VAP

We are fortunate that we have one of the easiest PS systems to "power purge" or "power flush" on the planet. With nothing more than a container full of fresh fluid, or a clean reservoir and a separate empty container to catch the purge or flush fuids with everything else, except a screwdriver for hose clamp removal, is provided by the car simply using it's built-in PS pump. The PS pump on the B4/B5 is nothing more than a belt-driven centrifugal pump. Meaning that even if empty of all hydraulic oil and full of air it will purge any/all trapped air and self-prime with oil as long as it has a reservoir (Pentosin can, M1 bottle or other container) of oil that it can pull oil from and it couldn't care less which.

The return line that normally goes to the top of the reservoir can be inserted in any container besides the reservoir to catch the purge/flush liquid. Only thng to be careful of and this should be obvious but I'm going to say it anyway; "the purge/flush catch container MUST be at least as large as the total volume of purge/flush oil used and preferrably larger." Ignore/disregard this and it's gonna get messy! You're NEVER gonna pack 2qts of purge/flush oil in a 1qt container!! Simple as that!

It's also important that any/all purging/flushng be done when PS hydraulic system is HOT. And for all the same reasons engine, transmission and FD oils should be drained when hot. There's a LOT more particulate matter trapped/suspended in hot oil than cold oil.

On a OEM reservoir equipped car I would do this in the following manner.

1. Drive the car at least 20 "city" miles with lots of subtle left-to-right/right-to-left turning to heat the hydraulic oil (probably Pentosin 11S or 7) and pull into the garage or spot where you're going to do the purge/flush. Turn the car off and immediately pull the upper PS reservoir's return line off and insert it's end into a suitable catch container. Once done restart the car and let it idle until pump starts to groan/cavitate. Trust me, you'll have no problem hearing when the pump/reservoir have run dry. This is "power-purging" old oil out.

2. Once reservoir is empty remove it's pump feed line and take it inside to the kitchen sink and clean it out via dropping a few paper towels down inside, filling it with hot water and lots of liquid dishwashing detergent and shaking it by hand in all directions. Repeat as often as necessary till zero black deposits remain. The goal is to get all sedimentary silt, particulate matter and debris out of the reservoir. Run brushes/q-tips up into the inlet/outlet hose barbs. When squeaky-clean inside and out rinse with warm water and shake some more until no foam develops. Set it aside and allow to dry or place in a warm oven, no more than 150F until no signs of water are visible. If you have a compressor blow lots of compressed air thru it capping off various inlets/outlets with your fingers. It's crucial the reservoir be completely clean & dry before reinstalling. Do the same with the internal strainer using a toothbrush and dishwashng soap inside and out. And clean the reservoir cap as well. Some can do the cap with reservoir at the kitchen sink and some can't due to electrical connection in cap.

3. Reinstall reservoir and lower reservoir pump hose making sure its hose clamp is tight/leak-free. Insert upper reservoir return line back into your "catch container", again insuring you have sufficient volume in that container to catch "all" your flush oil without over-flowing. Fill reservoir to the top (but not so full it runs out the upper return line hose barb) with PS flush fluid of your choice. Start car and allow +/- 1qt ("at least" 2 reservoirs full) of flush oil to cycle through the system until reservoir again runs dry and pump cavitates. If on the outside chance your pump doesn't want to self-prime then cover return line hose barb on top of reservoir with one finger and blow into the reservoir while sealing the raised threaded cap neck around your lips (hey you just washed it remember). If this happens it's time to start shopping a new pump as it's internal vaned impeller is VERY worn if it's unable to self-prime without blowing into the lid neck. This is "power-flushing" using clean/new oil of the type you plan on using in your PS hydraulic system to flush all remaining old oil out of the hydraulic system.

4. Reinstall upper reservoir return line and clamp securely (if installing a Magnefine filter in the return line to reservoir now is the time to do it). Top up with PS fluid of your choice and install the reservoir cap. Go for another drive and take your PS fluid with you in case pump groans/cavitates while you're out on the test-drive. Check fluid level upon return. Recheck fluid level the next morning after car sits overnight and top-off if necessary. With the benefit of a power-purge/power-flush and an inlne magnetic/particle filter you'll be driving with a cleaner PS hydraulic system than your car had as driven off the dealer's lot with zero miles when brand new! And it's gonna get even cleaner as-you-drive!

You could also prime from your oil container in step #3 like the 11S tin can or M1's bottle but if you've cleaned your reservoir it's easier and less work using the reservoir.

If swapping from 11S to M1 or even a blend of the two fluids you should definately do the above procedure after a week of driving as there seems to be mounting evidence it is gonna find stuff to clean that's been hiding in these PS systems for 15 years or longer and release it into the circulatory system.

Now I'm outta here to practice what I've preached.

90QuattroKid

but i got a question, so you mean flush the system with old PS fluid? or just flush with any oil...like motor oil. or do they actually make "PS flush fluid". i only have 2 quarts of 11s and that stuff is expensive. just seems like flushing with the old fluid really wouldn't do much good?

VAP

old/dirty oil out of the system. "Power flushng" means pumping new/fresh oil into and out of the system which "flushes" all remaining/residual/old/dirty oil remaining in the hydraulic system components during "power purging" which gets fully flushed out during the "power flushing" cycle with fresh/new oil.

Power purge system of old oil first (step #1`). Power flush system with 1 full quart of the new oil you plan on using in the system long-term (step #3).

NEVER "flush" with dirty oil or you're right back to repeating step #1!!

"purge dirty/flush clean"

Far as I know there is no PS system purging/flushng product available OTC. And even if there were it would open a whole 'nother can of worms by not knowing compatibility between 11S, M1 and/or an 11S/M1 "blend."

90QuattroKid

so i'd have to buy extra pentosin 11s to purge....i can't afford that lol

dtompsett

You could always purge with M1, then fill with 11S. Since as Mance has found, the two mix well together.

Bernie

Or did you not have another person to cycle it for you while flushing?

VAP

so "if" there's residual fluid it's not very significant if even measurable.