[urq] Doing the brake shake...not a dance I enjoy!

[Justin Riley]

Ok,  My turn to ask those that may have had a similar problem in the
past.  I have been trying to isolate an extreme shake from the front end
while braking.

Here is what I have done so far:

Checked pads. 

Replaced worn front control arm bushings.

Checked mating surface of rotor to hub.  Checked rotors for warpage

Checked caliper mounting bolts on carriers and calipers, lubed with
SylGlide.

Replaced half-shaft that had torn cv-boot, incase shake was caused by
play / wear in cv joint.

Checked torque on subframe and strut bearings.

Replaced "bomb" .

 

The symptoms:

When I initially start the card and use the brakes the first and second
times are ok,  after I have driven a mile or so, the shake is present
during braking.

The shake manifests itself in the steering wheel, and causes occilations
that can be seen in the hood.  It feels very much like a warped rotor or
uneven caliper grab.

Occasionally, the brake pressure warning light will come on, but not
every time.

 

The suspects:

Hydraulic assist system, specifically the pump or valve body under the
bomb.  Suspected due to steering wheel feel while braking, seems more
firm, less assisted.

Secondary suspect, the brake bias valve, only because it has a small
leak.

 

Thoughts or suggestions are welcome....

 

Thanks,

Justin R.