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#26 |
Senior Member
![]() Join Date: Mar 2003
Location: Colfax-California
Posts: 8,543
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Re: Proportioning Valve Keeps Tripping?
That's what I was getting after, 1/2 vs 3/4 have swapped lines back and forth regarding the placement of the residual valves.
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#27 |
Active Member
![]() Join Date: Apr 2021
Location: Santa Cruz, NM
Posts: 100
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Re: Proportioning Valve Keeps Tripping?
I like Mike B's master cylinder bleeder lines. I was thinking about a tee off the proportioning valve port with a bleeder screw, or straight to a bleeder screw with an adapter (if manufactured), or a tube nut with hard line and vinyl hose. Isn't there a brake line coupler on the frame rail? Maybe you could bleed from there also. I think you're right, it's more likely that you have an air bubble near the start of the rear brake line. Good luck.
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#28 |
Senior Member
![]() Join Date: Jun 2022
Location: San Ramon,CA
Posts: 504
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Re: Proportioning Valve Keeps Tripping?
I rigged up one of these from the old lines(after I lost the plastic pieces that came with the MC). I prolly would have never bothered with syringe bleeding had I known at the time that thrashing on the brakes creates thousands of tiny bubbles through cavitation, as does applying stupid heavy vacuum
__________________
1970 C10 Custom longbed 350/350 |
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#29 |
Senior Member
![]() Join Date: Mar 2014
Location: Toano, VA
Posts: 874
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Re: Proportioning Valve Keeps Tripping?
This weekend I tried the power bleeder. No dice.
I am beginning to believe I am pulling air, but not leaking fluid. I have heard numerous times now about wheel cylinders bringing mystery air in. These wheel cylinders are probably 8 years old, never used. That being said, I never had fluid in the system to test them. I am going to replace them and recheck. Everytime I go to bleed the rears, I get micro bubbles and sometimes very small ones, but regardless I get a stream every time I open the bleeder. I ran nearly a gallon of fluid through them and still had the same situation. I also rebled the master cylinder to ensure no air is trapped in it, and it bled clean.
__________________
"Sometimes I do serve as a good bad example. Glad to be of service." My Build Thread (1967 C10, lowered, EFI, daily truck): http://67-72chevytrucks.com/vboard/s...d.php?t=830809 |
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#30 |
Registered User
Join Date: Jul 2008
Location: Eastern Oregon
Posts: 2,337
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Re: Proportioning Valve Keeps Tripping?
Kyle I applaud your persistence ! Keep at it ! Lots of people will learn from your experience..Jack
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71 C-20 07 Magnum RT AWD |
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#31 | |
Senior Member
![]() Join Date: Jul 2000
Location: North Texas
Posts: 3,490
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Re: Proportioning Valve Keeps Tripping?
Quote:
FYI, if you are pulling fluid trough the bleeder valves using a vacuum pump like a MityVac, you will almost always see bubbles from air creeping in between the hose and bleeder valve.
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Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! Last edited by MikeB; 03-18-2024 at 05:52 PM. |
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#32 |
Senior Member
![]() Join Date: Apr 2016
Location: Cypress, TX
Posts: 3,716
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Re: Proportioning Valve Keeps Tripping?
What are the full specs for the kit, or webpage where it is sold?
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#33 |
Registered User
Join Date: Apr 2022
Location: Moorpark, CA
Posts: 758
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Re: Proportioning Valve Keeps Tripping?
It is not uncommon to pull air from bleeder nipples being loosened to bleed at the threads. A thin coat of silicone on the bleeder nipple threads prevents this. Do not use Teflon tape.
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#34 |
Registered User
Join Date: Apr 2010
Location: So Cal
Posts: 1,437
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Re: Proportioning Valve Keeps Tripping?
He stated that he is using the speed bleeders. They come with a thread coating, although this coating could have deteriorated. A common problem with vacuum bleeding is sucking air past the bleeder threads unless the threads are wrapped.
