Why is a hydraulic cylinder leaking or drifting?
A leaking cylinder area or an attachment that will not hold position needs a machine-specific assessment. Keep clear of the load and stop affected work. A drift symptom does not prove that replacing cylinder seals will resolve the concern.
Application & limits
Commercial trucks and equipment. Match the installed engine or machine, year and serial number before testing.
What the symptom or code tells you
Cat technical-analysis guidance treats cylinder drift and cycle-time measurements as machine-specific. Its Cat 323 example cannot supply a pass/fail limit for an unidentified machine.
Describe external fluid and unwanted movement separately. A photo of an oily rod is different evidence from a report that a boom settled while parked. Neither observation alone establishes the internal cause or an on-site repair scope.
Information to send
Use details already available from the normal operator position or your records. Do not run a test or approach a hazard to collect them.
- Machine and attachment make/model/serial.
- Which cylinder/function is affected and when the symptom was noticed.
- Existing safe photos of the leak area and rod condition, without entering the load zone.
- Load/attachment position, access restrictions and any recent hydraulic work.
What the mechanic assesses
The mechanic determines whether the request needs a leak inspection, controlled hydraulic testing, cylinder removal or shop assessment under the correct procedure. Supply, lifting/support equipment and repair location are confirmed before work. Do not perform a drift test or disconnect a line for a booking photo.
Prepare a repair request
Text the machine or vehicle, exact symptom and location. We confirm scope, safe access, parts needs, pricing and availability before a visit.
Serving Langley, Port Kells and the Lower Mainland service area. Readers elsewhere can use the source references and contact a qualified local service provider.
Related service & guides
Sources & applicability
Editorial update: . Public manufacturer and authority references checked on this date. Current vehicle-specific procedures and superseding information must be matched to the actual application before diagnosis or repair.
- Cat hydraulic-system technical analysis
Undated Cat guidance using a Cat 323 example. Cylinder drift, cycle-time and testing specifications are machine-specific. No generic test procedure is reproduced.
- Cat hydraulic repair guidance
Undated manufacturer guidance. A technical assessment can include cylinder drift, cycle time and pressure; use the exact machine manual.