gallilaw

So I am driving along at highway speeds and the car is running fine. Engine smooth, suspension okay, transmission fine.

I come to a tollbooth and gradually slow down. As soon as I press the brakes in a friendly way, I start to get significant vibration in (I believe) the front end. The vibration gets worse as I apply more pressure to the brake pedal.

I can feel vibration through the pedals and the steering wheel, and I can see vibration in the hood. It feels as if one or more rotors is/are warped, or have high and low spots.

After leaving the toll plaza, I gradually accelerate. The vibration stays the same or actually gets worse as I speed up. Over the next few minutes, as I attain highway speeds again, the vibration can get pretty bad. After a few minutes at cruising speed, the vibration gradually decreases and then disappears, and the car runs fine again with no discernible vibration.

This can happen every time the car has been running at highway speed, and I press the brakes, even if all I'm doing is performing a test to see if the condition still exists.

The vibration has nothing to do with road conditions. Happens on rough or smooth roads, on concrete or black top, and even in transitions between the two.

A very good local shop, that is very trustworthy, looked at the car a few weeks ago and found nothing wrong with the brakes. But it seems like a brake problem to me. Let me know if you can think of something else.

I have sometimes wondered if it might be a bad master cylinder, that doesn't "release" fully when I take my foot off the brake pedal. I've wondered if that problem might leave pressure in the system, that might prevent the calipers from fully releasing, with the result that the pads cause friction and elevated heat, etc. etc.

If I can't conclusively diagnose the problem as something other than brakes, I'm considering radical measures: replacing the master cylinder the calipers and the pads.

If I have to go that way, it would help if you could point me to alternative master cylinders, calipers and pads that I should use instead of new or remanufactured OEM parts.

Thanks for your help.

njmaxseltd

iTrader: (19)

1) You have a caliper that's sticking, possibly just the guide pins.
2) You have brake pad material transfer (warped rotors) from the excessive heat caused by #1.

You need to replace the front brakes, rotors, pads, check and lube guide pins and exercise the calipers to make sure they're not seizing up.

JvG

I have noticed that the brake hoses will start to peel apart from the inside out. When they do they can cause temporary blockages. They will bend out of the way under high pressure, like pressing on the brakes. The peeled section can act like a one-way valve and prevent fully releasing the brake pressure. This could cause the problem you have.