Ak. Mal

I have already purchased the S.S. O-ring calipers from Vettebrakes. They are sitting on my workbench waiting for the rest of the system to be purchased.

I am going to replace the master cylinder and the power booster. They are in pretty gnarly shape and I want to replace everything at once. However, I've never replaced either of them and could use a little advice.

I plan to attach the master cylinder to the booster before installing. To remove the old, I unbolt the booster from the firewall and disconnect the brake pedal and brake lines from the m.c. Before I install, I have been told to bench bleed the system. I understand the concept of putting fluid in and getting the air out prior to install, but how do I do it properly?

Also, I need to flush the hard lines. What would be the best method of doing so?

Finally, I have read a lot of posts about making sure that when the new rotors are mounted to make sure they are within spec for rotor runout. How do I measure that? Does anybody have any pics of that procedure? I'll be honest, I was just gonna slap the new rotors, pads and calipers on until I read how important this is. Just want to make sure I get everything done right the first time. I hate redoing things to fix mistakes.

And before anyone suggests it, I do plan on replacing the rubber lines with new ones.

wcsinx

I wouldn't. The added weight and bulk of the MC hanging off the booster will just make it that much more of a PITA to install. It doesn't take any longer to attach the MC to the booster in or out of the car.

Just a tip on the removal of the booster. I wouldn't even bother trying to take the clevis loose from the pedal. I tried it that way initally, and I couldn't get the pin to budge. The pedal side booster rod however will just pop right out of the booster. So I just yanked the booster without the rod and then unscrewed the rod from the clevis. That worked out a lot easier for me at least.

I personally don't bench bleed per se. What I've always done in the past was to hook up the MC bleeder tubes with the booster and MC installed in the car, and then "bench" bleed via the pedal. Give it ~10 long, slow pushes as far as you can, refill reservoir, cover MC with towel, then give the brake pedal a few quick hard stabs, repeat process until no more bubbles.

Just bleed the brakes dude. The hard lines will get flushed in the process. :confused:

Does your car feel like one of them vibrating hotel beds when you hit the brakes? No? Good. Yes? Bad. :lol:

Ak. Mal

My car sat for the last 10 years and the master cylinder right now is in VERY poor shape. When I removed the calipers, the fluid that came out was brown sludge. I don't want to hook the calipers up to the lines until they have been flushed. I think I'll just follow your suggestion and keep a bucket under each corner of the car and empty the mc a couple times.

As for the rotor runout, I guess I have just been spooked by all the posts here regarding it. I think I will address it if I have vibrations after everything is installed.

Thanks for the advice.

wcsinx

Oooooh ok, I gotcha. Yeah, you can gravity bleed the lines like that, or you can just go pick up a vacuum bleeder and suck 'em clean.

I was halfway joking. You really should put a dial caliper on the rotors to measure runout. *whipers* but I'd probably just slap it all together and see if I got any vibration. :lol:


[Modified by wcsinx, 4:46 PM 4/9/2004]

R. Bruno

I hate doing stuff twice and so I understand wanting to replace the system all at once, but replacing the booster is not necessary in my opinion. Leave the booster alone and replce the rest. It will simplify the job considerably. :cheers:

wcsinx

What's wrong with replacing it as a preventative measure as long as he has everything else torn down? :confused:

Ak. Mal

That is exactly why I am changing it now.

R. Bruno

[QUOTE]
What's wrong with replacing it as a preventative measure as long as he has everything else torn down?

Nothing wrong with it. Just one guys .02. Go for it-nothing like a new set of brakes. :cheers:

GTR1999

:iagree: with Rob only because he's smart guy.

Well,... also because it's a bugger to get the booster out without removing the dash,which is another bugger at times. Save yourself some time and aggrevation bench bleed the M/C in a vise. Go to NAPA and get the metric brake line adpaters and cut one end off and curl it into the M/C reservoirs. Fill them with fresh fluid either DOT 3 or 5 depending on your preference-but don't mix them. I use DOT3 and bleed the system every year or two, DOT 5 fill not turn muddy from moisture but you have to be sure to remove all the old DOT 3 first. Back to bench bleeding,use a screwdriver to plunge the M/C piston about 1" and watch for air bubbles in the fluid,after several strokes you should be ok to install. Don't buy the plastic "HELP" line of bleeders you fine in the parts store,they're not metric and don't seal. I also used the syringe bleeder and it's ok but the 2 metal lines work the best.
Installing new rotors will not garantee you don't have runout. I installed new USA made rotors and had up to .009" runout. You have to check them with a dial indicator and the bearings must be in spec to get an accurate reading.
Ask questions as you go.
Gary

Ak. Mal

Well, I stopped by the parts store tonight and purchased everything. I went with a m.c./booster that were already pre-assembled. I already have the interior stripped out of the car. The dash is in the basement on the workbench next to the calipers actually.

Don't think for a minute I won't be asking questions as I go.

About the dial indicator, someone please educate me. I have searched google for info on dial indicators and how to use them and not come up with any 'visual aids'.

