[xj40] Brake pedal vibrating back

When I exceed 45 MPH and press down on the brkae pedal, it
vibrates back, the faster I go the more it seems to fight back. Ae
30 MPH, I barely feel it. Mechanics tell me there is nothing
wrong. Could it be rust in the disks or wheel problem? Wgere
sgould I start looking? Not driving it until I get this
resolved. Barney–
RevDoc
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

Rev.
A bit of history may help.
I,e, has the car been stored for a lenght of time?
But for now two thoughts come to min, as detailed below.

When you are coming to a gentle stop can you feel the car slow and then ease
up adn then slow again in a regular pattern?
If it does I would be inclined to think that the rotors have what is known
as disc thickness variation.
It only needs to be a small amount and what happens is the pads are going
in and out of the caliper causing the pedal to oscillate under your foot.
The other option would be that the ABS is kicking in for some obscure
reason.
I take it that your mechanic has taken the car for a drive?

Unfortunately you may have to drive the car to determine what the cause is
:slight_smile:

Regards Robin O’Connor
'92 XJ40 4.0 Ltr
Auckland NZ----- Original Message -----
From: “RevDoc” crest2963@aol.com
To: xj40@jag-lovers.org
Sent: Tuesday, June 26, 2012 4:07 PM
Subject: [xj40] Brake pedal vibrating back

When I exceed 45 MPH and press down on the brkae pedal, it
vibrates back, the faster I go the more it seems to fight back. Ae
30 MPH, I barely feel it. Mechanics tell me there is nothing
wrong. Could it be rust in the disks or wheel problem? Wgere
sgould I start looking? Not driving it until I get this
resolved. Barney

RevDoc
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting
services and resources including Photo Albums, Event Diary / Calendar, On
Line Books and more !

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

In reply to a message from RevDoc sent Mon 25 Jun 2012:

Barney…

Sounds like one or both of your front rotors are warped. A very
common problem that results in your symptoms. Normally however
the brake oscillation is much more noticeable at lower speeds as the
car is comming to a stop.

Replace the front rotors or have them turned (trued). Most auto
part stores provide this service. They will first check them to
ensure there is enough thickness remaining before they do this.
If they are beyond turning then you will have to replace them,
around $100-150 for the pair.

Check your front brake pads and unless they are fairly new replace
them also.–
Groove
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !