Ever wondered if brake fluid can freeze in cold weather?
Well, it doesn’t usually turn solid, but it can thicken enough to affect braking performance.
Let’s dive in and explore the freezing point of different brake fluid types, warning signs to watch for, and some preventative measures.
This Article Contains:
- Can Brake Fluid Freeze in Cold Weather?
- 4 Warning Signs Your Brake Fluid Has Thickened
- 4 Factors Affecting the Freezing Point of Brake Fluid (+ What to Do)
- 3 Best Practices for Handling Thickened Brake Fluid
Can Brake Fluid Freeze in Cold Weather?
While brake fluid doesn’t typically freeze solid, it thickens and loses effectiveness at extremely low temperatures, depending on its type and moisture content.
Common brake fluids, such as DOT 3, DOT 4, and DOT 5.1, begin to thicken at temperatures below -40°F (-40°C). Meanwhile, DOT 5 (silicone-based) brake fluids remain fluid down to about – 55°F (-48°C), making them far more resistant to freezing.
However, once you open a brake fluid container, it gradually absorbs moisture from the air, which degrades the fluid and raises its freezing point.
To avoid moisture contamination and other issues, it’s best to have a mechanic flush and refill your brake fluid.
Next, let’s explore how you can tell when your brake fluid isn’t flowing properly.
4 Warning Signs Your Brake Fluid Has Thickened
Your brake fluid may have thickened if you notice any of these signs:
- Illuminated brake warning light: Moisture or ice in the brake system can trigger the brake warning light, signaling a problem with pressure or fluid flow.
- Stiff brake pedal: Thickened brake fluid makes it harder for pressure to move through the lines, causing a stiff brake pedal.
- Grinding noises or uneven braking: Frozen spots or air pockets caused by moisture can lead to uneven brake pressure, resulting in grinding noises or brake imbalance.
- Reduced braking power: Thickened fluid won’t move easily through the brake lines, causing a delayed braking response.
TIP: If you want to understand the impact of cold weather on brake fluid in detail, read our comprehensive guide on How Cold Weather Affects Brake Fluid.
So, why does brake fluid thicken in the first place?
4 Factors Affecting the Freezing Point of Brake Fluid (+ What to Do)
Here’s why brake fluid can thicken and what you can do about it:
1. Brake Fluid Type
Silicone-based fluids like DOT 5 are non-hygroscopic, meaning they don’t absorb moisture and are more resistant to freezing.
Meanwhile, glycol-based fluids, such as DOT 3, DOT 4, and DOT 5.1, absorb water over time, which can lead to internal corrosion in the brake lines.
What to do: Always use the fluid type recommended by your vehicle manufacturer. Moreover, to avoid damage, leave the brake fluid replacement to a professional mechanic.
2. Moisture Contamination
Because glycol-based fluids absorb water, even a small amount of moisture can drastically reduce their freezing resistance.
What to do: To remove absorbed moisture before it freezes, flush and replace your brake fluid every two to three years (or as your manufacturer recommends).
3. Brake Fluid Age and Condition
Old, degraded brake fluid loses its protective properties and becomes more prone to thickening.
What to do: Have a skilled mechanic flush and replace your brake fluid if it looks brown or cloudy.
4. Parking Spot
Parking outdoors in sub-zero temperatures exposes your brake fluid to extreme cold, increasing the risk of thickening.
What to do: Park in a garage or sheltered space. If that’s not an option, consider using an insulated car cover to retain warmth.
Now, let’s check out what you can do if your brake fluid has already thickened.
3 Best Practices for Handling Thickened Brake Fluid
Follow these tips to ensure your brake system operates safely in freezing conditions:
- Warm up the vehicle gradually: If your brakes feel sluggish in cold weather, let the car idle for a few minutes to gently raise system temperatures before driving.
- Inspect for leaks or moisture buildup: If the pedal remains stiff even after the car has warmed up, frozen moisture in the brake system may be restricting fluid flow. To identify moisture buildup, check for any leaks or damage near the master cylinder and brake lines.
- Schedule a fluid flush if symptoms persist: Thickened brake fluid may usually be contaminated with water. To prevent loss of braking performance, it’s best to have the system completely flushed and refilled.
Keep Your Brake Fluid Flowing Smoothly with AutoNation Mobile Service
Thickened brake fluid can affect your car’s stopping power and compromise your safety.
How can you ensure the fluid remains in top condition?
Reach out to AutoNation Mobile Service.
Our trained technicians will come to inspect, flush, and replace your brake fluid right from your driveway. We also back all our services with a 12-month, 12,000-mile warranty for peace of mind.
Book your appointment so we can keep your brakes responsive and your vehicle safe in any weather.