1998 BMW 528i Air

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/ ~uel Tank and Fuel Pump
4 Remove tank sending unit:
Disconnect electrical harness connector.
Disconnect hose (arrow).
- Unscrew threaded collar from fuel level sender.
NOTE-
BMW special spanner 16 1 020 should be used to remove
and install the threaded collar. Damage to the collar may
result if the special tool is not used.
Slowly withdraw assembly from tank, allowing fuel to drain
off. If necessary, push level sender arm toward sending
unit to facilitate removal.
CA UTIOW-
Do not bend fuel level sender arm.
4 Once level sensor unit has been lifted partially out of tank,
disconnect tank siphon hose by pressing tabs (arrows).
- Installation is reverse of removal
Attach tank siphon hose to sender unit firmly.
Use new sealing ring at tank collar.
. Be sure that fuel sender float points in same direction as
during removal.
- Reconnect harness connector.
Fill tank and
check for leaks by running engine.
CAUTION-
After finishing repairs but before starting engine, be sure
there is at least
5 liters (1.5gallons) of fuel in tan/(. The fuel
pump will be damaged if run without fuel.
Tightening
torque
Tank collar loclting rlng to tanlt 35 Nm (26 lb-ft) -

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7 .- A Fuel Tank and Fuel Pump
Siphon pump, removing and installing
The fuel compensating siphon pump equalizes fuel level
between the two fuel tank lobes.
- Drain fuel tank as described later,
WARNING -
Fuel may be spilled. Do not smoke or work near heaters or
other fire hazards.
- Remove left and right fuel level sensors and fuel pump as
described earlier.
4 Once left side level sensor unit has been lifted partially out
of tank, disconnect tank siphon hose by pressing tabs
(arrows).
- The tank lobe siphon pump is held to baffle in bottom of right
tank lobe. Release retainer and lift out pump.
- Installation is reverse of removal.
Attach siphon pump to right side baffle.
Attach tank siphon hose to left sender unit firmly.
Use new sealing ring at tank collars
Be sure that fuel sender floats point in same direction as
during removal.
Reconnect harness connectors.
. Before starting engine, fill fuel tank with at least 5 liters
(1.5 gallons) of fuel.
Check for
leaks by running engine.
Afler finishing repairs but before starting engine, be sure

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Fuel Tank and Fuel pump/
- Remove suction hose from tank filler neck carefully to avoid
damaging filler neck baffle plate.
CAUTION-
After finishing repairs but before starling engine, be sure
there is at least
5 liters (1.5 gallons) of fuel in tanlc. The fuel
pump will be damaged if run without fuel.
Fuel tank, removing and installing
- Remove fuel tank filler cap and drain tank as described
earlier.
- Disconnect negative cable from battery.
CAUTION-
Prior to disconnecting the battea read the battery discon-
nection cautions given in
001 General Cautions and
Warnings.
- Remove rear seat bottom cushion. Peel forward lip of carpet
from beneath seat cushion and carefully peel back insulation
to expose fuel tank access cover on left and right sides. Re-
move covers.
Disconnect right side supply hose and
electr~cal harness
connector (arrows).
D~sconnect left side return hose and electrical harness
connector.
Working inside car, disconnect parking
bralte cable ends
from parking brake lever. See
340 Brakes.
Lift car and support safely.
Make sure the car is stable and
we/ supported at all times.
Use a professional automotive lift
orjack stands designed for
the purpose. A floorjaclc is not adequate support.
- Remove complete exhaust system and heat shield. See 180
Exhaust System.
- Remove drive shaft. See 260 Driveshaft

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160-22
Fuel Tank and Fuel Pump
4 Working underneath car, pinch off supply and return fuel hos-
es (arrows), then disconnect hoses from rigid metal lines.
- Remove right rear wheel and wheel housing splash shield.
4 Worlting at right rear wheel housing, loosen hose clamp
(arrow) and disconnect filler pipe from tank.
- Support tank from below. Remove tank strap mounting bolts.
Lower and remove tank, disconnecting right side vent and
other
hoses/electrical connectors as necessary.
Always use new seals, gaskets, O-rings, and hose clamps.
lnspect hoses and replace any that are chafed,
dr~ed out or
cracked.
lnspect heat shield and replace if corroded.
Inspect rubber buffers and
hers on fuel tank, support
straps and on underside of body. Replace rubber parts that
are hardened or damaged.
- After finishing repairs but before starting engine, fill fuel tank
with at least
5 liters (1.5 gallons) of fuel.
CAUTlOI+
The fuelpump will be damaged if run without fuel.
* If the filler neck has been removed from the body, be
sure to reattach the
neck grounding screw (where ap-
plicable). Check electrical resistance between the
ground tab and wheel
hub. The resistance should be
no
hiaher than 0.6f2
Tightening torques
Fuel tank to body 23 Nm (17 ft-lb)
Hose clamp
8 -13 mm dia. 2 Nm (18 in-lb)
Hose clamp 13
- 16 mm dia. 3 Nm (27 in-lb)
Hose clamp 42
- 48 mm dia. 4 Nm (36 in-lb)

