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Discussion Starter · #1 ·
I have a 57,3100 chev pickup with a CPP firewall mount P/B kit. After two different boosters, from them,problem still remains. Brake pedal will not return last 1/4"-1/2" or so. Brakes bind. With vacuum disconnected,driving vehicle, brake pedal returns completely and firmly. Everything is new,no binding anywhere, pedal has return spring,etc. Booster pin is adjusted with a gauge. All the usual areas to check/confirm have been done. Brake system works great otherwise. I am convinced it's a cheap overseas booster that's the problem. CPP believes otherwise. I get, "there's nothing about a booster that could cause this". Well, then why does the pedal return VERY good with out vacuum applied, while idling/driving vehicle? Am I missing something here?

Talked to a booster rebuild shop, and they said definitely a booster issue.Maybe they said that in order to sell me a booster, but I'll give them the benefit of the doubt for now. Any thoughts?

Was looking at MBM brake boosters. USA made? Got to get this bullcrap resolved.:thumbup:
 

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Sounds like the booster to me. Maybe try an actual gm unit? Sometimes oe parts are the best choice. (not oe for your truck, i mean off a standard car like a nova or chevelle)
 

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WFO
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I have a 57,3100 chev pickup with a CPP firewall mount P/B kit. After two different boosters, from them,problem still remains. Brake pedal will not return last 1/4"-1/2" or so. Brakes bind. With vacuum disconnected,driving vehicle, brake pedal returns completely and firmly. Everything is new,no binding anywhere, pedal has return spring,etc. Booster pin is adjusted with a gauge. All the usual areas to check/confirm have been done. Brake system works great otherwise. I am convinced it's a cheap overseas booster that's the problem. CPP believes otherwise. I get, "there's nothing about a booster that could cause this". Well, then why does the pedal return VERY good with out vacuum applied, while idling/driving vehicle? Am I missing something here?

Talked to a booster rebuild shop, and they said definitely a booster issue.Maybe they said that in order to sell me a booster, but I'll give them the benefit of the doubt for now. Any thoughts?

Was looking at MBM brake boosters. USA made? Got to get this bullcrap resolved.:thumbup:
For them to say there's nothing within the booster that could cause this is ludicrous.

There's a valve that seals the side of the booster nearest the pedal so there's vacuum on BOTH sides of the diaphragm when the brake pedal is not applied. This valve opens when the brake pedal is depressed, which allows atmospheric pressure to enter the pedal side of the booster, allowing the vacuum on the master cylinder side to help apply pressure to the MC.

If this valve isn't sealing the pedal side when the brake pedal isn't depressed, the vacuum on the MC side of the diaphragm will pull the pedal downward.

Here's an interactive representation of a vacuum operated power brake booster.
 

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What I would do is contact CPP via email directing your email to the owner, senior manager and manager of customer service and again explain your problem. Then explain how your problem and how its being handled by their company is currently being discussed on Hotrodders.com. Explain that the collective concensus is that there is a problem with their unit and perhaps the other members of this site might take their business elsewhere where their concerns are addressed better. Point out that after service is what brings customers back and word of mouth brings new customers in or keeps them away. Then explain that you probably talked to the wrong person the first time and ask who would be able to resolve this issue because you know they want to keep you as a happy returning customer. You might also point out that Hotrodders.com is the largest and busiest automotive website in the world.
Never hurts to try. :thumbup: BB
 

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Discussion Starter · #5 ·
Thanks much for the very much appreciated replies everyone.
I just had a gut feeling that the booster is causing this. I feel more convinced now.
However, they did send me a different booster a few weeks ago,hesistantly, and it has the same issue. Now I guess you could assume that since both boosters have the same issue, that the problem lies elsewhere. OR, both boosters are at fault, as well as maybe countless others.
Everything they sell has a lifetime warranty,and I will not talk harshly about any vendor but aggravate me enough and I will. When an overseas made product is faulty, the vendor won't tell you this. So it's hard to get customer satisfaction being that,that's the way it is. I feel that in all actuality, they should keep sending me these cheap overseas disposable boosters until I get a good one.
Oops, starting to rant. I guess I was thinking of the advice they gave me, which was to relocate the pedal to booster push rod, on the pedal.Try drilling a different hole on the pedal. Maybe I need to change the angle of the pushrod. WHAT???? I bought a PREENGINEERED FULLY ASSEMBLED BRAKE ASSEMBLY KIT.
I am under the assumption MBM boosters are USA made. I will probably just eliminate the source altogether and hopefully get lucky with MBM. Whatcha think?
 

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WFO
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Thanks much for the very much appreciated replies everyone.
I just had a gut feeling that the booster is causing this. I feel more convinced now.
However, they did send me a different booster a few weeks ago,hesistantly, and it has the same issue. Now I guess you could assume that since both boosters have the same issue, that the problem lies elsewhere. OR, both boosters are at fault, as well as maybe countless others.
Everything they sell has a lifetime warranty,and I will not talk harshly about any vendor but aggravate me enough and I will. When an overseas made product is faulty, the vendor won't tell you this. So it's hard to get customer satisfaction being that,that's the way it is. I feel that in all actuality, they should keep sending me these cheap overseas disposable boosters until I get a good one.
Oops, starting to rant. I guess I was thinking of the advice they gave me, which was to relocate the pedal to booster push rod, on the pedal.Try drilling a different hole on the pedal. Maybe I need to change the angle of the pushrod. WHAT???? I bought a PREENGINEERED FULLY ASSEMBLED BRAKE ASSEMBLY KIT.
I am under the assumption MBM boosters are USA made. I will probably just eliminate the source altogether and hopefully get lucky with MBM. Whatcha think?
You did verify the pedal is returning fully and that the pushrod is adjusted/sized so that it's not bearing down at all on the pushrod seat?
 

