Removal and installation, checking of the thermostat (BMW 3 Series E36)

As the engine warms up, the thermostat opens a large cooling circuit. If the thermostat fails, the engine overheats. This is determined by the increased temperature readings on the temperature gauge while the radiator remains cold. But a thermostat defect can also manifest itself in the fact that it remains open even after the liquid has cooled. This is determined by the fact that the engine does not warm up to its operating temperature or the temperature gauge needle deflects more slowly than before or in winter the heating power is insufficient.

Caution: If the engine overheats after a short distance, the cause may be limescale deposits in the radiator.

Removal

Remove the fan shroud.

Drain some of the coolant into a container. Models 316i, 318i, 318tds, 325td/tds:

Please note: On models 316i, 318i produced since September 1993, the thermostat is rigidly built into the housing and therefore cannot be removed.

Unscrew the thermostat housing cover (from the front of the engine).

Note: On a six-cylinder petrol engine the bolts are of different lengths, so to facilitate subsequent installation mark the bolt locations. In addition, the suspension bar should be removed beforehand.

Mark the installation position of the thermostat and remove the thermostat.

Examination

Heat the thermostat in a water bath. The thermostat should not touch the walls of the vessel. Monitor the temperature with an appropriate thermometer.

At a temperature of approximately 80°C, the bimetallic spring of the thermostat begins to expand. The thermostat reaches its maximum opening at approximately 95°C.

Check the opening and closing of the thermostat and the compliance of the opening temperature with the value engraved on the thermostat housing. If there are any deviations, replace the thermostat.

Installation

Clean the contact surfaces on the body and cover.



Models 320i, 325i, 328i: Install the thermostat so that the arrow points up, see illustration.



Models 318is/ti, 318tds, 325td/tds: Install the thermostat so that the air outlet is at the top, see Fig. W 1843.

Lightly lubricate the new thermostat O-ring with glycerin and insert it, see the illustrations in the "Removal" subsection.

Models 318is/ti, 320i, 325i, 328i: Be sure to replace the paper gasket.

Install the thermostat housing and tighten the bolts evenly to a torque of 10 Nm.

Caution: Do not overtighten the bolts. On models 3201, 3251 do not forget to install the suspension bar. Tighten the suspension bar bolts (thread M8) to 20 Nm.

Install the fan shroud.

Fill with coolant and bleed air from the cooling system.

Warm up the engine until the fan viscous clutch engages. If there are leaks, tighten the bolts slightly.