Pulling Back

When a problem persists, it’s usually minor… but the vehicle still cannot be released to the customer until it is corrected.

Some stubborn problems ý like brake pulls ý can be resolved easily enough when you stick to the basics.

If the vehicle didn’t have a pull before the brake work was done, start by making sure the problem isn’t related to vehicle hydraulics or some other system. Common culprits include air in the system, or a problem with the proportioning system or master cylinder. Also, the vehicle could require an alignment or be experiencing front-end issues, or bad wheel bearings or tires. The list goes on and on. But where there’s no obvious cause for a brake pull, here’s are some things you can do to help correct the problem as quickly and effectively as possible.

Binding components

Shims which restrict brake pad movement or which allow greater movement on one side are likely to cause pulling problems. This is most often the case if there was heavy build-up of corrosion in the caliper and the surfaces weren’t properly cleaned-or if the surfaces were aggressively cleaned with a grinder to save time. Tolerances are often incredibly small and the tiniest amount of foreign material may cause pulling. Check the pads to make sure they "float" correctly in the brackets. Remember to clean the mating surfaces thoroughly without distorting the surface. If the brake shims aren’t being replaced, they should be thoroughly cleaned of corrosion and grime, and then securely reinstalled. If a vehicle develops a sudden brake pull immediately after brake work, binding components may be one of the easiest things to check.

Contaminated friction surfaces

Ensure these are clean and free of grease or fluids. Greasy finger marks or excess lubricant which makes its way onto the friction surfaces may be the source of braking problems. Once the brakes heat up, the grease may spread and worsen the problem. Brake fluid may also cause problems if it contaminates the linings or friction surfaces – something to keep in mind if the hydraulic system was opened or the caliper was leaking. Also, be careful when cleaning the discs or drums. Using the incorrect solvent to clean the surfaces may cause problems rather than repair them.

Caliper problems

In the same way that shims can cause problems, caliper pistons can bind or leak when moved backwards, causing problems when the brakes are applied on a road test. The brake hoses, which connect to the calipers, could also cause problems if they’re damaged internally (often from clamping the hose to remove the caliper without spilling hydraulic fluid). Carefully inspect the caliper and hoses and make sure the parts move freely and retract as required.

Adjustments

Rear drum brakes or cables can cause problems if not adjusted correctly or if they bind or hold their position. Sometimes simply removing a brake drum which hasn’t moved in a while is enough to cause problems. Checking parking brake operation might be enough to make a cable stick. Quickly checking the rear brakes for problems is often the fastest way to correct problems. Make sure the cables and levers retract fully and don’t leave the parking brake partially applied. Vehicles which use the "drum/disc" system may be more susceptible to problems-checking the lever or adjuster mechanism from the back of the backing plate may reveal the source of the problem.

These steps could save diagnostic time and prevent a minor concern from becoming a major headache.