chevyguy1969 Posted January 19, 2008 Share Posted January 19, 2008 coming back from big earl's tonight my brake warning light came on and the pedal go really soft (made for a really tense ride to the house SO was using her passenger side brake pedal even more tahn normal for those who were there) . I got the vette home with no real issues checked out fluid is full no evidence ofd leakage anywhere. So i'm going to change the Master Cylinder. Question has anyone that has bench bleed one of these willing to give me some advice as this the one thing i have never atemped before. TIA for any help sent this way Link to comment Share on other sites More sharing options...
anmracing2 Posted January 19, 2008 Share Posted January 19, 2008 That sounds pretty scarry!!!!! Unfortunately I've never did a bench bleed so I don't know exactly how either. Seems to me it would just be like a gravity bleed but Chad would probably know for sure.....Good luck...Andrew Link to comment Share on other sites More sharing options...
chevyguy1969 Posted January 19, 2008 Author Share Posted January 19, 2008 More nerve racking then anything. Not knowing if the brakes are going to work the next time you push the pedal = Link to comment Share on other sites More sharing options...
ChadC Posted January 19, 2008 Share Posted January 19, 2008 I dont nnow what a bench bleed is. I for got what year is your vette? is it a 69 like your sig says Link to comment Share on other sites More sharing options...
Eddie44 Posted January 19, 2008 Share Posted January 19, 2008 His Vette's a 79 according to his profile. Ed or Chad should jump in here soon. Good Luck! Link to comment Share on other sites More sharing options...
1EvilC5 Posted January 19, 2008 Share Posted January 19, 2008 Here is something I pulled off the internet. I have only done it once in my lifetime that I recall.After successfully rebuilding a master cylinder (or when fitting a new one) it is a good idea to bench bleed the MC before installing it in the car. This will fill the MC with fresh air-free fluid and in effect "prime" it for integration with your car's hydraulic brake system, making your on-the-car brake bleeding a little easier. The basic idea is to create mini hydraulic system on your bench. You can use old brake line fittings if you have them but I didn't so I purchased a master cylinder bleed kit from my local auto parts store. A new MC may include the necessary parts already. The kit should consist of a number of plastic fittings which are designed to fit in the outlets (usually two, front and rear) of your MC. One end of the fittings will be threaded and the other will have a round smooth hose adapter. Thread the appropriate fittings into the outlets on your MC. The kit will also contain a length of plastic hose. My kit had black hose but I found some spare clear hose and used it instead - this will allow viewing of the air bubbles passing through the hose. My kit also had a plastic clip used to hold the two pieces of hose together and clamping to the edge of the fluid reservoir. Clamp the cylinder firmly in a bench vise so that the cylinder area is level. If it is pointing upwards the air will remain in the cylinder. Slide the hoses onto the fittings. Cut the hoses just long enough to reach into the reservoirs and remain submerged - the shorter the length of hose the better. Place the other ends of the hoses into the fluid reservoirs (you'll probably have hold them in place somehow because once you start pumping they'll want to flail around in the air and spray brake fluid everywhere). If you can get a helper that is ideal.Fill the reservoirs with new brake fluid, and pump the piston slowly and evenly, full strokes. I used a big Phillips screwdriver because its tip doesn't damage the piston and the handle gives you something to lean against. I would not worry about the fluid getting recirculated because it is brand new and you are creating a temporary hydraulic circuit with the hoses which will not become contaminated with dirt. The air which is still in the system at this point will be bled out. Pump the cylinder until the tubing contains no more air bubbles and no new ones emerge from the MC on the down stroke. On my MC this took about 15 strokes some may require more, some less. Keep going until the air stops as this will make the task of bleeding the brakes in the car much simpler. When all the air is out, mount the cylinder in the car. Here you have to be careful to prevent the fluid still in the hoses from spaying your car and any other painted objects nearby - brake fluid is a great paint remover! If you decide to remove the hoses before installing on the car, make sure to plug up the fittings - I just held the hoses up while transferring from bench to car. Once the MC is mounted in the car, remove the fittings and connect the brake lines. You'll lose a little fluid but the check valves in the cylinder should stop any major leakage. Now you are ready to bleed the brakes in your car and it should be a lot easier than if this step was avoided. Link to comment Share on other sites More sharing options...
