Once you notice something off with the air dryer of your semi-truck, the best thing to do is have it repaired or replaced.
That way, you can prevent further damage to your semi truck’s compressor and filtration system.
However, bringing your semi-truck to an automotive may not always be the most accessible and most convenient option. Thus, you may need to know how to bypass the air dryer of your semi as a preventive measure.
Here’s how you can bypass the air dryer of five popular semi-trucks.
A Short Answer on How to Bypass the Air Dryer on a Semi-truck:
To bypass the air dryer of your semi-truck, you must first take off the line to the compressor. That way, you can attach the air dryer piece on one side. Then, take the line from the air dryer to the wet tank to connect it with the piece attached to the compressor.
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What is an Air Dryer on a Semi-truck, and How Does it Work?
The air dryer is in the filtration system of your semi-truck, located between the compressor and the air brake reservoir.
Its primary function is to remove the water vapor and liquid from the air discharge of the compressor before it reaches the air brake system.
When the warm air enters the air compressor, moisture will appear on its walls. It will then drain down into a purge valve. It is where filtration happens to set apart the air particles circling on the compressor.
During that point, the governor will start to kick into gear. It will then signal the purge valve to open and release any contaminants. That way, the air brake system maintains being clean and long-lasting.
When Should the Air Dryer on a Semi be Bypassed?
To find out if you need to bypass the air dryer of your semi-truck, you will first notice if there is any sign of air leaks.
Air leaks are the most common signs of a bad air dryer. Thus, you need to check this regularly on your semi-truck.
Clogs can also cause problems in the filtration system, so it is another reason you bypass the air dryer to prevent further blocking of the purge valves. It can also wear out the seals.
You also need to observe any electrical issues on your vehicle, such as the compressor signs.
If it keeps changing, starting, or stopping, it indicates that the circuit breakers and the pressure valves are also having problems.
Do You Need an Air Dryer Bypass Kit?
An air dryer bypass kit or device compresses any vehicle’s air system.
You need to use an air dryer bypass kit to conduct a safer way to bypass the air system of your semi-truck.
It also includes all the essential tools you need to conduct the process, such as an intake port, output port, and a configured port connecting to the air governor.
Also, the air dryer bypass kit has a mounting plate for easier installation.
How to Bypass the Air Dryer on Volvo?
Bypassing the air dryer of semi-trucks is almost similar to any truck brand. However, some may have more specific procedures due to their build, model, and other parts.
For Volvo trucks, bypassing their air dryers is such an easy fix since the inlet line to the air dryer from the compressor, and the inlet line to the wet tank from the air dryer is easy to connect as long as it has the proper fitting.
Here’s how you can do it. First, take off the line to the compressor. Then, attach the air dryer piece to the airline.
Take out the line from the air dryer to the wet tank and connect it again using a quick connect tool.
How to Bypass Air Dryer on an International?
One of the common reasons you need to bypass the air dryer of an International truck is air leakage.
Thus, here’s what you should do to prevent it, as it also affects the overall performance of your semi-truck.
First, take the two lines attached to the air dryer and connect them using a half-inch pipe coupler.
That way, you can move the two lines away from the air dryer, prevent air build-up from the bottom, and prevent you from releasing the brakes.
The entire procedure is simple. However, if the problem persists, it is better to look for a replacement. Remember, bypassing is only a temporary fix.
How to Bypass Air Dryer on Freightliner Columbia?
Disconnect the airline connecting the air tank and the air compressor. You can find the air tank airline somewhere at the bottom, while the one for the compressor is on the top.
Once you disconnect both the airlines, connect them all to help you bypass the airdry system. It usually happens when a Freightliner Columbia experiences a leak in the air drive.
When you hear noises of possible air leaks, especially around 60 psi and up, you consider bypassing your semi-truck.
However, you may still need to bring your semi-truck to a mechanic to ensure everything will work fine for more prolonged usage.
How to Bypass Air Dryer on Peterbilt?
It is also more common for Peterbilt trucks to experience air dryer problems. Hence, bypassing the air dryer is the most convenient way to fix the issue immediately.
But before you do that, ensure you check the air intake plumbing to the compressor for possible blockage.
Then, bypass the air dryer for testing. You can do it similarly to the instructions written above. You only need to disconnect the two lines connected to the air dryer and combine these two altogether.
If you still experience air leakage on your Peterbilt, try to disconnect and plug the signal line into the air dryer. It is the small line from the air governor unloader port.
That way, you can ensure that the air does not flow back to the unloader valves.
How to Bypass the Air Dryer on Kenworth?
Using an air dryer bypass kit is more beneficial for your Kenworth truck. The steps are similar to the above procedure, but since you will use equipment, you must consider other necessary steps.
You may need to drain the entire air system by opening all the drain valves on all the reservoirs.
Ensure all residual pressure has been removed and the air dryer drained to 0 psi. Release the air supply line from the compressor to the inlet port.
Remove the air line located in the dryer discharge port and install a T fitting into the discharge port.
Reinstall the discharge line from the branches of the T-fitting. Then install the air supply line into the remaining T-fitting port.
Charge the system to cut out pressure and use liquid soap to test the T-fitting for air leaks. Your semi-truck may then be returned to temporary service.
How to Bypass AD-IS Air Dryer?
The AD-IS air dryer combines the air dryer, governor, purge reservoir, and several charging valve components in one module.
To bypass it, ensure all residual pressure has been removed, and the air dryer purge reservoir drained to 0 psi.
Then, release the air supply line from the compressor to the inlet port.
Remove the safety valve from the AD-IS air dryer and reservoir system body. Note that a short puff of trapped air may vent from the safety valve port as you remove the valve.
Install a T-fitting into the port. Using any adapters, reinstall the safety valve in one of the branches of the T-fitting. Then, install the air supply line into the remaining T-fitting port.
After testing the T-fitting for any air leakage, you should use a soap solution after charging to system cut-out pressure to return your semi-truck to temporary service.
Are There Any Pitfalls of Bypassing the Air Dryer on a Semi?
The downside of bypassing the air dryer on a semi-truck is that there is no guarantee of experiencing an issue again with the air dryer.
The primary function of an air dryer is to get rid of moisture in the air. When bypassing, you will need to drain the tanks. However, it won’t harm the moisture in the air inside.
Besides moisture, the air dryer also removes oil vapor which causes damage or swelling to air valve seals.
Thus, you may need to deal with a purge valve or air compressor problem now, and bypassing the air dryer will not make any changes. It is better to bring your semi-truck to a mechanic for a guaranteed fix.