More Power Steering Pump awesomeness - 6v92

JT4SC · March 31, 2015, 11:10:17 AM

Hey guys, I changed the PS filter in the resevoir and cleaned the PS filter on the return line. I then poured some new ATF in, started her up, turned the wheel back and forth to get the air out of the line then checked to see what would happen next.

First, while looking through the eye glass at the top of the resevoir I could see the fluid level in the resevoir went down a little when I turned the wheels, and little air bubbles (what appeared to be almost foaming at the top) appeared in the eye glass (Picture attached).

I turned the bus off which caused the fluid to rapidly fill the resevoir and leak out the top vent like it was doing before. I then turned the bus back on, checked the eye glass and the fluid was now back down, in fact lower by approx 1 inch than it was before I turned the bus off.
I could see in the eye glass the fluid was bubbling just like if you were boiling water. I turned the wheel a couple more times, then turned the bus back off. Again, the fluid level in the resevoir quickly went higher, although this time it didn't go out the vent. When I turned the bus off the fluid color was still red.

Finally, I checked itge eye glass about 1 hour after I turned the bus off, and now the fluid in the eye glass is no longer red but a dark brown almost black (picture attached). Any ideas on how and why this happened?

eagle19952 · March 31, 2015, 12:55:59 PM

not fully sure but, is your check sequence specified running, or nor running ?

relative to the sight glass >are you adding to it running or not running ?

cavitation/foaming is most often related to a suction side leak.

JT4SC · March 31, 2015, 12:59:34 PM

First I added to it not running, then when the resevoir went real low after I started the bus (because of the fluid it lost when I took the pressure line filter off) I added another quart when it was running.

bevans6 · March 31, 2015, 02:12:35 PM

My experience was that it took a while for the level to level out, so to speak. It's a big reservoir, it it's a stock size window used for many different applications (I have the same window on a couple of motorcycles and a milling machine) and I don't think the level is particularly critical. The colour difference is surely the new fluid cleaning out old gunk, and if you wanted to you could clean it up by changing filters and changing the fluid again after a few hours. The filter is on the output (on mine anyway) so the dirty stuff is going to concentrate in the tank.

Brian

eagle19952 · March 31, 2015, 03:16:50 PM

PS. it has also been my experience that eventually a cavitating pump/one that sucks air eventually needs to be replaced.

The source of the air has to be found, or the new pump will suffer a premature failure also.

One of the most common causes is having a 90 degree fitting at the point the suction line enters the pump.
Design parameters (best practice) says to have 10x's hose id. in a straight length to feed.

a clogged inlet side filter in a hydraulic system can do the same thing. were I you I would disassemble the pump and check gears and wear plates for pitting and scoring...

JT4SC · March 31, 2015, 03:55:05 PM

Thanks fellas, I just want to take her to the beach a few miles away, then will probably get the pump looked at by a pro. Thank you again for all your help, I appreciate the insight on this board - you guys are the best!!

digesterman · March 31, 2015, 03:57:25 PM

Sounds like your pulling air in somewhere on your suction side of the pump, your pressure and return lines are of course under pressure so finding the air leak into the system shouldn't be that hard to find. A clogged filter on the suction side could cause a leak between the filter and the pump, if indeed you have a dirty filter.

Most leaks on a hydraulic system are on the pressure side and return, those are longer runs but easier to find (pool of oil). Until you find the source of the leak I wouldn't be changing your fluid, change and flush system after you find and fix problem. Cleaning filters or screens now goes without being said of course. Good luck

BTW some pumps could pull air through a bad seal, that is possible depending on the design. Fluid power is fascinating, nothing to be afraid of tackling

TomC · April 01, 2015, 07:25:39 AM

If you're oil is discolored dark, you maybe pulling in engine oil through the pump. Good Luck, TomC

digesterman · April 01, 2015, 07:29:17 AM

Could be TomC

JT4SC · April 01, 2015, 09:17:51 PM

Quote from: TomC on April 01, 2015, 07:25:39 AM
If you're oil is discolored dark, you maybe pulling in engine oil through the pump. Good Luck, TomC

The fluid I can see through the eye glass window is a normal red color when the engine is on; the black only appears when the engine has been off for an hour or so.

There is definitely an air leak somewhere because I can see the fluid in the resevoir bubbling like it's boiling water when the engine is on.