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power brake issue

There is a glaring problem here guys that can’t be overlooked on ANY brake system. He has engine vacuum at the booster but no vacuum “suck” after shutting off the engine and pulling the check valve off the booster. He is loosing vacuum in the booster.
 
rumcustom said:
There is a glaring problem here guys that can’t be overlooked on ANY brake system. He has engine vacuum at the booster but no vacuum “suck” after shutting off the engine and pulling the check valve off the booster. He is loosing vacuum in the booster.
Click to expand...
Thanks Rum, you've been a big help, but correct me if I'm wrong. The check valve lets vacuum into the booster but does not let it out. As it seems mine was letting vacuum out. Immediately after shutting off engine there is no vacuum at all. When i remove the valve and place a vacuum on the side that goes into the booster it just sucks out the other end. Upon looking closely the rubber disc inside looked like it was not flush
I cut the valve open and unfortunately i dropped it but the disc was not against its seat. I though maybe there should be a spring but i could not find one. What there is a little "tit" molded into the plastic and a small hole in the seat. This holds the rubber disc in the cylinder of the valve. When i put the disc back on the tit and applies a vacuum on the part going into the booster it held. So it looks like the disc inside came off its tab. I have to say the check valve is cheaply made, i would think the designers could come up with a better idea. I cant find the right size in the auto parts store so i will cal Booster Dewey tomorrow
Do you guys think this is the problem? Im hopeful as pulling that booster does not look like a fun filled dayLOL. Thanks
 
steve from staten island said:
Thanks Rum, you've been a big help, but correct me if I'm wrong. The check valve lets vacuum into the booster but does not let it out. As it seems mine was letting vacuum out. Immediately after shutting off engine there is no vacuum at all. When i remove the valve and place a vacuum on the side that goes into the booster it just sucks out the other end. Upon looking closely the rubber disc inside looked like it was not flush
I cut the valve open and unfortunately i dropped it but the disc was not against its seat. I though maybe there should be a spring but i could not find one. What there is a little "tit" molded into the plastic and a small hole in the seat. This holds the rubber disc in the cylinder of the valve. When i put the disc back on the tit and applies a vacuum on the part going into the booster it held. So it looks like the disc inside came off its tab. I have to say the check valve is cheaply made, i would think the designers could come up with a better idea. I cant find the right size in the auto parts store so i will cal Booster Dewey tomorrow
Do you guys think this is the problem? Im hopeful as pulling that booster does not look like a fun filled dayLOL. Thanks
Click to expand...
The running engine pulls a vacuum on the booster. It pulls air out of the booster, through the check valve, and into the engine and creates a partial vacuum inside, which gives the assist needed with power brakes. When the engine is shut off air will not suck back into the booster if the check valve is working properly. After you shut the engine off, the booster should hold a vacuum until you pull the check valve out of the booster itself.
 
rumcustom said:
The running engine pulls a vacuum on the booster. It pulls air out of the booster, through the check valve, and into the engine and creates a partial vacuum inside, which gives the assist needed with power brakes. When the engine is shut off air will not suck back into the booster if the check valve is working properly. After you shut the engine off, the booster should hold a vacuum until you pull the check valve out of the booster itself.
Click to expand...
The booster does not hold a vacuum at all when the engine is off. With the engine running if i pulled the check valve out, i hear a distinctive sound of rushing air. So i assume the booster is holding vacuum.
All roads are pointing toward a bad check valve. My question is with the car in actually operation how much would a defective check valve affect braking. Thanks
 
Hmmm. Good question. I suppose if the engine vacuum was always high enough all the time then you wouldn’t theoretically need a check valve unless the engine stalled while driving.
Hate to hear next week you had to pull the booster if it turns out to be something else. You can’t get a match on the check valve at NAPA?
 
What happened was i broke the first valve accidentally. I only tried discount auto stores and couldn't get what i needed, so Dewey sent me a replacement.
Tomorrow i will try a real auto parts store. Im still calling Dewey booster and talking to them. I really want to believe the booster is ok and its the check valve. Thanks ever so much
 
Use your mouth to see if the check valve works. Blow through both sides, only one side should let you blow through. Even if the check valve isn't checking your booster should still work while the engine is running I would think.
 
The check valve is not working for sure. The rubber disc inside came undone from its seat. Everything i read says the check valve not working will give you a hard pedal and affect stoping. My question is how and why. The engine is running and has vacuum. I thought on deceleration vacuum goes higher, so the booster would work.
Now I'm wondering about the other end of the booster were the brake pedal connects. Is there a adjustment there? If rod on that end has slightly holding open would the booster work right. We know when you step on the brakes the air rushes in and the vacuum then assists and pushes the master cylinder rod.
Im going to wind up pulling the drivers side bucket seat and seeing whats going on up there
 
Hey Steve. Did you ever fix your brake problem? I was wondering what the issue was
 
rumcustom said:
Hey Steve. Did you ever fix your brake problem? I was wondering what the issue was
Click to expand...
Ok so i installed a dual diagram booster. The problem is a little better but brakes are still not working as they should. I have to stand on the pedal to get the brakes to lock up. There just not right
What i should have realized is when i bled the front discs. I ordered a pressure gauge and adapters from Summit, it wasnt expensive. I have to check the pressure at the calipers. I have a stinking feeling I'm going to find a low pressure. Will let you know what happens
 
steve from staten island said:
Ok so i installed a dual diagram booster. The problem is a little better but brakes are still not working as they should. I have to stand on the pedal to get the brakes to lock up. There just not right
What i should have realized is when i bled the front discs. I ordered a pressure gauge and adapters from Summit, it wasnt expensive. I have to check the pressure at the calipers. I have a stinking feeling I'm going to find a low pressure. Will let you know what happens
Click to expand...
Well?
 
Joe66satellite said:
Well?
Click to expand...
Sorry Joe. I think in retrospect there was more than one issue. The engine vacuum could be better and after the engine is rebuilt we will see how much vacuum I have. The brake booster was a single diaphragm and I went with a dual diaphragm which helped but the biggest factor was the master cylinder. I did not have enough pressure at the calipers, that was the problem. Eventually I talked with Dr Differential and this guy is very good, he explained many things and I wound up using a booster with a smaller piston which gave me the pressure boost I needed. After that the brakes felt much better. I found out the hard way that cheaper disc brake conversions can be problematic at times
 
steve from staten island said:
Sorry Joe. I think in retrospect there was more than one issue. The engine vacuum could be better and after the engine is rebuilt we will see how much vacuum I have. The brake booster was a single diaphragm and I went with a dual diaphragm which helped but the biggest factor was the master cylinder. I did not have enough pressure at the calipers, that was the problem. Eventually I talked with Dr Differential and this guy is very good, he explained many things and I wound up using a booster with a smaller piston which gave me the pressure boost I needed. After that the brakes felt much better. I found out the hard way that cheaper disc brake conversions can be problematic at times
Click to expand...
I think you're right and I'm dealing with that now thank you
 
steve from staten island said:
\

I meant to say Master with a smaller piston
Click to expand...
Yeah I figured it out I guess I know all about it I've been reading enough on this wonderful website and all of the knowledge out there and a guy can't help but get his problem solved just by tuning in thank you Steve and may you be well
 
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