[Philip]

When you get it on the road let us know your experience.

 

[70 nialator]

Plan "B"... damn e-bay junk. This time I'll use the real deal..

 

[oldzy]

What kind/size rear sway bar is that

 

[70 nialator]

Okay... now for the things no one tells you...... Sorry about the long read.. but if you are here there is probably a reason and this might help someone.

There is also a combination valve in the Chevelle braking system (located in the driver's side inter frame rail). IF you are installing a adjustable proportioning valve for the rears... it should be installed in the system AFTER the combination valve, not off the master cylinder rear port.

Your current master cylinder is also worthless now. (at least mine was) I did the research and the oldsmobile toronado came with 4 wheel disk brakes.. This master cylinder will also bolt right up to your existing booster and costs... get this.... 15.00 bucks at O'reileys!

After fighting a NO FLUID to the rears situation for 2 days.... I was under the impression I had tripped the combination valve. Everything I read says this is a safety device so if the front or rears fail, the valve will move to cut off fluid to either the front of rear depending on where the failure occurred. After reading hours and hours of MISS INFORMATION on how to re-center or reset this valve... I started playing with compressed air. (the entire system was compromised anyway)

I was able to blow air from the rear line starting at the master cylinder and it came right out the caliper in the rear (with the bleeder removed). Could also blow from back to front (disconnected from the master)

The dash is not currently installed thus I have no brake light either... IF tripped the combination valve BROWN wire will be grounded. You can use a multimeter to ground and check... I did, and had no tone.
After all this I removed the rear brake line again from the master cylinder and stomped the brake pedal (just because I was pissed) still ONLY WENT 1/2 way down and almost NO fluid came out. (NEW less than a year ago and maybe has 50 miles on it) That's where this comes in.... . I did the research and the oldsmobile toronado came with 4 wheel disk brakes.

After 2 days.. I HAVE fluid in the back

 

[Schurkey]

I'm having a hard time understanding this post:

Okay... now for the things no one tells you...... Sorry about the long read.. but if you are here there is probably a reason and this might help someone.

There is also a combination valve in the Chevelle braking system (located in the driver's side inter frame rail).

WHAT YEARS? Far as I know, no combination valve before 1970.

IF you are installing a adjustable proportioning valve for the rears... it should be installed in the system AFTER the combination valve, not off the master cylinder rear port.

A combination valve has a proportioning valve built-in. You would not want two proportioning valves in the system.

Your current master cylinder will is also worthless now. (at least mine was) I did the research and the oldsmobile toronado came with 4 wheel disk brakes.. This master cylinder will also bolt right up to your existing booster and costs... get this.... 15.00 bucks at O'reileys!

Part number???

After fighting a NO FLUID to the rears situation for 2 days.... I was under the impression I had tripped the combination valve. Everything I read says this is a safety device so if the front or rears fail, the valve will move the cut off fluid to either the front of rear depending on where the failure occurred. After reading hours and hours of MISS INFORMATION on how to re-center or reset this valve... I started playing with compressed air. (the entire system was compromised anyway)

I was able to blow air from the rear line starting at the master cylinder and it came right out the caliper in the rear (with the bleeder removed). Could also blow from back to front (disconnected from the master)

The dash is not currently installed thus I have no brake light either... IF tripped the combination valve BROWN wire will be grounded. You can use a multimeter to ground and check... I did, and had no tone.

Proves that the safety warning light switch wasn't blocking fluid flow.

Every GM safety switch I've worked with is self-centering once the fluid pressures in each hydraulic circuit are balanced. If there are some GM switches that have to be manually re-set, I don't know about them. I would suspect that the switch was defective.

I have worked with Ford safety switches that had to be manually re-set. At least SOME (if not all) Ford switches were not spring-loaded and therefore not self-resetting.

After all this I removed the rear brake line again from the master cylinder and stomped the brake pedal (just because I was pissed) still ONLY WENT 1/2 way down and almost NO fluid came out. (NEW less than a year ago and maybe has 50 miles on it)

With a dual-circuit master cylinder, the pedal will only go down as far as it takes to build pressure in the front brakes, when the rear circuit is opened up. The pedal will be low but not on the floor, and the front brakes will work. So, yeah, not a lot of fluid will come out the rear brake hydraulic circuit. Without knowing how much came out...it's hard to know if it was a normal amount or not.

