Hi all, We have an early Bobcat 763 (square headlight model). The machine is pretty low hours, it had a complete filter service a year ago and has maybe run 80 hrs or less since then. It gets run regularly but not for long. Anyway about a week we began using it to run loads of dirt down a steep hillside. We then back up the steep hill (it has steel tracks) empty. Its quite a climb and the machine has to work to make it. A few days ago it began to make some clicking noises when reversing. We worried it was low on hydraulic oil, we checked it and added maybe only a ½ gallon. The clicking continued and the machine began to lose power for lifting and forward/reversing. Now it will barely move, and the arms lift very slowly. As the machine was losing power it was affecting the drive (LH & RH) evenly so it wasn’t pulling to one side or the other also the lift arms were becoming slow. The engine starts and runs fine. My first thought was maybe when on the steep incline air was being introduced in to the hydraulic line, but now I am thinking that perhaps the main hydraulic pump is beginning to fail (clicking noise) or perhaps the drive belt is slipping/worn or maybe there is a tensioner problem. My question is if the main hydraulic drive belt is worn would that also affect the lift arms, I did some google searching a read forum topics but usually when a drive pump issue is mentioned the machine’s lift arms still work this makes me fear it’s a problem with the main pump and not the individual LH/RH drive pumps. We replaced the spin on hydraulic filter in the back just to be sure. The fluid looks clean. We checked the 10 micron in-line filter out of the tank and it looked OK not new but not excessively dirty. There appears to be a second inline filter in one of the lines leaving the pump but we did not check that. Any ideas?
763 drive and lift arm slowdown
- Thread starter zepper
- Start date
First thing to check is the drive belt and tensioner, that would be the main cause of all hydraulics slowing down. Not sure on the clicking noise unless the brakes are not releasing and you have worn brake discs, the machine will drive thru the brakes making a loud clicking sound but you would also feel it jerking. Could be a piece of belt slinging around making that sound I guess.
Thanks for the reply. I guess it seems silly that I haven't checked the belt yet. In my defense the bobcat isn't kept at home. When we had the trouble we just assumed it was hydraulic fluid related and messed with that until we ran out of time and had to leave. Then after some thought and research i realized it could have been the belt. Hoping to look at it this weekend. Brakes not releasing could make sense for the clicking. Thanks, I'll post back next week after i have some time to look at it this weekend.
flyerdan
Well-known member
- Joined
- Mar 7, 2009
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The hydrostatic and hydraulic pumps are inline and both driven by the belt so if both systems are acting slow or weak that would be the likely culprit.
I'd guess that the tensioner has partially failed, allowing torque to slam the tensioner to the stop, then it goes back to take the slack out of the belt and the torque slams it again. That would account for the slow operation and the noises. If so, it's an easy and relatively inexpensive fix.
Thank you for reply. I did not know that both pumps were inline and driven off the belt. Potentially good news, fingers crossed. I spoke with my dad, the original owner of the bobcat. He couldn't recall ever having replaced the belt in the 23 odd years he's owned the machine. How would i tell if the tensioner has failed? I saw that they get greased under a dust cap and planned on checking that, but beyond a dry tensioner that is all chewed up metal, what would i see?
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Remove your battery and flywheel cover and you will see the belt and tensioner assembly. Just one bolt holds your tensioner assembly on, use a 9/16 socket and remove the bolt and take the whole tensioner assembly off and inspect it. Depending on your serial number either it'll be a fixed tensioner or it'll be a spring loaded tensioner, the spring tension doesn't usually work well and needs to be freed up if you're able to reuse your tensioner. Post your serial number and we'll find out for sure which tensioner you have.
The machine serial number is 512230444. The machine ran just fine this morning when it was cold. I inspected the belt and didn't notice any signs of damage but it did seem loose I would estimate the play in the belt was about an inch. Working on getting the tensioner off right now.
the tension tensioner spins very freely without any signs of resistance the belt looks okay there is no visible fraying or worn spots. there is a spring around the outside of the tensioner and the pin that moves in the mounting bracket. I don't know if the pin is in the correct position.
The operator actually reported that there was squealing when it was slowing down not that it was clicking as I earlier said.
I've seen belts that look ok but are glazed, for lack of a better word, and still slip with proper tension. So you do have the spring tensioner, install your bolt barley snug and use a pry bar on the top of bracket, you should see a small arrow on the tensioner, pry till it gets to about 2 o'clock if I remember correctly. The old tensioner may not spring due to being stuck, just keep working it till it frees up.
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