Help with vehicle brake problem

[cj7]

Do you have a mechanic buddy that has a computer that the two of you could test drive with it? They are supposed to be able to check the functions of all the sensors and if the system is 'talking' or not. just another thought.
(if I had one you would be welcome to it)

Did anything get lodged in between the pad and rotor? or get burned into the pad or rotor?

If you have it jacked up can you turn the rotor by hand? Does each side seem to drag evenly?

 

[bczoom]

Hey Rick,

Sorry I haven't responded. Been out of town for the last 10 days.
To answer a couple things.
Re. checking it out with a computer, the dealer already did that and all seems well.
Outside of the punishment they've taken from the extreme heat, the pads and rotors are OK. No uneven wear or anything.

I still haven't done anything with the vehicle but I think I'll take this approach.
Order new rotors and pads but don't install until the problem no longer occurs.
Order and install new hoses. Hoses and calipers are what the dealer says will fix it but I think I may be experiencing what happened to "Lazy". I'm not going to replace the calipers since they've been checked out by 3 places (including the dealer) and the piston, slides... are all fine.
If the hoses don't fix it, I'll start the process of disconnecting the traction control, ABS...
I'll obviously get the tire pressure problem addressed.

Brian

 

[TCBoomer]

A couple other things come to mind....

1) Contaminated fluid--is the master cyl cover seal swollen, even slightly? Petroleum based contaminates will cause the seals to swell. Those 5 min oil change centers are sometimes known for incorrect fluid top offs. Even dealers have been known for this too...I've seen it. If petroleum based contaminates are present, then the complete hydraulic system will have to be serviced. The cyls could be flushed and rebuilt, the lines flushed, but the ABS pump and valve block assembly would have to be replaced. Also all hoses would have to be replaced.

2) Misadjusted brake pedal switch--has anyone, including yourself, recently been working under the dash near the brake pedal switch? I'm not familar with MB's switch design, but if it's adjustable and it was possibly bumped, it could cause the pedal to not return completely. You wouldn't notice it during short trips, but long trips = heat, and heat = expansion. Even a slight switch misadjustment could be the culprit.

 

[bgott]

And, are you the only driver? Maybe you have a left foot braker driving the car. Left foot brakers keep their foot resting lightly on the pedal and that causes lots of heat and wear. You don't do that, do you? I always check for wear and dirt on the left side of the pedal in cars I've worked on with re-occuring brake problems. That has saved me countless hours of pulling my hair out chasing phantom brake problems. Left foot brakers will jump up and down and do cartwheels screaming about how the problem isn't their fault, but, if you can get them to change their habits the problems seem to magically go away. /forums/images/graemlins/tongue.gif

 

[bczoom]

TCBoomer,

To be honest (shhh... don't tell anyone else), this is the only vehicle that I actually have the brake fluid periodically changed. It's been a couple years but I believe it was done correctly (by the dealer) .

Nobody has been near nor under the dash. Wouldn't the brake lights remain on to establish this condition?

Brian

 

[bczoom]

Brad

Yes, I'm the only driver.
The only times I use my left foot when driving are:
When I'm looking for the high-beam switch... I'm learning but it still seems like a habit.
While watching a NASCAR race. I don't want my RPM's to go down while cornering.

Brian

 

[DaveNay]

As aggravating and difficult to diagnose mechanical problems have been on cars for the last 100 years, we now have to look forward to the fact that as many as one third of new car warrantee claims can be attributed to software bugs.

New York Times article.

This means that if there is any connection between the computer, and the brakes (ABS, traction control, or <diety of choice> forbid any kind of "brake by wire" system), then there may be absolutely no mechanical problem whatsoever, and yet the computer could decide to apply maximum brake pressure to any or all wheels at any moment, including while driving at 70 MPH down the interstate. /forums/images/graemlins/shocked.gif /forums/images/graemlins/shocked.gif /forums/images/graemlins/shocked.gif

I am exaggerating somewhat, but it is still a very real issue with modern computer controlled vehicles.

Dave

 

[TCBoomer]

Flushing the fluid is something that many overlook today. Chances are if the dealer did it a couple yrs ago, you should be fine. Just make sure the cover seal is not swollen.

As for the brake lights staying on...no they wouldn't because depending on the style of switch, the switch would still make contact with the pedal, and turn off the lights. But if it was pushed in the barrel clip further, it would prevent the pedal from fully realeasing. That would keep the brakes partially applied...even if only slightly.

 

[TCBoomer]

Software conflicts are very common today. Even aftermarket alarms and remote start systems are causing issues. I deal with this almost all the time.

I've seen 2 way radios cause ABS activation when the radio was used on certain GM vehicles. But you knew the ABS activated because you could hear/feel it working. The fix...reprogram the computer with new software.