Brake System Compromised by Power Steering Fluid

sjackson.butte · Oct 18, 2018

I'd like to start off by saying, I know I'm an idiot for not checking the bottle first. I accidentally added power steering fluid to the master cylinder in my 97 Mazda B4000. I emptied what I could from the Master Cylinder as soon as I realized my mistake and topped it with brake fluid. That was before I ran the engine or went anywhere.

I fear there is still contaminants. I ran my truck for a week before problems started and have now lost use of my brakes. So now I'm wondering how much of my brake system needs to be replaced. All help is appreciated. Thank you.

ericbphoto · Oct 18, 2018

I'm not sure if that would have any effect on internal seals in the brake system. But if it were me, I would bleed the whole system with good clean brake fluid until you get good fluid out of each bleeder. Then see how everything acts.

If, while bleeding, you get a lot of black fluid coming out, I would suspect compromised seals. In that case, replace wheel cylinders, rebuild/replace master cylinder, rebuild/ replace abs valve then fill and bleed the system.

That's just my 2cents.

This message composed solely of recycled electrons. Go green!

Dirtman · Oct 18, 2018

What exactly were the problems you started experiencing and how have the brakes failed? Pedal to the floor?

Technically speaking power steering fluid (Im assuming you used typical mercon or dexcron atf based power steering fluid) is hydraulic fluid, it just doesn't have the heat resistance of brake fluid. Some old power steering systems used dot 3 brake fluid. That being said I cant see it destroying seals but it would boil too fast causing severe brake fade and eventually no brakes. However if all you did was top off the master cylinder and immediately suck it all out I cant see that even causing catastrophic issues. Did you actually bleed the system with the power steering fluid in the master cylinder reservoir? I.e. is pwer steering fluid all the way through the lines?

Why were you filling the master cylinder? This should only be done during bleeding. Were you servicing the brakes or did you just see the reservoir low and top it off?

Like eric said I'd start with a massive full brake bleed but more info on whats going on would help determine how bad the situation is.

adsm08 · Oct 18, 2018

I have seen this before. You need to replace EVERYTHING. And by EVERYTHING I mean the brake booster, and any friction material/hard parts that haven't been exposed to the brake fluid can stay.

PS fluid/Trans fluid will ruin the rubber seals on anything in the hydraulic system. And it is denser than brake fluid, so as soon as you put it in the system it started sinking.

Master cylinder, lines, calipers, wheel cylinders, hoses, it all needs to go.

Ranger850 · Oct 18, 2018

The power steering fluid made the rubber O rings in the brake system swell up and sealed the lines closed. You will have to get all fluids out of the whole system. Then replace any rubber parts. You will notice what has been effected, easily. Then refill fluids and bleed the system.

When the rubber makes contact with petroleum based product, it swells up. When I worked at a brake shop, we would always get customers from the Jiffy Lube down the road, saying they just left them and now there brakes don't work. Check the fluids and there was PS fluid in the reservoir. The fact that you got a while before it took effect means you left some in the lines.

Lime adsm08 said. It's all bad

adsm08 · Oct 18, 2018

Dirtman said:
Technically speaking power steering fluid (Im assuming you used typical mercon or dexcron atf based power steering fluid) is hydraulic fluid, it just doesn't have the heat resistance of brake fluid. Some old power steering systems used dot 3 brake fluid. That being said I cant see it destroying seals but it would boil too fast causing severe brake fade and eventually no brakes.

PS fluid is mineral oil. DOT3 is largely acetone. Mineral oil destroys the types of rubber used in sealing brake systems.

Dirtman · Oct 18, 2018

adsm08 said:
PS fluid is mineral oil. DOT3 is largely acetone. Mineral oil destroys the types of rubber used in sealing brake systems.

Never would have thought that.

adsm08 · Oct 18, 2018

Dirtman said:
Never would have thought that.

I've seen it happen. In about three days, or less, his wheel cylinders are going to blow out, if they didn't already.

At my first auto tech job my mentor got fired over one of these, and it wasn't even really his fault.

E250 work van, the company that owned it had one guy who did all their light maintenance. He accidentally put ATF in the brake reservoir, knew it was bad, but didn't know exactly what to do about it. They had it towed about three blocks to us, never touched the pedal. Tom thought we had gotten to it quick enough, since nobody touched the brake pedal, and pulled the brake res, bench bled the master, and flushed the rest of the system out with a few quarts of fresh fluid. He thought he had gotten it good enough, and had done the right thing by trying to fix the van without charging the customer an arm and a leg for a whole new brake system. About two days later it was back leaking from the wheel cylinders and calipers. It was then we determined the contamination was systemic because ATF is denser than brake fluid, and it had gotten through everything before it was even on our lot. Service manager said we'd eat the cost, but he fired the guy who worked on it first.

Brake System Compromised by Power Steering Fluid

sjackson.butte

New Member

ericbphoto

Overlander in development

Dirtman

Former Middleweight Moss Fighting Champion

adsm08

Senior Master Grease Monkey

Ranger850

Doesn't get Sarcasm . . .

adsm08

Senior Master Grease Monkey

Dirtman

Former Middleweight Moss Fighting Champion

adsm08

Senior Master Grease Monkey

Sponsored Ad

Sponsored Ad

Staff online

Members online

Today's birthdays

Member & Vendor Upgrades

Latest posts

Truck of The Month

Recently Featured

Follow TRS On Instagram

Latest Album Photos

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store

Sponsored Ad

Sponsored Ad

Sponsored Ad

Amazon Deals