Thermostat — Removal, Installation and Checking (BMW 7 Series E32)

The thermostat opens a large circuit of coolant circulation when the engine warms up. If the thermostat remains closed due to a fault, the engine will be too hot. This can be determined by the temperature gauge needle being in the red area and the radiator remaining cold. A faulty thermostat can also remain open after the engine cools down. This can be determined by the engine not reaching its operating temperature or the temperature gauge needle rising more slowly than before or the heater not working effectively in cold weather.

Caution: When the engine becomes hot after a short trip, this may be due to the radiator being clogged with limescale deposits.

Removal

Remove the fan.

Drain some coolant and collect it.

Remove the hose from the thermostat housing (from the front side of the cylinder block), to do this, loosen the clamp.

Remove the bolts and the engine lifting eye. Release the wire sheath from the clamps and remove it.

Unscrew the bolts and remove the thermostat housing cover.

Mark the position of the thermostat and remove it.

Examination

Heat the thermostat in a container with water. The thermostat should not touch the walls of the container. The temperature should be measured with a suitable thermometer.



At a temperature of about 88°C, the thermostat valve will begin to open. The opening temperature of the thermostat is also indicated on its surface.

Check whether the thermostat expands and closes again and whether the opening temperature corresponds to the value indicated on it.

Note: The thermostat valve stroke must be 8.0 mm.

Installation

Clean the sealing surfaces of the housing and cover.

M52 series: Insert the thermostat into the cylinder head so that the arrow on it points upwards.





M51 and M30 series: insert the thermostat so that the air bleed valve is facing upwards. It is located in the recess of the cover when installed.



Lightly lubricate the new O-ring with glycerin and insert the ring.

Series 52: Always replace the flat paper gasket.

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

Caution: Do not tighten the bolts too tightly. On a 6-cylinder petrol engine, do not forget about the engine lifting eye. Tighten its mounting bolts.

M70 series: Insert the thermostat with the air bleed valve (1) facing upwards. Install a new seal (2).



Secure the wire sheath with clamps. Install the fan and its cover. Fill the system with coolant and bleed the air from the cooling system. Warm up the engine until the viscous coupling turns on the fan. Check if the radiator is warm at the bottom and if there are any leaks on the thermostat housing. If there are any leaks, tighten the bolts a little.







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