Recurring 7M-GE Head Gasket Failure - Switch from OEM Composite to MLS Gasket

Engineadvanced✓ OP Confirmed

Problem

OEM Toyota composite head gaskets on the 7M-GE repeatedly fail on the exhaust side, where thin brass pieces allow the fire rings to bulge and break into coolant passages. This failure also causes divots in the head and block surfaces. Even with ARP bolts/studs torqued properly and premium fuel, the OEM gasket design is prone to eventual failure.

Recurring head gasket failure (poster went through 3 OEM gaskets)Fire ring deformation on exhaust side of every cylinderThin brass fire ring retainers folding over on exhaust sideDivots eaten into head and block deck surfaces from gasket movementCoolant breach from fire ring area into coolant passages

Root Cause

The OEM Toyota composite head gasket has a weak design on the exhaust side, with only thin pieces of brass keeping the fire rings from bulging into the water passages. Over time these brass pieces fold, allowing the gasket to deform and fail. A contributing factor is inaccurate ignition timing advance caused by using a cam sensor signal to interpolate crank position, which can cause ignition events up to 4 degrees off from assumed crank position, leading to intermittent mild detonation that accelerates gasket failure.

Confidence

High confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted December 2023 on SupraForums.com