BMW 3 (E46). Manual — part 93

Table a. Cooling system test
pressures

Component

Test pressure

psi)

Radiator cap

2 bar (29 psi)

CAUTION!

Exceeding the specified test
pressure could damage the radiator
or other system components.

Combustion chamber leak test

-

If you suspect that combustion
chamber pressure is leaking into
the cooling system past the
cylinder head gasket, use an
exhaust gas analyzer to test the
vapors rising from the coolant at
the expansion tank.

CAUTION!

Use an extension tube above the
reservoir neck to maintain
distance between the top of the
coolant and the gas analyzer
nozzle. The gas analyzer is
easily damaged if it is allowed to
inhale liquid coolant.

While running engine to check
for causes of overheating,
observe coolant temperature
carefully in order to avoid
engine damage.

Thermostat, checking

If the engine overheats or runs too cool
and no other cooling system tests

indicate trouble, the electrically heated
thermostat may be faulty.

Check for thermostat diagnostic fault
codes (DTCs) using BMW scan tools
DIS or MoDiC or equivalent. DTCs
pertaining to cooling system
malfunctions are listed in

Table b

.

See also

OBD On Board Diagnostics

at the back of this manual.

Table b. Cooling system fault
codes

BMW
fault
code

Explanation

Possible
cause(s)

10

Engine
coolant
temperature
out of
predefined
range

Faulty
thermostat or
cooling fan.
Faulty wiring
to cooling fan
or
thermostat.

222

Insufficient
coolant
temperature
signal to
permit closed
loop operation

Faulty
thermostat.
Faulty
thermostat
electrical
circuit.

170-3

Cooling System Service

Coolant, draining and filling

WARNING!

Allow the cooling system to cool
before opening or draining the
cooling system.

-

Raise front of car and support
safely.

CAUTION!

Make sure the car is stable and well
supported at all times. Use a
professional automotive lift or jack
stands designed for the purpose. A
floor jack is not adequate support.

-

Remove splash shield from under
engine.

Loosen radiator bleed screw at top
radiator fitting (arrow).

-

Remove cap from radiator
expansion tank. Set temperature
controls to full warm.

-

Place 3-gallon pail underneath
radiator.

Remove drain plug (arrow) on bottom
of radiator.

WARNING!

Coolant is poisonous. It is especially
lethal to pets. Clean up spills
immediately and rinse the area with
water.

Place empty 3-gallon pail underneath
exhaust side of engine block. Loosen
and remove engine block coolant drain
plug (arrow).

Note:

The block drain plug is located on the
exhaust side of the engine block at
cylinder 2.

-

Reinstall radiator and engine
block drain plugs using new
sealing washers.

-

Before refilling radiator:

Switch ignition to ON.

Set temperature controls to full
warm.

Set blower control to low.

-

Using a coolant mixture of 50%
antifreeze and 50% distilled water,
fill expansion tank slowly.
Continue until coolant emerges
from bleed screw. Cooling system
capacity is listed in

Table c

.

Note:

Be sure radiator bleed screw is
loose when filling cooling system.