Master Cylinder Rebuild

[jvandyke]

Originally Posted by markandson Did a little searching and came up with this thread that you should review, it might help.

Yep, read that this afternoon. Thanks.
Got the kit today. Here's pics. No idea if it has what is needed or quality or anything, but here it is. I'm sure I'll have questions as I get into it.
From AutoZone part number 22523 from BrakeWare

[markandson]

Looks better than the kit I used from OGTS, mine was seals only, no pistons.

[jvandyke]

Alright, got her off fine. Undid the banjo bolt, no problem. Going to see how far I get tearing it down. FSM says "remove static pressure valve" is that the check valve on the one outlet port? Wish they'd use the same terms from one page to the next, FSM author must have gotten a bonus for not using the same term twice. Does the brake warning switch need to come off? Doesn't say so, let sleeping dogs lie if possible.

[namba209]

Jeff, pay real close attention to the innards of the MC as they come out, and make sure they go back in the same order as they came out. I'll tell you now, putting the spring in between the two pistons is a bear. You have to compress the spring and thread one piston in to the other. Lotsa fun.

The pressure differential switch does not have to come out for a rebuild, it's in the lower chamber between the front and rear chambers.

[jvandyke]

Pressure warning switch came out fine anyway but I'm stuck at the same place others have been: can't get guts out. Don't have much of an air compressor, just a small one for tires and toys, would you have to block off all the ports or just the one's involved in the front brake area?
Sure sounds like something is holding it all in yet but there's nothing left to pull out I'm pretty sure except there's a plug (allen head) in the end, that can stay put, right? off the "balancing chamber" for the sensor, don't think that's involved.

[namba209]

Never used a compressor, just pulled the snap ring and wahser, then kept pushing in on the piston and letting it snap back, eventually it all came out.

[BQS4]

Originally Posted by jvandyke Pressure warning switch came out fine anyway but I'm stuck at the same place others have been: can't get guts out. Don't have much of an air compressor, just a small one for tires and toys, would you have to block off all the ports or just the one's involved in the front brake area? Sure sounds like something is holding it all in yet but there's nothing left to pull out I'm pretty sure except there's a plug (allen head) in the end, that can stay put, right? off the "balancing chamber" for the sensor, don't think that's involved.

Jeff;
I have run across a M/C or two that have a small bolt/screw holding the back section of the M/C guts in. Just a tiny bit of this screw/bolt is sticking into the bore. You might want to give another look.

[jvandyke]

I looked hard for a pin but don't see one. Sure sounds like a stop somewhere, pretty distinct hard knock sound when it bottoms out. I hope there isn't a misaligned something in there.
Wondering about holding the exposed piston shaft, probably mangle it but I have new one with the kit. Drill through the end, bolt it to the garage, strap the MC to the trailer hitch and take off, something would give.
Also starting to think about bench bleeding. Looking to get a kit at NAPA but will probably end up having to cobble something even then as I seriously doubt a kit will have all the fitting I'd need on a 3 outlet metric MC. Also, you pretty much have to have the reservoir off to reinstall MC so it would seem to me that you'd introduce air anyway.

[West Coast GT]

If Namba says not to use compressed air, then you should follow that advice.
With that said, I didn't need much air. After putting my fingers over the over open ports, I applied air to the port that is at the far end of the MC, the end that points to the front of the car. It doesn't take much air, and I used a rubber tip on the hose, just pushing it with enough pressure to form a weak seal.

And I did not bench-bleed, or pre-load, the MC because I did not want to drip fluid on my new paint.

[jvandyke]

I did the same air thing but didn't work for me. Fingers and rubber tip on air hose. Will fiddle and see what happens. Thanks for the input, as always.

[tomking]

post a picture of your MC for all of us to see. There are pins in some, there are bolts in some, some have nothing but the circlip to hold it all together.

[markandson]

If you opt to use air I would put something like a towel tied around the end of the MC so that when it shoots out you don't damage the piston or yourself, it can come out like rifle bullet.

