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Discussion Starter · #1 ·
Have a clean, low mileage, (120000), Chevy 2500hd. I use it to tow my fifth wheel. I recently had the power steering lines leaking, so did a complete replacement including return lines. I flushed and filled with Royal Purple synthetic power steering fluid. Almost immediately after completing the job, my pump started making noise. First it was just a soft hum, then while turning, and/or braking it would growl. It gradually would make at least some noise all of the time. I must admit that I had not been replacing the fluid as I should have. I went ahead and replaced the pump. I again flushed and filled with Royal Purple. The pump runs quiet now, except under hard braking with the fifth wheel hooked up. There is no noise while steering. Everything is quiet when the truck is not loaded. Heat also may be an issue. The pump will stay quiet until the fluid gets hot. I have read about power steering coolers, but the truck is not equipped with one. I am interested in speculation as to my use of Royal Purple, and also the possibility of retro-fitting a power steering cooler. It seems GM has discontinued the OEM units for that vintage. I know Dorman makes some. Also what other issues might I be missing. Hydro-boost is original, as is the steering gear box. I'm running stock tires, and no lift kit. What do you think?
 

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Discussion Starter · #2 ·
Have a clean, low mileage, (120000), Chevy 2500hd. I use it to tow my fifth wheel. I recently had the power steering lines leaking, so did a complete replacement including return lines. I flushed and filled with Royal Purple synthetic power steering fluid. Almost immediately after completing the job, my pump started making noise. First it was just a soft hum, then while turning, and/or braking it would growl. It gradually would make at least some noise all of the time. I must admit that I had not been replacing the fluid as I should have. I went ahead and replaced the pump. I again flushed and filled with Royal Purple. The pump runs quiet now, except under hard braking with the fifth wheel hooked up. There is no noise while steering. Everything is quiet when the truck is not loaded. Heat also may be an issue. The pump will stay quiet until the fluid gets hot. I have read about power steering coolers, but the truck is not equipped with one. I am interested in speculation as to my use of Royal Purple, and also the possibility of retro-fitting a power steering cooler. It seems GM has discontinued the OEM units for that vintage. I know Dorman makes some. Also what other issues might I be missing. Hydro-boost is original, as is the steering gear box. I'm running stock tires, and no lift kit. What do you think?
I used an OEM AC Delco pump for the replacement.
 

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I installed an OEM cooler about 2 years ago. I wasn't convinced that it was needed, but it couldn't hurt. The reason I picked OEM is that it was designed to fit existing mounts in the truck. Also, I don't like Dorman for anything that I need to depend on to get me somewhere. I'm sure if you search these forums, you will find posts about the part number and installation.

AS for fluid, I don't run expensive fluid but I do a complete change every 2 or 3 years, same with brake fluid.
 

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My '06 came from the factory with a PS cooler. I wouldn't suspect anything wrong with the fluid your using as that stuff has had a good rep for many years now. I know a lot of people go for the lesser "lifetime warranty" part at the parts store, but trust me when I say that non of them are s good as the original AC Delco parts. That lifetime warranty doesn't mean squat if your having to change it out two or three times. Maybe hit up a local wrecking yard for a factory cooler. I'm sure someone out there has done that conversion.
 

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Found my trans cooler in my maintenance log. It's a

ACDelco 15821239​
I don't know if it will fit your truck without any mods, but likely any mods would be pretty easy.
 

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Which brand of pump did you install? Is it possible you have a restriction in one of the new lines?

I recently had new lines and new Napa pump installed and I had a loud hum while turning along with a slight shudder (fluid cavitation type) in the brakes. Thinking I got a bad pump, I exchanged it for another new Napa pump and have the same noise and same shudder. I’m starting to suspect the new Napa pumps for these trucks just aren’t up to standard. Or possibly that the mechanic who done the work the first time put a little too much bend in one of the lines.
 

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Discussion Starter · #7 ·
longball, I bought an OEM AC Delco from Rock Auto Parts. It's branded AC Delco. I also purchased OEM lines from RAP. Only change from line installation was to Royal Purple. I went with that because of recommendations on these pages. There are no lines to bend to the best of my knowledge. All of my lines came with the bends already made, and fit perfectly. I even have a new OEM return line from the hydro boost back to the pump that has the curves molded into it. I'm going to retro-fit an 8.1 GM 2500 HD Power steering system cooler to fit, (per recommendations on these pages), since the OEM for the Duramax has been discontinued according to my searches. I was able to find one on Amazon using part number 15293847. I like the idea of staying OEM as I am not interested in sitting on the side of the road with a 34 foot fifth wheel. I would like to know if anyone here has the OEM part number for the AC Delco power steering fluid used in the trucks with a hydro boost. I can't determine if there is a specific fluid recommended by GM for that system because of higher heat because of the brake booster.
 

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Get rid of the synthetic power steering fluid. Regular Dino power steering fluid is all you need. Last fluid replacement I did to mine I used just the inexpensive Mag 1 fluid from RAP. Seems to be working just fine.

