Have a 94 Cat 312 with 7000 hours on it. The machine is strong with basically no leaks. Hydraulics are smooth and engine seems to run smooth as well. However, there is a vibration all across the RPM ranges. Worst at 1, smoothest at 8. Best I can tell, the pump bolts directly to the motor, but is there a coupler or disc between the two that may be going out causing the vibration? I thought it may be as simple as the motor mounts, but after looking over it again yesterday, I'm not so sure. At idle, you can obviously see the pump shaking with the motor, but at 8 the motor and pump appear to stable by the eye. Any suggestions on what to check? Thanks.
check the rubber coupling and the engine mount damper.
As above. Separate the pump from the motor and you'll find a flexible coupling in between. The most likely cuplrit.
Does any have a diagram they can share if the coupling and how it hooks to the motor? Also anyone know the part number for the motor mount bushings? Thanks.
PM me with your e-mail address and the Machine Serial Number. There are about 20 different Serial Number prefixes of 312, it would be nice to narrow that down a bit ....... Do not post the above info here please.
There are a lot of possibilities here. Have you got a damaged fan? Does the vibration disappear when you load up the hydraulics? Loose pulleys or vibration damper on crank pulley, alternator belt damaged? I doubt it'll be the drive coupling, a quick check is to get someone to rock the crankshaft with a spanner while you listen for a clonking at the coupling. I've taken the engine out of a 315 and the coupling was absolutely shot, but there was no noise when it was running.