R. Bruno

Ah, so you have the car partially dissassembled- now I see why you are doing the booster at the same time. That makes sense. :yesnod: Ask Gary gtr1999 about the dial indicator. He sleeps wih one under his pillow. Right Gary? :thumbs:

triadecho

I just finished major brake work pretty much as you describe. It was the first time I have ever done it.

The master cylinder should be bled on the bench before doing onto the car. The rebuilt I got at Auto Zone had bleed hoses and a good set of instructions.
Once the bubbles stop, it's ready to go on.

To bleed the brakes, I worked LF,RF,LR,RR with the car up on jack stands. Be real careful to not run the master cylinder dry or you will have to start all over again. Have your assistant pump the brakes slow in and quick release. It takes around 7 or 8 pumps to purge the old dirty fluid. I bought a plastic bottle with a fitting which goes over the bleed valve which was real handy.
Hold the bottle above the bleed valve and watch for bubbles in the clear plastic tubing. The backs have 3 bleed valves. I worked from supplly line to inside then outside front and outside rear.

It's a joy to have brakes again. I don't pretend to be an expert and wasted more brake fluid than ever got into the system. Just keep it off the paint.

Good luck>

triadecho

Rotors:
Mine were below the 1.2 inch minimum stamped on the outside of the rotor so I replaced all 4. Auto Zone ordered them overnight for $60 each.

wcsinx

Trust me, that method will NOT get all the air out of the MC. The cylinder really needs to be stabbed in hard and fast a few times to completely purge it. I've seen it many times. People will install a bench bled MC and still have mushy brakes, so they assume it's in the lines/slaves and they go on and bleed the hell out of the wheel cylinders until they harden up. But what they're actually doing is sending the remaining air in the MC down the lines to eventually come out a cylinder bleeder. My way is messy (that's what the towel is for) but it works.

O'Shark

I just did a MC replacement a couple of weeks ago. I did the bench bleed in my vice. Go to NAPA and ask for a bench bleeding kit. You'll get an assortment of plastic fittings and a length of plastic tubing. Put a fitting in each outlet and run a piece of tubing from the fitting back into the MC. Make sure that the end of the tubing stays below the fluid level. Push on the piston with a blunt object. I used a socket extension to push the piston with. I had to pump it several times to get the air out. My brakes are 100% better now. They're actually pretty good for a manual braking system.

GTR1999

Ask Gary gtr1999 about the dial indicator. He sleeps wih one under his pillow. Right Gary? :thumbs: [/QUOTE]

Hey Rob, You're right and I'll tell it's a real problem when I get poked in the eye in the morning! :D

Dail indicators are available from tool suppliers,MSC,Harbor freight,ENCO all have them for under $30 including a mag base.

Since you have the dash apart it makes sense but be sure the booster you get is exactly like the original. Last year a forum member had a big problem with a replacement booster from either advance or auto zone. If I recall correctly the rod was not the same length and after he gotit together there was no pedal.

As for bench bleeding I stand by what I said. I was out in the last car I did today and the pedal is as firm as it was 6 months ago.

Gary

Ak. Mal

Alright, I have all the parts now. Last night I started to remove the booster. I could only reach the nuts on the lower two studs that pass through the firewall. Anyone got any secrets on how to get to the top two?

Also, how does the brake pedal arm attach to the rod from the booster? There is a large nut that has two flat sides and it appears to thread into the pedal arm. Is that correct?

wcsinx

Top right is accessible with just a deep well socket and a little Corvette yoga. Top left I've heard is a PITA, but fortunately for me bubba left it off when the last booster was installed in my car. :D From what I've heard, you can get to it with a combination of jointed/wobble sockets and extensions. Or you could just hack the stud off the booster from the engine bay. (no, I didn't just say that ... :lol: mine held with 3 nuts for many years apparently)

Uuuhhhmmm ... I think the "nut" you're referring to is actually the pedal clevis. It's a U-shaped piece of steel with a threaded hole at one end where the booster push rod screws in. The other side is attached to the pedal with a pin (pivot).



see that thing at the far end of the booster? that's the pedal clevis



better view of the clevis hooked up to a hydrobooster

Ak. Mal

Oddly enough my back does feel better from my late night Corvette Yoga session. However the bracket that holds the center console in place, I fear, has left a permenant imprint on my back.

Which would be easier, unthread the nut and remove the booster then try to rethread the new on back in or remove the clevis? If the latter, how do I do it? I didn't spend much time examining that part since it was late and I was fighting with the top two nuts.

Which actually leads me to another question. Slightly below and very much in the way of the top left stud (as seen from inside the car) is an electrical relay looking device attached to the clutch pedal arm. What is that? I know the neutral safety switch has been disconnected on my car and I'm thinking that is what it is. More like hoping that is what it is so that I have one less part to purchase.

wcsinx

Neither, just pull the booster out and the rod will pop right out of it. Then you can just unscrew the now dangling push rod from the clevis. I first tried to pull the pin out of my clevis, and I couldn't get it to budge. I don't know how anyone else got that pin out because there's no room under there to pry on it, and at least for me it was stuck on there like a mother.