Last updateWed, 20 Sep 2017 9am

On The Road

Fluids are the lifeblood of a vehicle

Q: I took my car in for a routine maintenance service and was told that my transmission and brake fluids need to be changed. This is the first time I have been told this, so I am just curious if it is really necessary.

A: Yes. Be happy that you have found a shop that checks those fluids for you. In fact, the fluids in your cooling system, power-steering system, automatic transmission and brake system are all products that go through temperature changes, have additive packages in them and are petroleum-based, just like your engine oil. Each fluid requires attention at regular intervals.

Your engine coolant turns acidic as it ages. When this happens, it damages the engine and cooling-system components. Coolant in good condition will be within the neutral range of the pH scale. A thorough service center will check coolant pH and recommend changes when needed before damage occurs.

Brake-system fluid collects moisture from the environment, along with worn metal from the brake system. These contaminants cause damage and premature wear to brake-system components, so the fluid-contaminate level should be checked at service intervals and changed as needed. Modern vehicles can boast brake-system components costing as much as $3,000 to replace, so changing the fluid when indicated can save a lot of money.

Power-steering-system fluid breaks down over a period of time and picks up wear particles from the system hoses. Worn-out fluid causes premature wear in the system’s pump and steering rack. Hose debris can block the system’s small passageways. Changing this fluid when needed can also save thousands of dollars in repair costs.

Automatic-transmission fluid works especially hard in doing its job of connecting the engine to the drivetrain. It both lubricates and serves as a coupling agent in the transmission. It goes through a wide range of temperature changes every time the vehicle is driven. When this fluid breaks down, the result is premature wear of components inside the transmission. Transmission replacement or rebuilding can cost $3,000 or more.

These fluids require monitoring and changing, and fluid replacement must be done in its entirety. What is known as a “drain and refill” only replaces, on average, approximately 20 percent of the old fluid, as the fluid is present throughout the vehicle systems, not just in the fluid receptacle. Special equipment is needed to ensure a 100 percent fluid change, so don’t hesitate to ask if your service center has invested in such equipment and can perform the service correctly.

Your vehicle’s fluids are its lifeblood. If you can’t remember the last time you had them checked, it is definitely time – especially as winter approaches.


Warren McCord is an ASE certified master technician who owns Dean’s Automotive in Mountain View. For more information, call 961-0302 or email McCord at This email address is being protected from spambots. You need JavaScript enabled to view it..

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