That's where this comes in.... I did the research and the oldsmobile toronado came with 4 wheel disk brakes.

Only the later models. No discs at all in '66, front only from '67 or '68 until middle-'70's. So again, what is the part number and what model years is it intended to fit?

After 2 days.. I HAVE fluid in the back

Excellent.

 

[70 nialator]

Sorry for the non specifics, my car year is listed in every post. My car: 70 Chevelle

The new master is also from a 70 toronado, I'll post the part number tomorrow as I'm clean now

A combination valve has a proportioning valve built-in. You would not want two proportioning valves in the system.

I do, several people including myself have experienced rear lock up and I want this to be adjustable, independent of the front, to each his own.

Every GM safety switch I've worked with is self-centering once the fluid pressures in each hydraulic circuit are balanced

Several of the threads I read also said this.....Just exactly how do you that if one side is blocked?

 

[70 nialator]

One more thing.. and I pray someone makes this a sticky... IF you ask a question and several people use their time and knowledge to help you, POST YOUR resolution! I can't tell you how many posts I read clear back from 2008 and further where the asker never revealed what worked! NOT COOL!

 

[70 nialator]

http://www.oreillyauto.com/site/c/d...25673&ck=Search_brake+master+cylinder_1225673_306&keyword=brake+master+cylinder

Looks exactly the same and bolts right up but the part numbers are different. The one I had may have just been bad IDK. Only sharing what worked for me.

 

[Schurkey]

Sorry for the non specifics, my car year is listed in every post. My car: 70 Chevelle

That's fine. Your Chevelle has a combo valve in the frame rail.

You stated that "There is also a combination valve in the Chevelle braking system (located in the driver's side inter frame rail)." which is not true of '69 and earlier Chevelles. That was my only point there--you made a generalization that's inaccurate for earlier Chevelles.

I did the research and the oldsmobile toronado came with 4 wheel disk brakes..

The new master is also from a 70 toronado, I'll post the part number tomorrow as I'm clean now

http://www.oreillyauto.com/site/c/d...25673&ck=Search_brake+master+cylinder_1225673_306&keyword=brake+master+cylinder

Looks exactly the same and bolts right up but the part numbers are different. The one I had may have just been bad IDK. Only sharing what worked for me.

A 70 Toronado does not have rear disc brakes, not even as an option.

I do, several people including myself have experienced rear lock up and I want this to be adjustable, independent of the front, to each his own.

Having TWO proportioning valves--one OEM and one adjustable--is not doing you any favors. If you're going to use an adjustable one, bypass or disable the non-adjustable one inside the combo valve.

ALL proportioning valves are independent of the front brakes.

Several of the threads I read also said this.....Just exactly how do you that if one side is blocked?

Blocked??? What do you mean by "blocked"?

AFTER the brake problem is fixed, after the brakes are bled--step on the brake pedal and the light should go out. When the brake system is functioning properly, the safety switch sees identical pressure in the front and the rear hydraulic system--and the internal springs push the plunger to the center, neutral position.

 

[70 nialator]

Schurkey, I've come to value your experience and maybe you can clear a few things up for me. I’m not claiming to be a brake expert by any means.

The existing factory OEM combo valve/purporting valve whatever it is…. Can this actually block fluid to the front or back (if tripped)? The reason I ask is because I also have line lock installed in the front and when its engaged the brake light will come on (as it should I assume) full pressure in the front and none in the rear. The light also goes right back off after I flip the switch and launch. Pressure goes away in the front and the system is equalized again. If anything would tip it, I would think the line lock would. So should I assume this is self centering?

Does the existing factory OEM combo valve/purporting valve actually dynamically control breaking bias and is it able to determine suspension changes, tire changes, passengers, stuff in the trunk..etc?

If this is actually a safety device I don’t really want to remove it, if it’s just a pressure switch that triggers the brake light I’m not sure why an adjustable prop valve after it would be a bad thing?

The adjustable valve is NOT in the system at this point, I removed it to eliminate at least one variable. Now that I have fluid in the back it would be great to know if I should really just skip it and finish this, or reintroduce it to the system again….

Blocked??? What do you mean by "blocked"?

Going back to this question - Can this actually block fluid to the front of back (if tripped?). How would you bleed the brakes to re-center the valve, if the valve is blocking fluid flow to one side? Seems like you might have to re-center the valve first, in order to bleed and equalize the pressure… what comes first the chicken or the egg

A 70 Toronado does not have rear disc brakes, not even as an option.