He also said he has tried a pressure bleater. I could see a problem with manual bleeding, if debris is holding the Speed Bleeder Valve open and the valve is not closed, each time the pedal is withdrawn. This wouldn't affect vacuum or pressure bleeding. My only conclusion from all of the above postings is that the Primary Section of the MC has failed.
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'67 GMC 2500, 292, 4spd, AC |
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#35 |
Senior Member
![]() Join Date: Jun 2022
Location: San Ramon,CA
Posts: 504
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Re: Proportioning Valve Keeps Tripping?
You could always let it gravity bleed :shrug:
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1970 C10 Custom longbed 350/350 |
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#36 | |||||
Senior Member
![]() Join Date: Mar 2014
Location: Toano, VA
Posts: 874
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Re: Proportioning Valve Keeps Tripping?
Quote:
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I have tried this as well. Still no dice unfortunately.
__________________
"Sometimes I do serve as a good bad example. Glad to be of service." My Build Thread (1967 C10, lowered, EFI, daily truck): http://67-72chevytrucks.com/vboard/s...d.php?t=830809 |
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#37 |
Senior Member
![]() Join Date: Jul 2000
Location: North Texas
Posts: 3,490
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Re: Proportioning Valve Keeps Tripping?
Might be a PITA to bypass the combination valve with temporary hard lines, but that would probably tell you where the problem is. Of course you would need the proper bending and flaring tools, along with fittings.
Is still don't see the problem being a wheel cylinder or something else "sucking in" air.
__________________
Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
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#38 |
Registered User
Join Date: Jan 2007
Location: Topeka,KS
Posts: 778
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Re: Proportioning Valve Keeps Tripping?
Have you tried adjusting the push rod between the the boostewr and master cylinder
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68' C20. 283CI w/55CC 305HO heads, NP435 Close Ratio, Corp. 14 bolt FF 3.21, 75' front end swap (everything but the X-member). |
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#39 |
Senior Member
![]() Join Date: Mar 2014
Location: Toano, VA
Posts: 874
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Re: Proportioning Valve Keeps Tripping?
UPDATE 3/28/24
I replaced the wheel cylinders for the rear axle, and the fluid is coming out completely air free now. I ran a ton of fluid to be sure with a pressure bleeder for extra insurance. The pedal feels more solid at this time. NOW, I am having a brake light come on the dash past 3/4 pedal travel. BUT, when this happens, when I bring the pedal back up past that area, it clears itself. So I am thinking I have or may be dealing with separate issues. Possibly the MC bypassing itself? I at this point get sick at the idea of bleeding brakes. LOL. Any further pointers or ideas?
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"Sometimes I do serve as a good bad example. Glad to be of service." My Build Thread (1967 C10, lowered, EFI, daily truck): http://67-72chevytrucks.com/vboard/s...d.php?t=830809 |
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#40 | |
Senior Member
![]() Join Date: Jul 2000
Location: North Texas
Posts: 3,490
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Re: Proportioning Valve Keeps Tripping?
Quote:
That shuttle valve is acting very strange. Could it be moving to the front? Are the front calipers installed with the bleeder screws on the top?
__________________
Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
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#41 | |
Senior Member
![]() Join Date: Mar 2014
Location: Toano, VA
Posts: 874
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Re: Proportioning Valve Keeps Tripping?
Quote:
I am curious - when the cap is off the master cylinder, and I press the brake pedal, there is a bit of brake fluid that 'shoots' up, to the point I just put a rag over it so it doesnt get all over the place. Maybe a few inches, is this an indication of anything?
__________________
"Sometimes I do serve as a good bad example. Glad to be of service." My Build Thread (1967 C10, lowered, EFI, daily truck): http://67-72chevytrucks.com/vboard/s...d.php?t=830809 |
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#42 |
Senior Member
![]() Join Date: Jul 2000
Location: North Texas
Posts: 3,490
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Re: Proportioning Valve Keeps Tripping?
That's normal. Kinda like a miniature Old Faithful!
__________________
Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
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#43 |
Senior Member
![]() Join Date: Jul 2000
Location: North Texas
Posts: 3,490
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Re: Proportioning Valve Keeps Tripping?
