Brake Lines

Brake lines and corrosion seem to go hand-in-hand. Corroded brake lines will leak, which should be immediately apparent by a complete loss of hydraulic braking power, which is exactly what happened to me (luckily in a parking lot).  Replacing these lines can be problematic, mostly because they can be in difficult-to-reach locations, and the fittings are also most likely frozen by corrosion.

Here is how the brakes work: The brake pedal pushes a piston through the firewall. This motion is assisted by engine vacuum by the brake booster (which looks like a large cylindrical object on the firewall). The hydraulic pump (or master cylinder) is mounted directly on the brake booster, and also contains a reservoir for the brake fluid.

Brake booster and master cylinder

Two lines from the master cylinder connect to the hydraulic control unit.  This is also mounted on the firewall, and is responsible for distributing the hydraulic pressure to each wheel. Four lines come out of the control unit and each one goes to a wheel. Under normal braking conditions, all four wheels will receive equal pressure. Under heavy braking, the front wheels receive a higher pressure. The lines to the two front wheels are  fairly short and are sheltered by the engine compartment, so they are not likely to corrode. The rear lines run the entire length of the vehicle underneath, and are exposed to road salt and water. This is where most of the corrosion can be found.

Replacing brakes lines is not a difficult task by itself, but replacing the full length of a brake line can be cumbersome because they involve a lot of bends and turns. Therefore, most people only replace the corroded sections by splicing in a new line. Brake lines are made of rigid stainless steel, and can be easily cut with a rotating pipe cutter. A new connection requires a union. Before connecting a union, the lines have to be fitted with male fitting and the ends of the tubes have to be flared. The shape of the flare is important because it forms a perfect metal-to-metal seal with the female end of the union. Most importantly, the flare prevents the tube from separating from the fitting under high hydraulic pressures. Double-inverted flare is the most common flare shape, and it is the type used in the Kia Rio (this information is hard to find online, but it is specified in the Kia Technical manual). The fitting threads are M10 x 1 (metric). The best and most economical tool I have found for creating tube flares is the Eastwood on-car flaring tool for 3/16 brake lines. It is easy to use and compact, and works on the Kia. Although pre-flared brake lines are cheap to buy, the exact length needed may not match up with standard lengths sold in stores. I had to cut off one end of the fitting and redo the flare for the correct length.

Eastwood on-car flaring tool
Double inverted flare with a new male fitting
With the union connected

The problem was not solved even after splicing in the new lines. I was unable to bleed the brakes because all four bleed valves were completely frozen. These are small 8 mm screws, so they are very easy to round off.

Attempting to remove one of them resulted in a broken screw, so it had to be drilled out. That ended up damaging the threads in the caliper, so the whole caliper had to be replaced.  Also, both of the rear bleed valves were completely stuck and it was much easier to replace the entire brake cylinder rather than try to remove them. Even then, I ended up having to replace the brake lines leading to the cylinders because the connectors were complete frozen, and I had to cut the line to extricate the cylinder. While I was at it, it was also prudent to replace the rear brake drum, shoes, bearings and hub nut. All in all, a majority of the brake system was completely overhauled.

New brake line between the brake hose and the cylinder
Brake shoes, hardware and cylinder.

The hub nuts that hold the rear drum have to be replaced every time. These are not available at regular parts stores, and has to be ordered online. Instead of the cotter pin, these nuts are crushed to align with the slot in the axle (known as staking). This is best done with an air hammer and an axle nut punch tool.

Staked axle nut
Axle nut punch tool and air hammer

The final step is bleeding the brakes to remove all air in the newly installed lines. Since the entire system was empty, first the master cylinder has to be filled and bled. This is done by removing the two outgoing lines from the cylinder, and using plastic tubes to run the line back into the reservoir. Then pump the pedals to purge out air from the cylinder.

Bleeding the master cylinder

Bleeding the wheels requires a vacuum suction to pull the fluid through the lines.  This is best done with the Pneumatic Brake Fluid Bleeder with Auto-Refill Kit. Connect a compressed air line to create a vacuum (using the venturi effect), and the fluid can be pulled in through the bleed valve and collected into the tank. It is important to not let the fluid level drop in the master cylinder during this process to prevent air from being re-introduced into the lines. The kit comes with an inverted bottle which will automatically fill the master cylinder as the level drops.

