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MG MGA - Master Cylinder push rod fork

Hi all. I'm in the middle of a few tries at rebuilding the MC and having some problems. I noticed that the original push rod fork pieces have been adjusted to different lengths. Unfortunately, now that they're out of the car, I'm not sure which is for clutch side and brake side. Does anyone know if the shorter length push rod goes with brake or clutch?

Also, for bleeding the hydraulic system, I saw someone on this board mention applying 10 psi of air at top of MC via a hole in the MC cap, and using one of those pin inflator fittings that you use to pump up a basketball or football. I assume they mean to drill a small hole in the cap that aligns with the hole on the underside of the cap, and, after using for this purpose, said cap can only be used for bleeding operation and can't be used for normal use. Any input on this?

thanks,
steve
Steve Nyman

Steve,
I have just done the same job as you are under taking. You will have to adjust the forks after you rebuild the master cyl. Also since you had to remove the pedals to get the cyl out, now is a great time to look at the pedals and check for wear on the pivot points. When you put them back together, make sure that the master cyl is fully retracted after the adjustment or the barkes may lock up, or the clutch may slip.

As for bleeding the brakes. The best way that I have found to do this by using a "Mity-vac" I had the whole system bleed in less than 10 minutes. That included all four wheels and the clutch. It is important that you watch the fluid level in the master cyl. If it gets too low you will have to re-do the whole bleeding operation.

JP Jim

Steve,
I used a homemade pressure bleeder and it worked great. I lucked out and found a steel cap that fit the master perfectly. I drilled a hole and soldered a barbed fitting to it. I pressurized it to about 10PSI. Then just went to each bleed screw, attached a clear plastic tube and opened the screw until the fluid came out without bubbles. Like Jim said, you have to watch the fluid level. I had to refill the master a couple times(mine is a 1500). One disadvantage of this simple homemade bleeder is that you have to relieve the pressure to check the fluid level. Many of the commercial pressure bleeders have a large clear reservoir that is pressurized and pumps fluid into the master under pressure.

PS you should relieve the pressure slowly. The first time I just opened the cap without relieving the pressure first. A little fluid shot out of the master. Luckily I was using silicone fluid.

Jeff
Jeff Schultz

Jeff

I did the same as you but with a commercial pressure bleeder. I was connected to a tyre as the pressure source and the 27 psi blew the silicon fluid everywhere! At least the shelf area is unlikely to rust. Good to know, though, that the MC and cap will take that pressure.

Steve
Steve Gyles

I bought a new master cylinder cap from Moss. It was plastic and I was able to remove the inner portion and use the cap with a ball inflating needle pushed into the vent hole. After bleeding the cylinders, I just replaced the inner piece in the cap and put it back on the master cylinder.
Ed Bell

JP Jim,
Now I have the two forks out of the master cylinder, one adjusted shorter than the other.
How should they be adjusted (how do you determine the correct length?)
Also, the clutch side in the MC is sticking in the back of the cylinder, and I've worked that piston back and forth a few dozen times. The piston seal is on correctly and the bore is smooth.

steve
Steve Nyman

You don't worry about the length, you just adjust until there is a little free play at rest. Free play should be somewhere around 1/8".

As for the sticking piston, I never had that problem. Does it only stick if you push it all the way in? Do you have fluid in it? If it is not sticking too badly, I would think it would free up. When you get fluid in the lines, the pressure from the slave would push it back when you release the clutch.
Jeff Schultz

Jeff,
Ok, thanks. Makes sense. Yes, clutch side only sticks when pushed all the way into bore. MC is full but just started the bleed process on brake side, haven't gotten to clutch. I'll press on and see what develops.
Thanks!

steve
Steve Nyman

This thread was discussed between 27/06/2007 and 28/06/2007

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