My brakes are driving me nuts! ... and not slowing me down! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ckhd · 02-17-2007, 10:47 AM

It's on my '72 'burb K10, power brakes. The brakes didn't work well when I bought it. The previous owner said he replaced the following: master cyl, booster, booster check valve, rear wheel cyls, all linings.

I get good vacuum to the booster, and the check valve will hold vacuum in the booster literally for days. When I bleed the system, I get a good flow of fluid at all four corners.

Now, I discovered that he used "Lucky's Really Nice Brake Shoes" for the rear, and the linings were cracked and falling apart, so I replaced those with some nice Raybestos shoes. I also made sure that the rear drums were adjusted out afterwards. I also replaced the front rotors (they needed turning and were too thin), and the front pads. At this point, I still couldn't stop, and after a little testing I realized that all my stopping was coming from the front brakes (I could lock the fronts up on a dirt road, but the rears just coasted right along). So, I changed the master cylinder. It still behaves exactly as it did with the last master cyl.

Anyone have any ideas? Is there a way to check pressures at various points, and if I can, what should the pressures be? I'm stuck at this point and I have to drive it to Flagstaff next week, and the traffic there is worse than anywhere else I've been (including Phoenix, L.A., San Diego). I'm afraid I'm going to end up smashing up my 'burb when I go.

poorboy · 02-17-2007, 01:17 PM

Have they been like that since you have owned it? You can check the pressure at the calipers and wheel cyld's if you have the gauges. My bro had a similar problem on a 73 Blazer. After he replaced the master he could not get the rears to work.Come to find out the master was backwards from the orig one. We reversed the lines and everythig worked great. You might have someone hold the pedal and start to break lines loose from front to back. Crack them lose just to make sure you have pressure to that point. If the p.o. installed all the parts to try and solve this problem and it did not help it could be the prop valve.

**kwmech** · 02-17-2007, 01:46 PM

Sounds like the prop valve-valve, has slid to the rear not allowing pressure to pass.

*rage'nrat638* · 02-17-2007, 02:01 PM

also the rod between the master and booster might be not adjusted correctly
not allowing the rod to retract fully and never pumping up the rear brakes

PanelDeland · 02-17-2007, 04:04 PM

Also colapsed brake hoses could cause this problem.

ckhd · 02-17-2007, 04:09 PM

OK, found what was wrong!

It was the proportioning valve. I couldn't find a replacement, so I remembered that I read somewhere that if you stood on the pedal with both feet, it would re-center it. I tried that with no luck... so I went to the parts store and bought some speed-bleeders, put them in the front calipers, cracked one open, and THEN stood on the pedal, with both feet. The pedal went clear to the floor, and after a second, I heard a "pop". tightened the bleeder, went out for a test drive and it now stops as well as my 1999 'burb!

Thanks for the help guys!

meathead95 · 02-17-2007, 04:17 PM

Quote:

Originally Posted by ckhd

OK, found what was wrong!

It was the proportioning valve. I couldn't find a replacement, so I remembered that I read somewhere that if you stood on the pedal with both feet, it would re-center it. I tried that with no luck... so I went to the parts store and bought some speed-bleeders, put them in the front calipers, cracked one open, and THEN stood on the pedal, with both feet. The pedal went clear to the floor, and after a second, I heard a "pop". tightened the bleeder, went out for a test drive and it now stops as well as my 1999 'burb!

Thanks for the help guys!

wow i have never heard of anything like that. what are speedbleeders?

ckhd · 02-17-2007, 04:24 PM

Quote:

Originally Posted by meathead95

what are speedbleeders?

Speed bleeders are bleeder screws with a check-valve in them. They allow you to easily bleed your brakes by yourself. They let brake fluid (and air) out, but not back in.

To use them, you crack them open about 1/2 turn, pump the brake about 5 times, then tighten. Don't have to have a buddy pumping the pedal and holding, and all the other fun things associated with bleeding the brakes.

In this situation, it allowed me to prevent the front system from builing pressure without introducing any air into the system.

meathead95 · 02-17-2007, 04:26 PM

ill be damned i have never heard of them. do all the parts stores carry them? are they expensive

*rage'nrat638* · 02-17-2007, 04:36 PM

good for you man..glad every thing worked out. today must be your lucky day

ckhd · 02-17-2007, 04:32 PM

Not all parts stores. Car Quest does, niether Napa near me did. They are in the "Help" section (those red-carded misc parts). Part number 12701 fit my '72.

