Coolant Dumping Into Oil After Rebuild - Dislodged Front Freeze Plug

Coolingintermediate✓ OP Confirmed

Problem

After a full 7MGTE rebuild (~300 miles), coolant was rapidly entering the crankcase. When filling the radiator with a sealed funnel, coolant could be heard pouring into the crankcase instead of filling the cooling system. Draining the oil plug produced coolant.

Coolant rapidly entering crankcase when filling radiatorCoolant coming out of oil drain plugCooling system would not pressurize or sealOne-way leak: coolant into oil but not oil into coolant

Root Cause

The front internal convex (dome-shaped) expansion/freeze plug had popped out and was sitting in the oil pan. A 19 PSI radiator cap (from a Mishimoto radiator) created excessive cooling system pressure that likely dislodged the freeze plug.

Confidence

High confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted July 2023 on SupraForums.com