Hydraulic elevator slow or not running on hot days
Reported Symptom
Hydraulic elevator operates slowly or intermittently during hot weather (summer). Car may inch upward slowly or not reach floors. Low-speed descent noted. Condition improves in cooler weather or at night.
Safety Warnings
- •Hydraulic elevator oil can be under several hundred psi — do not open any hydraulic system fittings without elevator mechanic. Oil temperature above 140°F is a fire risk for hydraulic fluids — ensure fire protection system in machine room is functional.
Possible Causes
- 1Hydraulic fluid overheated — above 140°F causes thermal thinning and control valve malfunction
- 2Pump motor overheating
- 3Cooling unit (if installed) not functioning
- 4Hydraulic unit in hot equipment room exceeding temperature limits
Tools Required
- Thermometer (for oil and room temperature)
- Flashlight
Diagnostic Steps
Measure machine room temperature and hydraulic power unit oil temperature (oil temperature gauge if installed, or contact thermometer on reservoir). Normal operating oil temperature: 80-120°F. Problem range: above 130-140°F.
Expected: Oil temperature below 130°F.
If fails: Oil overheating: causes oil to thin and flow control valves to malfunction. Improve machine room cooling.
Check machine room ventilation: hydraulic elevator machine rooms require adequate ventilation. In summer, room ambient may exceed limits if ventilation is inadequate.
Expected: Machine room ambient below 90°F with adequate ventilation.
If fails: Add ventilation fan or air conditioning to machine room. Hydraulic oil temperature will follow ambient room temperature closely.
If elevator has a hydraulic oil cooler (some modern systems): verify cooler fan is running and cooler is not blocked.
Expected: Oil cooler fan running, no blockage.
If fails: Clean or service oil cooler. Cooler fan failure: replace fan.
Report to elevator service company for oil condition inspection: hydraulic oil should be changed per service contract schedule. Old or contaminated oil has degraded viscosity characteristics and compounds heat problems.
Expected: Elevator service company inspects and services hydraulic unit.
If fails: Schedule oil change and oil analysis. Overheated oil breaks down faster — may require earlier oil change.
Solution
Hydraulic elevator heat problems require improved machine room cooling. Adding AC or ventilation fan to the machine room is the most effective solution. Oil change with fresh fluid helps but does not address root cause if room is too hot.