1972 Vega troubles

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1972 Vega troubles

Postby cerealkiller » Mon May 28, 2018 11:19 am

Greetings all,I CAN NOT get a Hard/ANY brake pedal on my car.I believe that my "Brake Pipe Distribution and Switch" are frozen/bad.My Shop Manual says this part is NOT SERVICEABLE/NONADJUSTABLE" and must be Replaced if bad.Anyone have one of these for my car?Are there any other year/make /models of car that is interchangeable with this item?The GM part number for this item is supposedly -GM 25509419.Can anyone help me with my plight?CLYDE? Thanks
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Re: 1972 Vega troubles

Postby cjbiagi » Mon May 28, 2018 1:51 pm

Have you tried plugging the outlets on the master cylinder and see if you get a hard pedal? My guess is a bad MC assuming you have no leaks.
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Re: 1972 Vega troubles

Postby cerealkiller » Mon May 28, 2018 6:11 pm

Hey Clyde,the Master Cyl on my car is the SECOND Master Cyl I have tried.The first M/C was a Cardone from Advanced auto parts.The problem was EXACTLY the same with my first M/C as with my second M/C.I figured the First M/C could be bad so I exchanged the first M/C for another one and the same problem exists.Lots of air came out of the lines both times but I finally achieved a SOLID stream of fluid with NO bubbles BUT the Brake Pedal goes to the FLOOR ALL the time NO matter what.My Original M/C,when it failed,had a serious amount of Orange Colored Sludge-Like Munge/Goop on/in it.Im guessing this GOOP plugged the Distributor switch as well and froze up the valve.My Vega had sat for a very long time (YEARS)before I got it so I believe the entire system was in Bad shape.The GM part number for my valve is 25509419 According to my Vega shop manual,PAGE 5-17 and is said to be NON-ADJUSTABLE and NON-SERVICEABLE.The valve is said to be Superceeded by part number 172-1353 in a Aftermarket made valve.I found a valve on E-BAY that is said to be CORRECT for my car.I did plug the ports on my M/C and the M/C held pressure just fine.What do you think?Thanks.Hope all is cool with you.
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Re: 1972 Vega troubles

Postby monzaaddict » Mon May 28, 2018 11:44 pm

You really nee d to give more info:

From your other posts you indicate you have non stock brakes. What master are you using? I am guessing the bore is too small. Cardone ,PN-131498 is a stock master cylinder.
Re: V8 Vega brake question/s

Postby cerealkiller » Wed Dec 20, 2017 9:18 am
Hello Smiley,The rear drum diameter is 11 inches.The shoe width is 2.5 inches wide.The front brakes appear to be standard Camaro,Monte Carlo style,11 inch rotors,single piston.The master cylinder was purchased from Advanced Auto parts,Cardone ,PN-131498.The master cyl bore size is .750.The front brakes were on the car when I acquired it.Dont know EXACTLY what the front brakes are off of.I have 2 sets of rear wheel cylinders from 2 different 9 " Ford rearends that are/were laying around.One rearend has a 1" wheel cyl bore with 2.5 shoes and the other 9" has a 15/16 (.940) wheel cyl bore with a shoe width of 2.25.I e-mailed Master Power brakes and they said either size wheel cyl bore will work fine.Naturally I'm concerned about spinning the car around in a panic stop or even everyday driving.Not being a expert in brakes I'm looking for answers from anyone who may have the same Front and Rear brake setup on there Vega or Monza and what they used on there car.Thanks
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Re: 1972 Vega troubles

Postby Smiley » Tue May 29, 2018 4:31 am

.750" bore master is too small for anything but original Vega brakes, what master cyl are you using now ?
Are the front caliper bleeders at the top ? if not the calipers are on the wrong side leaving air trapped in them.
Are the rear brakes adjusted ?
The piston in the distribution block floats to turn on the brake malfunction light if one half fails, even if it was stuck it would not cause a low soft pedal.
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Re: 1972 Vega troubles

Postby cerealkiller » Tue May 29, 2018 6:16 pm

Hello Smiley,Im using a STOCK replacement Vega M/C.The calipers are where they belong .All 4 corners bleed fine.The rear brakes are adjusted fine.Someone said if the METERING Valve is bad this is my problem.How would I know if the metering block is bad?What are the Symptoms of a BAD Metering Valve?My Vega Shop Manual says "The brake pressure differential warning switch is a NON-ADJUSTABLE ,NON-SERVICEABLE part,if Defective,Replace it.I found a replacement PROPORTIONING valve on E-BAY that cross-references to the stock GM part number-25509419.The Replacement valve is a Large Brass block like every GM car has nowadays.I can only guess that either the M/C is TOO SMALL or the Meterring block is Bad.What do you think?
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Re: 1972 Vega troubles

