The old drum brakes....again - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jdhcth · 02-09-2008, 10:08 AM

Recently my front manual drum brakes on my 67 LWB started to fade. The brake light would come on when I pressed hard. It would brake unevenly so I figured it need wheel cylinders(they look original) and new shoes.

In the last 2 months I had installed a new MC so upon putting new wheel cylinders and shoes on I figured my problems were over. Well they weren't.

Just got it all back together, bled 'em and test drove. The hardly work at all. I was out of ideas. I let it set for a while, and tried it again.....they were BETTER! What the????? But at the end of the 2nd test drive the were fading again.

This sounds like they need more bleeding but I've bled and bled.

The drums don't look bad, I have not had them turned yet. ANY IDEAS?

My proportioning valve seems to be letting plenty of fluid down, when I bleed there is a lot of fluid. It does not have the little needle valve on the front of it like some models. OH and my brake light doesn't come on anymore.

Thanks,
JD

HavinSomeFun · 02-09-2008, 10:12 AM

could have a faulty MC.

slammed1 · 02-09-2008, 10:23 AM

Bleeding the old way of pumping,pumping can cause a MasterCylinder to act up. I like to open the bleeder on the right rear with the master cyl cover off and let the fluid gravity bleed for a few minutes working to the left rear then right frt and lastly to the left frt. New mastercylinders require bench bleeding first or you will introduce tons of air to the system while bleeding the rest.
Dont forget the drum brakes need to be adjusted as close tot he drums without serious dragging so they are in proper adjusment which makes the pedal feel tighter. Drum brakes out of adjustment can cause low pedal problems.

68gmsee · 02-09-2008, 10:40 AM

If there's a brake problem to be had, I've had it at some time or another.
Need to know what you mean by "fading" though.

To me, it means that when you depress the pedal and the brakes engage, they will start to slip (fade) therefore taking a longer distance to stop with the same amount of pressure on the pedal. This can be caused by shoes being glazed over by oil, grime or brake fluid, overheating, etc. The drums can also get glazed and cause fading. Some brake shoes sold these days may not have the "grabbing" or friction of other makes so supect that also.

If you are referring to another problem disregard this.

slammed1 · 02-09-2008, 10:45 AM

Very true and a "fade" could be mistaken for an internally bypassing master cylinder.

02-09-2008, 10:08 AM	#1
jdhcth Registered User Join Date: Dec 2005 Location: Houston, TX Posts: 51	The old drum brakes....again Recently my front manual drum brakes on my 67 LWB started to fade. The brake light would come on when I pressed hard. It would brake unevenly so I figured it need wheel cylinders(they look original) and new shoes. In the last 2 months I had installed a new MC so upon putting new wheel cylinders and shoes on I figured my problems were over. Well they weren't. Just got it all back together, bled 'em and test drove. The hardly work at all. I was out of ideas. I let it set for a while, and tried it again.....they were BETTER! What the????? But at the end of the 2nd test drive the were fading again. This sounds like they need more bleeding but I've bled and bled. The drums don't look bad, I have not had them turned yet. ANY IDEAS? My proportioning valve seems to be letting plenty of fluid down, when I bleed there is a lot of fluid. It does not have the little needle valve on the front of it like some models. OH and my brake light doesn't come on anymore. Thanks, JD

02-09-2008, 10:12 AM	#2
HavinSomeFun Still Just Havin Some Fun! Join Date: Jun 2007 Location: Piedmont, Oklahoma Posts: 1,145	Re: The old drum brakes....again could have a faulty MC. __________________ a green one with some stuff done to it....

02-09-2008, 10:23 AM	#3
slammed1 1972 Chevrolet SWB Join Date: Jan 2008 Location: FT Smith AR Posts: 512	Re: The old drum brakes....again Bleeding the old way of pumping,pumping can cause a MasterCylinder to act up. I like to open the bleeder on the right rear with the master cyl cover off and let the fluid gravity bleed for a few minutes working to the left rear then right frt and lastly to the left frt. New mastercylinders require bench bleeding first or you will introduce tons of air to the system while bleeding the rest. Dont forget the drum brakes need to be adjusted as close tot he drums without serious dragging so they are in proper adjusment which makes the pedal feel tighter. Drum brakes out of adjustment can cause low pedal problems. __________________ My New thread with pics (not my build thread yet.) http://67-72chevytrucks.com/vboard/s...46#post2573646 1972 Chevrolet 1/2 ton short wide bed,68 frt clip Project. 1980 Camaro Inherited when father passed,68K Miles 2003 Ford Mach1 FUN as Hell!! 2002 Dodge Ram 5-8 slam Rolling BillBoard (Gone not forgot) 2004 Dodge Ram HEMI 10" lifted on 37's and 2wd.

02-09-2008, 10:40 AM	#4
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: The old drum brakes....again If there's a brake problem to be had, I've had it at some time or another. Need to know what you mean by "fading" though. To me, it means that when you depress the pedal and the brakes engage, they will start to slip (fade) therefore taking a longer distance to stop with the same amount of pressure on the pedal. This can be caused by shoes being glazed over by oil, grime or brake fluid, overheating, etc. The drums can also get glazed and cause fading. Some brake shoes sold these days may not have the "grabbing" or friction of other makes so supect that also. If you are referring to another problem disregard this.

02-09-2008, 10:45 AM	#5
slammed1 1972 Chevrolet SWB Join Date: Jan 2008 Location: FT Smith AR Posts: 512	Re: The old drum brakes....again Very true and a "fade" could be mistaken for an internally bypassing master cylinder. __________________ My New thread with pics (not my build thread yet.) http://67-72chevytrucks.com/vboard/s...46#post2573646 1972 Chevrolet 1/2 ton short wide bed,68 frt clip Project. 1980 Camaro Inherited when father passed,68K Miles 2003 Ford Mach1 FUN as Hell!! 2002 Dodge Ram 5-8 slam Rolling BillBoard (Gone not forgot) 2004 Dodge Ram HEMI 10" lifted on 37's and 2wd.



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