Road Test

Road Test

Visual Inspection Chart:

Carry out a road test to compare actual vehicle braking performance with the performance standards expected by the driver. The ability of the test driver to make valid comparisons and detect performance deficiencies will depend on experience.

The driver should have a thorough knowledge of brake system operation and accepted general performance guidelines to make good comparisons and detect performance concerns.

An experienced brake technician will always establish a route that will be used for all brake diagnosis road tests. The roads selected will be reasonably smooth and level. Gravel or bumpy roads are not suitable because the surface does not allow the tires to grip the road equally. Crowned roads should be avoided because of the large amount of weight shifted to the low set of wheels on this type of road. Once the route is established and consistently used, the road surface variable can be eliminated from the test results.

Before a road test, obtain a complete description of the customer concerns or suspected condition. From the description, the technician's experience will allow the technician to match possible causes with symptoms. Certain components will be tagged as possible suspects while others will be eliminated by the evidence. More importantly, the customer description can reveal unsafe conditions which should be checked or corrected before the road test. The description will also help form the basic approach to the road test by narrowing the concern to specific components, vehicle speed or conditions.

Begin the road test with a general brake performance check. Keeping the description of the concern in mind, test the brakes at different vehicle speeds using both light and heavy pedal pressure. To determine if the concern is in the front or rear braking system, use the brake pedal and then use the parking brake control. If the condition (pull, vibration, pulsation) occurs only with the parking brake, the concern is in the rear brake system.

If the concern becomes evident during this check, verify it fits the description given before the road test. If the concern is not evident, attempt to duplicate the condition using the information from the description.

If a concern exists, use the Symptom Chart in order to isolate it to a specific sub-system and condition description. From this description, a list of possible sources can be used to further narrow the cause to a specific component or condition.

Brakes noisy

Possible Source(s):
- Brake pads.
- Brake discs.

Action(s) to take:
* GO to Pinpoint Test A. Pinpoint Test A: Brakes Noisy

Vibration when brakes are applied

Possible Source(s):
- Wheels require balancing.
- Wheel hub nuts.
- Caliper mounting bolts.
- Brake pads.
- Foreign material/scratches/corrosion on brake disc contact surfaces.
- Excessive brake disc thickness variation.
- Excessive brake disc runout.
- Wheel bearing wear or failure.
- Suspension bush wear or failure.
- Steering bush wear or failure.

Action(s) to take:
* Go to Pinpoint Test B. Pinpoint Test B: Vibration When Brakes Are Applied

The brakes pull or drift

Possible Source(s):
- Tire pressures/wear.
- Calipers.
- Brake pads.
- Brake discs.
- Wheel alignment adjustment.
- Wheel bearing.
- Suspension bushes and ball joints.

Action(s) to take:
* GO to Pinpoint Test C. Pinpoint Test C: the Brakes Pull or Drift

The pedal feels spongy

Possible Source(s):
- Air in brake system.
- Leak in hydraulic system.
- Brake booster/master cylinder.
- Brake pads.

Action(s) to take:
* GO to Pinpoint Test D. Pinpoint Test D: the Pedal Feels Spongy

The pedal goes down fast

Possible Source(s):
- Air in brake system.
- Leak in hydraulic system.
- Brake booster/master cylinder.
- Brake pads.

Action(s) to take:
* GO to Pinpoint Test E. Pinpoint Test E: the Pedal Goes Down Fast

The pedal goes down slowly

Possible Source(s):
- Air in brake system.
- Brake booster/master cylinder.

Action(s) to take:
* Go to Pinpoint Test F. Pinpoint Test F: the Pedal Goes Down Slowly

Excessive brake pedal effort

Possible Source(s):
- Brake pads.
- Brake booster.
- Vacuum pump.

Action(s) to take:
* GO to Pinpoint Test G. Pinpoint Test G: Excessive Brake Pedal Effort

Brake lockup during light brake pedal force

Possible Source(s):
- Brake pads.
- Calipers.

Action(s) to take:
* GO to Pinpoint Test H. Pinpoint Test H: Brake Lockup During Light Brake Pedal Force

Brakes drag

Possible Source(s):
- Parking brake control applied/malfunction.
- Seized parking brake cables.
- Seized caliper slide pins.
- Seized caliper.
- Brake booster.
- Pedal gear.

Action(s) to take:
* GO to Pinpoint Test I. Pinpoint Test I: Brakes Drag

Excessive/Erratic brake pedal travel

Possible Source(s):
- Hydraulic system.
- Brake pads.
- Brake discs.
- Hub and bearing assembly.

Action(s) to take:
* GO to Pinpoint Test J. Pinpoint Test J: Excessive/Erratic Brake Pedal Travel

The red brake warning indicator is always on

Possible Source(s):
- Fluid level.

Action(s) to take:
* FILL the system to specification.

CHECK for leaks.

Possible Source(s):
- Brake fluid level sensor.

Action(s) to take:
* INSTALL a new brake master cylinder fluid reservoir.

Possible Source(s):
- Parking brake control.

Action(s) to take:
* RELEASE and ADJUST the parking brake.

Possible Source(s):
- Electrical circuit.

Action(s) to take:
* For additional information, refer to the approved Jaguar diagnostic system for analysis/rectification of the concern.

Slow or incomplete brake pedal return

Possible Source(s):
- Brake pedal binding.
- Brake booster/master cylinder.

Action(s) to take:
* GO to Pinpoint Test K. Pinpoint Test K: Slow or Incomplete Brake Pedal Return