[200q20v] Flushing hydraulic system

C1J1Miller at aol.com C1J1Miller at aol.com
Thu Sep 14 11:58:11 EDT 2000

In a message dated Thu, 14 Sep 2000 10:38:44 AM Eastern Daylight Time, "Rob Winchell" <rbw at swiftcorp.com> writes:

<< My car has "regular" Pentosin in it (7.1), not the 11S. I'd like to replace
it all with 11S, but am not sure the best way to go about it. I'm thinking
something like this:

* drain resevoir (and clean)
* drain hoses going to/from bomb (after de-pressurizing)
* drain hoses to/from pump
* fill everything with 11s
* run for a while
* drain everything again
* fill up again with 11s
* That's it

Do I need to go to this extent? It says not to mix them, so I'd like to get
out all the 7.1 I can.



I don't know how significant it is to fully flush the system, but you are right, Pentosin says don't mix.
The reservoir to bomb will take around 1 liter of fluid, as I recall; there may be another liter or less total in the lines, rack, and pump.

I'd elevate the front wheels of the car, relieve bomb pressure, disconnect the line at the bomb, and drain the system from there (low point).  Then I'd remove the line from the bottom of the reservoir, and turn the pump by hand a couple times to see if more fluid could be drained.  Then I'd move the steering from lock to lock to free up any more stored fluid.

How old are the lines?  Any leaks in the pump, or rack?  My rack appears to be weeping slightly, although I haven't cleaned it to see if that's the issue/source.
If the lines are old, and the rack leaks, wait until you change the rack, then replace with new.  I believe the rack fails as the inner seals go out of round; rebuilt ones apparently don't do this any more.  The fluid gets dark and contaminated with rubber from the various hoses, and most rack re-manufacturers require new lines/fluid to get their warrantee.

Anyone price new lines/hoses?

I think the main difference in 11S and 7 is the upper operating range; as summer is almost over, the old style fluid would likely be fine until next spring...

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