Land Rover Defender: Brake System - Diagnosis and Testing

PRINCIPLES OF OPERATION

For a detailed description of the Brake System, refer to the relevant Description and Operation section in the workshop manual.

INSPECTION AND VERIFICATION

CAUTION: Diagnosis by substitution from a donor vehicle is NOT acceptable. Substitution of control modules does not guarantee confirmation of a fault, and may also cause additional faults in the vehicle being tested and/or the donor vehicle.

NOTES:

• If a control module or a component is at fault and the vehicle remains under manufacturer warranty, refer to the Warranty Policy and Procedures manual, or determine if any prior approval program is in operation, prior to the installation of a new module/component.
• Generic scan tools may not read the codes listed, or may read only 5-digit codes. Match the 5 digits from the scan tool to the first 5 digits of the 7-digit code listed to identify the fault (the last 2 digits give extra information read by the Jaguar Land Rover approved diagnostic equipment).
• When performing voltage or resistance tests, always use a digital multimeter that has the resolution ability to view 3 decimal places. For example, on the 2 volts range can measure 1mV or 2 K Ohm range can measure 1 Ohm. When testing resistance always take the resistance of the digital multimeter leads into account.
• Check and rectify basic faults before beginning diagnostic routines involving pinpoint tests.

1. Verify the customer concern
2. Visually inspect for obvious signs of damage and system integrity

Visual Inspection

3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step
4. If the cause is not visually evident, verify the symptom and refer to the Symptom Chart, alternatively check for Diagnostic Trouble Code(s) (DTC) and refer to the DTC Index
5. Check the Jaguar Land Rover (JLR) claims submission system for open campaigns. Refer to the corresponding bulletins and SSMs which may be valid for the specific customer complaint and complete the recommendations as required.

ROAD TEST

Perform 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. When 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 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

SYMPTOM CHART

PINPOINT TESTS

Brake Disc Corrosion Inspection

NOTES:

• Jaguar Land Rover braking systems are designed to achieve peak performance under a broad range of driving conditions. Jaguar Land Rover's priority is the safety of its braking systems, and they are designed to perform in all circumstances, however the brake may, dependent on the environment and driving style, produce the occasional noise. This does not impair the operation or performance. Brake noise is an issue facing many vehicle manufacturers and Jaguar Land Rover are constantly working in conjunction with the leading brake caliper and brake pad suppliers to develop design solutions which reduce brake squeal noises.
• Jaguar Land Rover Limited offers no warranty and is not responsible for any repair or replacement to the vehicle, part or accessory that is required as a direct result of: Normal wear and tear this includes brake pads, brake discs, and any other friction related components. The list is not exhaustive. Defects or damage caused as a result of the vehicle being used in motor sport events, or for any purpose other than normal, private, or commercial use. Brake pads, brake discs, and any other friction related components are covered against manufacturing defects for the duration of the manufacturer's warranty.
• Most JLR brake pads now utilize NAO brake pad friction material technology. This creates a 'transfer layer' on the brake disc, whereas previous brake pads use an abrasive friction mechanism, which leads to greater pad and disc wear. This NAO transfer layer has a dull metallic appearance.
• However, some situations with low brake usage, or through the use of non- JLR approved wheel cleaners, can lead to a build up of surface corrosion on the disc (see guidance below and in workshop manual Diagnosis and Testing) - this surface corrosion build-up does not adversely affect brake performance.

1.

NOTE: If the brake disc(s) is similar to illustration E245239, This is not a manufacturing defect and is not covered under warranty.

Light corrosion - If the disc(s) condition is as illustrated and within the service wear limit REFER to: Specifications (Brake System - General Information, Specifications). This is not detrimental to braking performance and brake disc replacement is not required.

2.

NOTE: If the brake disc(s) is similar to illustration E245550, This is not a manufacturing defect and is not covered under warranty.

Light corrosion - If the disc(s) condition is as illustrated and within the service wear limit REFER to: Specifications (Brake System - General Information, Specifications). This is not detrimental to braking performance and brake disc replacement is not required.

3.

NOTE: If the brake disc(s) is similar to illustration E245238, This is not a manufacturing defect and is not covered under warranty.

Moderate corrosion - If the disc(s) condition is as illustrated and within the service wear limit REFER to: Specifications (Brake System - General Information, Specifications). This is not detrimental to braking performance and brake disc replacement is not required.

4.

NOTE: If the brake disc(s) is similar to illustration E245551, This is not a manufacturing defect and is not covered under warranty.

Uneven corrosion with pitting - If the disc(s) condition is as illustrated and within the service wear limit REFER to: Specifications (Brake System - General Information, Specifications). This is not detrimental to braking performance and brake disc replacement is not required.

