⭕ Stored pressure
serious
Where you meet it: ABS accumulators · air conditioning systems · fuel rails · gas struts · hydraulic accumulators
What you need to know
- Some ABS systems (Teves Mk II, older Mercedes and Volvo) hold 2,000+ psi and must be depressurised by pumping the brake pedal 25–40 times with the ignition off before you touch a line. Otherwise you risk a high-pressure fluid injection injury — which looks like a pinprick and is a surgical emergency.
- Depressurise the fuel rail before disconnecting it — petrol vapour ignites from a static spark.
- Air conditioning refrigerant is under pressure and venting it is illegal in most jurisdictions; it must be recovered by a certified technician.
- Gas struts and shock absorbers are pressurised and will fire the rod out if cut.
The rule: NEVER crack a hydraulic or refrigerant line without confirming the system is depressurised.