Power Steering/Hydraulic Systems Analysis

[andyshane]

A question for our engineering types: after a night with temperatures in the teens two weeks ago, I started dripping hydraulic fluid. The culprit was identified by mechanics in Maryland as a cracked radiator core, the leak minor enough to continue home to Texas. In Tennessee, the rate of leakage had accelerated. As I poured the coals to the rig coming out of a KOA in Newport, a sudden brown geyser appeared in my mirror, the steering hardened. I eased onto the shoulder, continued another quarter-mile to a truck repair shop. Sure enough, the core had a inch-long crack along an aluminum weld.

That evening, I put on a new filter, installed the repaired core, leak-checked it, pushed in the distended bypass indicator. We had normal ops for the next three hundred miles, day of driving. 

Then, in Arkansas, the unthinkable: an hour into our day, the steering hardened! I parked and dashed to the engine compartment. Oddly, the repaired radiator was dry as a bone. Rather, fluid was gushing from around the filter. 

Now, this isn't my first rodeo. I've replaced that filter several times, did it in accordance with instructions. It is one of those with a large gasket that has to be tucked up, inside the housing. But, I'd carefully traced my finger around the entire circumference, assured that it was postioned correctly, tightened to specs. Now, a quarter-inch loop of gasket protruded, alongside the filter. Damned. I wiped everything down, drove the toad to a nearby store and bought yet another batch of hydraulic fluid.

Having reinserted the gasket, I snugged the filter extra tight, refilled the system, ran it and retightened. My installation had not been any different than many times before, but the gasket -- they tend to be a bit oversized -- popped out nonetheless.

But, I'm concerned because the bypass indicator on the filter housing  is extended, will not reset. 

 

Right now, we're ops-normal, but I'm not comfortable with this.

Any thoughts?

[wolfe10]

Andy,

There are several different ways to control hydraulic pressure. Is this system unique to your power steering, or is it tied in with the hydraulic fan for your side radiator? Separate pressure regulator (that would bleed off excess PSI back to the reservoir or pump)?  Monaco Corp would be my first call to determine exactly how the system works.  Also verify the correct fluid.  There is no "here is the correct fluid for all".  I have worked on these systems that use: ATF, hydraulic fluid or 15-40 engine oil.  The correct fluid is important.

Hard to believe this is simply a "cold is viscous" issue. We have all done a lot of miles in cold conditions with these same systems.

[andyshane]

Hey, Brett 

  Sorry it took so long. When I posted this, I turned to the mother-in-law and said you would definitely have the answer; and, that I wouldn't be surprised if the answer came within minutes.
  A technical glitch kept me from signing in, earlier.

 This bus came to us with zero manuals, so I downloaded a Dynasty manual for the next year, same chassis. It calls for ISO 46 hydraulic fluid. The filter specified for my mount/engine is the MS Filtri CSG100P10A with a 10 micron rating. The NAPA 1759 and WIX 51759 that cross-reference are also 10 micron filters; but, I notice that "None" is the listed "By-Pass Valve Setting-PSI: None."  Additionally, if you trace the MS Filtri model to Fram, it cross-references back to a different NAPA number. 

Of course, I've used the NAPA and Wix variants in the past, with no ill effects. Still, considering what is at stake, I'll first order an MS Filtri replacement, plug it in, and see if the bypass pin extends.

Meanwhile, I'll poll other Patriot Thunder Owners and see if they're directed to use Dex III or ISO 46. And, keep degreasing my repaired radiator. The oozing of hydraulic fluid that persists means nothing, for the first month, after I painted the entire engine and compartment with the stuff!!

 

[andyshane]

Well, that young man's tig welding repair lasted two years. 

Lately, I noticed a faint but ominous fogged area on the hydraulic cooler, made a mental note to check connections. They turned out to be dry, and meticulous cleaning followed by examining the repaired core/tank seam after driving confirmed wetness: the leak had returned. It was tiny, a mist from somewhere in the vicinity of his weld.