5.

NOTE: If the brake disc(s) is similar to illustration E245552, This is not a manufacturing defect and is not covered under warranty.

Uneven corrosion with pitting - If the disc(s) condition is as illustrated and within the service wear limit REFER to: Specifications (Brake System - General Information, Specifications). This is not detrimental to braking performance and brake disc replacement is not required.

6.

Brake pad to brake disc surface contact area measurement instruction

• Section (A) is 100% of the brake disc working surface. To workout 30% section (B) of the brake disc working surface follow the below steps.
• Step 1. Measure section (A) of the brake disc working surface. Example 60mm.
• Step 2. Divide the measurement from step 1 by 100. Example 60mm ÷ 100 = 0.6mm.
• Step 3. Multiply the total of step 2 by 30. Example 0.6mm × 30 = 18mm
• Step 4. This will give 30% section (B) of the brake disc working surface.

  Example 18mm.

7.

NOTE: If the brake disc(s) is similar to illustration E245240, This is not a manufacturing defect and is not covered under warranty.

Heavy pitting with corrosion - It is not necessary to replace the disc unless the corroded region covers more than 30% of the brake disc working surface.

8.

NOTE: Brake discs are recommended to be replaced in axle sets.

Severe pitting and corrosion - If the disc(s) condition is similar to the illustration. Replace the brake discs.

9.

NOTE: The use of non- JLR approved wheel cleaners can cause accelerated corrosion of the brake disc.

• Use of non-Jaguar Land Rover wheel cleaners - Evidence of use of nonJLR approved cleaners may be indicated where discoloration/corrosion of brake caliper/springs occurs.
• SSM73952 and SSM73953 - Brake Caliper Discoloration - provides guidance to use of wheel cleaners.
• The pictures shown illustrate typical calipers on vehicles that are corroded due to using unsuitable cleaning agents
• Corroded calipers, due to using unsuitable cleaning agents, are NOT covered by warranty.

COMPONENT TESTS

INTEGRATED POWER BRAKE CONTROL MODULE

1. Check the hydraulic brake system for leaks or low fluid

BRAKE MASTER CYLINDER

Usually, the first and strongest indicator of anything wrong in the brake system is a feeling through the brake pedal.

The tandem master cylinder is internal to the integrated power brake control module In this system, pedal feel is provided by an internal pedal feel simulator. It operates as a Brake By-Wire system. The driver pressure is not directly connected to the brake calipers. The Integrated power brake control module monitors for air and leakage in the brake system. This can also be tested using the Jaguar Land Rover diagnostic equipment

Normal Conditions

The following conditions are considered normal and are not indications that the brake master cylinder is in need of repair

• Modern brake systems are designed to produce a pedal effort that is not as hard as in the past. Complaints of light pedal efforts should be compared to the pedal efforts of another vehicle of the same model and year
• The fluid level will fall with brake pad wear

Abnormal Conditions

Changes in the brake pedal feel or brake pedal travel are indicators that something could be wrong in the brake system. The diagnostic procedure and techniques use brake pedal feel, warning indicator illumination and low brake fluid level as indicators to diagnosing brake system concerns. The following conditions are considered abnormal and indicate that the brake master cylinder is in need of repair:

NOTE: Prior to carrying out any diagnosis, make sure the brake system warning indicator is functional

• Brake pedal goes down fast. This could be caused by an external or internal leak
• Brake pedal goes down slowly. This could be caused by an internal or external leak
• Brake pedal is low or feels spongy. This condition may be caused by no fluid in the brake master cylinder, reservoir cap vent holes clogged or air in the hydraulic system
• Brake pedal effort is excessive. This may be caused by a bind or obstruction in the pedal/linkage
• Rear brakes lock up during light pedal force. This may be caused by damaged brake pads, a partially applied park brake, a damaged wheel speed sensor or bearing failure
• Brake pedal effort erratic. This condition could be caused by the integrated power brake control module or incorrectly installed brake pads
• Brake warning indicator is on. This may be caused by low brake fluid level

NON PRESSURE LEAKS

Any reduced fluid volume in the brake master cylinder reservoir may be caused by two types of none pressure external leaks

Type 1: An external leak may occur at the brake reservoir cap because of incorrect positioning of the gasket and cap.

Reposition cap and gasket

Type 2: An external leak may occur at the brake reservoir mounting seals. Repair such a leak by installing new seals and make sure that the brake reservoir retaining bolt is correctly installed

DTC INDEX

For a list of DTCs that could be set on this vehicle.

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