I tried bleeding my rear power drum brakes with family leg help tonight. I had just replaced the wheel cylinders right and left side.

There was brake fluid in the lines when I removed old cyl's and I drove the car around the block 2 days before to see how new discs in the front were working. That's when I found out I needed new rear whl cyl's. I could not get the brakes to grab at all.

Well, I got it all back together now and tried to bleed the rear brakes the problem is I'm getting no fluid thru the rear lines. My brake system is new all but some parts of rear brakes and br/lines. I'll try to use a vacuum bleeder on it tonight. I did a search but alot of the links were broke. Oh and yes I bench bled the MC and it is full. I never had this problem before with any car. Thanks

Meteringing valve pin has moved to the forward brakes.

Chiltons, 1973, states:
"On cars with front disc brakes, it will be necessary to hold in the metering valve pin during the bleeding process. The m/valve is located beneath the master cylinder and the pin is situated under the rubber boot on the end of the valve housing. This pin may be taped or held by an assistant."

The pin is probably pushed forward. Open the rear wheel cylinder bleeder, and push back on the m/v pin. Should have seen the BRAKE light come on if the electrical lead (brown) was hooked up.

The pin on the metering valve is for use with a pressure bleeder and vaccum bleeder when bleeding the front brakes only. It won't affect the rear brakes.
Some early 70's ford brake valves would shut off the rear or front lines if they had a leak and needed to be re centered by bleeding the opposite end! Not GM luckliy.

You might try bleeding at the master cyl lines before going to the rear, just crack the fitting while pressing the pedal. Put some rags underneath the MC.

David,

Not sure what you mean. What will bleeding that way do and what's the chances of messing up my bench bleed job? Are you saying unscrew the fitting that's in the master cyl (back bowl) for rear line? Or in the combo valve (The one that the brown wire plugs too)? I thought Everett was on to something then I read your post. :(

Remember I have a 70 Nova combo valve now not the camaro one. This one is mounted parallel with the f/wall. Just thought I'd mention that incase it could change things.

What is causing this? I tried vacuum bleeding them today and with -25 lbs of vac I got a few drop in the jar and the level didn't drop at all in the MC. I'm trying gravity bleeding right now but after a few hours not one drop out of wheel cyl.

It seems something is blocked up but like I said p/booster, MC and all but rear lines are brand new and although the brakes didn't work that good the other day because of bad wheel cyls they did work so I had to be getting br/fluid back there. What else can I do? Thanks

:confused:

RamJam, did you checked the rear rubber hose, at the center of the rear end? I don't recall if you already replaced it, mine got stuck and caused that same simptom. graemlins/clonk.gif Good luck...

ORENCH, How's it going?

[ 10-09-2004, 10:35 PM: Message edited by: RamJam ]

follow your brake lines from the drums back to a T on the rear end cover, the T has a hose connected to it, the other end of the hose is connected to the brake line at the body. That hose might be bad.

You can bleed the lines where they connect to the master cyl. Just pretend the line is a bleeder screw and have someone depress the pedal while you unscrew the brake line a little and let some fluid out. If there is air it will make a noise and some foam will come out. It's just a simple way to make sure there isn't an air bubble there.
Are you sure your combo valve is plumbed correctly? Are your brake lines in good condition?

Another thing to check is, the master cyl piston must return to the full rear position to uncover the replenisment port in the reservoir. If your pushrod is not allowing full return of the piston, it won't allow fluid to be pumped.

There are two different master cyls with two different hole depths for the pushrod and two different pushrod lengths for the booster.
Make sure you have the correct matchup.
David
http://ourworld.compuserve.com/homepages/David_Pozzi/mcrear.jpg

[ 04-22-2004, 09:38 PM: Message edited by: davidpozzi ]

Ok David I'll check that hose tomorrow.
So if I unscrew that br/line at the MC it won't mess up my bench bleed right?

I'm pretty sure the combo is plumbed correctly. I did it a while ago so I'm having some doubt but if I remember right alot of the fittings were a certain size to fit only certain outlets and I had them marked from removal.

Someone mentioned in one of the posts I found in a search that if the p/booster pin size isn't exactly right you won't open the back bowl or something like that. Could this be a problem even with a new match set of M/C and P/B? Thanks

Sorry David apparently you were still filling your reply out and I only read part of it before that's why I asked about something that is now in your post. smile.gif

I read about the pins on your site before and measured mine before installing it and it matched up but like I said about that search post they said if you can't comeback far enough with the pedal it won't open either. That could be it I'll look at that tomorrow too. If you think it could be problem. How do I check that?

[ 10-09-2004, 10:36 PM: Message edited by: RamJam ]

Bleeding at the master cyl will show you if there is a travel problem. If you get nothing out of the line when it's backed off, then it will narrow down the problem to the master cyl or linkage. The booster should control the return of the pedal and the pedal should not hit the rubber bumper or anything else, or it may prevent full return of the master cyl piston.
did you convert from manual to booster?
David

That makes sense.

Yes, I had no power brakes before front disc conversion and yes I have the pin in the right hole on the pedal. smile.gif

David,

I just got done bleeding at the MC. At first there was a lot of air and then I got a good stream of br/fluid.

