Hi folks, last week I took on a job troubleshooting a 1993 JD 710D backhoe that belongs to friends of mine and has been broken down in the woods all winter. Reportedly the machine was being turned around in a narrow space at idle speeds when there was a nasty grinding sound and she stalled and quit and couldn't be started again. When they first tried troubleshooting back in the fall they managed to get the engine running once but had no hydraulics and the machine promptly stalled again. When I try to crank the engine the starter engages with a clunk but does not turn the engine over. The starter is brand new and known to work properly. Both batteries are also brand new and fully charged, with freshly cleaned terminals. I tested the solenoid on the Main Hydraulic Pump Stroke Control Valve and found 2.8 Ohms across the switch (which I believe is a good result, but correct me if I'm wrong). And I also actuated the valve manually, but it felt awfully crunchy and the oil leaking out was full of small flecks of metal fragment. I went ahead and drained the radiator and hydraulic oil cooler for better access. When I drained the hydraulic oil cooler I found the same metal flecks there. I couldn't conduct any flow or pressure tests on the charge pump or main pump since the engine wouldn't run. With the oil cooler and radiator removed I uncoupled the main hydraulic pump from the engine crankshaft and now I can turn the engine over by hand ( whereas before it was impossible). I cannot, however, get the shaft of the main pump to turn, which I thought I would be able to do easily. My diagnosis at this point is that something up stream of the main pump ( or the pump itself) is creating all this metal and this has caused the main pump to fail which in turn puts resistance on the engine and won't allow it to crank. I'm going out today to remove the Hydraulic oil filter and drain the reservoir to see where the metal is in the system. I needed to order a wrench to finish removing the main pump, so I'll do that when the wrench gets in. I am NOT a mechanic, and so I would appreciate any advice you might have on what steps to take next to identify what component is creating metal flecks and also the best way to proceed with flushing the system. Thanks, Aaron
Welcome to HEF Aaronef ! Since you have access to the pump see below.
Definitely sounds like a blown pump, good thing it didn't shear the end of your crankshaft. Pull the pump and inspect as suggested, and drain all hydraulic oil and pull filters. Most likely needs a new pump by the sound of it
Thanks for your warm welcome! I'll inspect the pistons that I can get to, and when I've got it out of the woods and onto a bench I'll break it down and take a look at those bearings. I appreciate your help!
Thanks for your advice! It's good to hear I'm on the right track, it's been a hell of a learning curve. I'm very thankful that it did not shear the end of the crankshaft. Do you have any suggestions on the best way to flush out the oil cooler before reinstalling it? I have a feeling a substantial bit of metal dust has accumulated in it. I was considering pouring Diesel through it since I don't believe there's any o rings or seals to worry about damaging.
Afraid I'm not sure, I don't think I'd wanna contaminate the system with diesel. May want to find a way to circulate oil through the cooler with some type of pump to try and flush the trash out, or maybe pull the cooler and clean it Inna parts washer or something of the sort
If there is metal in it replace it. Good idea.
My first guess is that pump is supercharged from the transmission pump, that was Deere's usual system. Metal could be from an imploded hydraulic pump itself which is not uncommon, or the transmission, where there is a long hollow nylon kind of suction screen usually, which is almost always unserviced and almost always plugged with friction material, and or metal shavings.