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changing power steering fluid


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#1 ranger952

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Posted 30 January 2004 - 11:33 PM

I am planning on changing my power steering fluid on my 98 silverado 1/2 ton tomm.
should I remove the fluid and put new in by disconnecting the lines and adding as the old fluid drains (while truck is running) or is sucking out the old fluid from the resevoir enough?
thanks for the help!!!

#2 JayMan

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Posted 31 January 2004 - 10:47 AM

I am planning on changing my power steering fluid on my 98 silverado 1/2 ton tomm.
should I remove the fluid and put new in by disconnecting the lines and adding as the old fluid drains (while truck is running) or is sucking out the old fluid from the resevoir enough?
thanks for the help!!!

The pump reservoir will only hold about 50% of the total system capacity. For something brand new, maybe you could get by with the "suck and add" method.

For something that old, I'd do a total flush.

Here is how I did my 2000 when it was one month old: siphoned out the reservoir, disconnected the return line to the pump and hooked up a plastic hose, which went into an empty 5 gal pail. Capped off the return port on the pump.

Filled up the reservoir. Jacked up and supported the front end so no weight was on the front wheels. That's important, you don't want any load at all on the pump while doing this procedure.

With an "assistant" in the cab, have your helper start the truck and very slowly turn the wheel lock-to-lock: do NOT hold against lock.

As the pump runs, the old skanky fluid will go out the tube into the 5 gal pail. Using a funnel, keep adding fresh fluid and keeping an eye on the color of the old fluid. Once you see new fluid coming out, you're done flushing. Tell the helper to shut off the motor.

Siphon out the pump again, remove the cap on the pump, and hook up the return line again. Fill the pump and with the fill cap still off and the truck still jacked up, have the helper start the motor and slowly do the lock-to-lock procedure to get the air out.

You'll have to be patient as this can take as long as 5-10 minutes. I like to stop the procedure every minute and let the fluid settle down. Once the procedure is done, put the fill cap back on and take the truck off the jack stands.

Surprisingly, at one month old, my truck power steer fluid was already quite dark. When I changed it, I used the regular dealer GM fluid and it stayed quite clean.

Last year, I flushed it again as I wanted to switch to the dealer "low temp" partial synthetic fluid. The fluid was still clean, and I've noticed at temps colder than -25 F, the power steering feels MUCH better when cold.

Note: you can also buy a special vacuum bleeder contraption that fits onto the top of the ps reservoir. When you're done flushing, you attach this gadget and give the vacuum pump a few pumps, it will draw all the air bubbles out. Not sure how much it costs.
Jerry

2000 GMC Sierra 4WD SLT Extended Cab, Sunset Gold Metallic, Sportside, Z71, 4.10 gears, G80 Gov-Lok, Z82 towing

#3 ranger952

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Posted 31 January 2004 - 01:16 PM

Exactly what I was looking for. Thanks Jerry!

#4 JayMan

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Posted 31 January 2004 - 06:03 PM

No problem.

Remember, it's a LOT of work. Don't say I didn't warn you.
Jerry

2000 GMC Sierra 4WD SLT Extended Cab, Sunset Gold Metallic, Sportside, Z71, 4.10 gears, G80 Gov-Lok, Z82 towing

#5 ranger952

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Posted 31 January 2004 - 09:34 PM

Well, it was a lot of work. Though putting in a pre cleaner might have helped. The problem isnt getting the fluid changed, it's getting the gunk out.
Anyway, it's done, works real good. Not too big of a problem, but JayMan's advice helped a lot. There is a lot of fluid that you cant get to by just draining the pump. You have to run it and it gets most of it.
Thanks again JayMan.

#6 99silveradoz71

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Posted 31 January 2004 - 11:23 PM

Capped off the return port on the pump.

Siphon out the pump again, remove the cap on the pump, and hook up the return line again. Fill the pump and with the fill cap still off and the truck still jacked up, have the helper start the motor and slowly do the lock-to-lock procedure to get the air out.

You'll have to be patient as this can take as long as 5-10 minutes. I like to stop the procedure every minute and let the fluid settle down. Once the procedure is done, put the fill cap back on and take the truck off the jack stands.

Just a few questions from the mechanically challenged. I have a Haynes manual and can see the pressure and return lines, so no problem there. You're disconnecting the return where it goes into the pump, not into the resevoir? Also, is there a cap there or is that something you have to buy or rig up? You mention syphoning out the pump again after new fluid has been run through. Is that the actual pump or via the resevoir? And then when removing the cap and reconnecting the return line, you add new fluid via the resevoir? and leave that cap off until the fluid settles to the fill line, then cap to get the air out? Thanks for any clarification. Yes, I'm a simpleton.
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#7 JayMan

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Posted 01 February 2004 - 12:04 AM

Capped off the return port on the pump.