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Fuel Tank and Fuel Pump 1
Activated carbon canister I fuel tank leak
detection unit
(LDP or DMTL), removing . . -
and installing
- Raise rear end of car and support safely.
CAUTION-
Make sure the car is stable and well supported at all times.
Use a professional automotive lift
orjack stands designed for
the purpose.
A floor jack is not adequate support.
- Remove left rear wheel and inner fender panel
Remove carbon canisterlfuel tank leak detection unit
(V-8 model shown):
Disconnect electrical harness connector
(A) from fuel tank
leak detection unit.
Pinch and remove quick-disconnect fittings at intake line to
air filter housing
(5) and hose to expansion tank (C).
* Remove mounting clamp and lower canister with fuel tank
leak detection unit.
Installation is reverse of removal.
Tightening
torques
Hose clamp 8 - 13 mm dia. 2 Nrn (18 in-lb)
Hose clamp
13 - 16 rnm dia 3 Nm (27 in-lb)
Running losses (312-way) valve,
removing and installing
The running losses (312-way) valve is located under the car
beneath the driver's seat, just ahead of the fuel filter. A protec-
tive covershieldsfuel system components from road hazards
and dirt.
The engine control module
(ECM) controls the operation of
the 312-way valve (pulse-width modulated). On engine start
up, the valve solenoid is energized for 20 seconds in order to
supply full fuel volume to the fuel rail.
After20 seconds, the
solenoid is deactivated and sprung closed (the bypass is
opened). This reduces the amount of fuel circulating through
the fuel rail and diverts the excess to return to the fuel tank
through the fuel pressure regulator.
The fuel injectors are supplied with pressurized fuel, but ex-
cess fuel is diverted to the fuel tank without first passing
through the fuel rail. This prevents the excess fuel from ab-
sorbing heat in the engine compartment, thus lowering the
temperature and amount of vaporization in the fuel tank.

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I Radiator and Cooling System
This section covers component repair information for the en-
gine cooling system.
Heater core replacement is covered in
640 Heating and Air
Conditioning.
Special tools
Special tools are necessaryfor belt-driven fan clutch removal
and also for pressure testing the cooling system.
4 Cooling fan counterhold wrench
(Tool No. BMW
11 5 030)
4 Cooling fan wrench
(Tool No. BMW
11 5 040)
< Expansion tank cap test adaptor
(Tool No.
BMW 17 0 007)
17 0 002 4 Cooling system pressure tester set
1 17 o 005 (Tool No. BMW 17 0 OOZi17 0 005)

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-
I Radiator and Cooling System
Mechanical thermostat
(M52 engine)
4 The mechanical thermostat relies on coolant temperature to
operate. While coolant is cold, it remains closed, and circu-
lating coolant bypasses the radiator for rapid engine warm
up. At higher coolant temperature, the thermostat progres-
sively opens to allow coolant flow through the radiator, thus
controlling engine temperature. Port
A restricts coolant flow
from radiator, and port
B restricts coolant flow to radiator.
Electrically heated thermostat
4 The electrically heated thermostat is DME map-controlled.
The engine control module (ECM) activates the thermostat to
maintain engine coolant temperature within a narrow range.
In case of failure of the electronics, the mechanical function of
the thermostat acts as a fail-safe.
Radiator and expansion tank
The radiator is a crossflow design. An expansion tank pro-
vides for coolant expansion at higher temperatures and easy
monitoring of the coolant level.
On cars with automatic transmission, ATF is circulated
through an additional heat exchanger (ATF cooler).
Mechanical cooling fan with viscous clutch
The mechanical cooling fan is belt-driven via a viscous fluid
coupling (clutch) attached to the front of the coolant pump.
The fan clutch controls the speed of the fan based on the tem-
perature of the air flowing through the radiator core.
Electric (auxiliary) cooling fan
The electric cooling fan is mounted on the bumper side of the
radiator.
In models manufactured up to
911 998 (M52 or 1997 M62 en-
gine), the electric cooling fan is controlled by a dual tempera-
ture fan switch mounted in the side of the radiator.

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170-5
Radiator and Cooling System
Fan switch calibration (M52, M62 engine)
coniprairoi OUt rlgnal
Auto. ciimilte ~ontioi inpuls via CAN bus
Electric fan activation:
Low speed
91°C (196°F)
High speed 104' C (21 9' F)
< In models manufactured after 911998 (M52 TU engine, M54
engine.
M62 TU engine), the electric cooling fan is controlled
by the engine control module (ECM) via the output final
stage.
The output final stage is mounted on the fan housing, next to
the fan motor. The fan is operated using a pulse width modu-
lated signal. Fan circuit wiring is protected by a 50-amp fuse.
Electric fan activation is based on the following inputs to the
ECM:
Radiator outlet temperature
Calculated catalytic converter temperature
Vehicle speed
* Battery voltage
Calculated
A/C pressure
When the vehicle is first started, the ECM activates the elec-
tric fan briefly at 20% of its maximum speed, then switches
off. This is for diagnostic monitoring. The voltage generated
by the fan when it slows down (acting as a generator) must
match the stored rpm values in the fan output stage toconfirm
that the fan is operating correctly.
NOTE-
If the ECM fault memory indicates a cooling fan fault, check
that the fan is not seized and that it spins freely.
When
A/C is switched ON, the electric fan is not immedi-
ately turned on.
After the engine is switched
OFF the fan may continue to
run at varying speeds for up to 10 minutes, based on cal-
culated catalyst temperature.
Transmission fluid heat exchanger
Automatic transmission fluid lines circulate transmission fluid
(ATF) to and from a heat exchanger at the radiator.
All 6-cylinder
models andV-8 models produced to 911998 are
equipped with a transmission cooler located in a cooling cas-
sette in front of the radiator.