[jvandyke]

Originally Posted by tomking post a picture of your MC for all of us to see. There are pins in some, there are bolts in some, some have nothing but the circlip to hold it all together.

Enjoy.
.Mac Web Gallery

Home from work, tried air again. Got up to around 20psi before my fingers couldn't hold it back anymore. No love. What's up with the socket over the piston end method, to apply force to the seal and not the piston itself? Tried that too. hmmmm

[namba209]

It looks like you have the two retaining bolts removed for each piston, so there's nothing that would keep the pistons from coming out, other than the seal backups hanging up in the circlip groove. The reason I didn't use compressed air on mine was simple, I have a cheapo little compressor that takes up to 15 minutes to get 125 psi. It works o.k. with an air brush and bicycle tires, but not much else.

[guyopel]

Jeff
With the photos I see that the plastic ret. ( You will not be reusing this part because you have the updated one piece unit ) is still holding the rear piston in place .. you can drill this in half and remove it and rear piston will come out .
Next step is to remove the front piston ret. screw on the bottom of the M/Cyl. besure to place a cloth or rag at the rear of the M/C because the spring may push the front piston out at You or bystanders . HTH
John

[jvandyke]

Got it. I decided to drill a hole through the piston end that was sticking out. Put old drill pit through the hole. Clamped bit in a vice, holding the piston still and tapped on the casing's bolt flanges with a hammer it came out. Then used air to push the front piston out. Not pretty but got it done. Had new piston in kit anyway. I guess it's one method. It did not want to come out.

[guyopel]

Good ,That works . You will not be reusing the white plastic ret. When you start to reassy. M/C and you will install the front piston assy. ( with new seals ) and hold it down in the cyl. and then install the piston stop screw ...this will hold the front piston in place . then you will install the rear piston assy. HTH
John

[jvandyke]

Got pistons rebuilt. All seemed to go together fine. I can see how compressing the spring to install the stop screw could be troublesome. Luckily I did this while my handy dandy 7 year old was around. I squeezed, he turned the screw. Easy.
Heading off to clean the bore out and reassemble.
PS stopped at Napa for a brake bench bleeding kit, $10 (Metric version, part number 700-1795). Has fitting for all three ports.
Not sure on the seal to booster though, kit supplied an o-ring, original looks like a square cross section one. Hmmmmmm

Although the bleeder kit had fittings that worked, they leaked and probably weren't all the correct threads. It still got the job done although, having leaks, and having to pull the tubes and fittings and the reservoir to reinstall in MC in car means you get air back in there I'm sure, but it's probably a better start than not bench bleeding at all.

[namba209]

Jeff, the o-ring is probably square because it's been in the machined groove and taken that set. The o-ring in the kit should be o.k. to use.

[jvandyke]

Bench bleed and buttoned it all back up. No troubles with hooking up lines, no cross threading. Big relief there. Pedal feels better already and I still have to bleed out the system. I remember last year there was a bit of discussion of the sequence for bleeding. FSM says this:
The correct sequence for bleeding
is bleed the wheel cylinder or caliper nearest the
master cylinder first in either circuit.
But most everywhere says the opposite.
Anyway, good progress, no major issues, is fun wrenching when everything seems to go alright.
Hope to bleed and test drive tomorrow.
Struggled for a bit on how to compress the front piston, push the seals in and set the snap ring all at once. A wire in the feeder port (per FSM) didn't seem to grab anything, luckily I found that the distance between the top of my stool and the bottom edge of the workbench was perfect to let me cram the MC between the two so the piston was partially compressed, then I could push seals in and set snap ring, turning the MC casing as needed. Sometimes you stumble on easy answers.

[jvandyke]

Brakes bleed with help of kids (see, they're good for something after all!). Using two person pump method.
Tested.
Wow.
So that's how the brakes are supposed to feel!
Amazingly better. Thanks guys.