A vehicle that sticks you to the dashboard, with even the most delicate application of brakes is common and luckily, easy to fix the problem. I’m a mechanic and you are in the right place to learn how to fix your super-sensitive brakes with next to no effort at all.
Brakes that stop abruptly are commonly caused by brake rotor contamination. Rust is the most common type of rotor contamination. It’s a common occurrence, especially in vehicles that lay idle for a time in damp conditions. Applying the brakes under normal driving conditions will clean the rotors and restore brake performance.
In this post, we’ll cover brake contamination types, how you can fix them, and how to prevent them in a little more detail.
Types Of Brake Contamination
As you’ve already learned, brake contamination is the usual cause of hyper-sensitive brakes, and you’ve also learned the most common type of contamination is rust.
And while contamination is the more usual cause, it’s not the only cause, but we’ll look at those other less common causes towards the end of the post.
For now, let’s look at the two most likely causes of super sensitive rusty brakes and oil-contaminated brakes.
Rusty Brake Contamination
When I say rusty brakes, I’m really mean one part of your vehicle’s brake system components in particular – The rotors. Rotor corrosion is common, and much more so in damp conditions and where a vehicle lays idle without moving for a couple of days. The reasons for this are easy to explain, but first here’s a fast breakdown of what the main brake components actually do.
Your vehicle’s brakes consist of four main components, they include:
- Brake master cylinder – creates fluid pressure to activate caliper piston as brake pedal is applied
- Rotor – fixed to the wheel hub and rotates with the road wheel
- Brake pads – rest either side of the spinning rotor awaiting application
- Brake caliper – employs a piston to force the brake pads against the spinning rotor, slowing and stopping the wheel
Of course, there are other important items, like brake booster, brake fluid, brake lines but you get the idea.
The reason rotor rust is common is because of the nature of both rotor makeup and its use. Rotors are made from cast metal. As the pad makes contact with the spinning rotor, it isn’t possible to coat the friction surface with paint, friction would simply strip it back to bare metal.
Therein lies the answer to why it attracts rust, it’s bare untreated metal. Damp air and a couple of days laying idle are perfect conditions for rust to form on the rotor’s friction surface.
Driving the vehicle and applying the brakes for the first time after the layup causes the pads to bind to the rotor’s rusty surface, which as you know causes you to spill your coffee all over the dashboard – not cool!
How to fix rust contaminated brakes
The fix for rusty rotors couldn’t be easier, they almost fix themselves. Drive your vehicle as normal, apply the brakes normally, not need to brake heavily. The normal braking action will cause the brake pads to clean the rust from the rotor’s friction surface. Within two or three brake applications, both pads and rotors will be clean and your brakes will feel normal again. See! told you it was easy.
All that said I’ve had to replace rotors and pads on many low mileage cars where shall we say the owners are less than enthusiastic driving far or fast. As a result, brake rotor corrosion builds up and eats into the surface of the rotor, damaging both the rotor and brake pad.
Oil Contaminated Brakes
Oil contaminated brakes are much less common than rust contaminated rotors. But oil contamination is more work to fix. This content is owned by moc.sotuaytsur. Unlike rust contamination, oil contaminates both the rotor and the pads. Both brake components will need attention before we can call them good.
But there’s another element to this repair we must consider before the brake system repairs can begin. And that is, answering the question – What and where is the source of the oil contamination?
Oil contaminated brakes are commonly caused by two scenarios:
- The environment, meaning other vehicles drop an oil slick on the highway
- Your own vehicle has developed a fluid leak
If the contamination is caused by another road user, we can go straight to the brake repair stage since we can’t do much about it, we chalk it down to bad luck.
If however upon inspecting your own vehicle, you find an oil leak. That, itself is a concern, but will obviously need to be repaired before any brake repairs are made.
How to fix oil contaminated brakes
Oil contamination is not difficult to repair but it will mean pilling the brakes down to clean and replace the pads. Brake pads are porous and tend to absorb oil, they are generally pretty inexpensive I would never attempt to try and clean them.
Here are the tools and supplies you’ll need to nail this repair:
- Axle stand
- Socket set & ratchet
- Long flat screwdriver
- Wire brush
- Bungee cord
- Torque wrench (optional)
- Brake cleaner
- Set of pads
- Permatex brake lube
You’ll find many of the tools and supplies I use here on the “Brake repair tools page” and if you need brake system parts, check out the Amazon link below.Amazon Brake Parts
The repair process is as follows:
- Remove wheel
- Turn steering wheel out
- Pop hood and loosen brake fluid reservoir cap one turn
- Using flat screwdriver lever back caliper piston
- Remove caliper clip (if fitted)
- Remove caliper fasteners
- Remove caliper and use bungee to support from coil spring
- Remove brake sensor (if fitted)
- Remove pads and discard
- Use brake cleaner and clean cloth to clean the brake rotor, both sides
- Clean caliper rails and pad clips (if fitted) and apply small amount of Permatex lube
- Clean caliper slide pins and apply coat of silicone grease (if fitted)
- Apply coat of Permatex to rear of pads and fit pads
- Fit caliper and fasteners (torque 20 lb. ft. (28 Nm)
- Refit caliper clip (if fitted)
- Refit road wheel and repeat the process on the opposite side
After completing the process on the opposite of the vehicle, tighten the brake fluid reservoir cap and the wheels should ideally be torqued to specification. Cars around 75 lb. ft. (100 Nm) – SUV and trucks approx. 100 lb. ft. (135 Nm).
IMPORTANT – Before driving your vehicle PUMP THE BRAKES SEVERAL TIMES
Failing to push the piston out to meet the pads will mean your vehicle has no brakes. You’ll know when you have done this successfully, the brake pedal will be firm.
The brakes will now need to be bedded in. Until the brakes are bedded in they won’t feel quite right. The process is simple – drive the vehicle at 30 – 40 mph and apply the brakes, repeat four to five times. Avoid heavy breaking.
After road test check brake fluid reservoir level.
How To Prevent Brake Contamination
There’s not much you can do about road contamination, it’s not very common, and no defense for it anyhow. You can prevent or at least reduce the possibility of rotor contamination by checking your drive or garage floor for oil leaks and dealing with them should you find the same.
Rotor corrosion is the bigger issue and it can be reduced by simply driving your car regularly (at least once a week) at highway speeds. In other words, drive fast enough to assist in breaking forcefully enough to remove that layer of rust buildup.
Parking your car in a heated garage would be great too.
Other Causes Of Contaminated Brakes
Contamination isn’t the only cause of grabby brakes, here’s a list of other possible causes:
- Warped rotors – replace
- Cracked rotors – replace
- Damaged brake pads – replace pads
- Faulty brake caliper – replace caliper
- Faulty flexi brake hose – replace flexi hoses
Note when working on brakes, it’s good practice to replace components on the same axle in pairs. In other words both front brake pads, both front rotors, both front calipers, and so on.
You may find the brake resources page useful, it’s a fluff-free guide to DIY brake repairs.
- About the Author
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.