How hot is too hot??

[Opti-Mist]

Bird has it right as to 100 degrees + ambient. As for oil too hot - really overheated oil has a distinct "burnt" smell to it that most anyone will recognize despite never having smelled it before. It will definitely be different from the odor of working temperature hydraulic oil.

 

[patrick_g]

I think that I recall that tissue damage begins at temps above about 115F with prolonged contact. Metal that you can contact for several seconds without getting first degree burns is not likely to be hotter than that. I use a non-contact IR thermometer to get a fair idea of the temp of things.

Pat

 

[IceStationZebra]

As far as the oil is concerned I have research this several times for my employers (off-road OEM's). Every 18°F increment higher doubles the oxidation rate of the hydraulic fluid (petroleum based) thus cutting its useful life in half, e.g. running a system at a consistent 201°F vs. 165°F would reduce the useful life of the fluid by 75%.
I have found two different numbers for the start of oxidation...140°F and 165°F. I'm not sure which is correct but the data I have leans towards 140.

Most rubber components are good to at least 200°F.

As far as the IR temp gun goes, don't expect acurate readings of shiny surfaces like chrome rods or of plastics. Painted surfaces work great.

ISZ

 

[J_J]

Some more data to consider.

Note that fluid temperatures above 82 C (180 F) damage seals, reduce the service life of the hydraulic fluid and in most cases, will cause the viscosity limits of the fluid to be exceeded. This means that the operation of any hydraulic system at temperatures above 82 C (180 F) is detrimental and should be avoided.

http://www.plantengineering.com/art..._Fluid_is_a_hydraulic_system_s_lifeblood_.php