Postby cjbiagi » Tue May 29, 2018 6:36 pm

I am confused because the original distribution block on 1975 and earlier H bodies is just a distribution block, it is not a proportioning valve like the part # you provided. Once you start swapping different brake parts everything changes. It sounds like you have large drums and larger calipers than stock. That is going to require a different MC to match those larger calipers and rear cylinders. I don't think the distribution valve is the problem......... Also, are you bench bleeding the MC before installing the lines? That is usually crucial to get all the air out of the MC BEFORE you start bleeding the brakes. If you are just bolting it on and adding fluid and then bleeding the brakes that is not the way to do it. But, most likely you need a MC to match the calipers and wheel cylinders you are using. You may need to get rid of that distribution block anyway, you probably will need a real proportioning valve to get the correct brake bias. Those rear drums are huge for a H body.
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Re: 1972 Vega troubles

Postby cerealkiller » Tue May 29, 2018 7:00 pm

I know how to bench bleed.Ive been playing with cars for 44 years and counting.If ANYONE believes that another Master Cylinder is necessary I wish someone would tell me EXACTLY what M/C I need.How does one actually figure what size M/C I need?Is there some kind of Chart or Reference of any kind to figure this stuff out?I cant imagine what other Info I can give anybody.All I can think of is already mentioned in previous questions/comments of mine.Should I just look (WHERE THE HELL WOULD I LOOK) for some other/any other auto that has 11"front brakes and 15/16 rear wheel cylinder bores to find out what M/Cs are used with that combo?My Shop Manual says if the Distribution Valve is bad,Replace it.With what?As I mentioned earlier the Stock Vega Metering block is part number-25509419 and MATCHES EXACTLY the part number of a Proportioning valve for sale on E-BAY.The guy selling the valve is from IRAN.He has a pic of the REPLACEMENT Valve in his pics and you can see the CROSS-REFERENCE number of my Original Valve MATCHES the GM part number on the GM parts box of his.The two Valves are Obviously TOTALLY DIFFERENT,at least VISUALLY,but my 1972 Valve has OBVIOUSLY been Superceded by a NEW part.Where does this leave me?Buy a NEW Mystery M/C or a NEW Prop valve,or BOTH?Anyone?
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Re: 1972 Vega troubles

Postby Smiley » Wed May 30, 2018 4:20 am

Use the smaller rear wheel cylinders that you have and a master with a 1" bore.
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Re: 1972 Vega troubles

Postby cosvega76 » Wed May 30, 2018 8:38 am

I agree with Smiley, although if you're keeping manual brakes, I'd suggest a 15/16" bore master.

It sounds like you have the early Monte Carlo front brakes, with the D52 pads and 2 15/16" bore calipers. I had the downsized (or, as it's referred to, Metric) Monte front brakes on my Vega years ago. That uses 2 1/2" bore calipers and D154 pads. I used both 7/8" and 15/16" bore masters with that setup, and preferred the 7/8", although the pedal was a little long. With your larger calipers, I'd still recommend the 15/16". The 1" will work, but it'll take a little more oomph.


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Re: 1972 Vega troubles

Postby monzaaddict » Wed May 30, 2018 6:10 pm

"The rear drum diameter is 11 inches.The shoe width is 2.5 inches wide.The front brakes appear to be standard Camaro,Monte Carlo style,11 inch rotors,single piston."

Could post a picture of the front brakes/spindles?
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Re: 1972 Vega troubles

Postby cerealkiller » Wed May 30, 2018 6:49 pm

Sorry don't have a Camera Phone.
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Re: 1972 Vega troubles

Postby Smiley » Thu May 31, 2018 5:54 pm

Measure the piston diameter of the front calipers, that will help determine the size of the master cylinder bore needed.
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Re: 1972 Vega troubles

Postby cerealkiller » Thu May 31, 2018 7:19 pm

Hello,my Piston Diameter is 2.830.Ive been told a 1" BORE M/CYL is what I need?What say you?Thanks
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Re: 1972 Vega troubles

Postby cjbiagi » Thu May 31, 2018 7:42 pm

Chuck is pretty knowledgeable on brake systems and recommended a 15/16" or 1" bore. So, it sounds like you are on the right course. Basically you need more volume because of the larger calipers. A larger bore will give you that volume.
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