Brake, transmission, power steering system flushing

  • 120,500 MILES
Wife took her car to independent repair shop to have car checked over. They tell her she needs to flush the brake system ($151 cost), flush the transmission ($173 cost), and flush the power steering system ($115 cost). The car has not towed a trailer nor has it been operated in dusty conditions. Toyota claims the automatic transmission fluid should not have to be changed due to type of fluid. I can't find in car manual maintenance schedule where Toyota calls for a filter change or adjustment.
Are the above system flushings routine? Thanks!

Do you
have the same problem?
Monday, October 21st, 2013 AT 8:19 AM

1 Reply

All manufacturers recommend changing the brake fluid at regular intervals but hardly anyone actually does that. Brake fluid loves to absorb moisture from the air, including through the porous rubber hoses and the rubber bladder seal under the reservoir cap. That moisture leads to corroded metal parts and one type of brake fade. Brake fluid is good for over 400 degrees. It can easily reach 300 degrees from prolonged stop and go driving. The water in the brake fluid will boil and turn to a vapor which can be compressed. That results in a mushy brake pedal.

You can do an acceptable job yourself by opening the bleeder screws and allowing the brake fluid to dribble out slowly. Loosen the cap on the reservoir so vacuum doesn't build up. That will prevent the fluid from flowing freely. Be sure to keep adding new fluid. If you don't allow the reservoir to run dry, you won't get any air in the system. Also, note the level of the fluid before you start, and fill it to the same level when you're done. Never fill the fluid to the top unless you just replaced the front brake pads. To do that, you have to push the pistons back into the brake calipers to make room for the new, thicker pads. As the old ones wore down, the pistons moved out and fluid filled in behind them. That's the self-adjusting feature of all disc brakes. When you push the pistons back in, that pushes the fluid back up into the reservoir. If it was filled previously, the fluid will run out, make a mess, and eat way any paint it gets on. That's why mechanics never top off brake fluid during other routine services like oil changes.

Flushing the power steering system is not a normal maintenance item. That fluid is typically good for the life of the car. If the flush is done in an attempt to solve a problem, it won't. If metal parts are grinding apart, or rubber seals are leaking, either internally causing loss of power assist, or externally and leaking onto the ground, new fluid isn't going fix those mechanical problems. The only time I've ever heard of new fluid solving a problem was in the '90s some Dodge diesel trucks had poor power steering assist at idle in real cold weather because the engines idled too slowly. A special "cold weather" power steering fluid solved that.

You'll get different opinions on transmission fluid flushes. Some people believe in them for preventive maintenance. Others believe they can cause problems shortly after having that service because the aggressive detergents used just before the flush can tear the fiber material off the clutch plates. My preference is a fluid drain and refill, (no flush), with a new filter at 36,000 miles. That was the standard recommendation from most manufacturers for decades. I have an '88 Dodge Grand Caravan with 248,000 miles that has had that service done once in its lifetime at 84,000 miles only because the $3.50 side cover rusted out and I had to drain some fluid anyway, so I did the filter right away too. I regularly drag around a tandem axle enclosed trailer that's bigger than the van, and the fluid still shows no signs of being overheated. Unfortunately newer automatic transmissions from all manufacturers are not as tough or reliable as this one that is based on the old rear-wheel-drive models. I DID have a problem a few years ago with shift valves sticking due to varnish buildup. That happened after I hit wide-open-throttle for the first time in many years and the throttle valve moved to an area where it hadn't been getting pushed to. That allowed that varnish to build up. The late up-shifts and failure to down-shift resolved itself gradually over a couple of months of normal driving with no chemicals or other service needed.

Obviously I'm not suggesting you ignore your transmission fluid. What I'm doing is not neglect; it's abuse. I won't even tell you that it's been over ten years and 110,000 miles since I drained the engine oil. I don't abuse any of my other vehicles that way and I don't want you to either. I do that to show my students what some engines are capable of.

The prices you were quoted seem rather high too but I don't know what they were planning on doing. A transmission flush requires a lot of fluid to be pumped through the system, then discarded. Most systems require a detergent to be added first, then the mechanic drives the car a few miles to circulate it. A rubber seal conditioner is usually added to the new fluid. I'm not convinced any of that is going to prolong the life of the transmission but others will have differing opinions. If you have a problem now related to leaking internal seals or varnish buildup, the additives may help. If there's a mechanical problem, no chemical in a can will solve that. If you aren't having a problem now, my feeling is there is a chance one could develop shortly after a flush.
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Monday, October 21st, 2013 AT 2:24 PM

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