Hmmmm, We also talked about the Cadillac Eldorado, I will verify the receipt tonight and change all above posting to reflect the correct information if I’m wrong.

 

[Philip]

Did your 70 have front disc from the factory? If not there is no proportioning/combination valve. Just the block containing a shuttle to operate the warning light.
The master cylinder you are using is a disc/drum master. It may have a residual valve in the rear brake outlet.
Your line lock is not installed correctly if the brake warning light is on when in use. It plumbs in after the combination valve.

Here is my set up, An 82 Corvette master, an 82 Eldorado 4 wheel disc combination valve and Hurst roll control after the combination valve. The Eldorado valve was only used because it was free. The valve from a 4 wheel disc Firebird, Corvette or any other late 70's - early 80's GM car will work too. It all works perfect with both the small rear discs originally installed and the 12" Camaro set up currently installed.

If you look closely at this drawing you will see how the combination valve works. The shuttle does not prevent flow when moved off center and will center again once fluid pressure is equal.

Does the existing factory OEM combo valve/purporting valve actually dynamically control breaking bias and is it able to determine suspension changes, tire changes, passengers, stuff in the trunk..etc?

It does not provide any bias changes for any other aspects of braking

 

[Schurkey]

The existing factory OEM combo valve/purporting valve whatever it is…. Can this actually block fluid to the front or back (if tripped)?

I've never known one to block fluid flow. I hear about this all the time on forums...but I've never seen one actually block fluid flow to the damaged hydraulic system. The master cylinder reservoir will empty if there's a leak.

The reason I ask is because I also have line lock installed in the front and when its engaged the brake light will come on (as it should I assume) full pressure in the front and none in the rear. The light also goes right back off after I flip the switch and launch. Pressure goes away in the front and the system is equalized again. If anything would tip it, I would think the line lock would. So should I assume this is self centering?

Yup. Self-centering. As Phillip has said, you may have the line lock in the wrong place--and yet I'm thinking it's kind of neat that you have a dash light that's illuminated when the front brakes are being held.

Does the existing factory OEM combo valve/purporting valve actually dynamically control breaking bias and is it able to determine suspension changes, tire changes, passengers, stuff in the trunk..etc?

It WILL change brake bias, but not based on anyting except rear brake hydraulic pressure. Either the proportioning valve built-into the OEM combination valve, or the older, stand-alone OEM proportioning valve sense rear brake pressure ONLY; the internal mechanism is adjusted at the factory via different spring tensions and such. Each valve part number may have a different pressure setting where it begins to restrict fluid flow. This is why the correct part number valve should be used on a non-modified car, or a valve from a vehicle having similar weight and weight bias should be selected for conversions. Or, bypass the original proportioning valve and install an adjustable unit.

In short, the OEM proportioning valve does exactly the same job as an aftermarket, adjustable proportioning valve--except there's no adjustment knob, the settings are "built-in" and cannot be adjusted except by disassembling the valve.

If this is actually a safety device I don’t really want to remove it, if it’s just a pressure switch that triggers the brake light I’m not sure why an adjustable prop valve after it would be a bad thing?

Are you dealing with a combination valve? As shown above, the combo valve has three main functions--holdoff (metering) valve for the front brakes, proportioning valve for the rear brakes, and a pressure-differential sensing safety switch in between.

The adjustable valve is NOT in the system at this point, I removed it to eliminate at least one variable. Now that I have fluid in the back it would be great to know if I should really just skip it and finish this, or reintroduce it to the system again….

I would not recommend using TWO proportioning valves in a rear hydraulic system.

Going back to this question - Can this actually block fluid to the front of back (if tripped?).

No. Well, sorta-kinda. The safety switch does not block fluid flow. The proportioning valve can restrict but not block fluid flow.

How would you bleed the brakes to re-center the valve, if the valve is blocking fluid flow to one side?

Valve doesn't block fluid flow.

Seems like you might have to re-center the valve first, in order to bleed and equalize the pressure… what comes first the chicken or the egg

The Ford system requires the brakes be repaired, then you pop open a bleeder screw on the hydraulic system that did NOT need repair. It's a real pain in the ass, because if you create too large of a leak, the safety switch goes from one extreme to the other without stopping in the middle. Then you have to open up the other hydraulic circuit. Eventually, you get the switch in the neutral position between the two extremes, and the light stays out.

