A4 1.8t Power Steering Rack Replacement and Flushing System

[THE MONSTER]

After finding that the Steering Rack needs replacing I decided to get a new one and fit it..it should arrive today..I want to flush the system before fitting the new Rack and make sure it is clean and free of contaminants..I was told by a guy that supplies and changes these Racks all the time for a living that you can use ordinary Audi Steering oil but it's expensive you can just as well use he say's ANY LHM fluid it's exactly the same and a lot cheaper and if you buy enough you can flush with that..can anyone point me in the right direction to flush the system without damage to the pump,don't really want to replace that as well..all comments appreciated...

 

[aragorn]

Just go to your factors and buy the correct stuff. Its not expensive.

Comma CHF11S is the stuff i baught.

Not really sure on flushing the system, bar starting the car with the return to the resovoir removed and let it pump some fluid out thru that first.

 

[THE MONSTER]

I found this Link to an A6 do you think this would be identical to an A4 system looks the same...turning off after 4 seconds or so and all that..

http://www.audipages.com/Tech_Articles/susp_whls_brake_steer/psflush.html

 

[Broken Byzan]

TBH you will lose so much fluid anyway during the change there will be little point actaully flushing it.

 

[THE MONSTER]

I know what you mean with that I know you will lose some but it's not an easy job doing the Rack I really want any contaminants out and fresh fluid in before the new Baby goes in...as any one seen the Link A6 looks same as A4..??..same principle..

 

[aragorn]

That A6 guide wont load for me, but most "flushing" guides are for when doing a fluid change, and as such they'll basically say start the car with the return line off to clear the pipes out.

In your case, if there WERE contaminants in the system, it would dump all of them THRU the new rack before reaching the return line.

What i'd do is this:

Remove the old rack, and drain the old fluid out.
Block up the pipe from the reservoir to rack (to enable you to refill the reservoir), put the Pump-to-rack pipe into a catch tray and put some new fluid in the reservoir.
Unplug the engine ecu, and spin the engine over on the starter until its drawn MOST of the fluid thru and dumped it out the high pressure line, (it wont take very long, 2-3seconds max i'd guess)

Then fit everything back together.

 

[THE MONSTER]

Basically what they are saying with the A6 car is undo the Return and put it in a bucket undo the supply and put a golf tee in to stop fluid coming out when you top up..this is done with the OLD RACK in the car before you put the new one in...then start the car and count up to 4 seconds stop the engine and empty the bucket if you have to that the return is going into..then top up fluid and repeat the process start engine count to 4 seconds and you will see clear fluid now coming out...that really is it..and if you wanted to be even more fussy you could repeat it when the new Rack was on..job done...

 

[aragorn]

You cant undo both the supply and return....

My method will use less fluid and achieve the same thing....

 

[THE MONSTER]

How much fluid would you need to get to do it all including Flush..

 

[aragorn]

A couple litres?

Its not a very big system.

Maybe buy 3 and return the 3rd one if you dont use it?

 

[Matt82]

ive flushed pas systems in the past by removing the hose going from the res to the pump, having the front wheels off the ground and have the wheels steered from left to right, it pushes all the fluid out the system

do the same (but with everything connected) to fill and bleed it

 

[phoenixv6quattro]

Flushed mine a few weeks back, as the old owner used the wrong stuff!! He filled it with that slick 50 boll*x. I know because there was an empty bottle in the boot. My system, on a 2.8, took just under 1 litre when lock to locked and bled etc. Thought it was too little so I phoned Slough audi and they confirmed it. 0.95 ltrs. I flushed it exactly how Matt82 described.

 

[aragorn]

Surely if you use matts method the pipes will still be full of the wrong stuff?

Letting the pump push the fluid thru the rack and out into a container seems a better way to me.

 

[phoenixv6quattro]

Just dissconected the bottom pipe which comes off the cooler, took the lid off the resevoir, jacked both front wheels up and with the engine off, full locked from left to right 20-30 times. Pushed all the fluid out. Wasnt a drop left in the system.

 

[aragorn]

how do you know the rack itself, the pump, the lines to and from the pump didnt all still have fluid in them?

 

[phoenixv6quattro]

Because i caught the fluid in my other halfs measuring jug(she would kill me if she found out!!!!) and all the fluid that came out measured just under a litre. Just like Audi confirmed. So I know for certain, it ALL came out, warts and all!!! Lol!!

 

[aragorn]

Fair dos!