I don’t recall any GMT800 series Duramax truck coming with a factory installed power steering cooler but those days in the dealer were long ago. Many add a cooler to their trucks and as I complete the rest of my steering system rebuild, I will add one to my truck as well.
 

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longball, I bought an OEM AC Delco from Rock Auto Parts. It's branded AC Delco. I also purchased OEM lines from RAP. Only change from line installation was to Royal Purple. I went with that because of recommendations on these pages. There are no lines to bend to the best of my knowledge. All of my lines came with the bends already made, and fit perfectly. I even have a new OEM return line from the hydro boost back to the pump that has the curves molded into it. I'm going to retro-fit an 8.1 GM 2500 HD Power steering system cooler to fit, (per recommendations on these pages), since the OEM for the Duramax has been discontinued according to my searches. I was able to find one on Amazon using part number 15293847. I like the idea of staying OEM as I am not interested in sitting on the side of the road with a 34 foot fifth wheel. I would like to know if anyone here has the OEM part number for the AC Delco power steering fluid used in the trucks with a hydro boost. I can't determine if there is a specific fluid recommended by GM for that system because of higher heat because of the brake booster.
I also bought the pre bent lines. Looking at a buddy’s truck though, his lines don’t look like mine. This line specifically. His original, factory line takes about a 30° angle straight to the pump without any of this mess. It appears as though this line flattens out in the middle of the forward most bend.



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Discussion Starter · #10 ·
I also bought the pre bent lines. Looking at a buddy’s truck though, his lines don’t look like mine. This line specifically. His original, factory line takes about a 30° angle straight to the pump without any of this mess. It appears as though this line flattens out in the middle of the forward most bend.



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The lines I received matched up to my originals perfectly. I will certainly look where you are pointing in the event I missed it.
I also bought the pre bent lines. Looking at a buddy’s truck though, his lines don’t look like mine. This line specifically. His original, factory line takes about a 30° angle straight to the pump without any of this mess. It appears as though this line flattens out in the middle of the forward most bend.



Sent from my iPhone using Tapatalk
Flattens out on the curve, and kinks at the 90. I'll have to check that one. Are those generic lines, or AC Delco?
 

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Discussion Starter · #11 ·
Get rid of the synthetic power steering fluid. Regular Dino power steering fluid is all you need. Last fluid replacement I did to mine I used just the inexpensive Mag 1 fluid from RAP. Seems to be working just fine.

I don’t recall any GMT800 series Duramax truck coming with a factory installed power steering cooler but those days in the dealer were long ago. Many add a cooler to their trucks and as I complete the rest of my steering system rebuild, I will add one to my truck as well.
Chevy Tech, did you try synthetics first, then replace them, or did you just stay with regular PSF? I'm ready to do just that, as feel that is where the problem is, just can't determine the best fluid to replace it with. Have been trying to get an OEM part number for the original fluid.
 

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Chevy Tech, did you try synthetics first, then replace them, or did you just stay with regular PSF? I'm ready to do just that, as feel that is where the problem is, just can't determine the best fluid to replace it with. Have been trying to get an OEM part number for the original fluid.
I’m not sure what you mean by “replace them”??

I’ve never used synthetic power steering fluid in a vehicle. I’ve heard of people using it when trying to get rid of weird power steering system noises but I’ve always used regular power steering fluid or the GM Cold Climate power steering fluid for vehicles run in really cold climates. It is just a slightly thinner viscosity fluid.
 

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Discussion Starter · #13 ·
I’m not sure what you mean by “replace them”??

I’ve never used synthetic power steering fluid in a vehicle. I’ve heard of people using it when trying to get rid of weird power steering system noises but I’ve always used regular power steering fluid or the GM Cold Climate power steering fluid for vehicles run in really cold climates. It is just a slightly thinner viscosity fluid.
Typo, replace "it", the synthetic fluid.
 

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Discussion Starter · #14 ·
I updated my Power Steering with a cooler. AC Delco for a 2500 HD with an 8.1 gasser. Part number 15295847. There was a part number available for the DMax, but everywhere I went it was discontinued. The cooler required some light bending on the steel lines to clear the intercooler. I made a steel connector to connect the return line from the steering gear box to the cooler line. Had the ends flared so it will not slip off. The other line that came on the cooler fit perfectly on the return port of the pump. I then replaced all of the Royal Purple synthetic with NAPA power steering fluid that is rated as a direct replacement for the AC Delco. I flushed a whole gallon through the system, but could not quite get the Royal Purple dye out of the fluid. Hopefully will not have any effect. Won't know if I was successful until I pull my fifth wheel into the hills in a couple of weeks. I'll let you know. System is quiet as can be right now, but haven't heated things up yet.
 

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Found my trans cooler in my maintenance log. It's a

ACDelco 15821239​
I don't know if it will fit your truck without any mods, but likely any mods would be pretty easy.
Bad post on my part. That was NOT the power steering cooler. Sorry for the misleading post.
 

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Discussion Starter · #16 ·
No problem, I was able to easily find the number on the GM parts sites. Actually bought the cooler on Amazon, (a little pricey), but I could get it in one day instead of a month which has been my recent experiences with the GM parts sites. Bolted exactly as if it were a stock replacement part.
 
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