Master Cylinder Rebuild

[mickelwait]

I am attempting to rebuild the brake master cylinder on my '71 GT and I'm unable to get it apart.

I have everything off the housing that can come off, but the pistons will not come out. I removed the snap ring and the metal washer behind it and now see a white plastic washer. I thought the pistons would just come out, but they will not. They move freely against the springs, but stop as soon as they hit whatever is behind this white washer.

Can somebody please give me some guidance?

[Stanley_P]

Make sure you have everything off the MC, including the
brake switch. I could stop by and look, I live in Versailles, KY
I rebuilt my MC with no problems at all.

Stanley P

[Dan]

I just purchased a rebuilt unit from Napa, it was about the same price OGTS charges for a rebuild kit.

[Gary]

Originally posted by Stanley_P .....I could stop by and look, I live in Versailles, KY I rebuilt my MC with no problems at all. Stanley P

Great! This is exactly what I hoped opelgt.com would turn into. Making connections so Opelers can help out Opelers who live nearby!

[mickelwait]

I went ahead and ordered a rebuilt master cylinder from CarQuest for about $45, but if you'd like to come by and take a look at it (Stanley P) that would be great!

How do we get in touch?

[Burst]

I redid mine last year with the OGTS supplied kit. I don't have the car here today, but I "think" I remember a small screw or bolt on the body of the cylinder besides the pressure switch that actually retained the pistons also. In any case removing everything on the cylinder body should do the trick.
BD

[baz]

the bit stopping you is part no 6
this is a manta cylinder but pin is same
(i think its in yhe hole bye the way)

[tomking]

OK guys, I have a question about this thread too. My MC is the type with the switch built in to indicate a brake fault. I got all the parts out ok except the brake fault switch. I cant seem to get it out anyway I try. Is there a trick here I am not doing? Plus, exactly where is that little piston retaining pin? My pistons came out alright but I didnt pull any small pin. Thanks.

[mickelwait]

I was also unable to locate the stop pin shown in the above view (part no. 6). By the above view, it looks like it should be in the rear piston fluid intake. My MC has two stop pins with bolt heads behind both the front and rear pistons. Everything is off the housing and nothin's coming out! My only thought is that a washer is rusted or corroded at the rear of the MC holding the pistons in there. The pistons do move freely against the springs.

tomking, I have the same MC and other than for cleaning purposes I don't know why you would really need to remove that switch on the lower part of the MC. Mine came out with the MC clamped to my work bench and quite a bit of elbow grease on the wrench.

[West Coast GT]

Help Please
I'm trying to remove the master cylinder to rebuild or replace.

I've:
Disconnected all three hydraulic lines
Disconnected the vacum line to booster.
Removed the four nuts holding the booster/MC body to the cross-member.

Have not removed the two bolts holding the MC to the booster.

The unit cannot move forward enough to allow the 4 booster studs to clear the holes.

It appears the reservoir must be removed before I gain enough room.

Is this correct?
And where does that third hydraulic line go to?
And I didn't find any electrical connections on the MC. Think this could be a non - OEM unit???

[nobody]

To remove MC only;
1 remove reservoir
2 remove the 2 bolts
3 pull MC forward to clear

The brake lines are 1 for rear brakes 1 for front left 1 for front right.
Reservoir is held by 2 grommet type seals, just pulls straight up.
Put a bucket under the thing before you pull it brake fluid eats paint.

[namba209]

I've taken the MC out without removing the reservoir, the drill is the same as nobody stated above. disconnect the three hydraulic lines, the two bolts and pull forward off the studs, it's a little tight, but with twisting and turning it will come out. I would put a rag or paper towels under the lines though, the brake fluid will eat the paint in short order. If you look at the drawing above in earlier posts, the electrical connection goes to item #8. It could be that the PO broke the male part of the electrical connection at that switch. Look for a loose wire with a female connection on it, that will be what is supposed to be hooked up on the MC. HTH.

Ron

[West Coast GT]

Thank you to Namba & Nobody. Yanked that reservoir right off, stanched the copious bleeding of my thumb, then removed the master cylinder.

Next question - Is the booster vaccum canister supposed to be full of hydraulic fluid? If yes, then everything's cool. If not, yeow!

And finally, have you guys found rebuilding a master cylinder to be worthwhile, or is this an exercise in futility? I tried it twice on an MG Midget I used to have - and found it just doesn't work out.

[baz]

[quote]Next question - Is the booster vaccum canister supposed to be full of hydraulic fluid? If yes, then everything's cool. If not, yeow!

well yeow is the word (wow flash backs to grease)
not a good thing time for that rebuild kit and a bandaid or 2

[West Coast GT]

Bummer. I figured it might be a bad thing.

Wish me luck guys, I just swiped my wife's turkey baster so I could suction that hydraulic fluid out of the booster canister. Since Thanksgiving was yesterday, she might not notice it's gone til Christmas rolls around next month.

Hopefully I'll remember to buy a new one before then. If not, well, its been nice.....

[soybean]

Now this is probably a very dumb question, but how does the reservoir come off? Does it just pull off? I read WestCoasts' post about yanking it off, but...I have an old MC to practice on, but I'd hate to tear up my spare. Thanks, Jarrell

[namba209]

Jarrell, futher down in previous posts, "Nobody" explains the reservoir is held in by a couple of rubber grommets. The same size is in both cylinders, if this is for a GT, the forward grommet just holds a fitting a hose from the bottom of the reservoir connects to. HTH.

[soybean]

Thanks Ron, I knew I'd seen it somewhere, just couldn't find it. "Oldtimers and CRS" catching up with me. Jarrell

[jvandyke]

Alright, my turn.
Am I right that the booster can stay put when removing the MC? If so, must be the push rod on the MC side just comes off? No need to undo the push rod and all that (which I've already done) from the booster side?
I've got other issues too. Middle fitting is too close to the failure sensor, no idea how the PO got it together like that. I can't get my flare nut wrench on it (no room) and from the looks of the fitting, neither could the PO! Thought about trying to undo the banjo fitting instead, big square nut, 15mm? Bad idea?
Or take the flare nut wrench to the grinder.

[namba209]

You're right, you don't have to mess with the booster or the rod that goes in to it. You'll have to tweak the reservoir a tad, to get the MC off the studs. I didn't have a problem pulling the lines off my MC. IIRC there's two lines up front for the front brakes and one in the rear for the rear drums. You could take out the differential pressure switch to access the line hard to get to, or pull the banjo fitting, watch out for the crush washers on both sides if it, too. Stuff a lot of rags under all the fittings, there will be a fair amount of brake fluid coming out of the MC fittings with the lines disconnected.

[West Coast GT]

I finally got tired of those difficult to reach brake line connections on the MC, especially the one way out front where its damn near impossible to get to. So I cut the brake lines in as convenient a spot as I could find.
Then double-flared the lines.
This allows me to install the brake line connections with the MC on the bench. Then connect the MC lines to the lines going to the slave cylinders via unions.

[jvandyke]

Guess I'll have to decide which fitting to go after (which I'm the least likely to destroy).
I think I'll try to crack that big square nut on the banjo fitting first as the flare nut looks like it's had it and I'd rather not disturb it.

[namba209]

All this discussion on the MC brake lines hard to get to, made me go look at mine. The rear one looks and is easy to access. The two front ones are a bit more difficult. I would suggest taking out the banjo fitting first then the one on the bottom front of the MC. Don't forget to use two wrenches on the rear line, and maybe some PB Blaster type penetrant first.