Bleeding the brake pump is a very simple job, but it is essential to make sure that the system is safe and free of air; the air is in fact compressible, while the brake fluid does not have this characteristic. You should first drain the fluid from the pump by placing it on a work table and then repeat the procedure after installation on the vehicle.
Steps
Method 1 of 2: on the Work Shelf
Step 1. Gather all the material
This method is much simpler than the one described in the next section, which is time consuming and may not even work; it's also much cheaper than taking the part to the mechanic, who can do a quick (and expensive) job using vacuum pumps. It is also an indispensable procedure if you are installing a new master cylinder. For this purpose you need to prepare:
- The master cylinder with a drainage kit;
- New brake fluid;
- A work surface or table equipped with a vice. If you do not have any of these surfaces, it is more convenient to move on to the method described in the next part of the article, which does not require a special working space;
- A wooden or plastic pin; make sure it is sturdy because it doesn't have to break halfway through the procedure.
Step 2. Remove the master cylinder from the packaging
Set aside the drainage kit that is included in the package and you will need it later.
If the new part does not have a reservoir, remember to disassemble the old one
Step 3. Lock the master cylinder in a vise
Stability is a key factor for this procedure. Before continuing with any operation, make sure that the piece is firmly fixed to the work table and that it is level.
- Grab the pump at the widest part and check that it is level; by doing so, the air can exit properly and the fluid can penetrate each crack evenly.
- The element must be securely fixed, but the vice must not be so tight as to dent or damage the aluminum parts; make sure that the plastic elements are not crushed or blocked when you insert the master cylinder between the shoes.
- If your work table does not have a vise already installed, you need to buy one that fits the surface.
- If you care about the aesthetics of the table, it is best not to use it, as the vice can leave visible marks in the wood or metal. If you don't have any other shelves available, place a rag between the clamp fastening system and the surface to avoid damaging it; However, be aware that this method offers no guarantees and that you proceed at your own risk.
Step 4. Prepare the drain kit
It should be included in the pump package and consists of two rubber hoses and two plastic threaded elements.
- These elements are threaded on one side, while the other should be smooth in order to connect the pipe.
- Also check the color of the tube. If it is opaque, you should replace it with a clear one because you need to be able to see any air bubbles trapped in the liquid.
- You can also decide not to use the kit because it is not essential; however, this article describes a procedure that does.
Step 5. Screw the threaded elements to the brake master cylinder drain nozzles
They are located on one side of the piece after the widest part.
Insert them in the holes taking care not to cross the threads badly and tighten them by hand
Step 6. Connect the rubber hoses
Once the plastic elements are installed, you can join the rubber tubes.
Step 7. Make the ends of these fit into a container
The container is used to collect excess brake fluid; accordingly, choose one you don't mind getting dirty.
- Consider attaching the tubes to the container in some way. When you start pumping the liquid, the free lines may move uncontrollably, spraying the fluid everywhere.
- An old coffee jar is perfect for this, although any cylindrical container with a wide opening will do.
Step 8. Fill the reservoir with brake fluid
If the tank empties during the procedure, you should start over.
- You should only use a fluid that is no more than two years of age.
- Check that the level is between the "minimum" and "maximum" mark and that it covers the ends of the two pipes. This fluid is very hygroscopic, which means that it absorbs moisture and degrades, damaging the seals; never reuse it.
Step 9. Set the master cylinder in motion
Proceed slowly to prevent air from entering the device or the wooden pin from snapping.
- Make sure that the piston does not come out of the base, otherwise you allow the air to enter.
- You have to close the tubes by pinching them every time you release the pressure on the cylinder.
Step 10. Push the cylinder and pinch the tubes
That way, you squeeze the liquid that squirts out as you release the ducts.
This method also prevents air from entering the device, as it leaves no gaps where it could seep
Step 11. Release the grip on the hoses to allow the brake fluid to flow out of the master cylinder and then pinch them again
Step 12. Repeat the procedure until there are no more air bubbles in the liquid
You can understand that you have completed the job when there are no more bubbles floating in the tank or container of used fluid
Step 13. Remove the pump from the vise without disassembling the drain kit
Step 14. Start mounting it on the vehicle
When installing the pump in a car, always keep it level and disconnect the drain hoses while connecting those in the system. If you do this correctly, it should not be necessary to bleed the entire brake line, but it is recommended that you discard the old fluid
Step 15. Remove the hoses and plastic inserts, then add the caps to the pump
These should be included in the package and prevent liquid leakage.
