Brake fluid vs. Power Steering fluid? - ZR-1 Net Registry Forums

Paul Workman · 04-28-2018

Being far from a chemical guru, I defer to someone here who is.

The situation: My son's friend accidentally put DOT 3 hydraulic fluid into the power steering reservoir (85 Caprice). Upon near immediate discovery, the steering was purged and the proper GM P/S fluid was reinstalled - the car wasn't driven more than 10 miles after the discovered mix-up occurred.

Question: What harm, if any, would result from inadvertently using DOT3 in place of (GM) power steering fluid have - especially in the very short-term? Hydraulic fluid is hydraulic fluid, yes?

WVZR-1 · 04-28-2018

I ain't no 'Guru' but I would expect very different seal composition for different fluid. Caught as quickly as you mention you could maybe be fine. As easy as a GM system with a box vs rack is to flush maybe a flush would be a 'to do'.

How long ago was it done? Days, weeks months.

How much was added to the system? A complete pint or a few ounces?

Paul Workman · 04-28-2018

Quote:

Originally Posted by WVZR-1

I ain't no 'Guru' but I would expect very different seal composition for different fluid. Caught as quickly as you mention you could maybe be fine. As easy as a GM system with a box vs rack is to flush maybe a flush would be a 'to do'.

How long ago was it done? Days, weeks months.

How much was added to the system? A complete pint or a few ounces?

Good questions - But, for the sake of discussion, let's assume it was just a few ounces (topping it off), and discovered almost immediately.

Here's the kicker... A "mechanic" (credentials unknown) recommended either getting rid of the car or doing a major P/S replacement. (The car was an 85 Caprice wagon in pristine condition - WELL maintained apparently. Know how rarely one sees one of these cars in any condition anymore - leave alone looking 'like new'?? So, when the car was sold to CAR MAX for $400...I think someone got ripped off big time!

A26B · 04-28-2018

"Dilution is the solution to pollution" I would recommend a few follow-up drain & flush cycles ASAP. Small price to pay to avoid problems.

Paul Workman · 05-09-2018

Quote:

Originally Posted by A26B

"Dilution is the solution to pollution" I would recommend a few follow-up drain & flush cycles ASAP. Small price to pay to avoid problems.

Noted with thanks, Jerry.

It's water under the bridge now. But, the topic remains "open", should a source of actual experience or expertise like to chime in!

mike100 · 05-09-2018

Saginaw steering pumps are pretty durable outside of particulate contamination. Brake fluid is more like a glycerine...I wonder if it dissolved in solution or if it is more like water and oil.

If it is lighter than oil, then you could siphon it off the top of the pump reservoir real easy.

George Maz · 05-09-2018

No worries, brake fluid is glycol based, steering fluid is petroleum based. Had you put PS fluid in the brake master ...that would've been a bigger seal issue.
I'd consider a follow up flush as a precaution, making sure to drain pump and rack by moving the steering wheel full rotations. Disconnect lines as necessary to facilitate this, engine off.

04-28-2018	#1
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,466	Brake fluid vs. Power Steering fluid? Being far from a chemical guru, I defer to someone here who is. The situation: My son's friend accidentally put DOT 3 hydraulic fluid into the power steering reservoir (85 Caprice). Upon near immediate discovery, the steering was purged and the proper GM P/S fluid was reinstalled - the car wasn't driven more than 10 miles after the discovered mix-up occurred. *Question: What harm, if any, would result from inadvertently using DOT3 in place of (GM) power steering fluid have - especially in the very short-term? Hydraulic fluid is hydraulic fluid, yes?*

04-28-2018	#2
WVZR-1 Join Date: Oct 2004 Posts: 1,884	Re: Brake fluid vs. Power Steering fluid? I ain't no 'Guru' but I would expect very different seal composition for different fluid. Caught as quickly as you mention you could maybe be fine. As easy as a GM system with a box vs rack is to flush maybe a flush would be a 'to do'. How long ago was it done? Days, weeks months. How much was added to the system? A complete pint or a few ounces?

04-28-2018	#4
A26B Join Date: Dec 2003 Location: Arcadia, OK Posts: 3,399	Re: Brake fluid vs. Power Steering fluid? "Dilution is the solution to pollution" I would recommend a few follow-up drain & flush cycles ASAP. Small price to pay to avoid problems. __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1*, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed.

05-09-2018	#6
mike100 Join Date: Feb 2011 Location: San Marcos CA Posts: 1,786	Re: Brake fluid vs. Power Steering fluid? Saginaw steering pumps are pretty durable outside of particulate contamination. Brake fluid is more like a glycerine...I wonder if it dissolved in solution or if it is more like water and oil. If it is lighter than oil, then you could siphon it off the top of the pump reservoir real easy.

05-09-2018	#7
George Maz Join Date: Dec 2014 Location: Long Island, NY Posts: 293	Re: Brake fluid vs. Power Steering fluid? No worries, brake fluid is glycol based, steering fluid is petroleum based. Had you put PS fluid in the brake master ...that would've been a bigger seal issue. I'd consider a follow up flush as a precaution, making sure to drain pump and rack by moving the steering wheel full rotations. Disconnect lines as necessary to facilitate this, engine off.