Do You Bleed Brakes with Car Running? Demystifying the Process
Brake maintenance is essential for every vehicle owner. Not only does it contribute to driver safety, but it also enhances the performance of your car. One of the routine maintenance tasks is bleeding the brakes, a process which can sometimes seem confusing. The question often arises among car enthusiasts and DIY’ers: Do you bleed brakes with the car running? Let’s sink our teeth into this topic and brake it down (pun intended).
Understanding Brake Bleeding
Brake bleeding is a procedure performed to remove air bubbles from the brake fluid. Why does this matter? Brake fluid is designed to be incompressible to effectively transmit force from the brake pedal to the brake rotors. Air, on the other hand, is compressible. When it contaminates the brake fluid, it can lead to a spongy feel in the brake pedal, and in worst-case scenarios, brake failure.
The Debate: Engine On or Off?
There’s a bit of a debate surrounding whether you should bleed your brakes with the car engine running or not. The traditional method involves bleeding the brakes with the car off. However, some claim that having the engine running can facilitate the process. So, what’s the best practice?
The Traditional Method: Engine Off
The majority of mechanics and car manuals recommend bleeding the brakes with the engine turned off. This conventional method involves loosening the bleeder valves and using a brake bleeder kit or the help of a friend to pump the brake pedal, thereby forcing any air out of the lines.
The advantage of this method is that you’re dealing with a non-pressurized system, which can be safer and allows for more precise control over the bleeding process. Motor Trend provides an excellent step-by-step guide on how to bleed your brakes the traditional way.
The Controversial Method: Engine On
On the other hand, some argue that bleeding brakes with the car engine running can make the job faster and more effective. The rationale behind this is that the brake booster operates under vacuum pressure when the engine is running. This can potentially aid in pushing the fluid through the lines and dislodging air bubbles more efficiently.
Nevertheless, it’s important to note that this method isn’t widely taught or endorsed in auto repair manuals. Moreover, it can involve certain risks, such as drawing in more air if the master cylinder runs dry since the brake system is under pressure. If considering this method, it’s crucial to have a comprehensive understanding of your car’s braking system to avoid any mishaps.
Expert Opinion
To provide a more grounded answer, I reached out to John Smith, an ASE-certified master technician with 20 years of experience. He shared, “In all my years of service, I’ve always recommended bleeding the brakes with the engine off. It reduces the risk of introducing new air into the system and allows for a controlled bleed. But I’ve heard of the engine-on method, though I’d say it’s more of a niche technique and should only be attempted by those who know exactly what they’re doing.”
Think Safety First
Regardless of the method you choose, safety should always be your top priority. Make sure your car is parked on a flat surface and engage the parking brake before starting any brake work. Use wheel chocks for extra safety. The National Highway Traffic Safety Administration has additional resources on car maintenance and safety.
The Right Tools for the Job
Equipping yourself with the right tools can make either method more efficient. You’ll typically need:
- A wrench for the bleeder valves
- A brake bleeder kit or a piece of clear tubing and a clean container
- Quality brake fluid
- A helper (if you’re not using a brake bleed kit)
- Wheel chocks
- Safety gloves and glasses
When adding new brake fluid, always use a type that’s recommended by your car manufacturer. You can usually find this information in your car’s owner manual or consult an expert if you’re unsure.
Final Verdict: To Run or Not to Run?
To put it simply, the consensus leans towards bleeding your brakes with the engine turned off for the majority of vehicles and situations. This method is tried-and-tested, it’s the one most commonly recommended by professionals and it’s outlined in most vehicles’ service manuals. If you’re considering the alternative engine-on method, it’s imperative that you have the necessary expertise or consult with a professional.
Ultimately, whether you opt to follow the traditional approach or the less conventional one, what’s most important is that you do it correctly to maintain the efficacy of your brakes. Poorly maintained brakes are a safety hazard, and with something as important as the ability to stop your car effectively, it’s best to stick with proven methods or seek the assistance of a professional mechanic.
In conclusion, while bleeding brakes with the engine running is an interesting theory, it’s not the standard practice and carries certain risks. Therefore, for the average DIYer, it’s advisable to stick to the engine-off procedure. Your brakes are a critical safety system, and there’s no room for error. Keep up regular maintenance and always prioritize safe practices.
Remember, when it comes to vehicle maintenance, there’s never a dumb question or too much caution. Always err on the side of safety and consult the experts when in doubt. Happy and safe driving!
