Hello, I need help troubleshooting a 2009 Gehl 6640, Tandem pump, hi and lo flow, duetz engine. This machine was bought at auction and I have been working on getting it running correctly. It was full of dirt and heavily leaking hydraulics, so far I've cleaned it out, taken out the dual hydraulic pump and had it resealed, added OTTs from Mclaren, it's a beast now only leak I can find is in one of the drive motors, but it is minor. The engine temp gauge on the panel does not work, but it seems to run ok. The problem I have is when I am leveling an area I get about 4-5 scoops of dirt carried to a pile 50-60 feet away before the hydraulic overheat light illuminates and alarm sounds and I have to shut down and let it cool. If I am working in the woods, not running as hard, it takes a bit longer but usually ends up overheating. I cleaned out the oil cooler with a pressure wash and some degreaser. I don't know what else to check, could the main relief valve be off? I'm not sure how to check/adjust it? How do I tell if the oil cooler is bad? what should the input and output temp difference be when read with a temp gun on the outside of the hose? any ideas would help, there are no gehl certified mechanics near me. Thanks!
What is the pressure between the pump and control valve as its overheating .... does it track straight
When was the hyd, filter last changed? Do you have a lazer thermometer to tell you the actual oil temp when the light comes on ? You could have a bad sensor. .
Hey Guys, thanks, sorry I didn't see there were replies before today. its been raining most of the last week so I have had little opportunity to look at it. I just replaced the engine temp sensor and gauge today to get a good idea of the engine temp. it is oil cooled so I figure there is at least a correlation, good news is the engine is not overheating, reads around 210 F when the hydraulics alarm. It does track straight, I have not checked the pressure between the pump and the control valve. I bought this: https://www.amazon.com/gp/product/B07RQ712W9/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1 hydraulic pressure test kit for this purpose, what is the best way to do this, do I get a T and put it in line between the pump and the control valve? looking at the parts manual, I'll attach a screenshot, is there a test port on the main relief valve? I am unfamiliar with them. I replaced all the fluid twice in the last 6 months before and after I had the pump rebuilt. replaced the filter the first time. I do have a harbor freight laser thermometer, the highest temp on the fitting at the end of the line going into the oil cooler is around 165F coming out is around 140, coming out of the hydraulic filter is 125 or so, I could not get to the manifold to read the temp there, I think the overheat sensor is on the manifold, the parts diagram shows a 230 degree temp switch there, I assume that 230 is the target temp to trigger the alarm, is that right?
I guess that if the highest temperature you measured at the cooler inlet was 165, then provided that was measured at exactly the same time as the "high Hyd temp" alarm was going off it would appear that the sensor/switch that controls the high temp alarm would be a prime suspect. However if some time elasped between the alarm going off and measuring temperatures at the cooler then the possibility exists that the cooler ought to be completely removed and cleaned internally & externally as a first step as opposed to cleaning it on the machine. I'm not sure what you did already, your OP is not totally clear on that point.
I immediately measured the temp after shutting down for the alarm, I definitely hope that it's just the sensor! I only cleaned the oil cooler externally, sorry I wasn't clear. I'll see about ordering a new sensor, I'm not 100 percent sure the switch on the manifold is the sensor that controls the alarm, but I don't see another probable culprit. Looks like a tough spot to reach!
What is hotter... the drive pumps or the main control valve
I think you need the advice of someone with more experience of Gehl. I was simply commenting on where it appeared to me that your OP was heading.
Not sure, I'll have to open the ROPS and lase the pump next time while it's hot, I'll be using it again on Tuesday. Do you mean the main hydraulic pump vs the main control valve, or the drive motors vs the main control valve?
No, you are 100% right on target, as ususal