Air Locks After Coolant Work

After any work that opens the cooling system, the engine overheats despite the system being full of coolant. The heater blows cold air. Temperature gauge spikes erratically.

The mid-engine layout creates natural high points in the cooling system where air pockets become trapped. Unlike a conventional front-engined car where the radiator cap is the highest point, the MGF/TF's plumbing runs up, over, and down through the car. Air pockets prevent coolant from circulating through the affected section.

1. 1 Bleeding the system requires patience. Park the car nose-up on a slope if possible. Fill slowly with the heater set to maximum. Run the engine with the expansion tank cap off until no more bubbles appear. Squeeze the hoses to help dislodge air pockets. Some owners fit a bleed valve at the highest point in the system to make this process easier. Allow the engine to cool completely and repeat the process -
2. 2 air pockets often reveal themselves on the second fill cycle