Power steering fluid in brake fluid

Tiny
JOE K
  • MEMBER
  • 2002 VOLKSWAGEN JETTA
  • 4 CYL
  • TURBO
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
Accidentally poured a little Prestone full synthetic power steering fluid in the brake reservoir. Immediately siphoned it out and did a flush and refill of the brake system. After reading up on full synthetic hydraulic fluids I am thinking I might have dodged a bullet. Anybody have the facts on full synthetic fluids possible effects on the rubber components of the system?
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Tuesday, January 9th, 2018 AT 2:43 PM

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Tiny
CARADIODOC
  • EXPERT
This is unbelievable. For decades we have mused over how everything comes in pairs. We will not see a strut job for weeks, then get two in one day. No broken tire belts for months, then two in the same day. I just answered a question involving contaminated brake fluid well over two minutes ago!

You are one of the few people who understand the significance of brake fluid contaminated with a petroleum product. Synthetic fluids have to be compatible with the petroleum-based versions they could get mixed with, so it stands to reason this power steering fluid can not be mixed with brake fluid.

Since you sucked the contaminant out right away, I doubt any harm was done. Every year I did a demonstration for my students where I dropped a wheel cylinder lip seal into two beakers, then added one drop of power steering fluid to one of them. The contaminated seal grew about twenty percent and became soft and mushy, but it took a week for that to show up. Even if you ran the contaminant through the lines to the wheel cylinders and calipers, it would not have made contact long enough to cause a problem. It sounds like you had the power steering fluid removed before you flushed the system, so I would be surprised if you ran into a problem.
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Tuesday, January 9th, 2018 AT 3:54 PM
Tiny
JOE K
  • MEMBER
I hope the quick removal and flushing worked. Not resting easy yet. But I did read that synthetics are not oil based so that might be on plus side. Also, have a call in to the manufacturer to see if I can get any information. And doing my own experiment with some rubber pieces in mixture of brake fluid and two different power steering fluids. I will check in if find anything out.
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Tuesday, January 9th, 2018 AT 5:18 PM

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