Siphon out the pump again, remove the cap on the pump, and hook up the return line again. Fill the pump and with the fill cap still off and the truck still jacked up, have the helper start the motor and slowly do the lock-to-lock procedure to get the air out.

You'll have to be patient as this can take as long as 5-10 minutes. I like to stop the procedure every minute and let the fluid settle down. Once the procedure is done, put the fill cap back on and take the truck off the jack stands.

Just a few questions from the mechanically challenged. I have a Haynes manual and can see the pressure and return lines, so no problem there. You're disconnecting the return where it goes into the pump, not into the resevoir? Also, is there a cap there or is that something you have to buy or rig up? You mention syphoning out the pump again after new fluid has been run through. Is that the actual pump or via the resevoir? And then when removing the cap and reconnecting the return line, you add new fluid via the resevoir? and leave that cap off until the fluid settles to the fill line, then cap to get the air out? Thanks for any clarification. Yes, I'm a simpleton.

I wasn't aware that Haynes even had a manual for the +1999 trucks. I have the "official" Helm shop manuals.

The reservoir is part of the pump. The pump should have two ports: the high pressure that provides assist to the steering box, and the low pressure which is the return fluid after it has passed through the external power steering cooler.

So, you undo the low pressure return hose, rig up about 4-5 feet of clear plastic tubing (I have rolls of the crap in my shop in different OD's), and stick the end into an empty pail. Why clear plastic tubing? So you can visually inspect the fluid as it gets pumped out. Once you see clear fluid, you're done.

To cap off the low pressure port so the pump wouldn't suck air, I used a rubber cap from a large assortment of vacuum line caps I have. You can pick them up at any auto parts store. They're mighty handy to have in a shop and I always find unusual uses for them; for example, I use them to cap brake bleeder screws that don't have factory caps so the bleeder screw won't corrode from the inside.

I had a bleeder screw snap off once, and that was enough.

When you're done you have to siphon the reservoir out again, since you have to hook up the low pressure return hose again. Otherwise you have a God Awful mess as most of the fluid gushes back out once you take that cap off.

Hey, I'm warning you, this is a MESSY job and a LOT of work!

So once the return line is on, top off the reservoir, but leave the cap off. With the front end still jacked up, have your "assistant" start the motor again, and very gently turn the wheel lock-to-lock but don't hold it against lock. This gentle lock-to-lock helps to purge the air from the ps pump.

In the above paragraph, all this time you're keeping an eye on fluid level inside the reservoir. If you let it dip too low, the pump will suck air and you're back to square one. Here's another tip I forgot to mention:

You can get those "on-off" valves for quart bottles at any parts store. I forget their name, but most of them have a yellow plastic body, and most have about 2 feet of clear plastic tubing with a cap on the end. The "on-off" valve has a screw in adaptor for "narrow" neck quart bottles and with that off you can hook it up to a "wide" neck like a Mobil 1 bottle.

With one hand you have a Maglite or another real bright flashlight aimed into the reservoir so you can see the fluid level. The other hand you have the fluid bottle and you have the plastic tube from that bottle in the reservoir: when the level gets low, you tilt the bottle up and more fluid goes into the reservoir.

You have to leave the fill cap off during this entire operation so you can bleed the air out. If the air is making the ps fluid get all foamy, shut the motor off and let it set 5-10 minutes to settle down. Hydraulic fluid will release air entrapment, but not instantly, and you'll need the break.

The dealer has a contraption, I think it's made by OTC, that uses a vacuum pump and an adapter to suck the air right out of the system. I haven't priced it, so have no idea how much it costs. I bet it isn't cheap though.

I'll say it again: a very MESSY job it's a LOT of WORK.
Jerry

2000 GMC Sierra 4WD SLT Extended Cab, Sunset Gold Metallic, Sportside, Z71, 4.10 gears, G80 Gov-Lok, Z82 towing

#8 JayMan

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Posted 01 February 2004 - 12:07 AM

Well, it was a lot of work. Though putting in a pre cleaner might have helped. The problem isnt getting the fluid changed, it's getting the gunk out.
Anyway, it's done, works real good. Not too big of a problem, but JayMan's advice helped a lot. There is a lot of fluid that you cant get to by just draining the pump. You have to run it and it gets most of it.
Thanks again JayMan.

You're welcome!

You have to be careful using any solvent with a hydraulic system, as it tends to attack the o-rings and you REALLY have problems. The flush is a pain in the a**, but it's old and time-tested.

If you thought THAT was messy, try the same "trick" with an automatic transmission flush.

I guarantee you will curse me and any potential future offspring and their pets.