Step 16. Replace the cap on the brake master cylinder reservoir
Otherwise, the fluid can come out.
Step 17. Do a braking test before driving the vehicle
You must make sure that the system works perfectly before driving the car.
- If the job has been done right, the brake should react promptly and sharply when you step on the pedal.
- If you have made a mistake, the brakes are "spongy" when you apply pressure on the pedal - it means that there is air in the pump.
Method 2 of 2: in the Automobile
Step 1. Gather the materials
Unlike when you bleed a new or disassembled pump, you can do this without buying new parts or tools. You need:
- A wrench or a screwdriver for drainage, since you have to loosen the screws that secure the pipes in their seat to let the fluid flow;
- A pair of pliers to pinch the hose connected to the brake master cylinder;
- A can of WD-40 or other hydrophobic solvent; the drain screw may be caked with oil or other contaminants and may be difficult to loosen. You can use the WD-40 to remove dirt and unscrew the small parts;
- Jacks: Since the master cylinder is located under the vehicle, you have to lift the vehicle to slide under the body. Check that the jacks are solid so that the car does not fall on top of you;
- A helper who takes care of pressing the brake pedal while you tinker with the pipes and screws under the car.
Step 2. Lift the car
This allows you to slide under the hood and work on the brake master cylinder.
- Keep the car stationary by locking the wheels and make sure it cannot move by parking it on a level surface.
- Do not disassemble the wheels because if the jacks fail, the tires offer some rebound and perhaps can save you an injury or even death.
Step 3. Place a container or jar under the master cylinder drain valve or under the hose connection spout
The container is used to collect excess brake fluid, so use one you don't mind getting dirty.
- Consider attaching the drain hose to the container in some way. When you start pumping, the free tube moves uncontrollably and could splash liquid everywhere.
- An old coffee jar is perfect for this, but any cylindrical container with a wide opening will do.
Step 4. Ask the helper to gently press the brake pedal several times
Have him inform you of his actions by saying "down" when he presses the pedal and "up" when he releases it.
Step 5. Ask him to maintain pressure on the pedal
At this point, you can start working on the pump.
Step 6. Disconnect the hoses connecting the brakes to the master cylinder
By doing so, it isolates the latter while allowing the system to be purged.
- If you are trying to drain the liquid only from the pump and not from the whole system, you must avoid that your actions interfere with the pump.
- Fluid is likely to start flowing immediately, which is why you should attach the drain hose to the vessel.
- Before the helper releases the pressure on the pedal, make sure you have connected the hoses again.
Step 7. Inspect the liquid
If there is air, you should see bubbles.
This is another important reason you need to have a container or jar; if you don't collect the fluid, you can't know if there is air or not
Step 8. Reconnect the hoses to the pump
If you don't, air can enter again.
Step 9. Ask the helper to release the pressure on the pedal
Step 10. Repeat the procedure until there is no more air in the pump
Don't forget to keep refilling the pump tank with more liquid, otherwise you will allow air to infiltrate and have to start over
Advice
- Buy new spare parts whenever possible, refurbished ones have a high breakdown rate.
- If the new element doesn't have a tank, you have to reuse the old one. Try to extract as much liquid as possible and if you want to clean some pieces, use only denatured alcohol or a specific cleaning product, as those based on petrolatum and water damage the seals.
Warnings
- If you have any doubts about the safety and reliability of the system, avoid using the vehicle but call a professional; its intervention is less expensive and certainly involves fewer consequences than an accident.
- Do not use oil to clean parts that come into contact with the brake system fluid, otherwise it will destroy the seals.
- Brake fluid is very corrosive on paint and on many plastics, even on crystals; if any drops fall on the body, remove them immediately.
- Finally, if your car is equipped with a sophisticated braking system, such as EBD, ABS or BAS, you may not be able to prevent air from entering the pump activator. If you have to work on this kind of plant, you need to contact a professional to drain the liquid instead of doing it yourself.
- Do not reuse the fluid that you have extracted or drained from the brake system, it could contaminate new elements and damage them.
