Thermostat replacement

Replacing the thermostat is timely if engine temperatures do not rise normally (thermostat stays open) or if the engine overheats (thermostat does not open).

You can prevent coolant from spilling onto the ground by using this "ladle technique": Pressure release: Open the expansion tank cap briefly and turn it back on. Tank relocation: Remove the expansion tank from its bracket and lower it down, for example onto the exhaust manifold or next to the fender. This lowers the coolant level at the thermostat housing. Opening: When you open the thermostat housing, at most a cupful of coolant will spill out.

The two nuts/bolts of the thermostat housing can be extremely tight or seized onto the head studs. Warning: Do not force it! If the stud breaks into the head, the job becomes much larger. Tip: Spray rust remover (e.g., WD-40 or MoS2) on the threads a few days before service.

Brand: The original part is often branded Wahler. It has proven to be extremely reliable in redblocks. Gasket: Always make sure the new thermostat comes with a new rubber gasket. Do not reuse the old, hardened gasket. Temperature: For winter use, an 92 °C thermostat is often recommended, and for summer use or heavy driving, an 87 °C or 82 °C model.

Lower the expansion tank (as explained above). Carefully open the two nuts on the thermostat housing. Remove the old thermostat and gasket. Carefully clean the housing gasket surfaces. Install the new thermostat (make sure it sits in the recess correctly) and place the new rubber gasket. Tighten the nuts evenly (do not overtighten!). Reposition the expansion tank, check the coolant level, and run the engine to warm. Top up coolant if necessary.

As the engine warms up, the upper radiator hose should stay cool until the thermostat opens. When the thermostat opens, the hose should warm quickly throughout.