Brakes not working - The 1947 - Present Chevrolet & GMC Truck Message Board Network

craig24671 · 11-10-2010, 05:02 PM

I put a new master cylinder and power brake booster on my truck and have bled the brakes twice and they still have to be pumped up to make them work WTH? Can someone help me

cdowns · 11-10-2010, 05:11 PM

have you followed the directions in the factory service manual for the proper way to bleed the brakes??

Sammy · 11-10-2010, 05:16 PM

Still has air. So hard to bleed these trucks. After a bench bleed on MC you can try disconnecting the lines at each brake cylinder one at a time to insure they are getting fluid. (It isn't unheard of getting bad new/rebuilt master cylinders from parts houses)
Due a search on brake cylinder bleeding this has been a previously asked question. With folks spending several days trying to bleed them.

Lee H · 11-10-2010, 05:42 PM

If you can't get the air out you should take your ride to a brake shop and have them bleed it. Your, as well as others, safety is at risk.

cparman · 11-10-2010, 08:45 PM

Is it a disc drum set up? My first move would be to be SURE the the rear brake are adjusted properly. Secondly, I would check the clearance between the booster rod and the master cylinder. Here is what I do:
Unbolt the master cylinder without disconnecting the brake lines, get a small ball of clay 1/4" stick it on the booster rod, and bolt the master cylinder back to the booster. then unbolt the master cylinder and see if it has crushed. If not your rod from the booster needs to be a bit longer. you only need 1/16" clearance. I have welded a bead onto the booster rod to correct this.

All of the above is AFTER you are sure you have no air in the system. I have done a bunch of disc conversions, and never get excited until I have checked the booster/master clearance

craig24671 · 11-10-2010, 09:17 PM

Thanks for the replies. I forgot to note that my calipers got super hot and I replaced the booster and master, and when i try to bleed the front fluid squirts back into the mastter in a solid stream, do ya'll think I possibly need to change the calipers to? I have never had a problem bleeding brakes by the way, it's a simple process.

11-10-2010, 05:02 PM	#1
craig24671 Registered User Join Date: Oct 2006 Location: Overton,Texas Posts: 148	Brakes not working I put a new master cylinder and power brake booster on my truck and have bled the brakes twice and they still have to be pumped up to make them work WTH? Can someone help me __________________ Spanky

11-10-2010, 05:11 PM	#2
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Brakes not working have you followed the directions in the factory service manual for the proper way to bleed the brakes?? __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

11-10-2010, 05:16 PM	#3
Sammy Registered User Join Date: Apr 2000 Location: Bonne Terre, Mo Posts: 3,005	Re: Brakes not working Still has air. So hard to bleed these trucks. After a bench bleed on MC you can try disconnecting the lines at each brake cylinder one at a time to insure they are getting fluid. (It isn't unheard of getting bad new/rebuilt master cylinders from parts houses) Due a search on brake cylinder bleeding this has been a previously asked question. With folks spending several days trying to bleed them. __________________ '69 Chevy Long Fleet & '71 GMC Short Step & Project "ODD BALL" "You can wash a pig, soak it in most expensive perfume. In the end it is still just a pig." ODD BALL build thread http://67-72chevytrucks.com/vboard/s...d.php?t=478629"

11-10-2010, 05:42 PM	#4
Lee H Registered User Join Date: Jun 2010 Location: Upland Ca Posts: 4,143	Re: Brakes not working If you can't get the air out you should take your ride to a brake shop and have them bleed it. Your, as well as others, safety is at risk. __________________ 1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703

11-10-2010, 08:45 PM	#5
cparman sharp as a marble Join Date: Jan 2007 Location: atlantic beach,florida Posts: 1,082	Re: Brakes not working Is it a disc drum set up? My first move would be to be SURE the the rear brake are adjusted properly. Secondly, I would check the clearance between the booster rod and the master cylinder. Here is what I do: Unbolt the master cylinder without disconnecting the brake lines, get a small ball of clay 1/4" stick it on the booster rod, and bolt the master cylinder back to the booster. then unbolt the master cylinder and see if it has crushed. If not your rod from the booster needs to be a bit longer. you only need 1/16" clearance. I have welded a bead onto the booster rod to correct this. All of the above is AFTER you are sure you have no air in the system. I have done a bunch of disc conversions, and never get excited until I have checked the booster/master clearance

11-10-2010, 09:17 PM	#6
craig24671 Registered User Join Date: Oct 2006 Location: Overton,Texas Posts: 148	Re: Brakes not working Thanks for the replies. I forgot to note that my calipers got super hot and I replaced the booster and master, and when i try to bleed the front fluid squirts back into the mastter in a solid stream, do ya'll think I possibly need to change the calipers to? I have never had a problem bleeding brakes by the way, it's a simple process. __________________ Spanky

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