Power Steering Flush Question......

[Big Blzn]

So, I did some searching and found a great thread about power steering problems and adding coolers and it answered 95% of my questions but left me with one unanswered. Here's the deal:

I am adding a cooler and while doing so come to find that it looks like the PO used ATF instead of the PS fluid so I need to flush, etc. My question is: I want to get a couple quarts of fluid and cycle a bunch of PS fluid through the system. I need to know the way the fluid cycles through the PS system. Does it go from the steering box through the cooler into the pump and then back to the box? Or, does it go from the PS pump throught the cooler and into the box and then back to the pump?

Also, when I flush the system with new fluid do I put the hose coming off the gear box into a new quart of fluid and a discharge hose on the return line off the pump to empty the old junk fluid. OR do I suck the new fluid up into the pump and discharge the old fluid from the hose off the box? Or, am I totally messed up on my thinking of how to flush the old fluid out and get some of the new fluid in. Hope I didn't confuse anyone on my question as I had to think hard about it while typing. Thanks.
Hoby

 

[Hogback Fabrication]

First, ATF works fine for power steering fluid. Synthetic PS fluid is better (its what I run) but ATF works fine for most.

You want the cooler on the low pressure side of the system.

The high pressure line has a threaded line at the pump side that goes to the steering box.

The low pressure line comes from the box to a hose clamp type connection at the pump. Basically you cut this line and plumb in your cooler here.

 

[Big Blzn]

Thanks for the reply Chris. I realized it was the low pressure side when I saw that whimpy hose clamp on the back of the pump so I guessed right then.

So, from your last statement the high pressure goes from the pump through the high pressure line to the box, right. If so, to flush my system I would put the hose from the pump into a bottle of fresh PS fluid to suck it up into the pump and the pump would send it thriugh the HP hose to the box and the old fluid would flow out of the low pressure port of the box into a bucket, right? Thanks.

Also, I have read on several threads here and an attachment from AGR that said to never use ATF as it lacks a lot of a certain additive that PS systems need to operate properly and not foam/bubble or something. Or is this just for hardcore and heavely used rigs?

 

[toomany]

So, from your last statement the high pressure goes from the pump through the high pressure line to the box, right. If so, to flush my system I would put the hose from the pump into a bottle of fresh PS fluid to suck it up into the pump and the pump would send it thriugh the HP hose to the box and the old fluid would flow out of the low pressure port of the box into a bucket, right? Thanks.quote]

Yes that would work.



FWIW: I use ATF in all my power steering systems. Out of the 6 vehicles that have a Saginaw style pump, I haven't had an issue with it.I can see how running ATF could cause some problems though. But for my rigs (the newest being an 88) the ATF is fine.

 

[Hogback Fabrication]

Thanks for the reply Chris. I realized it was the low pressure side when I saw that whimpy hose clamp on the back of the pump so I guessed right then.

So, from your last statement the high pressure goes from the pump through the high pressure line to the box, right. If so, to flush my system I would put the hose from the pump into a bottle of fresh PS fluid to suck it up into the pump and the pump would send it thriugh the HP hose to the box and the old fluid would flow out of the low pressure port of the box into a bucket, right? Thanks.

Also, I have read on several threads here and an attachment from AGR that said to never use ATF as it lacks a lot of a certain additive that PS systems need to operate properly and not foam/bubble or something. Or is this just for hardcore and heavely used rigs?

Power steering fluid comes from the pump at ~1200 psi to the steering box through the threaded high pressure line. It comes back through the return line (the one with the hose clamp) at less than 15 psi (probably more like 3-5).

ATF is the recommended fluid for most GM power steering pumps, at least the ones in our trucks. Its mentioned in a bunch of GM manuals, for sure ATF is generally the recommended fluid.

I run synthetic power steering fluid in my crossover/hydro assist setup (with extended reservoir and cooler) because it will reduce heat and stand up to higher temps better; really the whole system holds a few quarts so we're talking about the difference between a few quarts of ATF (say, $8) vs. 3 quarts of synthetic PS fluid (say, $20).


IMO, that extra tiny bit of money is worth the better fluid in my steering system. A burned up pump or steering box will cost you much more, even it they are warrantied. Not to mention losing a wheeling trip or driving time.

 

[Hogback Fabrication]

Also, if you in someway want to flush your PS system stay FAR, FAR away from the high pressure side of the system.


When the truck is running, any kind of pinhole leak in a hydraulic system can go straight through your skin and kill you. High PSI hydraulic systems are nothing to mess around with.

If you want to flush the PS system, deal with the low pressure side when the truck is not running.

 

[Big Blzn]

Awsome guys. Thanks for the heads up and great info. Much appreciated. Let's see tomorrow how I can fock up a seemingly simple task.

 

[dyeager535]

Which manuals recommend ATF? And I assume it's Dexron, not some other type?

I checked my '91 manual, says Power Steering fluid part #xxxx or equivalent, no mention of ATF.

IMO it seems like the ATF breaks down from the heat, as it always smells burnt coming out of the pump. Not to mention that later on the power steering coolers seemed to be standard (perhaps only based on GVWR, or towing package, since I see it on K5's) and if they were coming from the factory with power steering fluid, which apparently has a higher operating temp, it would seem possible that ATF isn't up to the heat, especially without a cooler.

I'm speculating of course, but I know my ATF smells like it came out of a hot transmission, and certainly looks burnt as well. I've never bothered to check the temp while running, that would probably answer the question. Over 250* or so is too much for ATF as I recall.

Not arguing, as its what I run, and have run (really only because I end up having ATF on hand, and not PS fluid lol), but I have no way of knowing if past failures were from the ATF, age, abuse, or all.

 

[Big Blzn]

Well, I got it all done and the tranny cooler installed as a PS cooler now. Didn't seem to take too long to bleed the system from air as I have heard on here. Maybe just luckly. BTW, Chris, you were right, my 72 shop manual does say ATF Dexron fluid to be used for steering. Iactually says something about using a specific GM fluid and if not I think gives another part Number. So, I just used a Valvoline ATF Merc/Dex something or other. Thanks for the help.

 

[cdoggwsu]

I just went down to the GM dealer and picked up a couple of quarts (i think it was 6 bucks a quart) of the genuine PS fluid. Why even bother with ATF? Is the cost savings really the primary motivator or was that just what GM recommended back before they made a specific PS fluid?

 

[dyeager535]

Cost is my primary reason...I bought a few cases of Dexron back in the day when it was on sale for like $.69/qt.

But it's not like you use a whole lot of PS fluid once the thing is up and running, as long as you aren't always replacing pumps.