P/S Flush Idea?? Need assistance from the pros...

[stricular]

Hello all,

I have been looking into flushing my power steering for awhile, as preventive maintenance. The procedures call for the technician(in this case, me)to(in a nutshell):

disconnect the return hose from the p/s reservoir and block off its "nub"

jack up then start the car

add fluid to the reservoir while somebody turns the steering wheel...

until clean, fresh, bubble free fluid comes out the return hose

The procedure is the similar for a lot of cars, so this could probably work for many applications:

My idea is to simply put a tee valve(I'm thinking ball type) into the return hose, then all you would have to do is turn the valve to "drain," and let it pump out. No need to disconnect anything. Then turn the valve back to the "thru to the reservoir" position, bleed, and you're done.

What do you think, good idea, bad? It seems like it would make it really easy to do.

Where could one get such a valve? What materials should it be made of? What temps will it need to withstand?

Sorry for the noobish questions,but I am no engineer, just someone who likes to do things right the first time.

I intend to have it permanently installed if that makes any difference. The type of valve that seems like it would be ideal would be a tee valve with three barb fittings. It should be manually operated,to keep the cost down.

Any help would be greatly appreciated. Thanks.

 

[GregLocock]

So what happens when that valve gets turned to drain in an accident, or by mistake, or ...?

I don't know how often people replace their PAS fluid, but this seems to me to be adding several error states for little gain.

There is little redundancy in the steering system, that's why we overengineer the thing.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[patprimmer]

Like Greg said.

Also, I have never in my life replaced power steering fluid and I have never had a power steering failure (other than thrown belts). I have run up some quite high mileage on a few cars.

What you are looking for is a 3 way valve, but don't do it. It is not a benefit and it is not safe.

If you must ignore the advice of people who are experienced in car design and maintenance, at least turn it to the return to reservoir position then remove the handle and store it in a safe place.

Regards

eng-tips, by professional engineers for professional engineers
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[NormPeterson]

. . . normal vibration, Greg?

I wouldn't want to rely on friction alone to maintain the valve's position and the integrity of the fluid boundary, which starts adding complexity and expense (a positive locking mechanism for the valve and some sort of "catch tank" for the drain line come to mind).

Intentionally adding a flow restriction in the return line (the valve itself, including its connections) doesn't sound like a step in the right direction, at least as far as pressure in the return line upstream of the valve is concerned.

I understand that certain larger production cars that are open-tracked do tend to overheat the PAS fluid, and require that it be changed from time to time. But the potential consequences of any failure in such a system greatly outweigh the relatively small time saving benefit on the preventive maintenance end of things.


Norm

 

[stricular]

Thank you for your opinions.

The faults with my idea seem to be(in order of importance):

1. The risk of the valve opening to "drain" inadvertently

2. The restriction created by adding in the valve to a system designed to have a certain amount of "flow"

As far as #1, I had envisioned using a valve with perhaps a hole in the handle(or simply drilling one out), so that I could strap it parallel to the hose in the "through to the res" position using any number of methods. As far as a "positive locking mechanism," I hadn't quite worked that out; I was thinking a marine grade ziptie

AS far as #2, this is what has really convinced me this is a bad idea. It's a good thing I asked, because this is something that I should have realized, but it had not occurred to me. I guess I should review my laws of fluid motion(or whatever those are called). Thanks!

So how about this simply to use as a service tool? Surely you can't find fault with that, since similar barb fitting setups are used to flush out/change ATF in peoples' automatic transmissions every day. Right? It seems like it would be easier to change the fluid out this way, and changing it out is something I am determined to get done, and am likely to do again.