Finding and Fixing Problems with Master Cylinders and Brake Boosters

Finding and Fixing Problems with Master Cylinders and Brake Boosters
Finding and Fixing Problems with Master Cylinders and Brake Boosters
Imagine you ’ re driving down the road and the lighter changes. You step on the brakes and. .. you start slowing down and your foot slowly sinks to the deck. then, nothing, you ’ ve got no brakes. But wait, when you check, the master cylinder is full moon ! You could take your car to a workshop and ( sometimes ) give to have it inspected/diagnosed, but this can be a time-consuming action that frequently requires an appointment. What if I told you that finding and fixing most brake problems that originate under the hood is actually pretty simpleton and you can normally do it in less than an good afternoon ? Well, it is, and I can. Keep reading .
First let ’ s lecture about what I mean when I say master cylinder and brake booster, as not all of us know yet. The master cylinder is the brake system component under the hood that sits against the firewall/bulkhead between the engine and passenger compartment fear in front of the steering wheel. On older cars, it ’ mho alloy and has a flat metal ( casting steels ) cover held on by a banjo that snaps over and into grooves on top of the cover. On newer cars this is an aluminum body with a formative fluid reservoir and a cam-lock ceiling. The brake promoter is mounted between the headmaster cylinder and the wall on newer or converted/upgraded cars. See the images above and below .
The Brake Pedal That Slowly Sinks to the Floor
I first have to mention that I don ’ thymine entail that the pedal sinks to the deck when you apply your whole to it. I ’ meter talking about the pedal point sinks to the floor with nothing more than normal brake atmospheric pressure applied. You know that a pedal that sinks to the floor is a polarity of a leak in the system and a lento sinking pedal point means a behind leak. however, you ’ ve spent an hour or more under the car looking, you ’ ve even used a escape detector kit. What ’ mho in truth got you scratching your head is the fact that the reservoir is full.

What I ’ ve just described is a bracken master cylinder that is bypassing. One or more of the inner seals on the piston inside have failed and fluid coerce is bypassing that/those seal ( mho ) and returning to the reservoir. The cook for this is either replacing the master cylinder or rebuilding it. Neither is truly unmanageable. Replacing is in and out with a slight detour, while rebuilding international relations and security network ’ metric ton much different than rebuilding calipers once you ’ ve got it off and apart in that both require you to ensure the cachet coupling surfaces are blemish-free. I ’ ll describe the R & R process below .
The Brake Pedal That Feels Like a Weak Spring
This is the brake pedal that goes far than normal and then feels like it wants to bounce back a small. Braking effect applied to the wheels is lower and you have to step on the pedal hard to stop the car. This is air in the brake lines. Air is compressible, while fluid international relations and security network ’ t. This property of brake fluid is what makes it ideal for use in automotive brake systems, while tune is pretty bad. The specify for this is to bleed the vent out of the hydraulic system, bleeding the brakes. I describe bleeding the brakes at the end of this article .
The Brake Pedal That Stays Hard but Doesn’t Stop the Car
Your car has power brakes but it feels like you have to stand on the brake pedal to get your car to stop, evening at city street speeds. It ’ south worse than the days before exponent phonograph record brakes if you ’ re old enough to remember them. The technical diagnosis for this condition is “ sludge in the lines and orifices ”. You see, brake fluid is hygroscopic, which means it absorb body of water ( even in a sealed organization ) which causes rust and sludge buildup. The combination of “ sludge ” can clog up the small orifices in the brake system a well as the little brake lines, reducing system efficiency .
You can verify this by scraping the tiptoe across the bottom of the fluid reservoir and seeing if anything sticks to it. The fix for this is to suction the honest-to-god fluid out of the victor and flush the organization, preferably with denature alcohol and then fresh fluid. This process is described in Step 7. If you have drum brakes I would highly recommend cleaning out the bicycle cylinders besides, which I ’ ll describe in a later article. besides, use entirely denature alcohol as anything else will deteriorate the rubber seals in the system.

You Hear a Hiss When You Step on the Brakes
There you are coming to a hold on clean or sign. You apply the brakes and as you ’ re coming to a stop, you hear a hiss that sounds like tune escaping from a tire or balloon or the sound a snake makes. Chances are you ’ re besides thinking to yourself that the pressure you ’ ra use is more than normal for power phonograph record brakes .
What you ’ re identify is a world power bracken promoter that is suffering a leak seal, either inside or out. A brake promoter extinct seal that ’ mho leak is likely to be accompanied by signs of wetness between the chief cylinder and baron supporter because it will cause the piston varnish on the headmaster cylinder to fail due to being put under a void. Your alone compensate choice here is to replace the power booster. If you ’ re seeing signs of escape from the master, you ’ ll besides either have to rebuild or replace it .
Removing the Brake Power Booster and Master Cylinder
You ’ ve got to remove the maestro cylinder in order to get at the brake booster. If you only need to replace the booster, you don ’ t need to pop open the brake lines on the master, so all you ’ ll want is a twist to remove the master ( normally 5/8″ or 9/16″ ) and a socket ( lapp size ) and extension ( s ) and possibly a pivot universal joint. If you ’ re not taking the master out of the cable car to work on or replace, skip to step two below :

  1. Loosen and remove the brake lines at the master cylinder.  These are usually either 3/8″ or 7/16″.  It is best if you use line wrenches, especially if the fittings look rusty as they’re designed to not round the corners of the fitting.  A little WD-40 can make this easier.
  2. Use a wrench to remove the two nuts that secure the master cylinder flange to the brake booster by turning them counter clockwise.  WD-40 again.
  3. Once you’ve got the nuts off, if you’re going to work on the master, remove it from the car and put it on your work bench or the ground for the moment.  If not, simply move it forward enough to slide off the booster studs.
  4. Inside the car and under the dash you will find either two or four (usually four) nuts or bolts securing the brake booster to the firewall/bulkhead.  This is easier with the socket and swivel.
  5. Disconnect the brake booster piston from the brake pedal.  This might be a nut and bolt connection or a pin through an eyebolt secured with a cotter pin or locking pin.
  6. Remove the booster from the car from the engine compartment.

Installing the New Brake Booster and Master

Installing the new power brake booster is just removing it in inverse, unless you ’ ve either worked on the master cylinder or replaced it .

  1. Slide the booster piston through the large hole in the bulkhead.  Align the bolt holes and push until the booster is flush to the bulkhead.
  2. Install and tighten the nuts/bolts securing the booster to the bulkhead and connect the piston to the brake pedal.
  3. If you’ve disconnected the master cylinder, you need to bleed it.  New masters come with bleeder kits which are nothing more than rubber tubes attached to plastic fittings.  If you’ve only rebuilt it, you can buy a bleeder kit for cheap at places like Autozone.  I’ll describe this later.
  4. Slide the master cylinder over the studs on the brake booster.  Install and tighten the nuts.
  5. If you’ve removed the brake lines, reinstall them and tighten them using a line wrench.
  6. Bleed the brakes following the directions in Step 10 of the linked article.

Bleeding the Master Cylinder
After attaching the new or rebuild headmaster cylinder to the brake promoter, thread the credit card fittings of the hemophiliac kit out into the cylinder ports and route the hose ( mho ) into the reservoir ( south ). BY HAND, lento depress the brake pedal. have person watch and let you know when no more air bubbles come out of the hoses. Remove the hemophiliac kit and reattach the brake lines to the maestro cylinder. Bleed the brake lines completely, rears foremost then fronts. If you have a vise mounted on a solid workbench and a boastfully Philips screwdriver, you can mount the master on the vise to bleed it. This is easier .

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Category : Car Brakes