A/C compressor

A/C systems are a bit mysterious, but super easy to understand and repair once you know what the different things do.  At the center of it is the compressor. It compresses the refrigerant and sends it to a spray nozzle, and then collects the drainage back into the compressor. The compressor squeezes the refrigerant gas into a liquid. This releases a lot of latent heat, so this gas-to-liquid phase transition takes place in what is known as a condenser. It looks exactly like a radiator so that most of the heat can be dissipated. The spray nozzle is known as the expansion valve, and is mounted on the firewall, usually on the passenger side. As the liquid refrigerant is sprayed, it will evaporate and cool. Therefore, this process takes place in the evaporator core, which is inside the passenger compartment attached to a blower fan.

My compressor failed catastrophically one night. It totally seized up, and the drive belt burned up in a cloud of smoke.  Whenever the compressor seizes up, metal shavings will end up into the downstream refrigerant lines. This means most of them will be stuck in the condenser and in the expansion valve, so these components should be replaced as well. Without it, the new compressor is almost guaranteed to fail (ask me how I know). In order to remove the condenser, the radiator and its cooling fan has to be removed. There are actually two cooling fans. The fan at the front of the vehicle cools the condenser, and the rear fan cools the radiator. After removing the rear cooling fan, the coolant has to be drained from the radiator and its hoses disconnected (including the transmission fluid coolant lines). The condenser is sandwiched between the radiator and the front fan.

Removal of the backside fan
Radiator removed
Old condenser
New condenser
Compressor ports taped off to prevent debris

During installation, it is best to seal the compressor ports with some tape to prevent debris from falling in. Even small amounts of debris could be catastrophic for the rotating surfaces of the compressor. The new compressor usually comes with the correct amount of refrigerant oil, but the condenser may not.

The expansion valve is relatively easy to remove and replace. All o-ring seals should be replaced at this time as well.

Old expansion valve on the firewall
Expansion valve removed
New expansion valve installed

Then the system is evacuated with a vacuum pump. Because the hole in the expansion valve is small, the system has to be pumped out from both the high and the low pressure sides. Additionally, since the refrigerant lines in the condenser are also extremely small, a long pump duration is necessary to pull all air out of the system- at least about one hour. Unfortunately, the vacuum gauges that comes with standard A/C manifold systems do not have enough sensitivity to show small changes in vacuum levels. It is not easy to tell if the system has reached its lowest vacuum level, or if it is still pumping. A useful trick is to pay attention to the sound of the vacuum pump when the isolation valve is turned on and off. If the system has reached its lowest vacuum level, and there are no leaks, there should be no change in sound. Even a small change in sound will indicate that there is a small flow coming from the A/C system. It may be hard to believe, but this process is far more sensitive than relying on the pressure gauge.

The Rio takes 20 ounces of R-134a refrigerant. A standard bottle/can contains 12 ounces, so a little less than 2 bottles is needed. Walmart sells these for less than $5 each. The standard technique is to disconnect the vacuum line from the pump after the evacuation, connect the refrigerant bottle, and purge the line with refrigerant by letting air out through the small valve located at the manifold. I was not happy with this technique because after spending all that effort to perfectly evacuate the system, we can still end up introducing air or moisture. Here is a better way: Remove the valve at the manifold and connect a separate yellow refrigerant charging hose to that port. Connect the refrigerant bottle to the other end, but leave the bottle closed. When you evacuate the system, it will create a vacuum everywhere up to the refrigerant bottle. When evacuation is complete, close the valve at the vacuum pump, close the high-side (red) valve, and open (or pierce) the refrigerant bottle. This will start pulling refrigerant from the bottle and into the A/C system. When one bottle is empty, close the valve at the low side (blue) inlet to isolate the A/C system, connect the new bottle, and run the vacuum pump again to evaluate the hoses. Evacuation should happen fairly quickly because you are only evacuating the hoses. Then start filling from the second bottle.  Stop short of completely running the second bottle empty because you only need another 8 ounces from the second bottle. Alternatively, you can use a weighing scale, but I have not been able to get a reliable reading from the scale with the hose still attached to the bottle.