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 Posted: Aug 27, 2018 06:29AM
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The piece was cut from a sheet of 1/8" steel plate.  It's thicker and more robust than the original so I don't think it is going to fail. (but thanks for the concern).  In any case, the MC is in pretty good shape but there is a minor score in the bore that may let some fluid past the seal so I'll be replacing it when it comes off the road in the fall.

1976 1000 (Current Project)

1975 1000 Donor

1969 Cooper (Future Project)

1971 Opel GT

1972 Corvette Stingray

 Posted: Aug 26, 2018 11:15PM
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US
Nice catch.

 Posted: Aug 26, 2018 04:53PM
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CA
Hi Corey,

Are you in Penticton? I live in Lake Country(Winfield). I have a few of these hanging about that you may be able to salvage parts from.

Ron

 

Cool

 Posted: Aug 26, 2018 03:29PM
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On my computer, they both look brass color

 Posted: Aug 26, 2018 02:41PM
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US
Both the old and new parts look like steel to me.

Your part looks a bit heavier/thicker than the original.  As long as you got the length right you should be OK.

Doug L.
 Posted: Aug 26, 2018 02:25PM
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Quote:

After a few hours with some 3 mil steel, drilling and filing, I ended up with the part in the attached pic.  All back together and bench bled without an issue.  I may end up ordering a new MC to have on hand, but this will should keep me on the road for a bit.
Steel? color looks like non-steel. Just curious.

Without knowing the required metals specification, is this a gamble? Of course , one could argue that the original was not so corrosion-resistant or strong either.  I admire your shadetree mechanic fix ( because I have been guilty of similar events) , but brakes are, well, life-saving.

 Posted: Aug 26, 2018 02:06PM
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Quote:
Originally Posted by dklawson
Quote:
Originally Posted by OKMini
 
  I will go for this option if I cannot fabricate the piece.

I suggest you thoroughly inspect the old MC first before spending time fabricating a replacement part.  If the failed part corroded away there is a good chance there is damage elsewhere in the MC.  
Yep, good suggestion.  I had already rebuilt this MC and it was generally in good condition.  The end of the piece that connects the pistons is hidden inside the piston end so I couldn't see its condition.

After a few hours with some 3 mil steel, drilling and filing, I ended up with the part in the attached pic.  All back together and bench bled without an issue.  I may end up ordering a new MC to have on hand, but this will should keep me on the road for a bit.

1976 1000 (Current Project)

1975 1000 Donor

1969 Cooper (Future Project)

1971 Opel GT

1972 Corvette Stingray

 Posted: Aug 26, 2018 12:43PM
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US
Quote:
Originally Posted by OKMini
 
  I will go for this option if I cannot fabricate the piece.

I suggest you thoroughly inspect the old MC first before spending time fabricating a replacement part.  If the failed part corroded away there is a good chance there is damage elsewhere in the MC.  

Doug L.
 Posted: Aug 26, 2018 08:45AM
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Quote:
Originally Posted by kd
Assuming that you have the interia valve on the rear sub-frame... you only need two brake fittings to change the fittings on your lines into the master. The yellow band Master is a much cheaper option.
You can order the conversion kit if you do not have a brake line flaring tool. Your 1976 Mini project is the car in question? The new master will have a fliuid level light with the built in float.  You do not have to attach anything to it .Left hand drive conversion pipes are Mini Spares number BAU5655MS
Deb
Thanks for the reply.  I will go for this option if I cannot fabricate the piece.

Cheers,

Corey

1976 1000 (Current Project)

1975 1000 Donor

1969 Cooper (Future Project)

1971 Opel GT

1972 Corvette Stingray

 Posted: Aug 26, 2018 08:07AM
kd
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CA
Assuming that you have the interia valve on the rear sub-frame... you only need two brake fittings to change the fittings on your lines into the master. The yellow band Master is a much cheaper option.
You can order the conversion kit if you do not have a brake line flaring tool. Your 1976 Mini project is the car in question? The new master will have a fliuid level light with the built in float.  You do not have to attach anything to it .Left hand drive conversion pipes are Mini Spares number BAU5655MS
Deb

Keith & Deb

Avatar:Turn 1 at the Glen

 Posted: Aug 25, 2018 03:08PM
 Edited:  Aug 25, 2018 03:09PM
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Well the good part is I know what the problem is.  Crappy part is the nature of the problem.  Although I seemed to have a decent pedal, the MC would not bleed, and after much frustration I removed it and took it apart.

As shown in the picture, the piece that joins the two pistons together corroded through and broke.  So no return on the front circuit.  If anyone has this piece and is willing to part with it, great.  Otherwise, there is an NOS one on Ebay right now for the princely sum of $325 Cdn.  Or, I just go with the GMC227 as a replacement, which may be a better option.

Current system is LHD front/rear split with the switch in the PDWA valve. If I go with the GMC227, I assume I can run the existing brake warning wires to the MC, but do I need the pressure reducing valve and conversion kit for the fittings.

Off the road for a while. 

