Misdiagnosis of problem resulting in comeback. Comebacks are not only a nuisance but can be a major problem if you have too many.
Not following a structured approach to the diagnosis of the complaint is one of the causes of comebacks that we will discuss today.
Apply a consistent effective approach to the diagnosis of all brake problems. The following approach will result in the accurate diagnosis of all brake problems:
- Think about the system
- Think about how it operates
- Think about the problem
- Generate a list of possible causes
- Diagnose and inspect in a logical manner
To effectively apply the above steps, it is important to have an understanding of what they involve and where the common mistakes are made. Here is a brief explanation of each:
- Think about the system: All brake systems are not the same and treating them the same can lead to misdiagnosis. The many different brake system configurations make it necessary to identify which type of system you are working on BEFORE entering the diagnostic stage.
- Think about how it operates: This step takes the information from step 1 and applies it to the system’s operation. Because of the many different system configurations there is a wide variance in how the systems operate. This step should answers questions like:
- Think about the problem: This should only be done after applying steps 1 & 2. An important part of this step is in the ability to separate a condition from a symptom. The customer may describe their “problem” as a pulsating pedal. The pedal pulsation is a symptom of something else wrong in the system. Some possible questions to ask yourself might be:
• What is the expected front to rear braking bias of the vehicle?
• What kinds of brake valve(s) is the system equipped with?
• What will effect pedal height?
• What will turn the red brake light on?
• When do the rear brakes self adjust?
• What will cause premature pad wear?
- Generate a list of possible causes: Most problems being diagnosed will have more than one possible cause. Two common mistakes at this stage are approaching the problem with an incomplete list or putting items on our list that can’t cause the problem being diagnosed. An example of this would be adding the master cylinder to our list for a low brake pedal. Conventional master cylinders cannot cause a low brake pedal.
- Diagnose and inspect in a logical manner: If steps 1 to 4 are done correctly this step should be simple. Steps 1 to 4 would allow you to generate a flowchart that will let you to pinpoint which item(s) from the list generated in step 4 apply to the problem you are diagnosing.
Bonus tip: Use this process religiously and it will work. It won’t work without steps 1 & 2 and they can’t be done without a good understanding of all the parts in the system.