Ticking Noise at Hot Idle - Oil Viscosity Increase with Lucas Stabilizer

Enginebeginner✓ OP Confirmed

Problem

1990 non-turbo 7MGE develops a ticking noise only when idling after being driven hard and reaching full operating temperature. The noise is not audible from the engine bay but is clearly heard from the driver's seat and through the wheels. Noise disappears above 1200 RPM.

Ticking noise at hot idle after hard driving (above 3000 RPM)Noise not present when driven casually below 3000 RPMNoise disappears above 1200 RPMNoise audible from driver's seat and side of car near wheel, but not from engine bayNoise localized to rear of engine near bellhousing via mechanic's stethoscopeNoise only present in hot weather / summer conditionsHistory of running 87 octane with multiple detonation events

Root Cause

Worn bearings (likely rear cam bearings or #6 rod bearing) causing ticking at hot idle when oil is thinnest and oil pressure is lowest. The combination of hot expanded metal clearances, thinned oil at operating temperature, and low idle oil pressure allows enough play in the worn bearings to produce the ticking. Previous detonation events from running 87 octane fuel likely contributed to bearing wear. The noise disappears at higher RPM because oil pressure increases.

Confidence

Moderate confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted August 2023 on SupraForums.com