My 753C recently started making a loud rattle and clacking sound in the engine compartment. Sounds like light metal colliding, and not a deep knocking. It seems independent of the engine itself, in thar engine runs OK as normal, and change in engine speed does not seem to have direct influence. Sometimes, speeding up engine causes the noise to quieten some, but not necessarily so. As best I could tell thus far, fan belt idler appears OK. The noise did not seem immediately threatening at the time, and I continued to use the tractor for another couple of hours with no obvious worsening of the noise. Due to a recent hand injury, it has not yet been feasible for me to dig into this problem. my best guess at this point is that the radiator fan or its bearings might have oartially failed, allowing the fan to collide with the cowling, or some such thing that is peripheral to the engine. Engine temperature has been staying OK. I am wondering if any of you have noticed a similar problem or know if there might be a common failure of the fan or other subsystems that migh explain this. I should have mentioned that this seems to be clearly unrelated to the hydraulic systems. thanks in advance for any pointers or advice.