you guys think good move or not.

Bad booster, Low vacuum at intake connection? They sell vacuum pumps just for that problem, like when you have a big cam.

 

[Propwash]

Obviously there has to be a explanation and not just a cursed '68 Dodge in your garage. Biggest reason people go basically backwards with there brake system is like krowbar mentioned, big cam, no/low vacuum....But there's always Canisters, hydroboost systems and electric vacuum pumps that can help cure that.

So a couple questions.......Did your mechanics vacuum test the engine to see how much HG you're pulling? Typically, you'll need about 15-20 for any decent braking. If your engine's already making good vacuum, possibly think about a bad rebuild on the booster or a junk check valve mounted on it. If you car is on the low end of that HG or a tad under, have you thought of using a canister, hydroboost or possibly an electric vacuum pump, like mentioned? Lower HG could either be from a bigger cam than you think or like Krowbar mentioned, vacuum leaks elsewhere. Heck, bad timing effects vacuum exponentially.

I guess the question I should have asked first is what is the symptom(s) and how was it troubleshooted down to be a cursed booster?

 

[Canadian1968CoronetR/T]

They did test vacuum, as long as I have rpm's up I have enough vacuum, I have good pedal on first stop then I have to apply a lot of pressure for next pump unless I put it in neutral. Any way the mechanic is a mopar racer, he claims they pull most boosters and go manual, a lot less hassle that way? So I guess that is what I am going to try for now.
Thanks for the input.

 

[krowbar]

They did test vacuum, as long as I have rpm's up I have enough vacuum, I have good pedal on first stop then I have to apply a lot of pressure for next pump unless I put it in neutral. Any way the mechanic is a mopar racer, he claims they pull most boosters and go manual, a lot less hassle that way? So I guess that is what I am going to try for now.
Thanks for the input.

Well then I would say you don't have enough vacuum. If you can only get enough vacuum at high rpm and not at idle then I think you have a hefty cam or vacuum leak.

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Or a bad rebuild on the booster. Spray carb cleaner around the vacuum lines to check for leaks.

 

[Cranky]

You say you have a small cam? How small is it? Even a small cam should produce good vacuum. How well does the engine run? As well as expected or is it somewhat sluggish off the line than you think it should be? What all has been done to the engine?

 

[Canadian1968CoronetR/T]

The engine has a 6 pack crank according to write up that came with car, it does not run or idle rough, thou?

 

[67 coronet]

easy way to answer this is to find out your vacuum at idle.just measure it.

 

[2quick]

I had kinda the same issue with my 66 satellite. Converted manual drums to power disc using Hemi style booster and a generic caliper kit. Make a long story short no matter what I did it just didn't seem to have enough assist from the booster, almost needed two feet to stop. I tried 3 different boosters, checked vac a hundred times, 17" at idle, Replaced check valve 3 times, Checked peddle and linkage alignment, tried adjusting then totally removed rear proportioning valve that came with kit, which helped some but not much.

So i was pulling the booster out a final time and for some reason a spring behind the brake rod that goes into booster fell out and i didn't notice till after the booster was reinstalled. Well low and behold PERFECT BRAKES!!!!! Not sure why it's there, probably to hold in the brake rod in place so it cant fall out, but It's been perfect know for over 15,000 miles with no problems. You may not want to do this, but as a last ditch effort it may just help anyone out there racking there brains or thinking of going back to manual brakes.