2012 Infiniti G (G37)

On pre-2013 VQ37VHR engines, the internal oil gallery gaskets located behind the front timing cover are made of a fragile paper composite. Over heat cycles, these gaskets degrade, tear, or blow out, bleeding high-pressure engine oil internally back into the oil pan before it reaches the upper valvetrain. This causes a dramatic drop in oil pressure to the Variable Valve Event and Lift (VVEL) phasers and camshafts. If ignored, valvetrain oil starvation can cause catastrophic engine failure. Nissan later updated the part to a metal-reinforced gasket. Remediation requires an extensive front-engine teardown involving 12 to 15 hours of workshop labour to remove the front timing cover and fit updated metal gaskets.

Symptoms: Check engine light with stored diagnostic trouble codes P0011 or P0021 indicating intake valve timing control performance, Low oil pressure warning lamp illuminating at warm idle...

Est. repair cost: £1,200–£2,200

The factory plastic heater hose coupler located against the passenger-side engine bay bulkhead degrades and becomes extremely brittle after repeated heat cycling. At higher mileages, the plastic fractures or shears completely under coolant system pressure, suddenly venting engine coolant onto the hot exhaust and ground. Because the coolant is lost within seconds, rapid engine overheating occurs. If the driver fails to shut down the engine immediately, cylinder head warping or head gasket failure can quickly follow. Replacing the fragile plastic connector with an aftermarket billet aluminium or brass barbed coupler is a standard preventative measure amongst UK specialists.

Symptoms: Sudden dumping of engine coolant underneath the passenger side of the vehicle, Sweet-smelling white steam billowing from behind the engine bay near the bulkhead...

Est. repair cost: £150–£400

On the G37 Convertible (HV36), the complex three-piece electro-hydraulic folding hardtop system is vulnerable to microswitch misalignment, hydraulic pump pressure loss, and weatherseal deterioration. Wear in the roof latching linkages or failed position sensors can cause the roof to stall halfway through its 25-second cycle. Furthermore, drying weatherstrips and clogged rear drainage tubes allow rainwater to seep past the C-pillar seals into the luggage compartment, soaking the boot floor carpet and short-circuiting the roof control module and the Bose audio amplifier located beneath the trim panels.

Symptoms: Folding hardtop stops moving mid-cycle and displays a roof malfunction warning on the instrument cluster, Audible chimes and refusal to unlatch or lock into the windscreen header rail...

Est. repair cost: £400–£1,800