:thumbs:
Jerry

2000 GMC Sierra 4WD SLT Extended Cab, Sunset Gold Metallic, Sportside, Z71, 4.10 gears, G80 Gov-Lok, Z82 towing

#9 jack1996

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Posted 01 February 2004 - 12:57 AM

Why are you guys changing the PS fluid? Is there a recommended time interval? a problem?

#10 JayMan

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Posted 01 February 2004 - 09:52 AM

Why are you guys changing the PS fluid? Is there a recommended time interval? a problem?

Well, like any hydraulic system, there are benefits to regular maintenance. There is no set time period, maybe once while new to get all the assembly trash out, then maybe every 3-4 years.

Otherwise, as the vanes inside the pump wear, all that metal circulates through the system, accelerating the wear. The recirculating ball system appears to last a long time under such treatment, but newer rack-n-pinion steering systems will experience problems.

With either system, all the trash will eventually cause check valves to stick, resulting in a noise or a loss of assist. Since the fluid will build up enough trash to act like a slurry, the pump wear increases as time goes on.

Some folks appear to get a million years out of a power steering system, some go bad within 5 years. Or at least folks put up with a stiff wheel, pump noise, etc. With rack-n-pinion, the most common ailment is "morning sickness:" o-rings have already been damaged by all the grit circulating around, and on cold startup the fluid leaks around the assist cylinder and you don't have assist.

Large commercial hydraulic systems use elaborate filters and sensors to avoid problems, and you're supposed to regularly service them. I suppose if one could rig up a filter of some sort on the low pressure side, you'd solve +90% of the problem right there. I have no idea where you'd find space to mount something like a filter head with a PH-8A or equivilant filter hanging from it.

Is it worth it? I dunno, it's your truck. If you lease or trade regularly I sure as heck wouldn't worry about it.

Though I still have my 1984 Ford F-150. I flush the ps system new, then every 2-3 years after. Still have the original ps pump, though I have replaced the hp hose a few times. Power assist like new. Those Ford pumps were crap and didn't last very long: ever hear a Ford in a parking lot giving off that moaning growwwwwlllllll from the pump??
Jerry

2000 GMC Sierra 4WD SLT Extended Cab, Sunset Gold Metallic, Sportside, Z71, 4.10 gears, G80 Gov-Lok, Z82 towing

#11 ranger952

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Posted 01 February 2004 - 01:20 PM

I was glad I changed it. The old fluid looked really bad. ALso, I had a groan from the pump on cold mornings. It was 10 degrees this am. No groan and the sterring seems to be better.
I use the philosophy if there is fluid somewhere on my truck, I change it! Was not that expensive. Synthetic power steering fluid isnt that much money wise, but it IS a mees like JayMan said.
BTW, I am getting the tranny fluid flushed and changed, but I am paying someone else to do that.
Also, yesterday, I also changed the diff fluid and transfer case fluid. Everything is ready for another year in CO. :-)
p.s. powerslot rotors and hawk pads come in this week. I just love this site!!!!!

#12 JayMan

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Posted 01 February 2004 - 04:46 PM

I was glad I changed it. The old fluid looked really bad. ALso, I had a groan from the pump on cold mornings. It was 10 degrees this am. No groan and the sterring seems to be better.
I use the philosophy if there is fluid somewhere on my truck, I change it! Was not that expensive. Synthetic power steering fluid isnt that much money wise, but it IS a mees like JayMan said.
BTW, I am getting the tranny fluid flushed and changed, but I am paying someone else to do that.
Also, yesterday, I also changed the diff fluid and transfer case fluid. Everything is ready for another year in CO. :-)
p.s. powerslot rotors and hawk pads come in this week. I just love this site!!!!!

Ah, a man after me own heart.

:thumbs:

Now if I could only find a woman with those attributes, I wouldn't be single anymore.

:lol:
Jerry

2000 GMC Sierra 4WD SLT Extended Cab, Sunset Gold Metallic, Sportside, Z71, 4.10 gears, G80 Gov-Lok, Z82 towing

#13 jack1996

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Posted 01 February 2004 - 05:54 PM

Jayman, Thanks. You answered my question perfectly. Makes sense, I guess I never thought to do it. But, this tread catch my eye becuase I have a 98 Tahoe and a 96 pick-up, The pickup takes much more energy to steer then the Tahoe. I get used to it but when I dirve the Tahoe, its a big difference! Would a fluid change be the problem here?

#14 JayMan

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Posted 01 February 2004 - 07:15 PM

Well, it wouldn't hurt.

If the pickup has been that way from new, then probably not. If this has been going on slowly over the years, then a flush to fresh fluid would be a step in the right direction.
Jerry

2000 GMC Sierra 4WD SLT Extended Cab, Sunset Gold Metallic, Sportside, Z71, 4.10 gears, G80 Gov-Lok, Z82 towing