It's old that might be problem. I'll get the new one on tomorrow. Then I'll try bleeding at the wheels again. I'm glad it doesn't seem to be a problem with MC or PB. Anything else I should replace back there while lines are empty? Thanks

[ 10-09-2004, 10:37 PM: Message edited by: RamJam ]

You should try bleeding at the outlet of the combination valve where the rear line comes out. This will prove the combo valve is not blocking anything.
I'd change the rear line which is a special line with a T fitting crimped on to it.

Make sure the lines are all good and are not twisted shut where they screw into the wheel cyls. Some people damage the lines when the flare nut rusts to the line and when they unscrew the flare nut from the wheel cyl, the line sticks to it and twists.
David

David,

I think I'm going to replace all the rear br/lines. I removed that old br/hose from the rear today and the one I got at parts store doesn't matchup. The new one doesn't seem to fasten to my brakt that bolts to the pumpkin.

I'm also thinking about getting rid of the Nova combo valve. It sits too close to my engine it will give me problems changing plugs. Can I use my old combo valve from my manual drum brake system or not? If not anyone out there got one for power disc and rear drum? Thanks

Starting at far left and going clockwise it's Pass front, line lock front or MC front, MC rear, Rear, Driver front.

According to your site I'm better off keeping the 70 style combo valve, right?

[ 10-09-2004, 10:38 PM: Message edited by: RamJam ]

Sorry, maybe it's my screen but I can't make out the red print.
You can use your old distribution block and try it. You may need to add an adjustable proportioning valve in the rear line, but I'd try it first without one.
You can trim it down even more if you run the rear of the master cyl to the rear brakes direct, (not thru any valves), then install a short line out of the master cyl with a T fitting to split to both front wheels. You won't have a functioning brake warning light, though.

Eliminating the combo valve will lose the metering valve, it's function is on my web page, it won't matter unless you drive on ice or snow.
David

Check above David I did some editing.

Bump

It looks OK to me.
David

Thanks David. graemlins/thumbsup.gif

Well David,

I had to take the whole combo valve off. I was removing the rear line from it but could not get the adapter fitting off. It was made of a real soft metal, looked like white metal. Well, Even after getting the combo valve off the booster I still could not get that fitting out.

Not even with an easy out. graemlins/sad.gif So I ended up ruining the side of the c/valve with the hex head on it(size I'm guessing is around 1"). Does anybody have an old one of these they will sell me? If I can't get one I guess I will use my old distrib block. I don't plan on driving it in ice or snow so it should be ok. What symptoms will I see if I need a prop valve in the rear line? Lock up right? There is a pic of combo valve on page one. Thanks

[ 05-01-2004, 08:40 PM: Message edited by: RamJam ]

Anyone, Anyone??

I also might buy a new after market c/valve or Prop valve whatever it's being called today. :rolleyes: Who's got the best price on these. I can't even find one in Summit or Jegs book. Remember I'm not talking about the $40 adjust one for rear line only. Thanks

RJ,

Expect to spend about $100 for a new combo valve. Give the guys at www.mpbrakes.com (http://www.mpbrakes.com) a shout on Monday they will fix ya up.

NPD has one for $61 but it's for 71-75 camaro. Do you think it matters? I'll check out MP. Thanks

graemlins/thumbsup.gif

Check here too: http://67.37.173.213/
Also check this forum's sponsor, Ground Up Restorations. There's a link at the bottom of this page.
David

David,

I'm going to try my luck in a j/yard tomorrow. What should I look for if I can't find a 70's Nova? Will 70's Chevelle combo valves work. The only one I'm sure won't work is trucks and all drum cars. Thanks

BTW: I got the rear brake lines bent up flared and installed. I borrowed a FT-12 New Britain flare tool. Worked great.

Ok, I got one at a j/yard today. It came off a 75? Nova 4 door. It looks like the ones the repro stores sell. It's made out of brass and mounts under the M/C but towards the driver side more on an angle. I like that idea it should be easier to get to the spark plugs.

Can I take this type apart w/out ruining it? One good thing the brake fluid that came out of it looked pretty clean. Thanks

I wouldn't try taking it apart. There isn't anything inside you can "fix". I'd just use it as-is.
David

David,

I was just hoping to be able to clean it out inside. I know when I got the old one apart the other day it had grit inside. Just wanted to avoid running this one with grit inside. I'm mostly afraid of getting it apart and not being able reseal it right. Thanks

Bump

I'd like to take this brass combo valve from 75? sedan Nova apart to blow it out good but I need to know if they reseal again? Thanks

Bump

UMMMM??

I would like to know how this works out for you. E-mail me with an update. I have access to the same part you found and would like to know if it works. Also about taking apart???? Could you clean it?

Thanks
Joe

ok,

I'll let you know. graemlins/thumbsup.gif

I've removed the rear outlet from the cast-iron type and had no problems. The rear plug is sealed with an O ring, I'd expect yours to have the same. There is a spring inside that does the proportioning. I've changed or shimmed the spring to change proportioning.
You could just connect it to your master cyl and flush it by pumping the brakes before you connect the lines.
David

[ 05-11-2004, 08:42 PM: Message edited by: davidpozzi ]

Ok David, I'll bleed it on the car. Thanks