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Index > Engine/Drivetrain > Thread: brake residual valve?
Thread: brake residual valve? [' This thread is 2 pages long: (1) 2 ']
tom93r1


Redlining
Posts: 457
posted December 05, 2014 01:11 PM

brake residual valve?

My REPU brakes have been quite dismal the last year or so, so bad that I can't lock them up no matter how hard I push. Since problems developed I have replaced rear cylinders, the master, and bled the brakes countless times. I am confident there is no air in the system. A friend who is more familiar with old muscle cars says the residual valve might be going, it is supposed to hold a little pressure to the brakes so the disks will self adjust, without it they fully retract was his thought.

Is there a residual valve in the REPU? Is it part of the proportioning valve? Does that theory make sense? It's not like there is much to the brakes and I have replaced everything except the lines and front calipers now.

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Hunter


Hauling
Posts: 172
posted December 05, 2014 03:29 PM

brakes

* is the vacuum booster working ?
* is it possible that you have a Courier master cylinder installed which might have a smaller main bore size ?
* hose to rear axle might be restricted

IMHO, the brake proportioning valve just proportions pressure front and rear but, who's to says that it, as well, is not restricted after all these years.

Namaste,
Hunter

       
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spokanerxdude


Hauling
Less cubes... More balls
Posts: 181
posted December 05, 2014 08:49 PM
Edited By: spokanerxdude on 5 Dec 2014 21:07

Hunter is right check all of them.

A little info on the proportioning valve starting with troubleshooting and then problem solving.

Dose your brake light go on and off when you operate your emergency brake? If so then the proportioning valve is probably not the problem because if the valve shifts it will turn on your brake light and it will stay on till the valve is shifted back to center. See below for how to shift the valve back to center.

The main purpose of the proportioning valve is to shift when something is leaking bad enough to cause a catastrophic lose of fluid, (severed hose or something of that sort). The valve will shift and block the leaking end (front or rear) so you will still have fluid left for the other end to work.

When bleeding the brakes you should remove the switch from the proportioning valve and block the valve from moving. A bolt with the tip ground to a point and then grind the point so there is about an 1/8" flat spot on the tip. Once your tool is made just screw it into the switch hole just snug not tight. You might have to make a trip to the hardware store to find the right bolt.

When bleeding WITHOUT the proportioning valve tool installed the valve can shift, at that point you will have to bleed the opposite end (front or back) till it shifts back to center.(brake light should go out when it centers). Learned all this back in my RX-2 days.
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tom93r1


Redlining
Posts: 457
posted December 08, 2014 08:33 AM

Hmm, guess I don't really know for sure that the booster is working, will try and check that out. No restrictions in brake lines to the rear, it flows quite nicely when I am bleeding. Master cylinder should be the right one, off top of my head I don't remember size but I verified it compared to what I found it should be.

I will check if brake line comes on with with emergency brake. I will also try re-bleeding with a bolt in the valve to stop valve from moving, never heard that one before.

Thanks for the suggestions! I have new brake hoses I will be installing as well, will update once all that has been done. I dislike working on brakes almost as much as I dislike working on electrical issues, so it might be a few weeks.

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Brad


Rotorhead
Posts: 1665
posted December 08, 2014 11:27 AM

The residual valve is in the brake master cylinder, inside the big threaded port for the rear brake line. It's a little black plastic dealy.

How tight do you have the rear shoes adjusted?

Have you put a mity-vac on the rear cylinders?

You should be able to pump the brake pedal to build enough pressure to lock the rear tires.

As for the proportioning valve, I've had the Brakes idiot light come on before due to low fluid. A rear cylinder was leaking badly, I knew the rear brakes were f**ked LONG before the light came on. But the system did do its job, front brakes still had some fluid mainly due to the master cylinder reservoir having fluid in the front half.

       
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tom93r1


Redlining
Posts: 457
posted December 08, 2014 03:24 PM

Ah, I didn't even think of that thing on the master being the residual valve. Makes sense now since what info I found on residual valves said they were for rear brakes only.

I adjusted the rears according to the manual a couple months ago. I think it was something like tighten until the wheel doesn't turn then back off a bit but I don't remember for sure.

I don't have mity-vac for bleeding, I have one of the pressurized jugs that pushes fluid in from the master. In my experience it has been easier to work with than the mity-vac, but ultimately should do the same thing.

I have tried bleeding brakes with that jug and by having somebody pump brakes and neither has done the trick yet. :(


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tom93r1


Redlining
Posts: 457
posted December 08, 2014 03:25 PM

Ah, I didn't even think of that thing on the master being the residual valve. Makes sense now since what info I found on residual valves said they were for rear brakes only.

I adjusted the rears according to the manual a couple months ago. I think it was something like tighten until the wheel doesn't turn then back off a bit but I don't remember for sure.