An independent parts store had them for $10 a pair, but they were out of stock. Car Quest charged me $15 a pair.

grayw0lf · 02-19-2007, 12:39 PM

I'd still be weary of that Prop valve. Have you considered going ahead & finding a replacement?

ckhd · 02-19-2007, 01:33 PM

Quote:

Originally Posted by grayw0lf

I'd still be weary of that Prop valve. Have you considered going ahead & finding a replacement?

Yeah, I actually have decided that the valve is bad. After I 'reset' it, it worked fine for about 3 stops, then it went back to not working. I reset it again, and for three stops again, it was fine, but it is now back to not working.

Anyone have any ideas on where to get one? I can't find one at any of the chain stores, LMC is the only place I've seen one and they want a fortune for it.

bretcopsey · 02-19-2007, 01:41 PM

Maybe just buy an adjustable prop valve from Summit?

http://store.summitracing.com/partde...5&autoview=sku

**WorkinLonghorn** · 02-19-2007, 03:00 PM

Bret,have you tried these? I need a way to keep my rear tires from skidding when the bed is empty.I think it is set for camper set-up. Thx

bretcopsey · 02-19-2007, 03:08 PM

Quote:

Originally Posted by WorkinLonghorn

Bret,have you tried these? I need a way to keep my rear tires from skidding when the bed is empty.I think it is set for camper set-up. Thx

I put one from Wilwood on my 68 Camaro many years ago and it worked great. It looks similar to the one listed here by Stainless Steel Brakes.

http://store.summitracing.com/partde...5&autoview=sku

Supposedly the Summit one is just the Wilwood one with a sticker on it-but a few bucks cheaper?
http://store.summitracing.com/partde...5&autoview=sku

And here is some useful information on installing and adjusting

http://static.summitracing.com/globa.../sum-g3905.pdf

02-17-2007, 10:47 AM	#1
ckhd Registered User Join Date: Oct 2000 Location: St. Johns, Arizona Posts: 2,660	My brakes are driving me nuts! ... and not slowing me down! It's on my '72 'burb K10, power brakes. The brakes didn't work well when I bought it. The previous owner said he replaced the following: master cyl, booster, booster check valve, rear wheel cyls, all linings. I get good vacuum to the booster, and the check valve will hold vacuum in the booster literally for days. When I bleed the system, I get a good flow of fluid at all four corners. Now, I discovered that he used "Lucky's Really Nice Brake Shoes" for the rear, and the linings were cracked and falling apart, so I replaced those with some nice Raybestos shoes. I also made sure that the rear drums were adjusted out afterwards. I also replaced the front rotors (they needed turning and were too thin), and the front pads. At this point, I still couldn't stop, and after a little testing I realized that all my stopping was coming from the front brakes (I could lock the fronts up on a dirt road, but the rears just coasted right along). So, I changed the master cylinder. It still behaves exactly as it did with the last master cyl. Anyone have any ideas? Is there a way to check pressures at various points, and if I can, what should the pressures be? I'm stuck at this point and I have to drive it to Flagstaff next week, and the traffic there is worse than anywhere else I've been (including Phoenix, L.A., San Diego). I'm afraid I'm going to end up smashing up my 'burb when I go. __________________ my 2¢ - t.i.o.l.i. Bowen 1968 K20 fleet 1969 K10 swb fleet 1972 K10 Suburban 1972 C10 lwb step 1992 K1500 'burb 1995 K2500 'burb 1997 C1500 'burb 1999 K1500 2000 K1500 'burb Why do I own so many Suburbans?

02-17-2007, 01:17 PM	#2
poorboy Senior Member Join Date: Jun 2006 Location: Oregon City, Or Posts: 758	Re: My brakes are driving me nuts! ... and not slowing me down! Have they been like that since you have owned it? You can check the pressure at the calipers and wheel cyld's if you have the gauges. My bro had a similar problem on a 73 Blazer. After he replaced the master he could not get the rears to work.Come to find out the master was backwards from the orig one. We reversed the lines and everythig worked great. You might have someone hold the pedal and start to break lines loose from front to back. Crack them lose just to make sure you have pressure to that point. If the p.o. installed all the parts to try and solve this problem and it did not help it could be the prop valve.

