[Qfrank]

I removed brake master cylinder to do some cleaning and inspection, and upon reinstall everything went well until the last banjo bolt closest to the intake, passenger side of master cylinder. After several attempts and it appears, I think that I have crossed threaded the threads on the master cylinder. What can I do at this point?



What size threads are they? Is a heli coil in order?



The bolt seems fine, but the threads on the cylinder do not.



Also I lost all the fluid in the reservoir, so I am thinking I have more work ahead of me, bleeding? I should have never removed it to begin with.



Thanks



FQ

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[flash]

i would replace the master cylinder. it's probably due anyway. any hydraulic leaks are very dangerous when you are talking about brakes, and i would not trust those threads even if you could repair them (and i'm pretty sure they are tapered threads anyway).

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[RS Barn]

Replace M/C

You should have better brake feel . Think of it as a performance upgrade

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[Qfrank]

It was the first and second thread on the M/C so Used a thread restorer from auto zone, with a 10mx 1.250 tap, and the banjo bolt went it real smooth, tightened up snug.



I need to check paperwork from <acronym title='previous owner'>PO</acronym>, and check if it has been replaced, I can't remember if it has.



This should work for now, but I will order new one for piece of mind.



Thanks guys.



FQ

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[flash]

i don't have a banjo bolt there. it's a standard brake line fitting. if yours is the same, i would be concerned that the tapered flare (not tapered thread as i misspoke earlier) is not seating fully and could leak under pressure.

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[Qfrank]

Yes standard brake line fitting. I will observe for leaks, and report back.



Once new one arrives, I will replace.

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[Qfrank]

Sure enough it leaks.



New one on the way.

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[flash]

i was afraid of that. bummer. well, at least it leaked when you weren't in need of those brakes

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[Qfrank]

Pedal goes to the floor during an autocorss at 60mph, quite a surprise. Previous master lasted 5000 miles, but 12 or so autocrosses.



Has ok pedal with moderate pressure but if you hold firm, it goes to the floor.



No loss of fluid, but fluid looks a little dirty.



Ordered new ATE master cylinder, previous one i installed was a girling, not sure if it was right one, and motive bleeder and super blue fluid.

Lets see what happens this time.



Anyone know if Girling was even correct? I have no markings on booster to say ATE, but most sources go with ATE master.



FQ

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[flash]

sounds like the high pressure line is about to burst

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[Qfrank]

Hey Flash.



Which one is that?

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[MB968]

[quote name='Qfrank' timestamp='1366157934' post='141476']



Has ok pedal with moderate pressure but if you hold firm, it goes to the floor.



FQ

[/quote]



Sounds like the master cylinder. Years ago they were designed with only one seal, and if the seal leaked, you would see it dripping from the master cyl. For some time now, probably since the late 80s early 90s, most master cylinders have the seal on the pressure side of piston as they always have had, and now a secondary seal where the rod leaves the master cylinder. This side of the piston is not supposed to see any pressure and is plumbed to the supply side of the piston. So, if the primary seal has a slow leak, you could hold pressure on it as you've noted and it would continue to go to the floor. Any brake fluid that leaks past the main seal just returns to the supply side of the M/C. I'm sure if you Google M/C/brake goes to the floor, you'll find diagrams (in case my verbage isn't clear).

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[flash]

masters in this car rarely fail partially. i have only heard of a handful failing at all, and it was always after somebody changed a slave or high pressure line, and failed to change the rest of the parts in the system, and usually in a car that did not have its system regularly flushed. you have to change them all at once, or the weak link then fails, on an average of 50% of the time. you also must flush the system every 2 or 3 years.



as for the symptom you have, this happens when the high pressure line is about to fail. there is a joint where the rubber part meets the hard line. it is well known for failing there. generally it swells like a balloon before it goes, but often people don't notice it until it's too late.



have somebody push down on the pedal while you look at the line. it's the one that comes out of the reservoir, and heads down along the engine to the slave down below.



if the master is leaking, you should be able to see the fluid level in the reservoir move, and likely see bubbles when you push on the pedal. it should also be "sweating" at the back side where the clevis goes into it.

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