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How do you tell if a Brake Combination Valve is Defective?
Can anyone tell me how you can diagnose a combination valve? I have replaced almost ALL of the front and rear brake components on my truck but the brakes are still terrible! I get very little nose dive on the truck when the brakes are applied with a lot of pressure and my only thought was that the metering valve component of the valve may be defective. Any thoughts?
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Re: How do you tell if a Brake Combination Valve is Defective?
Just my 2 cents but, I had an 81 do this same thing, you practically had to stand on the pedal to make it work. I went thru and changed a bunch of stuff and ended up living with it. I sold the truck to a friend who drove it into the ground and never cared to fix anything. I ended up buying it back a year or two later and as soon as I drove it I knew it needed a booster. I guess it was just slowly on it's way out when I had it and he could have cared less. When I was trying to diagnose it, it still held vacum if u pulled off the hose and the pedal sunk when u started it. I guess I'm trying to say maybe it's the booster, you never can tell seems like!
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Re: How do you tell if a Brake Combination Valve is Defective?
Been there, done that.
Replace your booster with a dual diaphram booster. It'll put you through the windshield. :) |
Re: How do you tell if a Brake Combination Valve is Defective?
Thanks. I have not yet replaced the booster. Like you mention, mine does hold vacuum and I stopped looking there. Do you know how to test a booster other than checking for leaks at the hose and fitting?
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Re: How do you tell if a Brake Combination Valve is Defective?
Like i said it didn't work for me but u might as well try it. Sit in the truck with the engine off apply the brake fairly firm and then start the truck, if it is working properly the pedal should drop when the engine starts. I'm not sure this is an official troubleshooting method, I learned it as one of those "grandfather" teachings in a shop I used to work at.
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Re: How do you tell if a Brake Combination Valve is Defective?
I just googled your symptom, and found this link:
http://autorepair.about.com/cs/troub...g/a/bl302a.htm hope this helps |
Re: How do you tell if a Brake Combination Valve is Defective?
Will the rest of my brake components work with a dual-diaphram booster? Or will I have to replace (again) the Master Cylinder? Is the dual-diaphram booster a 3/4 ton unit, or for a later year truck? The reason I am asking is when I go to NAPA I just want to ask for the correct part. Thanks.
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Re: How do you tell if a Brake Combination Valve is Defective?
You will need to make sure the MC is designed to work with the new booster. The push rods can be of different length.
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