Problem with hot hydraulics

Wesbo · Jul 22, 2006

Was mowing with my 4200 today. About 4 hours at 1800-2000 rpms. The steering starting getting glitchy (usually butter-smooth) and when I tried the 3ph, it raised in jerks, like the pump was starving. Even the hydraulic lift on the MMM could barely move. The problem grew worse the longer I stayed on. Plenty of fluid in the sight glass.

I shut down and gave it an hour's rest, and then everything was back to normal. Smooth steering, 3ph up and down very smoothly.

I have the stuff to do a hydraulic service, but I won't know if that fixes anything until I mow for another 4 hours... Sure would like to hear any ideas...

Thanks

Lobo56 · Jul 22, 2006

Are you using low viscosity HY-Gard or the regular HY-Gard? I’ve had that happen using the low viscosity HY –Gard when working the tractor hard in Temperatures over 90 degrees.

Wesbo · Jul 23, 2006

I don't know which fluid is in it; I haven't serviced the transmission since I bought it used.

BillyP · Jul 23, 2006

Wesbo said:
I haven't serviced the transmission since I bought it used.

That's most likely your problem. Change the hydraulic oil, filters and clean the suction screen and I bet your problem will go away.

EDIT:
I'd do it ASAP

AKfish · Jul 23, 2006

I just did the hydraulic service on my tractor at 520 hours. The guy I bought the tractor from told me that when he changed the engine oil and filter, he also changed the hydraulic filter each time. So, I didn't worry too much when I hit the 500 hr. mark and the transmission service was due.

While I don't work my tractor in 90 degree temps, I've been working the tractor pretty good digging up stumps with the backhoe. I began to notice that the hydraulics were not up to the performance that I'd become used to -- steering was jerky and the tractor needed another 100-200 rpm to work the hoe at the same speed.

Well, I was amazed at how dirty the sump filter was! The canister hydraulic filter wasn't too bad (I already changed that out after 50hrs with new engine oil). And the hydraulic oil looked darn near as good as the new stuff I put in the tractor!

But the the long and short of this is --- follow the service recommendations that are in your owner's manual. Those service intervals are on target.

AKfish

therebarely · Jul 23, 2006

Heat in a hydraulic system is caused by wasted energy. This is almost always caused by hydraulic flow going over the relief valve. There could be many causes for this, relief valve dirty or plugged, spools on the directional valves could have dirt in them, or one of the hydraulic functions could be jammed. If there is excessive cylinder leakage it could cause heat also, especially the 3 point lift cylinder. Heat is always wasted energy, and almost never caused by the suction side of the system, but by the pressure side. If there is a suction problem, you will hear the hydraulic pump cavitate and shreak wildly. Hope this helps.

Wesbo · Jul 23, 2006

The manual mentions removing and cleaning the suction screen in solvent. What sort of solvent? Diesel? K-1?

Or is the suction screen the sort of part that I should just replace once I've got the old one out of there? Just want to know before I start taking stuff apart...

Thanks

AKfish · Jul 25, 2006

I agree with therebarely's comments regarding heat buildup in the hydraulic system. Heat buildup from friction somewhere in the system is a sure sign that there is a restriction at some point and excessive operating pressures are likely occurring as well.

While I didn't experience excessive heat buildup from the dirty suction (sump) filter (warmer... but I was running the engine faster, too); I did note more noise coming from the hydraulic pump whenever I engaged the system --- turn the steering wheel, extend the stablizer pads, etc.

And of course, my steering was jerkier. But, no cavitation noises or herky-jerky motion from the 3 pt.

Nonetheless, if you're close to the recommended service interval; it's a good thing to take care of it -- it should be done regardless. Diesel fuel and a good air compressor will do the job on the suction filter.

Of course, as mentioned -- something -- metal filings, etc. could be lodged in one of the directional valves.

If that's the case; it would seem that an individual or particular hydraulic function would be notably degraded i.e., bucket curl or dump, etc. You might be able to isolate the problem in that manner -- or at least begin looking in that direction.

AKfish