I have a 6115d tractor that, when the pto is engaged, slowly has the temperature creep up to to the point where the stop light comes on. This can be anywhere from 45 min to 1.5 hours depending on rpms and implement. This happens on bailer, batwing mower, hay cutter.
I'll list all of the things I have done but what I think is a key to this is the temp difference between the inlet on the hydraulic oil cooler is only 4 degrees hotter than when it comes out. This can't be enough can it?
My one thought was that the oil bypass valve wasn't allowing the oil through the cooler but I removed the output hose, started the engine and oil came out. The flow rate I can't confirm but it was a lot. Regardless, any flow going through the cooler should cool more than that shouldn't it? with only a 4 degree drop, it picks up more than 4 degrees as it goes through the system so builds and builds.
Here is all I have done with no change in results:
After an hour of bush hogging with a batwing mower OR bailing hay (anything with the pto), my hydraulic oil temp creeps up to over 156F (as measured at the sight glass and oil cooler with IR gun) and eventually the stop light on the tractor comes on.
- Changed Hydraulic oil and filter
- Ensured coolant is topped off at max fill
- Removed output hose from cooler to and made sure oil is flowing out
- Made sure rocker arms are not up
- Confirmed oil level is between the lines on the sight glass
- Made sure the engine radiator and fuel cooler are normal temps. Hydraulic cooler is the only one hot
- Confirmed with JD that there is no sump filter that could be clogged. Its only filtered by the hyd. filter
- Attempted to bleed air from the cooler but not sure how to do that since the input and output are on the bottom.
- Used only hyguard oil and filter
- Cleaned the cone-shaped caps on the tractor(I don't know what they are called) where hydralic cylinders get locked in place. LIke a float valve. They were pretty cruddy inside.
- Washed all coolers (radiator, oil, fuel) thoroughly
- Cleaned air filters
- Removed hydraulic cooler and ran water through to confirm there is flow.
- tested temp diff on input/output of hydraulic cooler. No matter what temp, there is only a 4 degree drop across the cooler.
- IR tested the hydraulic cooler itself. The small tubes are about 10 degrees cooler than the main tubes. But the main tube exit is still only 4 degrees cooler. The bottom small tubes are a good bit cooler than the others. Might indicate that one set of coils is clogged. But that shouldn't cause this I would think.
OTHER INFO OF INTEREST:
When the PTO is engaged and the engine is revved, some oil dribbles in from the top of the sight glass and it has air bubbles. Eventually makes the sight glass a little cloudy from the bubbles. After stopping, they clear within 10 min.
ONLY REMAINING GUESSES:
Air bubbles in hydraulic oil not normal and causing the overheating or accumulate in the cooler until it is turned off
Internal hydraulic leak (how would I know?)
Open the bleed valve on the radiator while running? Not sure how that can help.
Check to make sure filler cap vents are clean