I don't have mity-vac for bleeding, I have one of the pressurized jugs that pushes fluid in from the master. In my experience it has been easier to work with than the mity-vac, but ultimately should do the same thing.

I have tried bleeding brakes with that jug and by having somebody pump brakes and neither has done the trick yet. :(

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spokanerxdude


Hauling
Less cubes... More balls
Posts: 181
posted December 08, 2014 05:05 PM

I worked for my Dad at his gas station for a few years, made the mistake of telling him I hated doing brakes, so guess who got all the brake jobs from then on lol.
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tom93r1


Redlining
Posts: 457
posted December 09, 2014 08:51 AM
Edited By: tom93r1 on 9 Dec 2014 08:52

So what you are saying is that you will be doing my brakes for me?

I wouldn't mind working on brakes if it wasn't for the brake fluid, nasty! My bicycle uses mineral oil instead of DOT fluid, much nicer if you happen to get it all over.

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Brad


Rotorhead
Posts: 1665
posted December 09, 2014 04:30 PM

I bleed all my cars with the pressurized plastic jug, it gets the job done, and is a 1 person job.

Say, if you pull on the e-brake do the rear tires lock up?

       
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tom93r1


Redlining
Posts: 457
posted December 09, 2014 07:10 PM

I haven't tested that either, I will try and get it on the road this weekend to test.

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tom93r1


Redlining
Posts: 457
posted December 20, 2014 06:26 PM

I think I need to bleed the brakes again but I did make some pretty good progress.
I completely drained the brake system and disassembled the proportioning valve. It was a mess inside. The valve had no movement at all due to the gunk that had built up around it. A few minutes in the ultrasonic cleaner and it was looking much better. Put everything back together and bled the brakes. Now it actually just feels like I just have an air bubble somewhere, I suspect the driver side rear as it seemed to bleed much quicker than I was expecting.

Now at least I can pump up the brake and it feels solid. Before it felt like a sponge no matter how much pumping and bleeding I did. Not sure if the proportion valve is related to my problem or if I just got something out of the system when I pumped it dry.

One more round with the bleeder jug and I will be ready for a test drive.

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tom93r1


Redlining
Posts: 457
posted December 23, 2014 08:24 PM

Well crap, I re-bled the brakes and still seem to have air in them somewhere. Might have to get me an assistant and try bleeding the old fashioned way. Wonder if there is air trapped in the proportioning valve now...

At least I was able to get the clutch bled successfully tonight.

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spokanerxdude


Hauling
Less cubes... More balls
Posts: 181
posted December 25, 2014 07:11 AM

If you didn't when you put it back in it couldn't hurt giving it a try. When I bleed I start at the master and work my way back to the furthest wheel. I know thats backwards form what everyone says to do but it seems to me if you make sure everything is air free on the way back you can't miss anything.
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tom93r1


Redlining
Posts: 457
posted December 25, 2014 08:30 PM

I just removed front calipers to bleed those again with bleeder valves turned to highest point and didn't get any air out that way. They I re-adjusted the rears and they were already just about right. Then I unbolted the proportioning valve, tipped it vertical to bleed them all again. This time I got a couple bubbles from the rear. Seems the valve might have been the issue, but I won't know until I test drive again. I really hate brake work beyond pad replacement!

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tom93r1


Redlining
Posts: 457
posted December 26, 2014 08:38 PM

After all that brakes still suck. Pedal feels firm now but no matter how hard I push I cannot lock up the wheels. Feels like I have at best maybe 70% stopping power.

Maybe I should replace pads, wear on them looks probably about half but who knows. Not much else I can replace at this point.

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spokanerxdude


Hauling
Less cubes... More balls
Posts: 181
posted December 27, 2014 06:46 AM

There is propably only one thing left and that would be the brake booster. I know it's a pain, but you might have to remove it and take it to a place that overhauls them.

Try and check it with a hand vacuum pump. Disconect the hose closest to the intake manifold and pump it down and see how long it takes to bleed off. Don't know what the spec's would be for that but it might give you and idea wheather it is good or not.
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tom93r1


Redlining
Posts: 457
posted December 27, 2014 06:01 PM

Today I replaced brake pads, O'Reilly had them for $15 so really had nothing to lose. Seems that fixed the problem.

I guess on the REPU 50% wear is about all the brake system can handle. I have had cars where the pad will wear right down to the pad backing and the pedal feels just fine right up until the pad is gone, not sure why the REPU is so much more sensitive to pad wear. I guess at least I don't have to worry about ever wearing the pad down to the point of chewing up the rotor.

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spokanerxdude


Hauling
Less cubes... More balls
Posts: 181
posted December 28, 2014 11:30 AM

Cool glad that fixed it.
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Allen Ervin, spokanerxdude@yahoo.com
509-998-9024

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