Out of caution, I pulled the cooler and took it to Kirby Radiator in Fort Worth. Owner Van Smith actually answered a Sunday night email message sent to the company, invited me to bring it up for immediate repair. When I got there, he and son Riley were waiting, amidst a beehive of activity, with maybe a half-dozen workers busily working on units. The two seemed out of place, like we should be in Operations together signing in for the Japan trip, or out playing golf. Riley lept on the cooler issue, had it cleaned and pressure-tested. He lamented that their repair team wouldn't be able to clean up the weld, since my leakage was internal as opposed the where tank and core meet. I mentioned that a beach trip with our neighborhood RV club was in the cards, he said if I stabilized the area with epoxy, chances were it'd last until he could re-core it.

It's a good time to mention that REV group cited replacement at $15,000. Riley took $60 for the cleaning and diagnostics, sent me happily on my way. That night, I used legacy JB Weld in the area, taping off a section and tilting the cooler on an incline in my shop. We all know that the "slow" original JBWeld thins as it cures; my hope was that it would wick into all of the nooks and crannies, arrest the seepage of hydraulic fluid temporarily.

While the unit was curing, I noticed something alarming: The hydraulic cooler is conveniently outboard, an inch in front of the side-mounted radiator. Having graduated from a clog-prone rear radiator rig, I was anything but complacent with the side unit, using a pressurized bottle sprayer to shoot it with degreaser from outboard and from inside the engine compartment, each trip, followed by low-pressure spray.

Well, "clogged" doesn't begin describing the mess that was packed between the two coolers. Fully a half-inch of black mud, mixed with grass clippings, coated the lower radiator. I'd patted myself on the back for maintaining a 190-194F window of coolant temperature no matter the slope or season; looking at the mess made me wonder how that could have been possible.

I misted the surface in Zep degreaser, waited ten minutes, and then delicately shop-vac'd it off. Three vac full batches of muck later, it was looking like a radiator again. That left the condensate tray below, inside which cleaning revealed a rusty lower tank section that had been buried in a shipwreck atmosphere of wet mud and grass. After rinsing the trough, I treated it with rust converter.

Since removing the outer hydraul cooler only takes five minutes, I'm setting up a 2-year maintenance task to repeat this critical "between the cores" cleaning, from now on. Sidemount owners might do the same: it looks spotless from outside, but is a clogged mess and corrosion time bomb, between the coolers!

 

           From the outside, this area appeared to be spotlessly clean! Rather than push the sludge deeper, gentle vacuuming followed by six or seven cycles of degreasing, did the trick.

 

 

I let it sit for 48 hours and then put the cooler back into place. It looked leak-free, so we finished our pre-trip prep and joined the convoy Saturday afternoon, planning two, 200-mile legs. The first safety check an hour later showed some leakage; it was nothing serious. The second stop showed a little more. Still, minor. At our overnight stop, I dripped all the way into parking. Rather than continue, we said farewell to the group and returned home in the morning, monitoring fluid quantity and keeping to the truck-services-lined Interstate. An hour after parking, I had stabilized to a foot-round mark of hydraulic oil, beneath the cooler.  The next morning, I dropped off the cooler with Kirby. They will send it to the big rig master of remanufacturing in Alabama; in a week, I'll have a new cooler. The cost: $700. As opposed to REV's $15K quote. Wow.

To my surprise, servicing this unit is a Beginner Level task, for those of us who DYI our own maintenance. The hose from our hydraulic filter can be drained into a small pail -- it amounts to less than a quart -- and then a drip plan easily catches two cups that comes out when unhooking both ends of the cooler. Only four bolts hold the cooler in place. Loosen those, and you're carrying a thirty-pound unit with two quarts of oil remaining inside. It can be leaned against a tree and gently washed, and I've already described the cleaning done around the area revealed by the removal. Installation is just as easy.

Oh. We cruise now at 10F cooler than before!

[rayin]

Thank you for the detailed articles. This reminds me to clean my Spartan radiator "sandwich" again this spring., and what to do if I encounter problems. I use aerosol air conditioner coil heavy duty cleaner.

My hydraulic filters are stacked inside the reservoir. Wish I had spin-on.

[wildebill308]

In the picture it looks oily, where is the oil coming from? Was this from the leak?

Bill