Engine Systems
What this domain actually tests
G1 engine work is inspection and service, not overhaul. You must know the lubrication path (pickup, pump, filter, galleries, drain-back), the cooling path (water pump, thermostat, radiator, hoses, pressure cap, fan, recovery bottle), the induction path (air filter, duct, throttle body, PCV/breather), and the accessory drive (serpentine belt, tensioner, idlers, mounts, seals).
Concepts you must own
- Oil grade: the first number describes cold flow (lower = thinner when cold), the second describes viscosity at operating temperature. Follow the cap or service manual, not habit.
- A red oil-can lamp indicates low oil pressure; an amber one indicates low oil level. Different sensors, different response.
- Coolant is mixed 50/50 unless specified; fill and burp a cold engine with the heater on full hot to open the blend door.
- Thermostats fail open (slow warm-up, weak heat) or closed (overheat).
- Stretch-fit belts and serpentine routing: record the routing before removal.
Traps
Questions often dress a simple fault in a customer complaint. Overheating with a cold lower radiator hose points to the thermostat, not the water pump. A cold-start chirp that fades is usually a worn belt or tensioner, not an internal bearing. Blue smoke on startup after sitting is valve guides or seals, not piston rings. Also watch for oil consumption confused with an oil leak.
Worked example
An engine stores P0128 (coolant temperature below regulating temperature). Watch live ECT data on a road test: if temperature climbs slowly and never reaches roughly 90 C / 195 F, the thermostat is hanging open. Replace the thermostat and coolant, then verify on a drive, not at idle.
Rule of thumb
Service oil and coolant at the severe-service interval, not the longest interval printed in the manual.