Hmmmm, We also talked about the Cadillac Eldorado, I will verify the receipt tonight and change all above posting to reflect the correct information if I’m wrong.

I've started a couple of threads on Toronado forums, trying to figure out the first year of 4-wheel discs on the E-body. Pretty sure it'd be '76--'77--'78, but I don't know for sure, and haven't gotten useful replies to my posts yet.



[EDIT]
If you have four-wheel disc brakes, you need to scrap the original combination valve anyway, because you no longer need the hold-off (metering) valve from a disc/drum system. Since you want to use an adjustable proportioning valve, you're already not using two out of three systems in the disc/drum combo valve.

I'd be looking for a stand-alone safety valve, and ditch the combo valve.

 

[70 nialator]

WOW... awesome input and THANK YOU everyone!

The master I purchased last night is a 10-1521 http://www.autopartstomorrow.com/part_numbers/143842-remanufactured-master-cylinder

I just left O'reilys again and they swear it's for a 4 disk car??

This is my current plan, (subject to change) please correct me if I'm wrong.
The valve I have on the inter frame rail is exactly like the one pictured above. IF I remove this and pull the "guts" out of it, it could still be used for a fluid distribution block for the fronts?

Then block the "from drum end of master cylinder" port and block the "to rear brakes" port. Essentially making it a distribution block for the fronts only. Not because I'm cheep, only because the lines are already there and fit.

Then run my adjustable from the master to the existing line that DID go to the "to rear brakes" completely bypassing the newly modified block.

This will make the warning light unless.. I get that. Any other problem I'm not thinking of?

EDIT - I can say will no reservation that this is the most in-depth, informative threads on the net about this subject, that I have found anyway. I read for HOURS looking for these answers. This really helps!

 

[Philip]

I just left O'reilys again and they swear it's for a 4 disk car??

You believe them over us?
The type of caliper you have does not require a large fluid chamber in the rear reservoir, but there are better options including a new one not a reman and an application designed for 4 wheel disc.

You can not modify the valve you have now and expect it to work reliably. Either use the adjustable unit by itself or add a 4 wheel drum block in place of the combination valve if you want the light to function.

 

[Tom Mobley]

one way to get around this deal with the front brakes keeping the pedal from going down enough to bleed the rears is to use one of the one-man bleeder deals on the front while bleeding the backs.

Normally the 4-wheel disc M/C is the late 60's-early 70s Vette part.

 

[Tom Mobley]

Schurkey: knows all, tells all. All you have to do is ask. Philip has been around the block a few times too. AFAIK he's about the only one that that tells the truth about these aftermarket rear caliper brackets and their poor engineering. The caliper bolts (as correctly engineered by GM) were never meant to be the thing that opposes the rotational force of the caliper during braking. These aftermarket brackets transfer that critical function from the bracket designed to absorb the load to the caliper bolts which are not.

And yup, this is what I have on my car just like most everybody else. Philip was smart enough to see the problem and used the Caddy rear setup but it has the unfortunate e-brake deal. He changed his out because of this but I don't remember what he used. I think he has some GM factory setup with the right type of bracket combined with the little mechanical drum brake inside the rotor. This is the "right thing" to have.

 

[70 nialator]

You believe them over us?

LOL I absolutely do not, just amazed at the amount of jacked up information out there. Really sad.... Thank God there a few willing to share.

 

[70 nialator]

I'm getting all this tomorrow. My line lock has "one in -one out" guessing that's why it was installed prior to the combo valve.
Only question I have is... where the hell did you get that crazy bracket to hold it all?

 

[Philip]

Tom I am using the rear brakes from a 2000 Camaro on the Nova now. The wagon will have the Camaro brakes at all 4 corners.

Darren that is a photo of the set up on my Nova. GM brakes work the same regardless of the car they are installed on. The 72 Chevelle wagon will have the same set up but the valve will be mounted in the Chevelle location on the frame.
The bracket for the combination valve is stock on the 75 - 79 Nova's. The Hurst Roll Control was mounted to the stock bracket.
If you post a photo of the back of the master cylinder or let me know if it has a deep or shallow hole in the piston I can recommend and application for a master cylinder.

 

[70 nialator]

It's the shallow with the short plunger rod. Thanks!!