One last brake ?? (hopefully) - The 1947 - Present Chevrolet & GMC Truck Message Board Network

motocrosschump · 06-07-2005, 09:43 AM

I have replaced all the wheel cylinders, brake shoes, and Master Cylinder. I have front brakes but no back. I have tried to bleed them the regular way and no fluids comes out. I bought a vacuum pump and nothing comes out. So I am sure there is something clogged somewhere. Other than taking all the lines off, is there a way to blow throw the lines without taking them off the truck?

smokekiki · 06-07-2005, 09:51 AM

Did You bench bleed the master?

boraxman · 06-07-2005, 10:19 AM

Compressed air?

355 · 06-07-2005, 10:23 AM

I had the same thing with my conversion to front disc. Two things were wrong, 1) The combination valve had shuttled and gave a hard pedal but no rear, 2) The outlet area on the distribution block to the rear was stopped up with junk. Cleaned out the crap and reset the combo, check this troubleshooting guide http://www.mpbrakes.com/troubleshooting.htm. Broke connections from the rear forward untill I did get flow. Hope this helps

motocrosschump · 06-07-2005, 11:04 AM

Quote:

Originally Posted by smokekiki

Did You bench bleed the master?

Yes..I believe I did it right according to the instructions

fastwillie 696969 · 06-07-2005, 11:43 AM

try bleed the mastercylinder again just pump up the brakes and hold them crack the line and wait for a stead stream of fluid once thats done then go back to the rear and bleed them if nothing comes out then go to and check the comb block crack the line where it goes into the block see if it bleeds out if not the it a bad mastercylinder

motocrosschump · 06-07-2005, 12:13 PM

Quote:

Originally Posted by 70blowngmc

try bleed the mastercylinder again just pump up the brakes and hold them crack the line and wait for a stead stream of fluid once thats done then go back to the rear and bleed them if nothing comes out then go to and check the comb block crack the line where it goes into the block see if it bleeds out if not the it a bad mastercylinder

crack the line on the MC??

I am ingorant when it comes to trucks. But I am learning.

More info...when using the vacuum pump the pressure keeps rising and rising like no air is being drawn out. Wouldn't that be a stopped hose? Please excuse my ignorance.

smokekiki · 06-07-2005, 12:22 PM

Crack the line =loosen the nut,just enough to get fluid flow.Do this at each joint,one at a time.

smbrouss70 · 06-07-2005, 12:28 PM

Just a thought, I had a similar problem before and it turned out to be a collapsed brake hose from the frame to the rear axle. I don't know if you replaced those or not. Mine looked fine from the outside but it separated on the inside to cause the clog.

70GMC_BOB · 06-07-2005, 01:48 PM

I also had the same callopsed rear brake hose problem that caused similar results. I would replace that hose. The only indication I saw was it was damp where the high pressure fitting.

motocrosschump · 06-07-2005, 02:15 PM

That might be it, I have replaced every rubber hose except that one, because it appeared to be in good shape.

You guys are the best..Will keep you informed.

70GMC_BOB · 06-07-2005, 02:18 PM

mine was on a 72 3/4 ton w/ a dana 60. everybody listed the wrong part. I had a guy at my local repair shop look in a book and found the correct part #. the only thing I don't like is the hose is 12" to long, but I was moving and need my truck so I had them coil ti and zip tie it.

Americanrider · 06-09-2005, 12:26 AM

"...when using the vacuum pump the pressure keeps rising and rising like no air is being drawn out. Wouldn't that be a stopped hose?"

Maybe a clogged bleeder? They are down there where are the road dirt and mud can build up, easy to pull and check.

06-07-2005, 09:43 AM	#1
motocrosschump Registered User Join Date: May 2005 Location: Texarkana, AR 71854 Posts: 397	One last brake ?? (hopefully) I have replaced all the wheel cylinders, brake shoes, and Master Cylinder. I have front brakes but no back. I have tried to bleed them the regular way and no fluids comes out. I bought a vacuum pump and nothing comes out. So I am sure there is something clogged somewhere. Other than taking all the lines off, is there a way to blow throw the lines without taking them off the truck? __________________ 2006 Titan SE Crew Cab Daily Driver 2005 Mazda Tribute (Wifes car) 1969 C10 SWB 350/3 Fleet "Max" 1969 Chevelle 2 door 350/3

06-07-2005, 09:51 AM	#2
smokekiki Mike Join Date: Jan 2003 Location: west chester pa Posts: 2,474	Did You bench bleed the master? __________________ 70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires

