Why did my hydraulics wimp out?

[Indian Territory]

Today in the 100° heat my hydraulics gave out and would no longer lift my heaviest implement. The tractor is a New Holland Powerstar 75 and is probably operating at the upper limit of its ability when lifting our Rain-Flo 2670 raised bed mulcher. I immediately suspected a combination of a very hot day and a hydraulic system that is probably working too hard. Then again, I don't really know what I'm talking about. Can a hydraulic system overheat and lose lift capacity?

I also hooked up a rented lime spreader that seemed to be poorly maintained. Could I have circulated their scuzzy oil into my clean reservoir? Would the pollution from a single dirty remote line be enough to cause my trouble? I wish I knew more about these things.

 

[Roadworthy]

If you have a filter screen it could be partially blocked. You could also have too much crud in your hydraulic filter. Was there possibly any water in the system of the attachment you used? Water could vaporize in the hot hydraulic fluid.

 

[oldnslo]

When oil gets hot it gets thinner and flows easier which can cause some pressure loss if their are enough leak paths.

Dirty filter would usually be more of a problem when cold vs hot.