HELP No fluid to rear brakes

[CopperNick]

Before you screwed that tool into the port, did you push the little rubber covered button at the front of the valve body first? Pushing on the button moves the spool valve back from the operating to the bypass position and then the pin on the end of the tool locks the spool in place so it is in continuous bypass until you remove the tool to release it.

And, of course, it is always possible that the aftermarket valve is a total dud as has been already pointed out.



Nick

 

[spongbob]

Okay so I'm stumped. My cutlass is getting finished up but I'm baffled by the last issue. I'm getting a trickle... no no make that a drip of fluid to the rear. The system is new, master cylinder, proportioning valve, blazer calipers, front hard lines, all soft lines, wheel cylinders. I can take the rear line off and hold my thumb over the rear of the proportioning valve when my boy is holding the pedal and I get a drip. Was doing the same thing with the old proportioning valve and master which was the only reason I changed them

Your gettin several suggestions I to have given thought to your rear pressure flow issue .Having a proportioning valve reducing /stopping fluid,I'm thinking to kick that cylinder back to center could be managed possibly 2 ways neither I have used yet but will try soon 1 first useing Air pressure shot through the rear brakline through the bleeder tap ? Or 2 secondly use a master cylinder or possibly a rear cylinder to reverse fluid through the line backwards ok you say then you will need to bleed the line back up to the front at the valve rear line connection ?.. and apply a pressure from a rear connected cylinder .Hypothetically if you can remove the rear line at the back of the valve without it twisting off as when the lines nut freezes (rusts tight) you could use a seperate Donor line and hook it to a mastercylinder or even the cars own master cylinder . ASSUMING " That you can match the outlets nut thread and size or couple some donor brake lines off some simular vehicle. What you want is to insite enough pressure to push the valve back into center.This idea comes with a lot of variables .like fitment connecting application of pressure time resources and practice expeiriance. If a line coupler could connect a sufficient short peice of line to the rear input line removed then joined the the rear output im thinking you could knock possibly that slightly rusted center unit back to center. At least is something to try also Otto zone has a bunch of flared nuts to fit lines 3/16 and 1/4" his negates you having to remove the valve or transmission bracket maybe releasing the front half and dang show it whos boss ps a line may reverse filled with fluid and a turkey butter injection syringe if you loosen the line at the front were it inters the valve .you people trying to blead a porches slave cylinder will like no know also picture this one brake hub off return springs removed cylinder filled from rear also line "CYLINDERS EXTEDED" after which said bleeding dune the brake lining is pounded with a large hammer while holding one side with some wedging means thereby you will get reverse pressure wah lah does pivet valve center ? are you getting fluid to rear put springs back on open bleeder 2 second and close then put the drum back on get in car try mashing the pedal do you hear the rear shoe expand? listen if so ? then you got your brakes back

 

[olds307 and 403]

I don't know if a solution was found. My 70S did the same thing. Pulled apart the proportioning valve, working fine. Barely any fluid through the new master cylinder, new rear lines and rear wheel cylinders. I even tried the old failing master cylinder, the same thing I bought a pressure bleeder that goes on the master cylinder. Put it on and pressured it up, instant fluid to the rear wheel cylinder bleeders and problem solved.

 

[69hurstolds]

A note when doing bleeding. SLOW is the operative word. If you take things slow, you shouldn't need the switch mounted holding tool for the shuttle valve. Although, it's not a terrible idea to use it just to make sure.

As the GM service manual suggests- Once off, press the brake pedal several times to bleed off the vacuum in the booster. Then, if air is suspected in the master cylinder, bleed the master cylinder by disconnecting the forward brake line to the master cylinder. Fill the resi with brake fluid until the fluid drains out the hole. Reinstall and tighten the brake line to the master.

Now, slowly press and hold the brake pedal, then slowly crack the line to the front reservoir, bleed air, then retighten. Slowly release the brake pedal and wait 15 seconds. Repeat, including a 15 second wait after releasing pedal (you have to wait every time you release the pedal, so drill that in your head), until all air is bled from the master. After you're happy with the forward tube bleed, now repeat the whole thing for the rearward brake line to the master cylinder. Again, wait 15 seconds after releasing the pedal for pressures to equalize.

