Question

leaks generally occur. a leaking hydraulic jack is unsafe to use, because a loss of hydraulic pressure will cause the vehicle to fall without warning. this is why you never position you under a vehicle without first supporting it with jack stands. a hydraulic jack can have external and internal leaks. an external leak means the hydraulic leaking to the outside of the jack. external leaks are easy to identify because hydraulic oil found on the out side of the jack. the major cause of external leaks is worn piston o - ring worn piston. internal leaking means the hydraulic oil leaks inside the jack, from the pressure chamber to another low pressure area. this type of leak is evident by the self - dropping of weight supported. this is often caused by a leaking release valve. identifying a leaking hydraulic jack - observe the outside of the jack for signs of relative fresh (moist) oil. the most common points are the piston o - ring, the release valve and the pumping valve. you can identity severity of the leak by observing how much oil is on and underneath the jack. an excessive quantity and fresh oil on and underneath the jack where it is stored means there is severe and the jack should be removed from service. a small amount of old, dry accumulated the piston however is considered normal, since the o - rings cannot completely prevent going to the outside of the jack. - to test for internal leakage, you can try to jack up some load with the jack in question. 20 minutes, observing how much height the jack has lost. for a normal functioning jack height drop should be almost imperceptible. if the jack drops significantly and there is no obvious leaks on the outside then it is most like caused by a leaking release valve. important: the load youre jacking during this test should be stable; with a backup support in place, to prevent the load from falling, should the jack suddenly fail. which type of leak requires more than a visual inspection to detect? internal leak. external leak.

Explanation:

External leaks are easy to identify by seeing hydraulic oil on the outside of the jack. Internal leaks are not visible from the outside and require testing by jacking up a load and observing height loss over time.

Answer:

Internal leak.