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76 MGB Brake Overhaul

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riley1489 Avatar
riley1489 Gold Member Bruce H
Great White North, QC, Canada   CAN
1953 Jaguar XK120
1959 Riley 1.5 "King George"
1973 MG MGB
In reply to # 3888670 by jseabolt 1) When I got to reading on this subject, it lead me to believe this valve also functioned as some sort of safety valve.

2) Is there a stop/limiter inside this brake union which makes it OK to bleed the brakes at the front first but not the rear?

3) Is this a "one time switch"? Meaning it's not spring loaded and once it trips, you have to replace it?

4) So as long as the O-rings are good, this shouldn't happen?

5) I haven't seen this mentioned but is there any harm in just removing the shuttle from the brake union? My fear would be it could possibly stick in one position. I guess as long as the braking system is OK this may not ever happen.

6) My next assumption would be the plastic body switch would now be exposed to excessive pressure when the brakes are applied and could blow. Some people mentioned using a bolt in place of the switch but so far I have not read anything about also removing the shuttle.

7) something else wrong with the brakes. Like the O-rings on the shuttle being worn out. I have never seen the brake light come on the dashboard.

1) as mentioned earlier this switch simply lights up the dash light to meet federal regulations at the time.
2) nothing in this brass block but the shuttle, (below)
3) switch is simply a spring loaded switch . FWIW this same switch is used on contemporary vehicles, Ford Mustang for one.
4) if O rings fail leak will occur
5) remove the shuttle as you wish. You will need to plug the switch hole with a bolt and sealing washer
6) this switch has no sealing function
7) if the O ring are compromised you will see fluid leaks, and evidence of paint damage at the flitch panel etc.

Bleed the brakes and find out all these answers

B



Check your ego Amigo!



Edited 1 time(s). Last edit at 2019-02-09 03:59 PM by riley1489.

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BH_MGB_brake PDW.jpg    30.8 KB
BH_MGB_brake PDW.jpg

jseabolt Avatar
jseabolt James Seabolt
Mount Carmel, TN, USA   USA
1977 MG MGB
In reply to # 3888709 by riley1489
In reply to # 3888670 by jseabolt 1) When I got to reading on this subject, it lead me to believe this valve also functioned as some sort of safety valve.

2) Is there a stop/limiter inside this brake union which makes it OK to bleed the brakes at the front first but not the rear?

3) Is this a "one time switch"? Meaning it's not spring loaded and once it trips, you have to replace it?

4) So as long as the O-rings are good, this shouldn't happen?

5) I haven't seen this mentioned but is there any harm in just removing the shuttle from the brake union? My fear would be it could possibly stick in one position. I guess as long as the braking system is OK this may not ever happen.

6) My next assumption would be the plastic body switch would now be exposed to excessive pressure when the brakes are applied and could blow. Some people mentioned using a bolt in place of the switch but so far I have not read anything about also removing the shuttle.

7) something else wrong with the brakes. Like the O-rings on the shuttle being worn out. I have never seen the brake light come on the dashboard.

1) as mentioned earlier this switch simply lights up the dash light to meet federal regulations at the time.
2) nothing in this brass block but the shuttle, (below)
3) switch is simply a spring loaded switch . FWIW this same switch is used on contemporary vehicles, Ford Mustang for one.
4) if O rings fail leak will occur
5) remove the shuttle as you wish. You will need to plug the switch hole with a bolt and sealing washer
6) this switch has no sealing function
7) if the O ring are compromised you will see fluid leaks, and evidence of paint damage at the flitch panel etc.

Bleed the brakes and find out all these answers

B

Ok once again I'm not familiar with all the changes made to these cars over the years. I don't see this brass junction on my 77 in the engine compartment as seen in another post.

There is a white plastic switch on the underside of the master cylinder.

I thought this could be the tail light brake switch but another search shows this switch on at least 80 models is activated by the brake pedal and not fluid pressure.

So just back the switch out three turns and bleed the opposite as you normally would? Starting with the driver's front?



http://s222.photobucket.com/user/turbofiat/library/?sort=2&page=0

1977 MGB
1980 Fiat 124 Spider (turbo)
1987 Yugo (1500 turbo)
1981 Trabant 601
1987 Citroen 2CV
1968 Ford Fairlane 500

riley1489 Avatar
riley1489 Gold Member Bruce H
Great White North, QC, Canada   CAN
1953 Jaguar XK120
1959 Riley 1.5 "King George"
1973 MG MGB
James,
Trying to help you out with this. It was you that linked to the brass union PDWA so I followed. Misleading for sure.

On your late model car this very same PDWA system applies, (O rings, shuttle, switch etc.) but is incorporated in the master cylinder. (below #17, #16 and #2 respectively)

Unscrew the switch as described in the manual, bleed normally, ensure a good level of fluid in the master cylinder reservoir (s) . Nothing special with Lockheed brakes.

B



Check your ego Amigo!

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Attachments:
BH_late model MC.JPG    32 KB
BH_late model MC.JPG

jseabolt Avatar
jseabolt James Seabolt
Mount Carmel, TN, USA   USA
1977 MG MGB
Thanks man. I am mechanical inclined, I am just new to this car. I have not even driven it other than in my driveway due to no brakes

I'm trying to research previously asked questions but either some people don't mention the year of their car in their posts and just assume verterean MG owners know what people are talking about or I overlook it.

Then when someone new comes along like me and sees a photo then wonders why is this part not on my car!

This car also seems to have allot of mismatched parts and those redundant shocks on the front that had me totally confused!

I also do allot of my research at work. I work 12 hour swing shifts so when the plant is not in the ditch I have allot of spare time on my hands.



http://s222.photobucket.com/user/turbofiat/library/?sort=2&page=0

1977 MGB
1980 Fiat 124 Spider (turbo)
1987 Yugo (1500 turbo)
1981 Trabant 601
1987 Citroen 2CV
1968 Ford Fairlane 500

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