Rick's Free Auto Repair Advice

Brake fluid flush

Brake fluid flush

If the shop recommends a brake fluid flush, here’s what you should know

Why does the brake fluid need to be flushed?

Brake fluid doesn’t last forever. Once its anti-corrosive additives wear out, internal corrosion sets in. Plus, brake fluid is hygroscopic, meaning it has an affinity to absorb water. Water in the brake fluid can reduce braking power as it heats to the boiling point and creates steam. That can happen during long hard stops like mountain roads. Water and brake fluid isn’t compressible, but steam is, so it can dramatically reduce braking. So yes, brake fluid does need to be changed periodically.

How often should you flush brake fluid?

Ah, that’s the 64K question. Some carmakers recommend flushing the brake fluid every 2-yrs. or 24,000 miles, while other carmakers don’t show any brake fluid change recommendations. Why the discrepancy?

Here’s a partial explanation of why some carmakers don’t list a brake fluid flush in their maintenance guide

General Motors, Ford, and Chrysler don’t include brake fluid flush recommendations in their maintenance guides. General Motors believes the extra additives in their factory fill of a Delco Supreme 11 DOT 3 brake fluid makes it a lifetime fluid. Plus, GM uses a different type of rubber brake hose that reduces moisture infiltration, so GM doesn’t consider brake fluid contamination to be a problem.

However, many import car makers do recommend brake fluid changes for preventive maintenance at specific time/mileage intervals:

Acura: 36 months
Audi: 24 months
BMW: 24 months, or when indicated by Service Inspection Indicator
Honda: 36 months
Jaguar: 24 months all models except 2009 XF (36 months)
Land Rover: 36 months
Lexus: 36 months or 30,000 miles, whichever comes first
Mercedes-Benz: 24 months
MINI 24 months
Saab: 48 months (all models except 9-7X)
Smart: 24 months or 20,000 miles, whichever comes first
Subaru: 30 months or 30,000 miles (normal service) or 15 months/15,000 miles (severe service)
Suzuki: 24 months or 30,000 miles, whichever comes first (Forenza & Reno), 60 months or 60,000 miles (Grand Vitara and SX4)
Sprinter van 24 months
Volkswagen: 24 months (New Beetle, City Gold, City Jetta), 36 months (all other models except Routan)
Volvo: 24 months or 37,000 miles (Normal), or 12 months (severe service)

What should you do when the shop recommends a brake fluid flush?

First, keep your service records in the vehicle so you search for the receipt showing your last brake fluid flush. Don’t get scammed into changing brake fluid more often than required. Second, ask the shop why they’re recommending a brake fluid flush. Are they recommending it because they actually tested the fluid, or is their recommendation based on mileage? Hopefully, they’re not making the recommendation based on the appearance of the fluid, because the color is NOT an indicator of the condition.

Brake fluid color is NOT an indication of its condition

Color is NOT always a proper indicator of brake fluid condition. It’s true that fresh brake fluid has a honey-like color. But in some vehicles, fresh brake fluid can turn dark in a matter of just weeks after a complete flush. Don’t let a shop convince you to get a brake fluid flush based on the color of the fluid. Insist that they test it, or test it yourself with the items below.

There are ONLY three ways to know whether brake fluid is good or bad

First, the shop can use a special brake fluid test strip.  The technician dips the brake fluid test stripstrip in the brake fluid reservoir, waits for 30-secs. and compares the strip color to a chart on the container. The strip tests for the presence of copper. High copper content means that the anti-corrosive additives have deteriorated and the system is corroding from the inside out. If the copper reading is high, you should definitely get a brake fluid flush.

Second, the shop can test the brake fluid’s moisture content with a battery-operated brake fluid moisture testertester or a  refractometer. If the fluid’s moisture content exceeds 2%, you should agree to a brake fluid flush.

Third, the shop uses an electronic tool to test the fluid’s boiling point. The boiling point is also an indicator of the fluid’s moisture content.

Even if your maintenance manual recommends a periodic brake fluid flush based on time or mileage, it’s not a bad idea to have it tested before agreeing to the service. If the fluid hasn’t accumulated moisture and the copper content is low, you can extend the change intervals.

If you want to test the brake fluid condition yourself, buy a package of brake fluid test strips (see below) or a moisture tester. Then YOU can decide when the fluid needs to be changed

How much is a brake fluid flush?

The entire flushing procedure takes about 30-mins. to 45-mins. Based on a shop labor rate of $125/hour, a typical brake fluid should run between $75 and a maximum of $150 plus the cost of the brake fluid. Brake fluid cost is minimal, usually less than $10. So the overall cost depends on the shop’s hourly labor rate. If the shop wants to charge more than $150 for a brake fluid flush, find a different shop.

©, 2016 Rick Muscoplat



Posted on by Rick Muscoplat


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