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Discussion Starter · #1 ·
Hey Folks,


A friend of mine has a 2013 LML 3500 4x4. Over the last 3 years, we've probably changed 9 to 12 power steering hoses on his truck. All pressure hoses. About 2/3 of the time it is the hose from the box to the hydroboost. The other 1/3 of the time it's from the booster to the box. In September 2021 he decided he'd had enough. We changed out the pump (suspected the pump and or pressure relief may be the culprit) and the brake booster, put 2 new lines on (all ACDELCO/GM stuff) and bled out as much of the old oil as we could and filled with new. Well, in February another line let go. It was replaced. Halfway through March, it failed again. This last week, he had two hydraulic hoses made that have a >5000psi working rating and a burst rating of >20,000psi. After installing the hoses and purging the system, the truck doesn't seem to want to steer unless over 1000rpm. The brakes are also... unimpressive. The steering system is primed with DEXRON-VI As it stands the truck is parked. Suspected the fluid might be a problem. But, ATF is an excellent hydraulic fluid and is no stranger to power steering systems. Then figured the hoses that were custom made were too small. He doesn't suspect they are. They're 3/8 hoses, just like the GM lines. So, we figure air might be in the system. Does anyone else have any idea as to what else it could be?

Also, does anyone know why the hell this truck would be popping hoses all the time anyway? All sorts of fluids have been tried. Standard power steering, AC cold climate, ATF, you name it. Doesn't seem to be fluid related in that regard. The hoses have popped in the middle of summer and the middle of winter, so it doesn't seem to be pressure related. Truck has 300,000km/185,000 miles.

And..

Yes, the hoses are hooked up properly on the booster, and the hoses are hooked up in the right spot on the box (port from booster and the cooler port.)

Thanks a ton!
 

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ATF of any kind is not the specified fluid for the power steering pump, steering gear or hydroboost for our trucks. For the price of power steering fluid (about $15/gal IIRC) I would flush out all the old and use the correct fluid. I don't know that the high pressure problem will be solved, but with all that has already been done, this will at least be the cheapest thing that has been done.

Moisture in the fluid when very hot will turn into steam, which can increase the pressure, but I wouldn't guess that it would be enough to rupture hoses or make fittings leak. I will note that I have replaced a couple of my pressure hoses and thought they were properly tightened, but they weren't, so had to give them a 2nd go. Never hurt the lines, just a leak at the screw in fittings.
 

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Discussion Starter · #3 ·
ATF of any kind is not the specified fluid for the power steering pump, steering gear or hydroboost for our trucks. For the price of power steering fluid (about $15/gal IIRC) I would flush out all the old and use the correct fluid. I don't know that the high pressure problem will be solved, but with all that has already been done, this will at least be the cheapest thing that has been done.

Moisture in the fluid when very hot will turn into steam, which can increase the pressure, but I wouldn't guess that it would be enough to rupture hoses or make fittings leak. I will note that I have replaced a couple of my pressure hoses and thought they were properly tightened, but they weren't, so had to give them a 2nd go. Never hurt the lines, just a leak at the screw in fittings.
You're right about it being the unspecified fluid. It was used in an attempt to see if the issue was primarily fluid related. I too agree that there is value in ensuring every fitting is properly tight. As it stands, there are no leaks on the system when the truck is running or parked. I think a flush and a burp may be warranted.

Thanks for the tip!
 

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Did you verify the lines were busting? or were they just leaking at certain points? Sounds like PS and steering gear are prolly shot now after so many blown lines and mixed fluid. Does it steer fine with the tires off and in the air?? My PS pump is going bad and sometimes tough to steer randomly. I replaced all lines with Hydros and added a PS cooler, now just waiting on my PSC pump to show up
 

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Did you use a OEM pump and booster? If not trash parts store junk and get OEM. I would also recommend the PSC brand for the pump. Have you done anything to the steering gear yet?
 
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