Rear Brakes self adjusting - The 1947 - Present Chevrolet & GMC Truck Message Board Network

CrashBob · 01-06-2011, 10:37 AM

Hey,

I recently did a complete brake overhaul on my '67 C20 and after driving it maybe 200 miles, the rear brakes locked up after I backed out of a parking space. I had to take off the wheels and back the adjusters down so I could get home.
When I got it in the garage to see what broke, everything looked fine. It has started to ''auto adjust'' again. Any ideas? I took pix before dis-assembly and put em back the same way. Also why are the adjuster slots on the drums? What a pain!

In advance, thanks for any help offered

CrashBob

68gmsee · 01-06-2011, 11:14 AM

The self adjusters should work only when the brakes are out of adjustment (at least that's the theory). So if they're adjusted properly, then definitely something else is wrong with them. I'll look up some pics for you.

Make absolutely sure that it's the brakes and not the rear rubber brake hose
swelled up internally. It's the one on the rear axle to the frame. It prevents the fluid from returning to the master cylinder. Common problem on these old trucks.

http://auto.howstuffworks.com/auto-p...rum-brake2.htm

GCncsuHD · 01-06-2011, 11:21 AM

Quote:

Originally Posted by 68gmsee

Make absolutely sure that it's the brakes and not the rear rubber brake hose
swelled up internally. It's the one on the rear axle to the frame. It prevents the fluid from returning to the master cylinder. Common problem on these old trucks.

This, when you hit the brakes, it will keep the pressure from bleeding off for quite a while, then when it does, it seems as if all is fine, till you use the brakes again.

CrashBob · 01-06-2011, 03:49 PM

Quote:

Originally Posted by 68gmsee

The self adjusters should work only when the brakes are out of adjustment (at least that's the theory). So if they're adjusted properly, then definitely something else is wrong with them. I'll look up some pics for you.

Make absolutely sure that it's the brakes and not the rear rubber brake hose
swelled up internally. It's the one on the rear axle to the frame. It prevents the fluid from returning to the master cylinder. Common problem on these old trucks.

http://auto.howstuffworks.com/auto-p...rum-brake2.htm

Ah Hah!! That hose issue makes a lot of sense! I will change it out as soon as I get back from a job in CA.

Thanks!

I've said it before and I'll say it again...This forum and the people on it can't be beat, the greatest!

CrashBob

cparman · 01-06-2011, 06:37 PM

I would think that if the rear brake hose was collapsed, and that was what was making the brakes stay on, you should be able to open the bleeders and relieve pressure? I have seen a brake drum that is too thin ( past minimum thickness ) flex so much that it allowed the self adjusters to keep on adjusting. To the point it burned the brake shoes clean off. Might check to see if the drums have plenty of meat left.

**oldgold70c10** · 01-06-2011, 08:34 PM

Had the same thing happen to me on my C20 burb last weekend. Turned out to be a frozen-up parking brake cable. Every time I would go backwards, the adjuster would adjust the shoes so it would grab harder going forward. As a temporary fix, I just cut the cable near where it goes thru the brake backing plate.

CrashBob · 01-07-2011, 09:22 PM

All good ideas on possible causes!
Thanks again

CrashBob

01-06-2011, 10:37 AM	#1
CrashBob Registered User Join Date: Jun 2004 Location: Utica Nebraska Posts: 244	Rear Brakes self adjusting Hey, I recently did a complete brake overhaul on my '67 C20 and after driving it maybe 200 miles, the rear brakes locked up after I backed out of a parking space. I had to take off the wheels and back the adjusters down so I could get home. When I got it in the garage to see what broke, everything looked fine. It has started to ''auto adjust'' again. Any ideas? I took pix before dis-assembly and put em back the same way. Also why are the adjuster slots on the drums? What a pain! In advance, thanks for any help offered CrashBob __________________ "Life is all about ass. You're either covering it,laughing it off, kicking it, kissing it, busting it or trying to get a piece of it.

01-06-2011, 11:14 AM	#2
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Rear Brakes self adjusting The self adjusters should work only when the brakes are out of adjustment (at least that's the theory). So if they're adjusted properly, then definitely something else is wrong with them. I'll look up some pics for you. Make absolutely sure that it's the brakes and not the rear rubber brake hose swelled up internally. It's the one on the rear axle to the frame. It prevents the fluid from returning to the master cylinder. Common problem on these old trucks. http://auto.howstuffworks.com/auto-p...rum-brake2.htm

01-06-2011, 06:37 PM	#5
cparman sharp as a marble Join Date: Jan 2007 Location: atlantic beach,florida Posts: 1,082	Re: Rear Brakes self adjusting I would think that if the rear brake hose was collapsed, and that was what was making the brakes stay on, you should be able to open the bleeders and relieve pressure? I have seen a brake drum that is too thin ( past minimum thickness ) flex so much that it allowed the self adjusters to keep on adjusting. To the point it burned the brake shoes clean off. Might check to see if the drums have plenty of meat left.

01-06-2011, 08:34 PM	#6
oldgold70c10 Who's got steelies? Join Date: Feb 2006 Location: Morrison, Oklahoma Posts: 1,026	Re: Rear Brakes self adjusting Had the same thing happen to me on my C20 burb last weekend. Turned out to be a frozen-up parking brake cable. Every time I would go backwards, the adjuster would adjust the shoes so it would grab harder going forward. As a temporary fix, I just cut the cable near where it goes thru the brake backing plate. __________________ 1969 C10 LWB W/ 250 I6 & 3spd 1970 C10 with '67 small window cab, 68 front end, blue; 305/TH350, 3.08 limited slip rear end, manual brakes, power steering; & 4-wheel drums-My daily driver. 1975 Chevelle Malibu Classic Coupe 350/th350 mint green 1970 C20 Suburban 350/700R4 4.10 gearing green & white 1978 Big 10 Silverado 350/th350, working ac, 2 tone blue-My summer daily driver 1983 GMC 1500 Sierra 305/SM465 2.73 rear end How to add a trip odometer to your 67-72 stock speedometer How to rebuild your Q-Jet My Truck Page My Youtube Channel

01-07-2011, 09:22 PM	#7
CrashBob Registered User Join Date: Jun 2004 Location: Utica Nebraska Posts: 244	Re: Rear Brakes self adjusting All good ideas on possible causes! Thanks again CrashBob __________________ "Life is all about ass. You're either covering it,laughing it off, kicking it, kissing it, busting it or trying to get a piece of it.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.