Frequently Asked Questions
“What is the proper sequence in which to bleed my brakes when using the Mityvac® pump for vacuum brake bleeding?”
When using the vacuum bleeding method to bleed brake systems on vehicles which are rear wheel drive the sequence should start with the wheel closest to the master cylinder and end with the wheel which is farthest from the master cylinder.
Example: LF wheel, RF wheel, LR wheel, RR wheel
However, when vacuum bleeding brake systems on vehicles which are front wheel drive the sequence will change. These systems use a diagonal configuration for safety purposes. On this system the sequence should start with the wheel closest to the master cylinder as before, however the next wheel in the sequence will be diagonally aligned with that wheel.
Example: LF wheel, RR wheel, RF wheel, LR wheel.
LF – Left Front RF – Right Front
LR – Left Rear RR – Right Rear
“When I try to bleed my brake system using the Mityvac® pump I am getting air bubbles in the line connected to the bleeder screw on the wheel cylinder and little or no fluid is being collected in the reservoir jar. I have tried several times to bleed my brakes without success. What is the cause of this problem?”
Usually this condition is caused by a small amount of air being pulled between the threads of the bleeder screw and the body of the wheel cylinder or caliper resulting in the appearance of several small bubbles in the line connected to the bleeder screw. This can be corrected quickly and easily. Before you begin to bleed the brake system we suggest that the bleeder screws be removed at all four wheels. With the bleeder screws removed assure all are clean and the passages of the bleeder screws are free of corrosion or debris. (A small paper clip will work well.) Next, be sure that all brake fluid, penatrating oil, and or grease is removed from the bleeder screw. (Brake cleaning solvent does an excellent job.) Apply a 2 to 3 inch piece of Teflon® tape to the threaded area of the bleeder screw only. Wrap the tape in the opposite direction of the rotation of the threads. This will prevent any see page of air from around the threads. Install each bleeder screw back into the corresponding caliper or wheel cylinder and lightly seat the bleeder screw. Now you are ready to begin bleeding the brake system! This may seem like quite a bit of work in the beginning, but, once you get started it should only take minutes to complete. In fact, the procedure outlined above is an important step when bleeding brake systems regardless of the method used. It is critical to be sure that each component in the brake system is in proper working order to assure a long lasting repair. Remember, the brake system is the most important system in your vehicle. If the brake system fails to perform correctly, the results could be disastrous.
“Why is it important to remove all air from the cooling system?”
If air is trapped inside the engine block or cylinder head(s), it will cause an overheating condition. This could result in very costly engine repair or possibly engine replacement. A radiator or fill tank can look full but it does not mean that the engine block or cylinder head(s) are full.
“How does the air get trapped inside the engine?”
Many newer model vehicle designs have lower hood lines and are more aerodynamic, which means that the engine is positioned higher than the radiator. While this promotes a more attractive, sleeker look, it creates a problem within the radiator. Basic physics tells us that water, which is part of the engine coolant, seeks a natural level. The coolant cannot be drawn into the engine efficiently because air exists between the upper portion of the engine block and cylinder head(s).
“How do you remove the air that is trapped in the upper portion of the engine?”
You vacuum it out using the AirEvac (P/N 04700) from Mityvac“. This is a tool that creates negative pressure within the cooling system (a vacuum). By creating this vacuum, it removes the trapped air and refills your cooling system while still holding your system in a vacuum. All fluid will be drawn from the coolant container into the system until it is full. (Ensure you have enough coolant mixture before performing this task.) Once the system is filled the vacuum will no longer exist because the coolant now occupies the void. No Air! No problem!
“Air never hurt my old vehicle. How can it hurt my new one?”
Radiators in the older vehicles were positioned higher than the engine. It used to be easy to just fill the radiator and run the vehicle until the thermostat opened and then top it off, put the radiator cap on and drive away. With newer vehicles, most manufacturers specify to purge the air out of the cooling system. If air gets trapped in the engine block or cylinder head(s) and it is run for any period of time it will cause “hot spots”. This will damage head gaskets, the cylinder walls and the entire cooling system. Overheating and expensive repairs will be the end results.