06-07-2005, 10:19 AM	#3
boraxman Keepin an eye out Join Date: Feb 2003 Location: So.Cal Posts: 3,921	Compressed air? __________________ 1970 Chevy C10 SWB 5.3 1996 Toyota Tacoma SR5 4x4 2007 Vespa GTS 250 Scooter ZIP 91351

06-07-2005, 11:43 AM	#6
fastwillie 696969 ~Rest In Peace~ Join Date: May 2005 Location: CALIFORNIA NOR CAL Posts: 9,707	try bleed the mastercylinder again just pump up the brakes and hold them crack the line and wait for a stead stream of fluid once thats done then go back to the rear and bleed them if nothing comes out then go to and check the comb block crack the line where it goes into the block see if it bleeds out if not the it a bad mastercylinder __________________ is it fast ? it has a lighting bolt donut? B___H please, I can remove 90% of your so called "beauty" with a kleenex

06-07-2005, 12:22 PM	#8
smokekiki Mike Join Date: Jan 2003 Location: west chester pa Posts: 2,474	Crack the line =loosen the nut,just enough to get fluid flow.Do this at each joint,one at a time. __________________ 70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires

06-07-2005, 10:23 AM	#4
355 Registered User Join Date: May 2005 Location: South Mississippi Posts: 81	I had the same thing with my conversion to front disc. Two things were wrong, 1) The combination valve had shuttled and gave a hard pedal but no rear, 2) The outlet area on the distribution block to the rear was stopped up with junk. Cleaned out the crap and reset the combo, check this troubleshooting guide http://www.mpbrakes.com/troubleshooting.htm. Broke connections from the rear forward untill I did get flow. Hope this helps

06-07-2005, 12:28 PM	#9
smbrouss70 Registered User Join Date: Sep 2003 Location: Rayne, LA Posts: 2,782	Just a thought, I had a similar problem before and it turned out to be a collapsed brake hose from the frame to the rear axle. I don't know if you replaced those or not. Mine looked fine from the outside but it separated on the inside to cause the clog. __________________ Steven "If dogs don't go to heaven, when I die I want to go wherever they went." -- Will Rogers R.I.P. Oscar R.I.P. Ratchet 1967 Pontiac GTO - Dad was the Original Owner 1970 Chevy 2wd SWB "Oscar's Truck" 1970 Chevy 2wd Blazer "Ratchet's Blazer" 2013 Chevy 2500HD Crew Cab Duramax/Allison Z71 LTZ "Brown Sugar" 2017 Chevy Suburban "BDB" 2020 Chevy Blazer Premier "Foxy" Member of Louisiana Classic Truck Club (LCTC) Shop Build

06-07-2005, 01:48 PM	#10
70GMC_BOB Registered User Join Date: Jul 2001 Location: Lynnwood, washington Posts: 121	I also had the same callopsed rear brake hose problem that caused similar results. I would replace that hose. The only indication I saw was it was damp where the high pressure fitting. __________________ 1972 chev c20 2wd lwb 350v8/th350. (dad's)1970 gmc longstep (9ft commercial bed), 1 ton, 2wd, 350/th400.

06-07-2005, 02:15 PM	#11
motocrosschump Registered User Join Date: May 2005 Location: Texarkana, AR 71854 Posts: 397	That might be it, I have replaced every rubber hose except that one, because it appeared to be in good shape. You guys are the best..Will keep you informed. __________________ 2006 Titan SE Crew Cab Daily Driver 2005 Mazda Tribute (Wifes car) 1969 C10 SWB 350/3 Fleet "Max" 1969 Chevelle 2 door 350/3

06-07-2005, 02:18 PM	#12
70GMC_BOB Registered User Join Date: Jul 2001 Location: Lynnwood, washington Posts: 121	mine was on a 72 3/4 ton w/ a dana 60. everybody listed the wrong part. I had a guy at my local repair shop look in a book and found the correct part #. the only thing I don't like is the hose is 12" to long, but I was moving and need my truck so I had them coil ti and zip tie it. __________________ 1972 chev c20 2wd lwb 350v8/th350. (dad's)1970 gmc longstep (9ft commercial bed), 1 ton, 2wd, 350/th400.

06-09-2005, 12:26 AM	#13
Americanrider Registered User Join Date: Dec 2004 Location: NW, WA. Posts: 1,421	"...when using the vacuum pump the pressure keeps rising and rising like no air is being drawn out. Wouldn't that be a stopped hose?" Maybe a clogged bleeder? They are down there where are the road dirt and mud can build up, easy to pull and check.



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