Howdy all, We've recently noticed that the steering on our CAT 420D requires more effort than usual. Shortly after that, the machine developed an unusual "squeak" type noise when the steering wheel is turned. Having next to no experience with CAT hydraulic systems, we thought that there was a separate power steering pump that may be low on fluid. We've since been told, however, that the "power steering" should run off of the main hydraulic system on the machine. If this is the case, I'm now considering a hydraulic fluid change. The machine in question has less than a 1,000 hours on it, so I'm a bit surprised by this ... But as I just mentioned: we have very little experience with this type of thing. The machine is a 2002 CAT 420D and I'd like to know, specifically, how to go about draining the hydraulic fluid from the system. Is there a petcock or a drain plug somewhere for this purpose? Being short on funds, any words of wisdom we can get will be greatly appreciated. Thanks very much for your time ...
I wouldn't start with changing oil, 1k hours isn't much. Have the filters been checked? It is infact the same pump for all the hydraulics on the machine but steering gets priority. Does it hold the line or do you have to constanly turn the wheel when roading? The drain valve is located on the pump suction flange.
I agree with Per Eriksson, 1000 hrs may be approaching the recommended time of hyd oil change, but I don't think it's the cause of your problem. As he said, steering and machine functions work from the same pump, the flow goes through a priority control valve which insures the steering always has oil flowing to it. Such as when your raising the loader while steering, the priority valve makes sure oil goes to steer when doing this. Do you have any problems at all with the loader or hoe functions? If not, then your problem is likely the priorty valve or something in the steering (steering orbit valve, steer cyl problem).