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Discussion Starter · #7 ·
You did verify the pedal is returning fully and that the pushrod is adjusted/sized so that it's not bearing down at all on the pushrod seat?
Yup. Pedal has free play,when it's fully returned. Double and triple checked booster to M/C bore pushrod clearance, with a gauge. 1/6"-1/32" clearance.
 

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Do you feel it's a booster problem when,as I mentioned, that the pedal fully returns when driving the vehicle with vac line unhooked from booster?
Yes, I believe it's a prob w/the booster. The valve I mentioned has a seat that has to hold vacuum, even a broken/weak internal valve spring has the potential to be the problem, but the booster would need to come apart to confirm this- something that's outside the ability of most guys, besides the poit that you shouldn't need to fix a problem not of your making.

Given the info you've provided and the checks you've made, if it's not the booster, I'm at a loss.

It shouldn't cause the problem, but have you checked the vacuum check valve between the engine and the booster?
 

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Discussion Starter · #13 ·
Yes, I believe it's a prob w/the booster. The valve I mentioned has a seat that has to hold vacuum, even a broken/weak internal valve spring has the potential to be the problem, but the booster would need to come apart to confirm this- something that's outside the ability of most guys, besides the poit that you shouldn't need to fix a problem not of your making.

Given the info you've provided and the checks you've made, if it's not the booster, I'm at a loss.

It shouldn't cause the problem, but have you checked the vacuum check valve between the engine and the booster?
Yeah, I checked the valve. All is good.
If no useful help from CPP, I guess I will have to take a gamble and try a different booster from another source. If all else fails, hydroboost it.
 

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Install a second return spring. With the engine running depress the brake petal and release. If petal returns fully try a few more times. If that fixes the problem that's good. If not and the petal dose'nt return without touching the petal shut the engine down and have someone pull the check valve from the booster. If the petal returns to the proper position you've got a bad booster, if not you've got a possible restriction in the brake system. It might be the fluid is not returning compleatly to the master cvlinder. Something to try.
BB
 

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I hope by now, your brake problem is resolved. Try going to MBM website, it may help you to trouble-shoot problem. They are very helpful on the phone...1-800-231-4125, talk to sales. Good luck!
 

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Did you ever get this problem figured out? Im having the same problem with my front disk conversion. Brakes seem fine when I test drive but the pedal falls short when returning, leaving my brake lights on. Ive tried to trouble shoot the problem but no luck so far. Im at the point where im ready to try another booster. don't know what else to do.
 

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Read this post with interest, and then.....

Nothing. Like a good book, and suddenly the lights go out. Or a movie and then "join us next week for the finale."

Anyway, I have a CCP booster 4 disc MC on my 56 F100 and it took a lot of tweaking to dial it in. It used the original pedal which is cast steel and very heavy. They recommended adding a return spring. It worked. But not totally. I had to adjust the length of the push rod 4 times, first over shooting and then under shooting, but finally, 1/6 turn on the adjusting nut (yes, ONE FLAT) made all the difference.

If the brake lights are staying on the brakes are dragging. Mine did the same. I carried an infrared temperature sensor, and my brakes got over 500*F. I finally hooked up the brake pressure light that was on the MC and it helped me see what was going on. If I pumped the pedal a couple of times, it would go out, telling me the proportioning valve wasnt quite centering. That 1/6 turn put it dead center and the pressure build-up went away.

Hope this helps, but you need to post your vehicle info and brake configuration for helping mine the best information quickly.

Good Luck!

John L
 

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Not sure whose system the question is referring to, but I get a strong 20" at idle. However, I am running a T-bird super coupe 3.8L V6 in my truck with a super charger, so I was warned that the performance would be hindered, and maybe that is why I need the additional return spring. But they are working great now.
 

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Thanks for the info jclars, and im getting between 15 and 20 on my vacuum. Sunday I moved my vacuum line from the carb to the intake but nothing changed. I can pull my car out of the garage, reverse & forward a few times and everything is fine. Go around the block and when I get back the brake lights are on and the pedal is not returning all the way only missing by about a 1/4 inch. Before I start the engine up I can get under the dash and work the pedal with my hand and the pedal returns excellent and has a good springy feel to it. Im convinced its nothing in the pedal or pedal spring. My 62 Impala has a stock spring on the pedal and its working fine without the booster rod connected to it. And, yes i did drill a new hole in the pedal and have already adjusted the brake light switch. Another thing, sometimes after about 10 seconds the pedal will finish returning but most of the time it wont. The kit i installed was a front disk conversion kit from ebay. New master, booster, front calipers, proportioning valve and brake lines. Earlier i messaged MBM (pirate jacks) and explained everything to them. Im waiting on a response. If they say its the booster and have an explanation of what im experiencing then ill go with a new MBM booster.
 
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