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Midget Brakes will not hold pressure

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Cujo

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Hello,

I am ready to run my 1970 Midget off a cliff. I have replaced all wheel cylinders and the master cylinder and rebuilt the front/rear switch. I still cannot get the system to hold pressure (all lines are bled and all cylinders are braking). That is when the pedal is pumped all the brakes work but as soon as you stop pumping for a second the brake pedal then goes straight to the floor with no pressure - and as I said it is a new master cylinder.
Any ideas or experience is much appreciated.

Thank you
 
Got a hole in a line.
I guess you would see fluid if you did.

Are you loosing fluid after all the pumping?
 
Often we equate no pedal with no fluid, while sometimes it's the stroke needed to push the shoes out that is taking the available fluid.
As Don says, if you aren't losing brake fluid, you are not leaking.
If you are, steel line, flex line, faulty part....

Run the adjusters out tight and see what you get for pedal.

Did you do anything else?
 
Not losing any fluid and brakes are working after several pumps - flex lines are not bulging and I tried running the adjusters all the way out and no change
 
I have checked every connection three times with someone in the car pumping the pedal - not a drop leaking - and have replaced every part. Clean stream with no bubbles coming out of each bleed valve and no bubbles in the master reservoir. My only thought now is my new master cylinder is defective
 
Did you bench bleed the master before installation?
Did you try removing the pressure line and bleeding it in the vehicle?
Just flush off brake fluid with water to neutralize it when done.
 
did not bench bleed the master - but I am getting fluid level change through the reservoir (in both halves) so is the piston not fully primed? I have never bench bled a master before - what is the ?

Thank you
 
Are all your steel lines going to the right ports on the junction block? Just a stab in the dark on this one. Good luck with the repair. Bob
 
I'm thinking master's the culprit. But I'm no expert
 
Pull the lines, one at a time (1970, dual MC right?), put your finger over the opening, have an assistant SLOWLY depress the brake pedal, allowing brake fluid to leak past your finger. Hold finger tight while they release pedal. When you "feel" clean fluid, replace the line (you can bleed via the line later) and do the otjer side. JUST to make sure.
 
:iagree:

Sounds like the MC has an air bell. In situ "bench bleeding" as Dave describes should yield a working system... you will need to go around it one more time at the ends, too.
 
Agreee with the two guys above.....may have air trapped in the high side of the brake line.

And here's a similar way to deal with this: you can have someone gently pump the pedal 3 or 4 times and hold down. Then just loosen one of the lines to the master cylinder a 1/4 turn or so until fluid spurts out. Tighten line, have assistant release pedal and repeat this several times (do both lines). This is messy so put plenty of rags around master cylinder (brake fluid eats paint).

By the way, this is the "MG" section of BCF (mostly MGAs, MGBs, T-Series, etc). The best place for questions about Sprites and Midgets is the "Spridgets" part of the forum.
 
aeronca65t said:
By the way, this is the "MG" section of BCF (mostly MGAs, MGBs, T-Series, etc). The best place for questions about Sprites and Midgets is the "Spridgets" part of the forum.
Click to expand...

This is really more of a big deal than you would imagine.
Work has gone on for YEARS to keep the published MG issues (and posts) less than the Triumph section.
We need to keep that "Midget" stuff over in the dedicated section to keep folks thinking that MG's have less problems than Triumph's.
 
Apologies on the post - maybe an idea to put "Not Midgets - use Spridgets" in the MG Post box though. I would think most "newbies" would not think to scroll down further for Spridgets as I did. I will rty the bench bleed and get back to you.
 
Bench bled the system - fluid immediately at both brake lines - re-bled each corner and the peddle is still doing the same thing. It will build pressure but once you stop pumping for even a second the peddle goes right to the floor again.
 
I have now moved the first question to the Spridget forum :smile:Bench bleeding did no good so I think I have a bad new MC
 
Cujo, don't leave us hangin here .
Please leave updates
 
Was a bad (new) master cylinder. Replaced it and everything works great - thanks for all your help and suggestions.
 
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