1976 1000 (Current Project)

1975 1000 Donor

1969 Cooper (Future Project)

1971 Opel GT

1972 Corvette Stingray

 Posted: Aug 24, 2018 09:08AM
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Another failure item is the front/rear flexible hoses as they close up internally and will let fluid past but not back thus locking up the brakes.

If in doubt, flat out. Colin Mc Rae MBE 1968-2007.

Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.

 Posted: Aug 24, 2018 07:07AM
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Quote:
Originally Posted by dklawson
If you can pump the brakes and they work with a firm pedal... and the pedal does not sink to the floor... it is likely to be a problem with the way the shoes were installed and adjusted, not the MC. 

I cannot tell you what to look for with PDWA failures except it's easy to mess up their spool centering during brake bleeding.  Actual PDWA failures can be seen with things like fluid coming out of the switch.
After my initial attempt to figure this out, it looks like gklawson may be the insightful one.

I pulled all 4 drums to check the installations and all the shoes were oriented properly.  I redid all the adjustments.  The rears were fine, but the fronts seemed to require quite a bit of movement.  After I re-adjusted the fronts I had a pedal again.  I'm still not happy with the feel as there is a bit to much travel, but at least they are working.  I'll still bleed everything to make sure there is no crap in the lines.

However, while I can see that too much space between the shoes and drums would require pumping before good contact is made, I don't know how this could lead to the total lock-up of the brakes.  If anyone can explain this it would put my mind at ease.

1976 1000 (Current Project)

1975 1000 Donor

1969 Cooper (Future Project)

1971 Opel GT

1972 Corvette Stingray

 Posted: Aug 22, 2018 07:46AM
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CA

I like to use the GMC227 master cyl, I put those in everything, I like the dual line split so if something goes wrong with one half of the system, there is still some braking. We have been running these in the racecar since we started 8 years ago and with something in the neighbourhood of 10,000+ race miles.

We have a full split system, with the front and rears completely separate, and using 5/8" cylinders at the back. Up front are the Mini spares 4pot alloy calipers. My Vintage racer has this setup, as well as a Vintage racer I am currently building. I have also used this setup in a 67 Traveller with drum brakes up front and it works a treat.

I know it doesn't solve your mystery, but it is a real-world solution if you can't get to the bottom of it.

 

Sean Windrum

1996 MGF VVC
1970 1275 GT Racer
66 Austin Countryman
63 997 Cooper (Under Construction)
63 MG 1100

 

 Posted: Aug 21, 2018 10:49AM
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Quote:
Originally Posted by mascherk
There is a good chance that you have boiled the brake fluid when the brakes were smoking. This will put air in the system. If this is the case you will need to bleed the brakes before doing any additional troubleshooting.

Kelley
Considering the rather nasty color of the fluid in the reservoir, i wouldn't bet against it.

1976 1000 (Current Project)

1975 1000 Donor

1969 Cooper (Future Project)

1971 Opel GT

1972 Corvette Stingray

 Posted: Aug 21, 2018 10:43AM
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Really sounds like a master issue, perhaps contamination and or swelled rubber parts or old too hard rubber parts. The only way the pedal goes to the floor with no puddles, after bleeding, and having had brakes is a master problem. That may not be the only problem but it's  where I would start.

 Posted: Aug 21, 2018 10:36AM
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US
There is a good chance that you have boiled the brake fluid when the brakes were smoking. This will put air in the system. If this is the case you will need to bleed the brakes before doing any additional troubleshooting.

Kelley

"If you can afford the car, you can afford the manual..."

 Posted: Aug 21, 2018 09:17AM
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I'm going to start digging into this tonight, but I did have another thing to ponder.

I'm not as interested in whether the installation is technically correct at this point, but rather whether or not the odd mix of parts could actually cause the lock-up and subsequent failure.  Its seems odd to me that the pedal will pump up and hold pressure, then if I let the pedal up, it will immediately go right to the floor with zero resistance.

Anyway, this 76 Canadian import has shown to be an odd mix of 75-77 parts so I didn't think much of it at the time, but when doing the brake system with the GMC159 master cylinder on the front/rear system, I originally ordered the GWC1102 rear cylinders with the 3/4" bore.  However, they would not fit the backing plates (pin holes on the wrong side) and when I measured the old ones, they had 11/16" bores.  So I ordered some GMC1129 cylinders and they fit fine.  1129's were used on Canadian minis with the GMC 159 MC, but normally with front discs, as shown in the attached chart.

I'd expect some difference in the pedal feel and braking from the smaller bore cylinders, but not completely failure.

Any thoughts on whether this could be a contributing factor?  To much pressure in the MC?

1976 1000 (Current Project)

1975 1000 Donor

1969 Cooper (Future Project)

1971 Opel GT

1972 Corvette Stingray

 Posted: Aug 20, 2018 02:50PM
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I have had this issue before. Loosen the master cylinder mounting bolts and drive it slowly around the block and see if it acts the same.

If in doubt, flat out. Colin Mc Rae MBE 1968-2007.

Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.

 Posted: Aug 20, 2018 10:38AM
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Thanks Sean - I'll have closer look when I am digging around.

Corey

1976 1000 (Current Project)

1975 1000 Donor

1969 Cooper (Future Project)

1971 Opel GT

1972 Corvette Stingray

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