Hydraulic system "gets tired" after period of use

   / Hydraulic system "gets tired" after period of use #1  

happycow

New member
Joined
Jun 13, 2004
Messages
6
Location
Los Osos, CA
Tractor
Ford 1720
Hydraulic system \"gets tired\" after period of use

Greetings:

I recently bought a used 1994 Ford 1720 with a newly installed FEL. I've used it for about 15 hours and everything has worked great. Yesterday, I was using it to move a big pile of dirt. After about 2 hours of work, the FEL and rear hitch abruptly quit working (wouldn't raise up as usual). They'd raise up, but only after a long delay and when they finally raised up, they'd hesitate or "chatter" and lacked power.

I drove back to the barn and let the tractor sit for 15 minutes. Everything worked fine after this brief rest. Today I used a box scraper on level ground (no FEL work). Everything worked great for about 30 minutes and then the same "chattering" started.

I don't have a ton of hydraulic experience but it seems as though there is air getting into the system. The hydraulic oil level is fine and the oil quality is great (the system was flushed and new oil/filter installed before I bought the tractor). I has been almost 20 hours since the new FEL was installed. There are no obvious leaks in any of the hydraulic system. Before the chattering starts, the system works great and the FEL is able to lift the front end of the tractor. So, I don't think there is anything wrong with the hydraulic pump.

Is this just air in the system? How long does it take for air to work itself out?

A friend has suggested that it might be some crud that broke loose and has plugged the filter. It strikes me that a plugged filter would always be a problem and not just cause trouble after 30 minutes of use.

I'd appreciate any ideas of what to check out. Thanks for your help!
 
   / Hydraulic system "gets tired" after period of use #2  
Re: Hydraulic system \"gets tired\" after period of use

happycow

Welcome to TBN. /forums/images/graemlins/smile.gif

You may have water in the transmission.
Have you checked the oil. It will have a milky look when the oil has been used for awhile.
The filter could be restricting flow when it gets hot.
 
   / Hydraulic system "gets tired" after period of use
  • Thread Starter
#3  
Re: Hydraulic system \"gets tired\" after period of use

Thanks for the reply and the welcome to TBN. Though obvious, I probably should have acknowledged that I was new to the group in my post. I spent a couple hours looking through past posts to see if this had been discussed (didn't see it) and was very impressed with the participation and information in the forum. Good group of folks!

Your reply makes sense--I've seen this "mayonnaise" phenomenon with water in oil in other instances. But I checked the oil (when both hot and cold) and it looks brand new--clear, clean and at the proper level.
 
   / Hydraulic system "gets tired" after period of use #4  
Re: Hydraulic system \"gets tired\" after period of use

I would change the hydraulic oil filter and hope that the pump is not the problem. You can drain off a small amount of fluid to see if there is water in the oil. The water will be on the bottom. Good luck.
 
   / Hydraulic system "gets tired" after period of use #5  
Re: Hydraulic system \"gets tired\" after period of use

James, air is rarely a problem in hydraulic systems. No bleeding is needed when changing hoses or filters and such.

While, I don't know the exact cause of your problem, I am sure that it is a matter of worn seals or other worn parts that, when heated sufficiently, allow too much pressure to bleed off. I've seen this a few times in older equipment.
 
   / Hydraulic system "gets tired" after period of use #6  
Re: Hydraulic system \"gets tired\" after period of use

A leak in the suction side of the pump could allow air into the system, but the oil would look foamy - well, tiny air bubbles - when hot.

Or, something worn on the pump. But it would take longer for the oil to cool back down again if this were the problem.

My guesses. Perplexing.

--->Paul
 
   / Hydraulic system "gets tired" after period of use #7  
Re: Hydraulic system \"gets tired\" after period of use

</font><font color="blue" class="small">( see it) and was very impressed with the participation and information in the forum. Good group of folks! )</font>

Flattery will get you anywhere! Can I wash your tractor for you? /forums/images/graemlins/smile.gif

Just on principle, it sounds like thin oil, hot oil, a worn pump, or a malfunctioning valve. Of course cause and effect could become blurred, because some of these problems could cause heat, and heat could cause some of these problems.

I would feel the hydraulic filter after a long run to see if it's unuaually hot. I would smell the oil for a burned odor, and check to see if it appears unusually thin. Worn pumps can sound noisy. Perhaps note the pump sound while cool and again after warmup.

Good luck, and welcome to TBN. Wish it were under better circumstances.
 
   / Hydraulic system "gets tired" after period of use #8  
Re: Hydraulic system \"gets tired\" after period of use

Just to add my two cents...

I doubt that your problem relates to clogging or a filter problem. When your tractor warms up, the viscosity of the oil gets thinner, so if clogging were a problem, it would be worse when the tractor is cool. If you are sure your fluid level is okay, my guess would be a heat related leak/seal failure. That failure could be letting fluid out or letting air in. Another problem might be a pressure relief valve that gets lifted after heavy use and then won't reseat properly. The next time you have the problem, shut the tractor down and lower both the loader and the 3PH for a couple of minutes and then restart/retry. If the power returns, it's probably a sticking relief valve. Either way, it's going to take pressure testing and probably a teardown to fix. /forums/images/graemlins/frown.gif
 
   / Hydraulic system "gets tired" after period of use
  • Thread Starter
#9  
Re: Hydraulic system \"gets tired\" after period of use

Thanks for the ideas. I added bit more oil this afternoon and tried it again. As in the past, I was able to get about 30 minutes of good FEL work in before the symptoms started again. I shut off the engine and lowered the FEL & 3PH. Fired it up less than 5 minutes later and everything worked fine. The FEL was able to lift the tractor front end without any hesitation.

Did some box scraper work after that and the problem reccured after just of few minutes of work. I could get it to work again affter turning off the engine briefly (less that one minute) however, the problem also comes back pretty quickly.

The oil looks fine when I check it--clear with no bubbles and no burnt smell. The filter is warm but not hot to the touch (can keep my hand on it easily). The pump is hot but I think not abnormally hot, given that it is attached to the engine block.

The system seems to recover ONLY after shutting down the engine. The oil can't lose much heat that quickly so there has got to be something physical (diversion or obstruction) that is keeping oil from the pump.

I think I may try replacing the filter just for grins, otherwise it looks like a call to Big Al the tractor mechanic. Is the screw on filter the only filter or is there a screen upstream of the filter than can be cleaned?

Thanks again for all the input!
 
   / Hydraulic system "gets tired" after period of use #10  
Re: Hydraulic system \"gets tired\" after period of use

On some tractors you can get to relief valves and control valves without having to go inside. I hope that's the case with your tractor because it sure sounds like a faulty relief valve to me. Please keep us posted on what you find out.
 
 
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