Think of the heat and pressure the rear system just handled, forgetting for a moment the fluid aspects...

 

The PS fluid boiled and expanded locking the brakes..............why only the rears; perhaps the boiling fluid also locked the bias valve.

One things for sure the PS fluid is now throughout the system causing untold damage to all the seals. If it was my car I'd never trust it again until all was rebuilt/replaced.

 

I understand. Is this everything? Brake pistons, brake lines, brake bias valve, brake master, clutch master, clutch slave, blue hose, brake flex hose, ABS...

I'm a little sick right now.

 

first of all, even though powersteering fluid is the wrong stuff, why did the rears lock up or drag so badly. oil is oil and yes, the wrong fluid doesnt have the right properties, what could have caused the dragging. was the fluid so thick, that it wasnt allowing the master cylinder to release the pads? why werent the fronts effected?? I think a good flush should do the trick as we are only talking rubber and seals in the system. I dont see any problem with pumping (not pressure pumping) the system at each caliper. if the system works, then you probably got it all out and shouldnt have any issues. I remember my motorcycle had dot 3 when it should have had dot 4. the fluid corroded all sorts of things and eventually the system was not working at all. pumped out the gross , ugly , now black fluid with chunks in it, and flushed it out with DOT 4 fluid. it was find afterwards and has been fine for 3 years now. the wrong fluid was in there a long time and caused issues. You had this wrong kind of oil in there for a short time so i dont think there would be any issues if you flush it out well.

my opinion only here!

MK

 

what tempurature does PS fluid boil? why only the rears. I doubt that is what happened. it probably is too thick of viscosity for the system and the fluid could not return to the reservoir. then, the brakes drag because the pads are not releasd from the caliper. the fronts might not have had such a big issue, why? because the valving of the fronts is designed to allow more fluid to move. the powersterring fluid was just too thick. I doubt the fluid could cause any seal or line isses at all. after all, its only been a short period of time.
You could have run water in the lines. it would boil and give you no pedal. however, it wouldnt expand and lock the brakes.

mk

 

Good idea. Email into Pentosin (Germany).

 

I'm with you. The only thing I noticed different about flush/bleeding the rears was the flush was a little slow.... drip drip drip. That was with the power bleeder at 10psi.

 

the system is a simple configuration of pistons, plungers, seals and rubber lines. If you look at the individual components, they are not going to be "eaten" away with powersteeing fluid. all the fluids are light oil based and have all sorts of additives and viscosity for their intended applications. BUT, they are still oils. a big flush and you will be fine. Im sure the boiling point of powersteeting fluid is well above brake fluid. the reason it was boiling over is that the fluid couldnt return and left the pads clamped down. you cooked the calipers and pads. I would be worried about their seals, but they can take a lot of abuse, which didnt wreck them. however, generally, the porsche brakes are more durable than most domestic models. If they work after a flush, they are probably ok.

mk

 

The bias causes this. what year do you have? anyway, now that you power bled them, use the pedal to bleed them now. thats the best way to finish off the bleed job. push the pedal down, close the valve, let the pedal back up, open the valve , repeat. (takes two people)
Ive ended up with air in the lines and a bad pedal by using the power bleeder only.

Looks like PS steering fluid has a flash point of 375 degrees. dont know what its boiling point is, but its probably like most light oils. It might be a lot lower than brake fluid, but i dont think it would cause any chemical damage.

http://www.cenex.com/%5CLinkedConten...NG%20FLUID.pdf

Both.. Brake fluid and Power Steering fluid are classed with Hydraulic fluids.
Although they will have *some* lubricating properties (for o-rings & seals), as well as differing properties, and additive packages depending upon their intended function, and specification.

"Major differences..
Power Steering fluid: high boiling point, low freezing point.
Brake Fluid: very low compressibility, high boiling point."

typical characteristics: Power Steering Fluid Container Size 32 Oz Amber Boiling Point 425 F Freezing Point -42 F Flash Point 450 F Pour Point -42 F Specific Gravity 0.862 @ 60 F Viscosity 56.0 cst SUS @ 100 F Viscosity Index 160 For Use With Most Common Brand Power Steering Systems For Autos/Light Duty Trucks

Looks like the boiling point is as good as most racing brake fluids!


mk

 

Just passed this on to my brother (ASE mechanic) who said he's seen it before... the car (96 Saab 9000 Aero) needed a full system replacement. The PS fluid ruined the master cylinder, and just about everything else in the system. The chemical properties of the PS fluid caused it to rapidly corrode the rubber brake lines and seals. $4k job on the Saab.

I'd replace everything... I'd say you'd be OK with a flush if you hadn't cooked the fluid already, but at this point, is your life worth that kind of gamble? Someone else's when you plow into their back end at a traffic light or a sudden stop on the highway?

 

One of the great things about these performance German machinery is their awesome stopping power.
Hate to compromise it any way.


Don't believe that I read someone suggests that oil was oil. [snicker]

 

the corrosion is not instant. It would take a long time for the corrosive effects, IF ANY to have an effect. I would be more worried about the heat the calipers saw. (as Heinrich said). if the flush works and the rears are ok, i wouldnt worry about it.

a "ASE" mechanic told my mom she needed new rear calipers and lines when she drove 4 miles with the ebrake on. it got the calipers hot, but there was no damage. I replaced the pads and flushed the fluid and all has been fine for 5 years. (by the way, she saved $1200) . rears are hardly that important anyway, most of the braking is on the fronts. one way to test the brakes , on the rear,is to take IR temp readings after a hard stop. temps should generally be about half the value in the rear.

mk

 

If someone put mobil 1 in my car, i would just drain it and replace it with amsoil and not worry too much about the residue.

mk

 

Ride shotgun with him after the flush!

Boiling fluids, in my admittedly limited experience, typically have pretty immediate and substantial effects on things with which they come into contact that are not ordinarily subjected to boiling fluids. (such as human skin).

BTW, nice pot shot at my bro, Mark. He's the most honest mechanic you'll ever meet. I can't really convince you of that just on my own say-so, given that I'm obviously biased (pardon the pun), but just check out the feedback he and his shop (Viking Automotive, Gaithersburg, MD) has received from Saab owners in the region. Speaks for itself, and he knows his stuff. Not saying you don't; just saying he's a pro and has dealt with this before.

 

Having experienced a failed brake master cylinder where I had to pump the brakes a few times in order to get them to work (double pump and pray) method. I became a firm believer of "you can only go as fast as you can stop". Even if you flush out the system and "all is good" you will never fully trust your brakes. Now if a seal starts to go bad you will need to do the entire system anyway. As much as it hurts now I would replace the system now and know it is working properly.
Thanks for being straight W/ this we have all overlooked things when working on our cars and it is hard to admit our mistakes but that is how we learn. It is when we take short cuts that we can realy get into trouble. This would be an area where it could realy be bad.