How to Add Air Brake Antifreeze to Your Vehicle

Adding air brake antifreeze is an important maintenance task for vehicles with air brake systems, especially in colder climates. Air brake antifreeze helps prevent moisture in the system from freezing in cold temperatures, allowing the brakes to operate properly. This article will guide you through everything you need to know to safely add air brake antifreeze to your vehicle.

Here’s a quick step-by-step guide:

1. Depressurize the air brake system – Drain air tanks to 0 PSI by pumping brakes and opening drain valves.
2. Drain moisture – Open drain valves at the bottom of air tanks to drain condensed moisture.
3. Access tank fittings – Remove an air line fitting from the top of the primary air tank.
4. Add antifreeze – Use a syringe or funnel to add 2-4 oz of air brake antifreeze through the fitting.
5. Reseal system – Securely replace air line fittings, then repressurize system by starting vehicle.

Why Air Brake Antifreeze is Necessary

Air brake systems use compressed air to operate the brake mechanism. The compressed air carries moisture, which can freeze inside the system when temperatures drop below freezing. This frozen moisture can prevent valves from operating correctly or even block air lines completely. Air brake antifreeze contains glycols and alcohols which lower the freezing point of any moisture present, preventing it from turning into ice. This allows the air system to function normally, even in very cold weather.

If antifreeze is not added regularly, results can range from loss of braking power to complete brake failure. No vehicle owner wants to discover they have no brakes when they need them most. Using quality air brake antifreeze is cheap brake insurance compared to the potential consequences.

Safety Precautions

Adding anything to a vehicle’s air brake system requires care to avoid disrupting brake operation. Here are important safety steps to take:

  • Ensure the vehicle is securely parked with the parking brake engaged before beginning.
  • Wear proper eye protection to guard against spurts of air or antifreeze.
  • Depressurize the entire air system before attempting to add anything to the tanks or lines.
  • Carefully clean up any spilled antifreeze to prevent slip hazards.

What You’ll Need

Gather the following items before beginning:

  • Air brake antifreeze (propylene glycol based)
  • Plastic syringe, funnel, or squeeze bottle to add antifreeze
  • Container to capture drained moisture
  • Rag for cleaning fittings
  • Wrench to remove tank fittings
  • Eye protection

Do not use ethylene glycol antifreeze. It can cause rubber seals and gaskets in the air system to deteriorate over time. The specific formulation of air brake antifreeze avoids this problem.

Step-By-Step Guide

Follow these steps to properly add air brake antifreeze to your vehicle:

Depressurize Air Tanks

The air tanks must be completely depressurized before attempting to add anything. There can be over 100 PSI of air pressure even when the system is off.

  1. Turn off the vehicle ignition switch and let the engine cool if recently run.
  2. Pump brake pedal 25-30 times to drain tanks.
  3. Listen for air leaks, continuing to pump pedal if needed to relieve all pressure.
  4. Check gauge readings at air dryer and tanks to verify 0 PSI before proceeding.
Air Dryer0 PSI
Primary Air Tank0 PSI
Secondary Air Tank0 PSI

Any remaining pressure could cause antifreeze to spray dangerously when fittings are removed.

Drain Moisture from Tanks

With the tanks depressurized, trapped moisture can now be drained out.

  1. Place a container under the drain valve on bottom of primary air tank.
  2. Slowly open drain valve using a wrench, allowing moisture to drain out.
  3. Close drain when antifreeze-colored liquid starts flowing.
  4. Wipe bottom of valve with a rag to clean fittings.
  5. Repeat moisture draining process for secondary air tank.

Add Air Brake Antifreeze

With moisture removed, tanks are ready for adding antifreeze.

  1. Remove an air line fitting using a wrench. Choose an easy access location at the top of primary tank.
  2. Attach plastic syringe, funnel or squeeze bottle to tank opening.
  3. Slowly add 2-4 ounces of air brake antifreeze, allowing it to flow down into tank.
  4. When finished, reinstall air line fitting securely.
  5. Repeat steps 1-4 to add antifreeze to secondary air tank.

Only air brake antifreeze should ever be added through air tank fittings, to avoid contamination and potential brake failure.

Repressurize System

With antifreeze treatment complete, the air system can be repressurized.

  1. Start engine and allow air compressor to run. Check that system pressure builds normally.
  2. Look and listen for any air leaks around fittings as pressure increases.
  3. Verify brake operation by pumping pedal repeatedly when tanks reach pressure.
  4. Check gauge readings again to ensure normal operating pressure is reached.

The vehicle is now ready for safe operation, with air brake antifreeze protecting against freezing temperatures.

Frequency of Adding Antifreeze

In very cold climates, air brake antifreeze may need to be added fairly often:

  • For daily use vehicles, check/add antifreeze every 1-2 months.
  • Even for intermittent use vehicles, antifreeze should be checked before winter.

Watch for signs of moisture contamination like valves becoming sluggish and air leaks increasing. This likely means it’s time to drain tanks and add fresh antifreeze. If problems persist, there could be an air leak allowing excess moisture to enter system.


Where do I purchase air brake antifreeze?

Air brake antifreeze is sold at commercial truck stops, auto parts stores, and online retailers. Major brands include Peak, Prestone, Shell, and Tri-Flow. The formulation approved for air brake systems will be stated clearly on packaging.

How do I dispose of drained moisture safely?

The moisture drained from air tanks may contain small amounts of diesel exhaust particulates and heavy metal contamination. Check regional hazardous waste disposal guidelines on whether it requires special handling. Typically it can be drained safely to ground unless drainage area flows directly to streams or storm drains.

Can I use windshield washer antifreeze?

No, windshield washer fluids use methanol and additives specifically for that system. Only antifreeze designed for air brake systems should ever be introduced into those lines. The wrong antifreeze could damage system components.

Correctly using quality air brake antifreeze protects against frozen air lines and valves in cold weather operation. Following the procedures outlined here provides affordable cold weather insurance for your vehicle’s critical braking system. Driving without sufficient antifreeze leaves you needlessly vulnerable to brake failure accidents. Stay safe this winter and keep your air brake antifreeze level topped off.

Similar Posts