Q: 2001 Corolla - PB, PS fluid change interval?

AFAIK, Toyota does not publish an official recommendation to change power steering fluid and brake fluid. I believe that the PS fluid in your car is automatic transmission fluid and does not need to be changed.

On the other hand, brake fluid can absorb water, and water can cause corrosion in internal brake parts. It is a good idea to flush brake the brake fluid every so often, I do it every other brake pad replacement, or about 80,000 miles, or 5 or 6 years.

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Terminology Alert: There is no special 'power brake fluid' - it's all regular brake fluid, the power is added by the vacuum booster, the big drum on the back of the master cylinder. The power booster has a big rubber and fabric power diaphragm and rubber seals inside, and there are rubber seals in the brake master cylinder, too.

There are no 'hard and fast' intervals for either, but generally you do the power steering and the brake fluid every 30K or 60K Major Service, or 'every few years' if the car is not driven much. (You're safe.) And there are good reasons why you want to do this, I'll list the big ones below.

The PS system doesn't generate much dirt, but it's a hydraulic system and you don't want what dirt has built up to stay in there forever. And like the transmission, you need the fresh fluid to replenish the lubricant and seal conditioner qualities, and keep it from oxidizing and developing varnish - hydraulic fluids do nasty things when they get old.

The brake fluid in most cars is hygroscopic, meaning it'll absorb any moisture out of the air whenever exposed. And the reservoir on the master cylinder has a vent to expose it every time you press the brake pedal... That water in solution gets down into the steel lines and the cast iron cylinders and calipers, and rots them out.

DOT-5 Silicone brake fluid will not absorb water, but few cars use it. If any water does get in it settles to the bottom in droplets with the same effects, but it's harder to flush out. And to confuse the issue even more, there's a mineral based DOT-5.1 brake fluid that will absorb water.

And as an extra added bonus >_< if the water concentration in the brake fluid gets high enough, and you stress the brakes on a long steep downhill stretch without downshifting (trailer towing adds even more stress) you can boil the brake fluid in the lines and have brake failure. Steam doesn't work real well in a hydraulic system...

(Want to experience what those "Runaway Truck Escape Lanes" with the big pits full of pea gravel are for? That's how you find out...)

You don't 'change' the brake fluid, you have them do a deep bleeding with lots of fresh fluid and pump all the old fluid out of the lines.

Another maintenance item that isn't on the list is changing belts and hoses, because rubber components deteriorate over time and with exposure to Ozone and contaminants.

Gates says to change the belts and hoses every six years (of course, they want to sell more belts and hoses) but 10 to 12 years is a more reasonable interval - or the first time you snap a belt or pop a hose sooner, you have the mechanic go through and change them all. Heater hoses and vacuum hoses, too.

Brake system wheel hoses too, they're rubber. And have the brake system wheel cylinders or calipers rebuilt with fresh rubber seals and cups at least every 10 years at the next brake job for that axle. And get a rebuilt master cylinder or power booster at the first hint of troubles, especially if they're past the 10-year mark.

Changing rubber items on a time or mileage interval (or when they start looking dry and showing cracking or checking) is always better than having an unplanned breakdown.

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I follow the same timeline for your brake fluid changes. I embellish it though with changing the power steering fluid at 100,000 miles and then every 50,000 afterwards. It may not be needed but it's cheap insurance in my mind.

It certainly doesn't hurt to change out the PS fluid for a little peace of mind!