If you are replacing the master cylinder, you should have been smart and bench bled it first and put plastic plugs on the master cylinder outlet ports when installing. Regardless of WHAT YOU DO, DO NOT GET BRAKE FLUID ON PAINTED SURFACES during any brake bleed operation.

Set up your brake bleeding deal, with your jar part filled with fluid, clear tubing, and bleeder wrenches as necessary. (G-bodies use tool J-21472 for the disc bleeds, and J28434 for the drum bleeders if you want GM tools for whatever reason). Start with the Right Rear first, then make sure the reservoir is filled with fluid. SLOWLY depress and hold the brake pedal, loosen bleeder, and watch for air bubbles. Ensure the tubing seals around the bleeder fitting your you'll get false air reading. Tighten fitting when fluid/air flow stops, then SLOWLY release brake pedal, wait 15 seconds, and repeat until all air is out of system. Ensure you don't run the master cylinder dry and refill as required.

Now do Left Rear, Right Front, and finally Left Front the same way.

Service manual states: "Rapid pumping of the brake pedal pushes the master cylinder secondary piston down the bore in a manner that makes it difficult to bleed the system." This is important as the secondary piston sort of floats in the master cylinder bore. Also, if you get too crazy and you're not using the threaded in shuttle valve holding tool, you run the risk of actuating your brake light switch and shifting the combination valve. It's supposed to work that way, but only in emergencies, not while bleeding the brakes.

A combination depressor too, J-23709, is used to hold the front metering valve "button" in on the combination valve when pressure bleeding the front disc brakes. Loosen the front combination hold down bolt on the frame and slide the tool in, tighten the bolt, and commence the pressure bleeding.

Just some stuff to consider if doing brake bleeds the old-fashioned way.

 

[84dragcutlass]

To update i did go ahead and get another combination valve so that i could start fresh. I was extremely frustrated because as you can imagine after all the swapping back and forth of components the brake fluid got everywhere and peeled the paint on my frame. So i got the car back on the ground and walked away from that particular issue to work on my intake for a while. However taking all the great advice i've gotten when i do install the new combination valve i now know to be way more careful when getting the fluid to the rear this time and to do it slowly. I think that ill get more than a trickle this time. I did go ahead and get a vacuum bleeder that uses a hand pump just to make things easier. One question i do have is do i have to pump the pedal when using this or will it draw the air out on its own?

 

[oldsofb]

Had the same issue. Here's how I fixed it. (Go straight to the 40 min mark)

Hutch

 

[69hurstolds]

Had the same issue. Here's how I fixed it. (Go straight to the 40 min mark)

Hutch

Nice vid! Although, just to make the differences apparent between Hutch's race car and mere mortal cars, per the CSM, stock G-body calipers use 33 lbs/ft torque on the banjo nut, and 18 lbs/ft torque on all the tubing nuts.

When working with stainless junk though, not sure that always applies as just properly seating those beeyotches can be a PITA.

 

[69hurstolds]

Imagine that...just watched Hutch's entire video and I totally forgot about mentioning that booster gasket being upside down.

 

[oldsofb]

Imagine that...just watched Hutch's entire video and I totally forgot about mentioning that booster gasket being upside down.

Had to give you credit for the catch. I didn't even notice until you brought it up. I would have put it back together correctly, but by then the firewall would have been sanded, cleaned, and painted. I would have never realized it was installed incorrectly 😀

Makes me wonder how many others made it out into the wild the same way.

Hutch

 

[69hurstolds]

Had to give you credit for the catch. I didn't even notice until you brought it up. I would have put it back together correctly, but by then the firewall would have been sanded, cleaned, and painted. I would have never realized it was installed incorrectly 😀

Makes me wonder how many others made it out into the wild the same way.

Hutch

If they never get torn apart, the world may never know. 🙂

I can see it plain as day in the Pontiac plant when your car was being assembled...

Earl: "Hey Jerry! Which way do these weird azz funky gasket thingies go on the booster?"
Jerry: "I dunno, Earl. Which way does it fit?"
Earl: "Either way. Don't seem to make no difference. That's why I'm askin'."
Jerry: "Fugg it. I reckon that gap up on top is for cabin ventilation. Yeah, that must be it. Slap it on and send it!"