HELP! Cant bleed brakes! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**tkeduk8r** · 12-23-2019, 12:05 AM

Just replaced the master cylinder and proportioning valve on my 85 K20 suburban. Pedal had been inconsistent and based on a couple other threads I decided to pull a proportioning valve out of a parts 84 C20, and install it along with a new master cylinder since I had to bleed the brakes any way. Got everything all reinstalled, and I set up to vac bleed the system out. Started with the right rear drum, loosen the bleeder screw, pull 20Hg/in vacuum, and 0 fluid flow. WTF??? Ive bled alot of brakes and teach students how to as well, as a teach a basic autos class at times. Everything worked OK pulling it into the shop, but this has got me puzzled. Any ideas???
--Mike

**mongocanfly** · 12-23-2019, 12:11 AM

Has that proportioning valve been tripped?
Did you bench bleed the master cyl?

**tkeduk8r** · 12-23-2019, 12:22 AM

Bench bled master as i always do.... no idea if prop valve has been "tripped".... is that fixable?
Mike

**mongocanfly** · 12-23-2019, 12:25 AM

If its tripped it needs recentered ...and theres a tool that holds it centered while bleeding

**mongocanfly** · 12-23-2019, 12:30 AM

There are better vids out there..just look ...
https://m.youtube.com/watch?v=xrjENVu1Bxk

wixthedog · 12-23-2019, 09:12 PM

I've been told you can recenter the combination valve by slamming on the brake pedal pretty hard but never had success. That screw in bleed tool is what you need though once you get it centered back. If you do not have that tool you can still bleed them just just have to bleed slowly instead of jamming on the pedal as usual.

Shugalou · 12-24-2019, 12:10 PM

I had a pain bleeding my brakes and I rebuilt the entire system - lines and all. Someone gave me some advice on the site to build a pressure bleeder and that solved my problems. If you want search up my post history and you'll find it in there.

12-23-2019, 12:05 AM	#1
tkeduk8r Senior Member Join Date: Apr 2001 Location: Alexandria, MN Posts: 1,462	HELP! Cant bleed brakes! Just replaced the master cylinder and proportioning valve on my 85 K20 suburban. Pedal had been inconsistent and based on a couple other threads I decided to pull a proportioning valve out of a parts 84 C20, and install it along with a new master cylinder since I had to bleed the brakes any way. Got everything all reinstalled, and I set up to vac bleed the system out. Started with the right rear drum, loosen the bleeder screw, pull 20Hg/in vacuum, and 0 fluid flow. WTF??? Ive bled alot of brakes and teach students how to as well, as a teach a basic autos class at times. Everything worked OK pulling it into the shop, but this has got me puzzled. Any ideas??? --Mike __________________ 63 C20 2WD, 230/SM420/4.11 73K 68 C30 dump truck, 327,SM425,4.56 66K original 68 C10 2WD SWB Stepper, 250/3-tree/3.73 66K.... Wifes 68 Buick Skylark Custom Conv., 350/TH400/2.56 In our family since '79 69 GMC 1500 SWB 2WD, 350/TH350/3.73 posi... 70 K10 SWB 4X4 4-sp,ps, pb, tilt, buckets, console, sliding back window (Need AC parts) WIP 72 Chevy K20 4x4 350/350/205/4.56 donor 72 Vette 350/M21/3.70 posi, triple black and super fast 84 Olds Cutlass Brougham 350/2004r/4.11 was Dad's

12-23-2019, 12:11 AM	#2
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,686	Re: HELP! Cant bleed brakes! Has that proportioning valve been tripped? Did you bench bleed the master cyl? __________________ Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver

12-23-2019, 12:22 AM	#3
tkeduk8r Senior Member Join Date: Apr 2001 Location: Alexandria, MN Posts: 1,462	Re: HELP! Cant bleed brakes! Bench bled master as i always do.... no idea if prop valve has been "tripped".... is that fixable? Mike __________________ 63 C20 2WD, 230/SM420/4.11 73K 68 C30 dump truck, 327,SM425,4.56 66K original 68 C10 2WD SWB Stepper, 250/3-tree/3.73 66K.... Wifes 68 Buick Skylark Custom Conv., 350/TH400/2.56 In our family since '79 69 GMC 1500 SWB 2WD, 350/TH350/3.73 posi... 70 K10 SWB 4X4 4-sp,ps, pb, tilt, buckets, console, sliding back window (Need AC parts) WIP 72 Chevy K20 4x4 350/350/205/4.56 donor 72 Vette 350/M21/3.70 posi, triple black and super fast 84 Olds Cutlass Brougham 350/2004r/4.11 was Dad's

12-23-2019, 12:25 AM	#4
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,686	Re: HELP! Cant bleed brakes! If its tripped it needs recentered ...and theres a tool that holds it centered while bleeding Attached Images __________________ Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver

12-23-2019, 12:30 AM	#5
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,686	Re: HELP! Cant bleed brakes! There are better vids out there..just look ... https://m.youtube.com/watch?v=xrjENVu1Bxk __________________ Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver

12-23-2019, 09:12 PM	#6
wixthedog Registered User Join Date: Sep 2019 Location: Magnolia, TX Posts: 225	Re: HELP! Cant bleed brakes! I've been told you can recenter the combination valve by slamming on the brake pedal pretty hard but never had success. That screw in bleed tool is what you need though once you get it centered back. If you do not have that tool you can still bleed them just just have to bleed slowly instead of jamming on the pedal as usual. __________________ Mike 1976 C10 RCLB - 350 - SM465 4 Spd - 4.5"/6" Drop Obligatory Build Thread HERE! 1979 C20 RCLB - 350 - TH350 Auto

12-24-2019, 12:10 PM	#7
Shugalou Registered User Join Date: Jan 2013 Location: Toronto, ON Posts: 458	Re: HELP! Cant bleed brakes! I had a pain bleeding my brakes and I rebuilt the entire system - lines and all. Someone gave me some advice on the site to build a pressure bleeder and that solved my problems. If you want search up my post history and you'll find it in there. __________________ Found my dad's old truck http://67-72chevytrucks.com/vboard/s...d.php?t=563321 Newspaper Article Publishing the quest find my dad's old truck http://www.theglobeandmail.com/globe...ticle12494281/



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