How to Diagnose Common Brake Troubles

Shake, side pull, binding, grabbing, grinding, squealing, overheating and soft / hard pedal issues.

When it comes to brakes, you need to find out the problem BEFORE replacing parts. Sometimes this is harder than it sounds. Here is a brief list of brake problem troubleshooting tips you may find helpful.

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Problem & Solution

Common among these chassis:

W108 W109
W110 W111 W112 Sedan
W111 W112 Coupe

Brakes and wheels get real hot when driving - This is caused by dragging brake calipers which can be due to a sticking caliper, plugged rubber brake hose, or a faulty master cylinder. See Kent's YouTube video on checking for sticking brake calipers. Replace rubber brake hoses if they are over 15 years old. Master cylinder would be the last thing to suspect.

Car pulls to one side during braking - This can also be caused by a sticking brake caliper or plugged rubber brake hose. Try to determined which brakes are dragging and check for sticking caliper first. You will also notice the pads on one side of the car may be worn more than the other.

Squealing brake noise when coming to a stop - This is usually caused by brake pads that are vibrating in the caliper. Add brake pad paste and if that does not solve the problem replace your pads with ones we sell at Mercedessource.

Steering wheel shakes during heavy braking - This indicates one or more of your brake rotors are warped. This is caused by age and/or over-heating. Replacing the suspect rotor or rotors almost always solves this problem.  When replacing rotors always install new pads.

Brakes make grinding noise when applied - Pads are worn down and making metal to metal contact on your brake rotors. This is a real safety issue. Do not wait to get your brakes inspected and repaired. If it is front pads making the noise you may also see the brake pad warning light illuminating on your dash.

Brake Pedal feels soft or goes all the way to the floor - This indicates you probably have air in your brake lines. Pressure brake bleeding is the best way to make sure you get all the air out. If you have done a complete bleed and are still experiencing the problem then it is likely your master cylinder needs replacement.

Brake Pedal feels hard when pushing on the brakes - This indicates that your brake booster is not working properly or is leaking. There is a seal between the booster and the master cylinder that often goes bad. If the seal is ok it could be a faulty brake booster but not always. The problem may be due to insufficient vacuum getting to the booster. Be sure to test your vacuum system before replacing an expensive brake booster.

Brake pedal jumpy  (ABS systems) - This means your ABS system is trying to come on even when not needed. Usually caused by dirty or faulty wheel sensors, air in the system, or an ABS controller going bad. See Kents YouTube video on ABS brakes.