Contour Enthusiasts Group Archives Forums General Troubleshooting how to check brake booster?

I change out the rear shoe and front rotor w/ pad 9k miles ago ,then I bleed all 4 brakes. after I bleed it,I make sure no air trap in the line ,( i used a brake vaccum pump w/ somebody monitor the reservior and refill it)but it done'st seem any better than before bascially no matter how much force I slam on the paddle, the brake just won't lock up even at low speed (well myabe below 15 miles)no mater how hard I try it still not clamping the disc , the rotor is perfect ( no rough sruface) , can somebody explain what is it happening? from my memory I dont have ABS even thought it's a 99 SE, if it does, I don't know where the ABS unit locate at, if I do have one i will try to bleed the abs unit first,(sometime I do feel like the pulse like another car equiped with ABS when it lock up the wheel)

can somebody tell me how to check if the brake booster is ok? I guess vaccum pump? if so what's the proper negative pressure? also how can I check the master cylinder is working fine , it done'st leak fluid by the way. ALL the Contour 99 SE came with ABS Unit from factory as a standard feature? if so where would it be locate at?

Thank in advance


This site is very helpful , THANK YOU THANK YOU THANK YOU THANK YOU AND MANY THANK YOU!

Carlos

ABS is an option, not all SE's came with it. If you have ABS, you will have a dash light for ABS. You can also see sensors and tone rings (toothed rings) on each wheel hub.

Brake lock up is not a desirable thing. You might not have a problem. Except for not locking up, how are the brakes behaving?

Brakes are never as effective when the pads/shoes are new before they have bedded into the rotors/drums. You may just need to drive it some more to allow everything to seat/bed in. I really want to stress this. Many people expect new brakes to be perfect right out of the box and they seldom are. You may be just expecting too much too soon.

Also the nature of the brake pad/shoe friction material can make a huge difference in brake effectivness. There are many aspects to braking charicteristics that are effected by material selection. For example some racing and high performance compounds are nearly useless until they are heated up. Some of the cheaper ones are soft and may stop well when clder but wear fast and fad badly when hot. And there are many stages in between.

A failed brake booster would make the brake pedal very hard to push. The booster assists you in pushing down the pedal. Try pushing on the pedal with the engine off and you will see what I mean. The booster does not do anything to make the brakes more effective, it only makes it easier to push the pedal.

When a master cylinder fails, the pedal will drop to the floor when you try to brake. At the biginning of failure, it won't hold the car if you are stopped on an incline without the pedal sinking to the floor with even foot pressure. That is, you stop on a slope and apply enough foot pressure to stop the car and no more. If you need to add more pressure to hold the car at rest and the pedal sinks, you may have a bad master. What happens is that the cups on the piston in the master will not hold fluid pressure so that the fluid by-passes and doesn't hold pressure.

As BigJim says, apply the brake with a firm, steady pressure.

The pedal should go down a bit and STOP. If it slowly keeps sinking, there's a problem.

If there are no external leaks the master is leaking internally. And should be replaced.

If you can pump up the brakes, the rears aren't adjusted properly. Or there's likely still air somewhere. With some systems, and especially ABS, the nominal way to bleed is with a vacuum pump. Hand held ones are probably US$30-40.

If the car has ABS there'll be another module that the master cyl. pipes go to. And it'll have an electrical connection.

Thank you for all the reply and all the exlpanation, it helps alot. but yeah, i've reseach alot and change out many other car pad and shoe . bascially, it's just a autozone pad and shoe, those pad and shoe should have broken in for at least serval thousnad miles before I post this message, so it's reasonable enought for it to broken in. I'm supecting the brake booster is not working properly, the reason is that it does not give me enought assist to apply the pressure to the brake, the pressure to the brake will only silghty increase even thought I step on the brake very hard. on the highway its' very diffuclt to stop the car, and the respond are very slow , so I though thte seal of the MC but the fluid still remain and I check all the line don't see any leak. thats the problem, can somebody explain how to test the booster?

I was saying it can't lock up the tire when I could do it ,of course I dont' want it to lock up .