02-17-2007, 01:46 PM	#3
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,600	Re: My brakes are driving me nuts! ... and not slowing me down! Sounds like the prop valve-valve, has slid to the rear not allowing pressure to pass.

02-17-2007, 02:01 PM	#4
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	Re: My brakes are driving me nuts! ... and not slowing me down! also the rod between the master and booster might be not adjusted correctly not allowing the rod to retract fully and never pumping up the rear brakes Last edited by rage'nrat638; 07-12-2007 at 06:56 AM.

02-17-2007, 04:04 PM	#5
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: My brakes are driving me nuts! ... and not slowing me down! Also colapsed brake hoses could cause this problem. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

02-17-2007, 04:09 PM	#6
ckhd Registered User Join Date: Oct 2000 Location: St. Johns, Arizona Posts: 2,660	Re: My brakes are driving me nuts! ... and not slowing me down! OK, found what was wrong! It was the proportioning valve. I couldn't find a replacement, so I remembered that I read somewhere that if you stood on the pedal with both feet, it would re-center it. I tried that with no luck... so I went to the parts store and bought some speed-bleeders, put them in the front calipers, cracked one open, and THEN stood on the pedal, with both feet. The pedal went clear to the floor, and after a second, I heard a "pop". tightened the bleeder, went out for a test drive and it now stops as well as my 1999 'burb! Thanks for the help guys! __________________ my 2¢ - t.i.o.l.i. Bowen 1968 K20 fleet 1969 K10 swb fleet 1972 K10 Suburban 1972 C10 lwb step 1992 K1500 'burb 1995 K2500 'burb 1997 C1500 'burb 1999 K1500 2000 K1500 'burb Why do I own so many Suburbans?

02-17-2007, 04:26 PM	#9
meathead95 computer illiterate Join Date: Jan 2001 Location: Des Moines, IA Posts: 6,446	Re: My brakes are driving me nuts! ... and not slowing me down! ill be damned i have never heard of them. do all the parts stores carry them? are they expensive __________________ 72 2wd blazer 72 swb 4x4

02-17-2007, 04:36 PM	#10
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	Re: My brakes are driving me nuts! ... and not slowing me down! good for you man..glad every thing worked out. today must be your lucky day

02-17-2007, 04:32 PM	#11
ckhd Registered User Join Date: Oct 2000 Location: St. Johns, Arizona Posts: 2,660	Re: My brakes are driving me nuts! ... and not slowing me down! Not all parts stores. Car Quest does, niether Napa near me did. They are in the "Help" section (those red-carded misc parts). Part number 12701 fit my '72. An independent parts store had them for $10 a pair, but they were out of stock. Car Quest charged me $15 a pair. __________________ my 2¢ - t.i.o.l.i. Bowen 1968 K20 fleet 1969 K10 swb fleet 1972 K10 Suburban 1972 C10 lwb step 1992 K1500 'burb 1995 K2500 'burb 1997 C1500 'burb 1999 K1500 2000 K1500 'burb Why do I own so many Suburbans?

02-19-2007, 12:39 PM	#12
grayw0lf Registered User Join Date: Apr 2004 Location: Clanton, AL Posts: 1,253	Re: My brakes are driving me nuts! ... and not slowing me down! I'd still be weary of that Prop valve. Have you considered going ahead & finding a replacement? __________________ 85' CUCV M1009!!! The newest addition! 6.2diesel, Th400, NP208, & only 36k miles! 70' C-10 LWB Fleetside - Looking good these days! 05' Dodge Neon 88' Winner Escape Sport 1750 - 4.3v6 94' Seadoo SP 84' Honda TRX200, bare nekkid. Just a frame & tires. Always looking for another project or any good deal!

02-19-2007, 01:41 PM	#14
bretcopsey Registered User Join Date: Oct 2005 Location: dayton, oh Posts: 327	Re: My brakes are driving me nuts! ... and not slowing me down! Maybe just buy an adjustable prop valve from Summit? http://store.summitracing.com/partde...5&autoview=sku __________________ My 51 project http://www.cardomain.com/ride/2285825 My 68 Camaro project http://www.cardomain.com/ride/2277404/1

02-19-2007, 03:00 PM	#15
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,883	Re: My brakes are driving me nuts! ... and not slowing me down! Bret,have you tried these? I need a way to keep my rear tires from skidding when the bed is empty.I think it is set for camper set-up. Thx __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

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