The Fluid Flushes Your Car Needs

A multitude of fluids are required to keep your car running smoothly. Flushing those fluids can help extend the life of your car.

All of your vehicle’s fluids, along with the chemical additives in those fluids that protect parts from wear and tear, break down and decompose over time. Flushing fluids according to your vehicle manufacturer’s recommended service intervals is the easiest and least expensive way to extend the life of your vehicle and make driving safer and more pleasurable.

Here’s what you need to know about fluid flushes.

Fluid Change vs. Fluid Flush

Changing a fluid simply means draining the old fluid and refilling with new, fresh fluid. The most familiar example of this is changing your motor oil.

Flushing a fluid adds a step between draining the old fluid and refilling with new fluid. For a fluid flush, all the old fluid is thoroughly cleaned out. One example of this is filling the radiator with clean water after draining the coolant, letting the engine run, then draining the water before filling with new anti-freeze.

While any vehicle fluid can be changed, flushing is highly recommended for coolant, brake fluid and transmission fluid.

To determine is a fluid needs to be flushed, use a clean white paper towel to check if your fluids are simply dirty and need to be changed, or if they are tainted or contaminated. If the latter, they need to be flushed.


Coolant, a 50/50 mix of water and anti-freeze, circulates throughout the cooling system and engine to help maintain optimum engine operating temperature. Anti-freeze, and the added rust and corrosion inhibitors and lubricating properties that protect your engine, deteriorate over time. That causes engine overheating and poor heater output.

Anti-freeze comes in many colors. If your coolant is murky or has sludge in it, or if there is rust buildup in the radiator, under the radiator cap or the coolant reservoir tank, that’s a giveaway your coolant needs flushing.

A DIY coolant flush every three to five years or 30,000 miles removes rust and scale. That helps prevent coolant leaks and engine mechanical problems. A DIY flush will cost less than $30. Repair shops have special equipment that does the job in less than half the time and costs around $130.

Brake Fluid

Brake fluid is hygroscopic, which means it absorbs moisture from the air even in a tightly sealed system. Moisture contaminates the fluid, causing brake components to rust, deteriorate and eventually fail. Another indication of contaminated fluid is brake fade, which causes the brake pedal to travel further, greatly increasing stopping distances.

Check the brake fluid and the master cylinder reservoir cap gasket. The fluid should be a clear yellowish to light brown. If the fluid is dark, has black gritty “floaters,” or the master cylinder reservoir cap gasket is mushy, it’s time to have your repair shop flush and replace the brake fluid and reservoir cap gasket. Depending on the make and model, expect to pay $85 to $120.

Automatic Transmission Fluid (ATF)

ATF should be a light red/pinkish color. Dirty ATF (deep red to dark brown) loses its ability to properly lubricate internal parts and cannot disburse heat. That allows sludge and varnish buildup, resulting in slipping or harsh shifting and possible part failures.

Like an oil change, ATF can be drained and the filter replaced. This leaves three to six quarts of old ATF in the transmission. Or you can have your repair shop flush and refill the transmission with all new fluid. Expect to pay $75 to $150 for an ATF change or $125 to $300 for a complete flush.

Motor Oil

Regular oil and filter changes are the best way to protect your engine. If your motor oil is thick, black or chunky, or you’re experiencing trouble caused by heavy sludge buildup (smoke out of the tail pipe, oil leaks, oil light on, erratic oil pressure readings, the Check Engine light is on), then flushing the motor oil and engine crankcase is an option.

Flushing the motor oil is usually a last-ditch effort to rescue a poorly-maintained engine and best left to the pros. An engine flush at a repair shop can cost well over $100.

Power Steering Fluid (PSF)

Check your owner’s manual to determine if your vehicle’s manufacturer recommends flushing the PSF. If not, check PSF fluid level and color; it should be reddish or light brown.

Power steering fluid breaks down from heat, friction, pressure and component failures. If the fluid shows signs of contamination  — turning black from degrading rubber hoses, or developing a silvery sheen from internal parts slowly grinding away at each other — flush the system. Also flush if you notice your power steering is noisy, or it takes more effort to turn.

Although you can empty the reservoir using a turkey baster and refill it with new clean fluid (less than $20), leave this one to the pros. Expect to pay between $70 to $120.

Before you attempt any DIY fluid flush, it’s vital to check the owner’s manual and buy the correct fluids for your vehicle’s make, model and year. Don’t presume or guess. And always follow local guidelines to properly dispose of hazardous waste materials after flushing your vehicle’s fluids yourself.

Bob Lacivita
Bob Lacivita is an award-winning ASE and General Motors auto technician, educator and freelance writer who has written about DIY car repairs and vehicle maintenance topics. His work has been featured in The Family Handyman, a Reader's Digest book and Classic Bike Rider magazine. He has been a career and technical educator for 25 years teaching automotive technology, as well as writing state, federal and organizational foundation grants. He also helped design a unique curriculum delivery model that integrates rigorous, relevant academic standards seamlessly into career and technical education.