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P/S fluid


Dave in Texas

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Has ATF ever been the recommended fluid for use in any GM vehicles? My old P/S pump was a groaner, so I bought a replacement. The replacement pump had ATF in it, so I'm thinking it was returned. The replacement pump is also a groaner and I bet the ATF did something to the innards of the replacement pump. This particular P/S pump was used on many '85-'91 GM vehicles. There are some manufacturers that recommend ATF in the P/S system, but I don't think GM has ever been one....Yes/No? I've only used GM brand P/S fluid in the 95k pump and installed it in the new(groaner)pump which will be returned later today. It's been awhile since I've dealt with a P/S pump: should a replacement pump have any residule fluid in it at all? Shouldn't it should be dry inside?

GM Reman 4.1 engine Dec '08

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ATF fluid is sometimes used to flush power steering pumps, and I'm not surprised that it is used to keep them sealed from air during shipping. As far as power steering fluid recommendations, there will be an SAE grade on the filler cap and in the owner's manual, and that is all that should be required.

If you have persistent groaning, perhaps you have an air leak in the return line? The first place I would check is the return line fitting right on the pump.

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If you have persistent groaning, perhaps you have an air leak in the return line? The first place I would check is the return line fitting right on the pump.

**************************

If there was an air leak in the return at the pump, wouldn't that be leaking fluid? No leaks present.....

GM Reman 4.1 engine Dec '08

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ATF will not hurt the power steering, BUT most power steering since the mid 70's or so,

was designed to use "power steering fluid". ATF was also was designed with certain coefficency

of friction values in mind; to lubricate and allow the friction disks to either slip or grab,

depending on the pressure exerted on the disks. ATF has seal swelling additives which

were be useful in the past, may actually shorten the life of the newer seals; by over

softening them.

Power Steering Fluid is basically just a hydraulic oil designed to work under certain temperature,

and pumping conditions. It also has additives to help prevent corrosion, and frothing inhibitors.

In short, it is best to follow the manufactures recommendations on fluid types to use.

First, be sure that the fluid reservoir is filled to the correct height. A level too low will allow air to

be drawn in with the fluid and cause the unit to "groan". Do not overfill, as the fluid gets hot and

it needs room for expansion.

Often the "groaning" is caused by stiff steering and/or suspension joints.

Lube ALL of the suspension joints, upper and lower ball joints, and steering connections.

Making sure that these items move freely, will lessen the hydraulic pressure required for turning.

Check your tire pressure, normally 30 PSI is fine.

A loose/leaking return line will not cause air to enter the system. It will however cause a drippy mess.

-George

Drive'em like you own 'em. - ....................04 DTS............................

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If you have persistent groaning, perhaps you have an air leak in the return line? The first place I would check is the return line fitting right on the pump.

**************************

If there was an air leak in the return at the pump, wouldn't that be leaking fluid? No leaks present.....

Not necessarily.

I have seen many such leaks on the suction side of a hydraulic system. There is little or no evidence of a leak on the offending hose or fitting. But the leak is small enough where it will not leak fluid at rest, but will allow air to be drawn into the system when operating. A clue would be air entrained in the oil. A severe leak would cause "foaming" of the fluid. A minor leak would cause the fluid to appear milky when running and clear after sitting overnight. The "milky" look would be due to microscopic air bubbles entrained in the fluid. Not to be confused with water contaminated fluids which usually won't clear up overnight.

As for your question about fluid in a replacement pump, Yes, there should be some preservative oil present. One would hope that it would be clear oil and not ATF. I know that ATF has been used as replacement fluid in power steering systems by some people for years. However, it is not the proper fluid for these systems.

I would suspect that you are correct in thinking that the replacement pump was a returned item.

You may want to consider replacing both the return and pressure hoses when you change out your pump. Hoses tend to deteriorate over the years and frequently the inner portion of the hose begins to detach and partially block flow. This could very well be the source of your groan noise.

Additionally some Cadillacs had a filter in the power steering line. This was located low on the right front side in my 94 SLS. It was in front of the wheel well and looked just like an inline fuel filter. I would change that filter, if present, along with the hoses & pump. The filter is not expensive, but it is not normally carried by parts stores and dealerships. I would resist using a "look-alike" fuel filter and get the proper filter from GM.

Replacing the pump, lines and filter (IF EQUIPPED), should solve your groaning noise problem.

Britt

Britt
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The PS fluid you would get at any GM parts counter is basically mineral oil with a long list of anti-foaming and anti-corrosion agents.

In the aftermarket, Valvoline SYNPOWER is the only PS fluid I am aware of that meets the GM specs.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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I've replaced both lines(no fun!). My '87 doesn't have a filter. I keep my car maintained properly, so there are no dry-joints/fittings. I've got a new adapter on the pump/resevoir with new o-rings. The return fit in solid, so I don't think it's an air-leak, but..... I'll take the replacement pump off and get another under the Lifetime warranty. Put everything back together, AGAIN, and see what it sounds like. (a neighbor gave me 5qts of GM P/S fluid sometime ago....I figured that to be a lifetime supply....maybe not!)

GM Reman 4.1 engine Dec '08

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just an FYI here. my 2k dodge truck came with PS fluid. the latest service bulletin says to only top it off with that type fluid. you can however do a full flush and use ATF4 which is synthetic. its says of course that the owners manual will say to use PS fluid to top off the system but it will perform better with a full flush and adding AFT4. i was getting an occasional whine in the dodge and decided to do a full flush and have aft4 now and it is quiet. makes me wonder if doing a flush and fill with syn fluid in the caddy would quiet down a noisy pump? also, what is the difference between old dodge PS fluid and new ATF4? is GM fluid similar in properties also?

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I emailed the company that supplied the pump and asked what they use to test their GM pumps. The reply was: they use ATF! I cycled the new replacement with GM P/S fluid and installed it. Done!

GM Reman 4.1 engine Dec '08

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