Full PAS flush and change

Technical Area Steering & Suspension
1

Hello!

Recently decided to relive my youth and I’ve bought another MK3 1.8 as a bit of a project!

Among other things, one of the maintenance items I want to do is a full PAS flush and fluid change, and I can’t think of the best way to do this.

I’ve done the turkey baster method before… Its a pain, takes forever and in my experience doesn’t give the best results.

I was really wanting to try a method like this on the bimmer forums whereby the person drains the reservoir and then completely bypasses it with new fluid being sucked in from an external source as the old is pumped into a bucket…

Whats everyone’s thoughts on this, or indeed the best way to go about it?

Any detailed advice/step by step instructions would be appreciated… I’m very handy generally, but I’ve also fallen foul of embarking on a job in the past and quickly regretting it so I really want to be 100% clear before I crack on!

Thanks! :slight_smile:

2

I changed mine last year.
rather than draining and flushing, I emptied the tank with a syringe and refilled.
Started the engine, turned from lock to lock a number of times, then emptied the tank with the syringe and refilled again.

It was no fuss and no mess.
I worked on the basis that whilst I probably didn’t change the whole lot, i did probably change 75% of it.

Car seems fine.

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I did same at the weekend, dripping turkey baster made it messy, but the extension tube I used allowed me to get a lot out. What came out was black. Now the new stuff has been added it still seems black, so I plan to do it again twice more. That should have replaced over 95% of the old stuff.

4

This is it though… The turkey baster method does get a bit out, but even when you think you’ve got most of it out, it will still look black.

I really want to just completely purge the whole system and know it’s nice and clean.

I was thinking about disconnecting the return line that it’s in the grill in front of the radiator and doing it that way, that will mean that it will also empty the reservoir at the same time, at which point I can just keep topping up the reservoir and it’ll eventually run clean, I’m really surprised that nobody has ever done it this way before?

This is why I feel I’m missing something… it can’t be that hard and will surely give a better result, I’m just fearful of barking up the wrong tree!

5

A campaign that Mazda did on Mazda5 CR, involved flushing the PAS. This was done in a similar way to your idea ChrisMK3. We would take the inlet and outlet pipes off the reservoir then draw fluid from a reservoir of flushing fluid and discharge it into a waste bucket by running the engine. Once, I think, 5 litres of flushing fluid had been drawn through we’d turn the engine off, reconnect the pipes and re-fill as normal with new fluid. The key is never to let the system run dry and working in a meticulously clean environment. Allowing any dirt into the system will do more damage than you’re trying to prevent. Even without being messed with, the PAS system on the NC is extremely reliable from build.

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6

I think I’m going to have a go at it come the weekend…

I’ve just found this video which perfectly illustrates what I’m wanting to do… I think it’s quite straightforward!

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7

Seems like a nice, controlled way to do it :+1:t2:

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I agree!

Fingers crossed it doesn’t turn into a s*** show… I’ll have to politely ask the missus if she can turn the wheel while I top up… I’ll try to document it all!

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I had a look at the reservoir when removing the battery box on mine today. It’s surprisingly deep and an additional piece of tubing on the end of the turkey baster would help to get it empty. The suction outlet is situated a couple of inches above bottom of the tank. The return hose at the top would appear to be the safest and easiest place to disconnect and add the draining hose as it is the highest point in the system and would be obvious if a leak develops after replacing it post flushing. I would be interested to know what fluid you are using to refill as it appears Mazda M-III power steering fluid is a pretty old school Dexron 2 type ATF which can be improved upon regarding heat tolerance and longevity.

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Hmm, if you look at the pump, the high pressure side goes to the rack, and the low pressure side comes from the thick tube attached to the top of the reservoir. There is an internal tube collecting fluid at the right level inside the reservoir to minimise picking up any sediment.

The tube from the cooler, with the low-pressure clamps, goes to near the bottom of the reservoir, but above the sediment trap or filter. The extended turkey baster will be useful to clean out the sediment trap/filter if you can get it past the baffle (I assume this reservoir has one too.)

If you leave the top done up on the filler when pulling the cooler tube off (as in that video) then there will be less loss of fluid before you can push on the blanking cap and connect the drain tube. Of course the top needs to be off once you begin the draining operation.

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That makes more sense. So the bottom hose has to be removed or a flex connection on the cooler hose lower down

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I would think the easiest access is either end of the ‘return hose’ from the outlet pipe from the steering rack heading for the cooler. Otherwise it means taking out water tank or air filter box or battery.

Bottom cover is easy, and gives good access to rack etc.

Cap the cooler pipe, and plug the drain tube into the hose end. Also be prepared to drain down the cooler pipe at some time. Then as per that video.

Rather you than me unless it’s up a couple of feet on a lift!

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The problem I have with the whole concept is that draining the tank with a turkey baster to below the suction in order to remove most old fluid is likely to cause suction line to drain back to tank and cause an airlock which may not allow the manual non engine method to overcome after fresh fluid is introduced to the tank. Most tank on pump style systems would likely be less problematic.

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So, I did this earlier…

Messy as hell which I didn’t expect… I tried the method of connecting a clear hose to the low pressure line and turned the wheel back and forth but the fluid didn’t come out how I thought it might or at all… A very slow dribble at best.

I connected my pipework to the low pressure like that goes from the top of the reservoir to the pump, on the reservoir side.

After deducing that nothing significant was happening… I decided to start the engine very briefly… Lots of fluid came out with considerable pressure and gave the whole engine bay a good coating… *insert swear word here *.

So, I had a rethink…

I reattached the line to the reservoir and detached the other end that’s connected to the pump… I’ve now got my hose adapter connected to the end of the low pressure return line (imagine it being between the pipe and the pump), the theory being that when I turned the engine over the previous time, the outlet at the top of the reservoir is where the fluid came out at high pressure, so now when I turn it over again I’ve got my hose connected to it and directed into a drain pan…

Next problem: can’t have the pump sucking air…

So, I filled a large container with 3 litres of clean fluid and then connected another length of hose to the metal hose adapter on the PAS pump itself with the other end going into my make shift reservoir full of clean new fluid, the idea being that the old stuff comes out of one end and is replaced with the new fluid being drawn in via the pump…

Then VERY quickly, started the engine, and gave it 4 full locks in either direction before the clean fluid ran dry (it moves through the system very quickly)…

Engine off, all pipework reinstated a sit should be and then a test drive with plenty of corners, including some lock to lock turns in a car park… Got back home, dip tested the reservoir and the fluid is crystal clear (or red).

No funny noises, steering is noticeably lighter and smoother, no leaks.

I’ll call that a success!

If anyone wants anymore specific information on this method get in touch :slight_smile:

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15

Based on your experience ChrisMk3 I decided to go for the coward’s method when tackling this job today. Car is a mk3.75 2013 2 litre with 28000 miles. I emptied the steering fluid tank with a turkey baster and some tubing all the way to empty which was 460 ml of old fluid. I topped the tank up to the max level with fresh fluid and then ran the engine and turned steering from lock to lock which dropped the level slightly. Topped off again and checked I used 460 ml of new fluid. I had worried that emptying the tank fully may affect priming of the pump but it did not seem to affect anything. The old fluid at 7 years old appeared quite clean still. I may use the other half of the litre bottle of Atf to repeat the process in a few months.

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