How to change the master brake cylinder - 1992 Chrysler Town & Country

Does the brake pedal go to the floor? Or does it stay up, and is hard to push...? Did you bleed the master cylinder? Also, you will need to bleed all 4 wheels connection to the brake wheel cylinders...you must start with the rear, farthest from the master cylinder, then other rear, then front farthest from the master cylinder, then other front...the bleeding of each line is a must, since you switched the master cylinder.

one of the pistons in the brake master cylinder is poss stuck at the bottom of its stroke or the return spring has broken, dont take any chances with brakes change that master cylinder

Master cylinder fluid piston has entered into a brake safe mode.
when the high pressure brake system is opened in any way, the brake master cylinder piston reaches to the far end of the master cylinder which trips the brake system warning light.

This brake light condition is due to sudden loss of brake fluid pressure on the right front brake caliper assembly during the replacement.

Left rear brake caliper bleed valve will ned to be "opened" until master cylinder piston travels into the opposite direction which "resets" the brake system warning light.

Dot 4 brake fluid recommened for most, but not all vehicles.
Reference vehicle to owners manual for replacement fluid is replaced under master cylinder brake system cap.

you must have a lot of air in system. the brakes need bleed to let the air out of system. did you bench bleed the master cylinder before putting it on car ! if not thats why no brakes. to bench bleed a new master cylinder, put it in a vise. fill it full or the proper level of brake fluid. push on the plunger with a dowel or another object. pump it till all air is out of master cylinder, you can tell when no air. it will be all fluid coming out of cylinder. keep checking brake fluid in master cylinder.make sure you push plunger in all the way.when all air is gone replace on car. if you do not loose any fluid from the master cylinder lines, then you can replace it without having air in system. bleed each wheel if needed. good-day!

Well, if you change a caliper or a brake line the fluid in the master cylinder should remain, even if the fluid leaks out.

However, if you are having trouble bleeding regularly, then use a vacuum pump with a 'can' or use a pressure bleeder (I prefer this method) that costs about $55 or so available on the Internet.

If you use a pressure bleeder, you'll need an extra master cylinder cap that has a hole drilled in it to accomodate the fittings of the pressure bleeder.

I know someone who had a Lincoln Continental that changed a brake line and had trouble bleeding it, and they used a vacuum pump and it bled easily using that method.

Some cars require that when you change the master cylinder, a brake scan tool is required to bleed the master cylinder that has air in it. But, if you did not replace the master cylinder, you should be able to use either the vacuum or pressure method to bleed the brakes easily.

Good luck on this repair.

Mushy / squishy brakes are usually caused by the brake master cylinder seals failing. You can buy a rebuild kit or a re-built replacement master cylinder. I would recommend the rebuilt master cylinder as all the detail work has already been accomplished and it is not a huge expense. The key is to make sure that your use a bleeder kit to "Pre-bleed" the master kit before installation. Your making sure that the master cylinder is free of air before installation. If you instal it with air in the system it wil take you the better part of a quart of brake fluid to bleed the whole brake system via the wheel cylinders. What will happen is after you install the master cylinder the brakes would still be mushy and until you got the residual air out of all of the lines it would appear and act just like it did before you changed the master cylinder.

Thanks for using FixYa,

Kelly

You changed the master cylinder and vacuum booster and have no leaks anywhere, but did you bleed the entire brake system after you did this work? A little bit of air in any of the lines will make the brakes ineffective.

One of the brake slave cylinder or hoses has a leak and is letting air in. Get it inspected to change out parts as needed.

I had this same problem on my 90 Jetta but it was the master cylinder that was the problem, I first replaced the master cylinder because it was leaking badly. The new master cylinder I put on was a manufactured defect, the internal piston inside the master cylinder was not machined enough (10mills too long) so when you applied the brakes the piston would not move far enough to release the brakes but after 20 mins they would slowly release themselfs just as you said your brakes do. The only thing that can cause this problem (if you have changed everything) is the master cylinder or the brake pedal itself, did you do anything to the brake pedal or near it to change its movemment ? Make sure the brake pedal once depressed returns fully to the float position where it should be. I would try another master cylinder preferrable a used one from another vdub the same as yours, eg year,model and country of origin some parts are different if it was made in Mexico or Germany. Its going to be a pain in the *** to have to replace the master again but I see no alternative. There is one more thing you can check I just thought of....check all your brake lines from the master to the calipers for any signs of dents or sharpe curves if the metal brake line is bent too much it will restrict the flow of the fluid returning to the master cylinder after brake pedal release but not during braking. Good luck

The master cylinder supplies the pressure to the brake fluid that travels between the maste brake cylinder resevoir and the brake caliper pistons (through the brake lines. If the master cylinder fails there will be insufficient compression of the brake fluid to make the calipers operate as designed. Leaks in the brake lines and/or cylinders is a possibility, and unrelated to functionality of the master cylinder. Also, pistons located in the brake calipers can form a corrosion ring on their inside walls if there is breakdown in the brake fluid or moisture that gets into the lines. Operating the vehicle when there is insufficient brake fluid in the master cylinder resevoir can also lead to air getting into the brake lines, causing bad working brakes. Air compresses more than brake fluid, and the master cylinder isn't designed to compress air in the brake lines. Sounds like a bad case of "lack of maintenance", as opposed to bad advice from the mechanics. That said, there's no excuse for bad installation. But, it's tough to improperly install a brake line since they are nothing more than hollow metal tubes. There should be no rubber connectors installed in the brake lines. When bleeding the brake lines one must remove all of the trapped air before you will see any fluid appear. If the valves in the master cylinder are not properly operating the master cylinder will not allow the brake fluid to get into the brake lines.

Hope this helps.