I've seen it mentioned on here that at some point the power steering fluid and brake fluids should be flushed and filled with fresh fluid. Two questions:

1. At what mileage interval?
2. What is the benefit or what is being prevented by doing this?

Thanks,

 

I'm told brake fluid absorbs water over time. Water does not like to compress like brake fluid. I flushed mine at 100,000 miles when I changed my 3rd and 4th brake caliper.

That being said, VW changed the brake fluid in my Jetta at 30,000 miles during one of the free services that came with the car

I've also driven 30 year old vehicles with original fluids and still stopped fine.

Guardrail

 

I go every 30,000 - 40,000 miles.

 

As for the power steering/brake booster, I just siphon a quart out of the reservoir about every second or third oil change, and throw a fresh one in. Seems to keep it happy. First time I changed the brake fluid at 120k, it looked like weak coffee.

 

Thanks for the replies, looks like I ought to git'er done. Although this little voice in my head keeps saying "but it's not in the maintenance schedule in the owner's manual".

 

It's a good idea if you plan on holding onto the truck for a long time.
Like others said there's lots of 20 year old brake fluid runin around but PM is key to longevity.
I've never actually flushed either. I use the replacement method. Brakes, suck the master cyl down, refill, drive for a day or 2 repeat. Repeat this about 5 times and you effectively get out over 90% of the old oil. Takes extra fluid but you dont have to bleed anything.
Same with the power steering except you dont need to wait. Just pull out as much as you can, refill, start the engine for a min to cycle and mix the fluid and repeat several times.

 

Brake fluid will slowly absorb water. How slowly depends on where you live. Here in the high desert of CO, it's pretty slow. near the coast, it would be pretty quick. It's not really a function of miles, but time.

Water compresses the same as brake fluid. But if it gets hot in the caliper, it will turn to steam. Then you lose the brakes. But just as important, the water will cause corrosion of brake parts like caliper pistons and MC bores.

Power steering fluid is a lot like motor oil, in that it is designed for specific purpose by combining base oils with an additive package. Time and temperature will cause it to break down. But it's a pretty slow process. Also, like motor oil, it will collect water, and cause corrosion and wear.

 

They actually don't use PS fluid. The fluid that is used is ATF4+. Check your manual.

 

To me, it is worth while to change both. Neither is expensive, or difficult to change- and it might save you a pump, abs unit, or other expensive part.

 

I do the brake fluid religiously every two years, and try to do the ATF in the power steering system every 50k. Just checked my maintenance records and I am long overdue on the power steering. Thanks for the reminder.

 

OK, I did this yesterday. Emptied the P/S fluid three times and the first time the fluid in the reservoir looked like the fluid I poured in, really clean. That was not the case with the brake fluid, as already said above, it looked like weak coffee. I plan to change it again this evening and again on Tuesday and Wednesday. Hopefully that'll do it.

 

IMHO I'd hit each wheel with a vacuum bleeder until you get clear fluid. That way you will have all the old nasty stuff out.