Grape Ape Posted January 19, 2008 Share Posted January 19, 2008 Sounds like the old days. I don't know how the new ones come these days but if they come with a bleed kit in the box, you should be set. If not, they should have something where you buy the Master Cylinder I would think. I might have one still around somewhere if you need it. Pretty easy stuff. The kit should have a couple unions and hoses in it. Put the Master Cylinder into a vice so you can push on the plunger end. Just screw the unions into the output ports and secure the hoses so they are going back into the tanks. Then fill the tanks with your choice of brake fluid and make sure the hose ends are covered with the wet stuff. Then get a screw driver or some other blunt object and push the plunger in to extract the air into the tank. Not to fast though as it might splash out on you. When all air is out, you should be ready to install it. Remove the hoses and install the lid. Ready to install. You will probably have to bleed the brakes when done though to make sure there is no air left in the system. Good luck with the repairs.1EvilC5 beat me to it. Oh well!!! Link to comment Share on other sites More sharing options...
1EVLC7 Posted January 19, 2008 Share Posted January 19, 2008 Great info Phil! Link to comment Share on other sites More sharing options...
chevyguy1969 Posted January 19, 2008 Author Share Posted January 19, 2008 Thanks Guys great information Link to comment Share on other sites More sharing options...
Ted Y Posted January 20, 2008 Share Posted January 20, 2008 Do you have stainless steel sleeved calipers? The original ones were prone to corrosion and pitting, causing air to enter the brake lines when you let up on the brake pedal, even without leaking any fluid. It's the air that gives you the soft pedal more than low fluid. I would inspect the linings of the caliper piston before replacing a master cylinder. I hear the master cylinders rarely ever go bad. Link to comment Share on other sites More sharing options...
chevyguy1969 Posted January 21, 2008 Author Share Posted January 21, 2008 I have allready bought the MC but this good infomation I am not sure about the the steel inserts as i havn't took the brakes apart on this one yet but if the problem persist that is where i will go next. Thanks again for the help Link to comment Share on other sites More sharing options...
a66bbvet Posted January 21, 2008 Share Posted January 21, 2008 Is that the reason you pulled out from behind us and pulled ahead when we left Big Earls? Have you done any work yet? I have a friend coming out Wednesday that was my mechanic while I lived back east. He could tell me the best way to handle this, but his wife has already told him that he was not coming out here to work on my car. If you do not get anything done with it this week, then let me know and I will give you a hand next week. Link to comment Share on other sites More sharing options...
chevyguy1969 Posted January 21, 2008 Author Share Posted January 21, 2008 That is exactly why i pulled out in front I didn't want to have a brake failure into the back of a fellow vetter. I changed the MC tonight and started bleeding the system still have two wheels left to do but the brake pedal is alot firmer and no light all ready thanks for the offer to help. If you noticed i was picking the cleanest lane to get in had a few tense momments on the 101 LOL. have a great day. Link to comment Share on other sites More sharing options...
chevyguy1969 Posted February 3, 2008 Author Share Posted February 3, 2008 WOW these cars are hard to bleed just finished up saturday afternoon. It took a while drove the car but the it felt like it had a bubble in it. Finaly after three quarts of fluid and tapping calipers i see the bubble pop out in the tube and the brake pedal is hard again. Next time it is a motive power bleeder for me.WOOO HOO time to drive again Link to comment Share on other sites More sharing options...
ChadC Posted February 3, 2008 Share Posted February 3, 2008 i hear ya. congrats on finishing the project. Link to comment Share on other sites More sharing options...
Bigfoot Posted February 3, 2008 Share Posted February 3, 2008 Sweet, and now more experience on the board. :thumbs Link to comment Share on other sites More sharing options...
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