If you have an ohmmeter, remove the brake warning switch, then set it on a workbench and check to see how sensitive it is. As I mentioned in a post above, the brand new one I bought would close (zero resistance) when the pin barely moved -- around .050". It could be that yours has a similar problem, so even when the pressure differential valve moves just a tiny bit, the pin moves up and closes the switch.
__________________
Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
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#44 | |
Senior Member
![]() Join Date: Mar 2014
Location: Toano, VA
Posts: 874
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Re: Proportioning Valve Keeps Tripping?
Quote:
__________________
"Sometimes I do serve as a good bad example. Glad to be of service." My Build Thread (1967 C10, lowered, EFI, daily truck): http://67-72chevytrucks.com/vboard/s...d.php?t=830809 |
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#45 |
Registered User
Join Date: Apr 2010
Location: So Cal
Posts: 1,437
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Re: Proportioning Valve Keeps Tripping?
>>should be pedal be harder/more firm with the booster set up when the motor is running?<<
Pump the pedal a couple of times and HOLD. You should have a very high, firm pedal. Start the engine. As vacuum builds, your foot and pedal will drop. The booster is designed to hold vacuum for 3 applications of the pedal. If the engine dies while driving, the booster should hold plenty of vacuum to give vacuum assist in order for you to get to the side of the road. Turn the engine off. Apply the brakes 3 times. The pedal should be higher and firmer after each successive application.
__________________
'67 GMC 2500, 292, 4spd, AC |
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#46 |
Senior Member
![]() Join Date: Mar 2014
Location: Toano, VA
Posts: 874
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Re: Proportioning Valve Keeps Tripping?
Well, heres an update again.
Pedal gets firm about 1/4 down, and feels OK when engine is OFF. But, when its running, its like its a 100% dry system. Put in gear (on jack stands) and brakes have zero effect in the rear, fronts I havent checked since I didnt have it actually move. I am at a huge loss right now because I have literally bled gallons through this system. Now I am thinking the MC is bad. Thoughts?
__________________
"Sometimes I do serve as a good bad example. Glad to be of service." My Build Thread (1967 C10, lowered, EFI, daily truck): http://67-72chevytrucks.com/vboard/s...d.php?t=830809 |
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#47 |
Registered User
Join Date: Apr 2010
Location: So Cal
Posts: 1,437
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Re: Proportioning Valve Keeps Tripping?
post #34
>>My only conclusion from all of the above postings is that the Primary Section of the MC has failed.<<
__________________
'67 GMC 2500, 292, 4spd, AC |
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#48 |
Senior Member
![]() Join Date: Jul 2000
Location: North Texas
Posts: 3,490
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Re: Proportioning Valve Keeps Tripping?
Do you have the tools, brake line, and fittings to bypass the combo valve? It may possible that the proportioning valve is limiting pressure to the rear WAY before it's supposed to.
Then again it might be a bad M/C like Richard says. Bypassing the combo valve will tell you where the problem is, or isn't.
__________________
Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
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#49 |
Senior Member
![]() Join Date: Jun 2022
Location: San Ramon,CA
Posts: 504
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Re: Proportioning Valve Keeps Tripping?
On old earth moving equipment, they'd sometimes use an oil can clamped to a hose to bleed hydraulic systems from the lowest point back to the reservoir.
You might try this with a big syringe from the farthest wheel cylinder. Looking for flow, and maybe trapped air. This way is messy, so rig up a drip pan and wash off any spilled fluid in the engine compartment Otherwise, I agree with the above and you'll have to get clever with swapping parts or plumbing to isolate the problem
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1970 C10 Custom longbed 350/350 |
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#50 | |||
Senior Member
![]() Join Date: Mar 2014
Location: Toano, VA
Posts: 874
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Re: Proportioning Valve Keeps Tripping?
Quote:
Quote:
Quote:
__________________
"Sometimes I do serve as a good bad example. Glad to be of service." My Build Thread (1967 C10, lowered, EFI, daily truck): http://67-72chevytrucks.com/vboard/s...d.php?t=830809 |
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bleeding, brake light, brakes, proportioning valve |
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