Master Brake Cylinder

[stanrob]

My master brake cylinder clearly needs rebuild or replacement. The pedal slowly sinks, requiring active pumping to hold on a hill. Gradually it's sinking faster. There's no loss of brake fluid.
New part quote is $137.
I believe the part is the same as the one I have in my dead 83 Hatchback (only 100k miles, but body messed up. I've begun trying to disinstall that one. My inexpensive 10/12mm Great Neck brake line wrench fits perfectly, but then it stretches and slips around. Suggestions?

[marlinh]

If you haven't rounded off the nut yet, sometimes tightening and then loosening the nut may work. If the wrench keeps slipping, you should have enough room at the master cylinder to put a pair of vise grips around the wrench to clamp it tighter on the nut. Those cheap flare nut wrenches are frustrating to use. Good luck

[dlb]

if the car you're removing the master cylinder from is for parts anyway, i would cut the brake line right by the master cylinder and put a socket or closed end of a wrench on it.

when i'm forced to use a flare nut wrench on a really stuck nut, i put it on the nut and then put vice grips on the business end of the wrench to keep it from stretching or snapping.

i got a rebuilt master cylinder from rock auto for really cheap last spring. even with the exorbitant cost of shipping to canada, it was still only $25 or something. others here have had bad experiences with rebuilt master cylinders but mine worked great.

[rer233]

+1 on the vise grips- might also help to smear some valve grinding compound on the flats of the fitting- gives the wrench better "bite."

Good Luck!

[Petros]

if the flats on the nut are buggered up take a file to them first and try and restore the "points" of the nut first. the grinding compound is a good idea too. I would also heat it with a heat gun or propane torch.

I have never hand an issue or problem when using the correct flare hose wrench, looks like this:



sometimes I have to work it back and forth, and the vise grips assist is not a bad idea. if the flats were already messed up you might just cut it off and than remove it on the bench with some large vise grips.

I have had bad luck too many times with a remanufactured master cylinders, some are good, many are not (right out of the box they can be junk). I would rather install a kit myself than risk using a reman. (make sure you know how to recondition the bore in the master before you try this). New is always best, but if you have a good used one available that would not be a bad choice either.

Make sure you bench bleed it before you install it.

If you are replacing the master anyway, you might consider the MR2 master and booster upgrade as I outline in the my brake up grade thread over in the repair guide section.

Good luck.

[stanrob]

At long last, here's my report, and THANK YOU for every suggestion you guys have offered! In Massachusetts, as you may have heard, we had 6+ feet of snow plus frigid temperatures, and I was confined to working outdoors. All my friends' garages were already loaded with junk. Finally some slightly better days arrived and I was able to shovel my way to the front of the 1983 parts car. The actual trigger for action was the complete failure of the front of my original part, leaving me with rear braking only, at the very bottom of pedal travel, in the dark, en route to an event I wanted to attend! (I turned around and limped home.)

First off, I sprayed PB Blaster on the 1983 Hatchback's bolts and connectors. That turned out to be a good move. I was able to start the brake line nuts with a visegrip, as one of you suggested. Long process, but I got the part off. That experience helped prepare me for removal of the 85TCW's part. I gradually learned I could use pliers to spin those brake line nuts off or on.

After final tightening with the brake line wrench, I suddenly realized I hadn't bench-bled the part, which was empty at the time. So I loosened and spun those nuts off again and used my vacuum test kit to do that bleed. After reassembly, I discovered I had near-perfect braking. What a great feeling, especially with annual safety inspection due! When the weather gets better, I'll bleed the individual wheels.