Brake issue or not?


#1

Hi: I have a 2000 Jeep Grand Cherokee with almost 200,000 miles, a lot of them highway miles. When the brakes are applied, the whole car shudders as it slows down. Also, when the car is cold, the brake pedal goes to the floor before engaging. Then once the car is used awhile, the brake pedal returns to normal. I’ve had the brakes checked out and have been told each time they are fine. What in the Wide World of Sports is going on?



Thanks - CherylfromAZ


#2

A worn steering rack can give you a shudder as you describe, as well as tie rods, but that’s not related to the brake pedal issue. When a pedal travels all the way to the floor it can be caused by air in the lines, and can be solved with some fresh brake fluid and bleeding, or your master cylinder is probably on its way out. Jeep Grand Cherokees do not age as gracefully as some makes of cars unfortunately. With this many miles I’d have it gone over thouroughly and inspect the steering and suspension. Also change your drivetrain fluids (transmission, transfer).


#3

The shuddering is most likely caused by warped rotors.

The other problem is probably air in the system. What may be happening is that as you drive the car and use the brakes you’re compressing the air, essentially “pumping the brakes” and that’l cause it to firm up. However, this problem could also be a faulty master cylinder and should be considered unsafe to continue to drive until it’s been diagnosed.

Try another shop.


#4

Thank you so much for taking the time to answer my question. You’re right about the Jeep not aging as gracefully as she could. I sure have enjoyed her company, though, so I’ll try to fix her up.


#5

I had rejected the possibility of warped rotors only because she said the brakes checked out OK. The simplest way to determine if this is an issue is of course to note whether the brake pedal pulsates at all while the car makes this shudder. If the pedal is calm with no feedback but you are experiencing shudder look to the rack and related components. I know people aren’t used to hearing about steering racks causing this, but it’s been the cure in my experience on cars with high miles sometimes.


#6

Another option. Always good to have a fall-back position. I was just saying to my husband that at a place like BrakeMasters you’d think they would check all options. Anyone know a good garage in Phoenix or Scottsdale?


#7

If you went and got one of those free, brake checks. Sometimes thy have the least experienced guy do them and many times they only check the pads.

You can buy a $4 caliper at a craft store (it doesn’t have to be accurate just consistent) and take off the wheel and check the rotor with it. Just close it on the rotor and turn the rotor around once, if there is a point where the caliper catches or is forced open some then your rotors are warped.


#8

unfortunately one brake shops idea of a brake check may not be the same as another.

typically a brake ‘inspection’ consists of looking at the ‘meat’ left on the pads, and judging how much is left before you go down to the metal.

there is more to decipher. it sounds as if you may have reached the extreme of your ‘brakemaster’s’ experience. go to another shop. try a local mechanic (with recomendations) ask friends, co workers, and others for their recommendations too.

how many miles since last brake job? were the rotors ‘turned’ last time, or replaced? and is this the original master cylinder? and are there any leaks under, or behind the wheels? is your brake fluid level low? (or do you have to add to it often?)


#9

CherylfromAZ,

Need a mechanic in Arizona? Try this: http://www.cartalk.com/content/mechx/


#10

Since the shop that said that is the same one that dismissed the “brake pedal to the floor” problem, I’m inclined to suspect that their entire diagnosis should be ignored. I’ll still bet the rotors are warped.

There’s actually a simple and pretty accurate test for warped rotors. With the wheel elevated, if you spin the tire by hand while you have a friend slowly apply the brakes you’ll actually be able to feel the oscillations. I’ve done this, and it works.


#11

Have someone also check the power assist canister. Sometimes, the cause of the pedal going to the floor when it’s cold is caused by a cracked or leaking vacuum hose going from somewhere on the engine to the power assist booster usually located on the driver’s side firewall. It’s a big round thingy. (Girl-speak). The hard plastic fitting on the booster itself could also be cracked/worn to the point where the booster isn’t holding pressure after sitting for a while, like overnight. The chattering certainly suggests warped rotor(s).


#12

Thanks to all! I am not a do-it-yourselfer when it comes to cars but I feel I now have a solid foundation on which to speak with a mechanic concerning all the issues. That in itself is a relief!