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master cylinder ID
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mmazz30 Offline
#1 Posted : Saturday, 21 August 2010 7:52:16 AM(UTC)
mmazz30

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Hi all,can anyone ID a m/cylinder i have.
The numbers i have are PBR 16AS P7210
I had the small dual diaphram booster(stato) on my HJ coupe for awhile(was going to do the disc rear convo)but never got around to it.Been driving this way for the last couple of years and then the rear seal let go of the m/cylinder about 6 months ago.This had the larger resi at the front to the front brakes.
Then i had a fairly new spare m/cylinder and large booster sitting around and i used the master with those numbers above.
This master has the smaller resi at the front,but still goes to the front brakes.All was ok and then my booster felt crappy last week,so i decided to fit the large booster back with its master and now i have a very weird pedal.It is good pedal but it feels like the initial travel comes on super hard and if sitting in drive,press the brake and release it actually holds the brakes on,then slowly releases.It comes off if i pull the pedal back with my toe.
I've checked freeplay between pushrod and back of m/cylinder...aok.
Check valve...aok.Pump pedal,engine off...goes hard,start engine and peadl drops like it should.
It felt like a sticky/rusted booster shaft,but i undid the master and the pedal stroke is smooth...aok
So i'm suss on that M/cylinder thinking maybe a drum brake master,but it was originally attached to a booster and worked ok when i had the small booster as well!
Got me buggered tonight and i will have another look tomorrow.
Just wanted to check those numbers.
cheers...mario

Edited by user Saturday, 21 August 2010 7:54:24 AM(UTC)  | Reason: Not specified
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Mike81973 Offline
#2 Posted : Sunday, 29 August 2010 7:12:32 AM(UTC)
Mike81973

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Hi Mmazz,
Repco will be able to tell you which master cyl is which.

This sounds like a dangerous game you are playing swapping parts around.

The pedal being hard then soft or what ever you said sounds like a missing reaction disc,
There should be a black neoprene disc between the push rod and where it locates in the Booster, these can easily be disloged if the push rod has been removed or fallen forward.

You sound like you are aware that some model master cylinders have a deeper hole that the pushrod sits into.

I also have experience with disc brake conversion to a HJ Statesman
the mistake some people make is that the modulater from the same HZ vehicle the brakes came from must be used not the HJ one, or you could have rear wheel lock up problems, you will also need to use the appropiate mastercyl of course, or at the very least remove the residual pressure valve that operates the rear brakes.
Changing the modulator will also require different brake failure wiring where it attatches to the modulator as HJ and HZ modulators are different.

HZ rear disc brake modulators are hard to get ( colour coded ) so make sure you have one of these before even thinking of doing the conversion or you are likely to have an accident.

Rear disc brakes from a HX Statesman are quite complicated and not something that I want to get into at this time as they had a anti lock system.

Mike

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Dr Terry Offline
#3 Posted : Tuesday, 31 August 2010 7:57:10 PM(UTC)
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I'm with you Mike, mario shouldn't be just swapping bits like that. But having said that, PBR produced several different m/cyls for HQ to HZ & most are interchangeable. The main changes were to the relative size of of the reservoirs, the position of the outlet ports & the removal of the residual pressure valve for the later rear disc version.

Mario's problem though appears to be booster related.

Mike, you mentioned HX rear discs. The HX series didn't get rear discs, these weren't released until HZ, but the HX Statesman range did have a Delco-Moraine anti-lock rear drum brake system as an option, which is unnecessarily overcomplicated.

BTW, by modulators, do you mean proportioning valves ?

Dr Terry

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HK1837 Offline
#4 Posted : Tuesday, 31 August 2010 10:40:12 PM(UTC)
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Mario, those master cylinders with the small resevoir at the front are not a direct replacement as far as I know. You also need the brake lines with it as the big volume resevoir is always for the front disc brakes. For some reason they swapped around. The steel brake lines changed at the same time. Normally you can get away with bending the lines around to suit, but I did get a new cylinder with my HJ Premier that had the same numbers as the alloy PBR one on it, but as well as the resevoirs moving the thread sizes stayed in the same place. hence it wouldn't fit. Plus I didn't want to wreck the original brake lines. I can't get a new alloy one to do the job I need, so i've sent Dr Terry an original cast iron example to get rebuilt for me.

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BIGCAV Offline
#5 Posted : Tuesday, 31 August 2010 11:10:45 PM(UTC)
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from my catalogue p7210 is a hq hj hx disc/drum combo master cylinder with m/vac
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Mike81973 Offline
#6 Posted : Wednesday, 1 September 2010 7:48:26 AM(UTC)
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Hi DR Terry,
I did mean the proportioing valve, I must have herd them referred to as modulators somewhere!
Of course there are many different ones as you will know.
first ones were black I think these from memory fitted HQ, J & X with HZ having the plastic two wire switch and most componetry not interchangable with the earlier ones.

Sedans, Deville Statesman, Caprice Statesman, Ute, PV, 1 tonner and Torana all having differing pressure settings depending on how much weight was over the rear axle, and weather they were disc or Drum rear, so lots of combinations!
Some WBs even had a load sensing valve so who knows what proporting valve these have, but I am not about to docunent all these in this topic.

The various master cyls also differing strength springs in , for instance a Torana one can look the same but have different pressures.

The dreaded Fords also used a similar Master cyl, so like you say, it pays to be certain, before swapping componets that may kill you.

I did make a mistake about the HX rear disc by the looks of things, I should check my books more often perhaps.
I have an excuse now I am over 50!

When ever I can I use the cast Iron ones too, but even these need to be the right ones.

The HZ SLE Statesman that I am doing up had a drum brake master cyl fitted so I soon ditched that one! good thing I checked!

Must always check others work as I have come accross lots of dodgey stuff by guys that should know better.


Mike


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Dr Terry Offline
#7 Posted : Wednesday, 1 September 2010 7:19:33 PM(UTC)
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Nothing wrong with being over 50, Mike.

With the proportioning valves, what you say is correct, there are many variations, but they fall into 4 main categories.

1. HQ style - This one is seen only on cars with front disc brakes & unlike like the others has no switch & is mounted under the car half way along the chassis rail.
2. HJ style - This one is mounted on a bracket attached to the RH upper control arm pivot mount. It has a single pin differential switch.
3. HX/HZ style - This one looks the same as the HJ style but has a 2-wire switch.
4. WB style - In similar fashion to Commodore m/cyls this one is incorporated inside the m/cyl itself. To complicate the issue late HZ & WB One Tonners had a load sensing valve in the rear brake line, if this is fitted then there is no proportioning valve inside the valve housing. They still get a switch, but no valve.

You mention the spring inside the different brake master cylinders varying in tension. These are purely a return spring & should have no effect on braking.

Dr Terry

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When calculating a car restoration budget, be as accurate as you can & then double the final figure. It will be closer to the truth.
If at first you don't succeed, just call it Version 1.0
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