1998 BMW 525i belt

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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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170-8
I Radiator and Cooling System
Common cooling system faults can be grouped into one of 4
categories:
Cooling system
lealts
Poor coolant circulation
Radiator cooling fan faults
Electrical/electronic faults
Cooling system inspection
- Check that coolant pump drive belt tensioner is functioning
properly and that belt tension is correct. Belt tensioner sys-
tems for the different models are shown in
020 Maintenance.
- Check condition of coolant pump drive belt.
- Checlc coolant hoses for cracks or softness. Checlc clamps
for looseness. Check coolant level and check for evidence of
coolant
lealts from engine.
- Check that radiator fins are not blocked with dirt or debris.
Clean radiator using low-pressure water or compressed air.
Blow outward, from engine side out.
- To check coolant pump:
Remove mechanical cooling fan. See Mechanical
(vis.
cous clutch) cooling fan, removing and installing.
Remove drive belt from coolant pump pulley. See
020
Maintenance.
Firmly grasp opposite sides of pulley and check for play in
all directions.
Spin pulley and check that shaft runs smoothly without
play.
NOTE-
The coolant provides lubrication for the pump shaft, so an oc-
casional drop of coolant
lealing from the pump is acceptable.
If coolant drips steadily from the vent hole, replace the pump.
- At normal engine operating temperature, cooling system is
pressurized. This raises boiling point of coolant.
Leaks may
prevent system from becoming pressurized. If visual evi-
dence is inconclusive, pressure test cooling system as de-
scribed later to help pinpoint hard-to-find leaks.
- If cooling system is full of coolant and holds pressure:
- Use an appropriate scan tool to interrogate engine control
module (ECM) for radiator fan or DME control circuit faults.
Checlc for loose or worn drive belt.
0 Test for failed thermostat or coolant pump impeller. Some
pumps may be fitted with plastic impellers.

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170-1 9
Radiator and Cooling System
Coolant pump Remove thermostat housing fasteners
(arrows) and remove
thermostat housing.
Installation is reverse of removal, noting the following:
- Keep sealing faces clean and free of oil.
Use new sealing gasket.
Fill system with coolant. See Coolant, draining and fill-
ing
(V-8 models).
Tightening torques
Block drain plug to block 25 Nm (18 it-lb)
Coolant hose clamp (32
- 48 2. 5 Nm (22 in-lb)
mm hose diameter)
Radiator drain plug to radiator 2
- 3 Nm (18 - 27 In-lb)
Thermostat cover to
coolant pump 10 Nm (89 in-lb)
Coolant pump, replacing (6-cylinder
models)
< The engine coolant pump is mounted in the front of the en-
gine in the timing chain cover.
- Drain cooling system as described earlier. See Coolant,
draining and filling (6-cylinder models).
WARNING-
Allow cooling system to cool before opening or draining sys-
tem.
- Remove cooling fan and fan shroud. See Mechanical (vis-
cous clutch) cooling fan, removing and installing.
- Remove coolant pump drive belt. See 020 Maintenance.
4 Remove coolant pump pulley bolts (arrows) and remove pul-
ley from pump.
- Remove nuts retaining pump to engine block.
NOTE-
The coolant pump is mounted on studs and retained by nuts.

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.," --
Radiator and Cooling System --- 1
insert two M6 screws (arrows) in tapped bores and tighten
uniformly until pump is free from timing chain cover (thermo-
stat and hoses have been removed for purposes of visual
clarity).
Installation is reverse of removal, noting the following:
Be sure to replace sealing O-ring and gaskets.
Coat O-ring with water-based lubricant during installation.
Refill with coolant. See Coolant, draining and filling
(6-
cylinder models).
Tightening torques
-
Coolant pump to timing chain 10 Nm (89 in-lb)
cover
Coolant pump pulley to coolant
10 Nm (89 in-lb
pump
Engine block drain plug to block 25 Nm (1 8 It-lb)
Radiator drain plug to radiator 2 - 3 Nm (I8 - 27 in-lb)
Coolant pump, replacing (V-8 models)
I 1 < The engine coolant pump is mounted in the front of the en-
gine in ;he timing chain cover.
1. Thermostat housing
2. Thermostat
3. Thermostat sealing O-ring
4. Water pump
5. Water pump gasket
- Drain cooling system. See Coolant, draining and filling (V-
8 models).
- Remove cooling fan and fan shroud. See Mechanical (vis-
cous clutch) cooling fan, removing and installing.
- Remove engine drive belts: See 020 Maintenance.
NOTE-
Mark direction of drive belt rotation if reusing belt,
- Remove vibration dampener. See 117 Camshaft and Tim-
ing Chain.
- Disconnect mass air flow (MAF) sensor electrical harness
connector. Remove air intake duct together with
MAF sensor.
- Disconnect coolant hoses from thermostat housing and cool-
ant pump housing.

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Steering and Wheel Alignment
Power assist is provided by a belt-driven pump at the lower
left front of the engine. The power steering fluid reservoir is lo-
cated at the left side of the engine compartment.
Power steering pump, removing and
installing
When working with power steering components, absolute
cleanliness is needed to ensure proper operation of the hy-
- Empty power steering fluid reservoir using clean syringe. Do
not reuse fluid.
- Raise front of car. Remove splash shield from under engine.
WARNING-
Make sure the car is firmly supported on jack stands de-
signed for the purpose. Place jack stands beneath structural
chassis points. Do not place jack stands under suspension
Darts.
Remove drive belt from power steering pump. See
020 Main-
tenance.
Remove alternator cooling duct
Remove fluid hoses from pump. Plug openings in pump and
hose ends.
Remove pump front mounting bolts
(A).
Remove fluid line support bracket (B)
Remove pump rear mounting bolt (arrow)
- Installation is reverse of removal, noting the following:
Make sure all thread bores, bolts, nuts, fluid couplings and
mating
surfaces are clean, and inside surface of multi-
ribbed-belt is free of grease and dirt.
Use new sealing washers when reattaching power steer-
ing pressure lines.
Make sure hoses have adequate clearance from chassis.
Install front pump fasteners.

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330-5
Rear Suspension
REAR STRUTS AND SPRINGS
(SEDAN MODELS)
Rear strut assembly, removing and
installing
Replace struts and coil springs in pairs only.
- Raise car and remove rear wheels.
WARNING -
Male sure the car is firmly supported on jack stands de-
signed for the purpose. Place jack stands underneath struc-
tural chassis points. Do not place jack stands under
suspension parts.
- Remove rear parcel shelf:
Remove rear seat headrests by pulling straight up.
Remove both rear roof pillar (C-pillar) trim panels.
Unbolt rear seat
belt anchors. See 720 Seat Belts.
Models with fixed rear seat: Remove rear seat backrest.
See 520 Seats.
* Models with fold-down rear seat: Remove rear seat back-
rest side sections. See 520 Seats. Fold down backrest.
* Working inside trunk, remove roller blind mounting nuts
and bolts, if applicable. Also disconnect roller blind har-
ness connector at right edge of rear seat backrest.
Gently pry rear speaker cover grilles and rear window defog-
ger grilles
(A) out of parcel shelf.
Carefully remove seat belt and headrest mount finisher
strips (B).
Remove
middle seat headrest anchor bolts (C). Remove
headrest anchor.
Remove expansion rivets (arrows) and lift out parcel shelf.
- Remove rear speakers.
- Remove rear wheels. Remove wheel arch trim
- Support rear wheel bearing carrier.
CAUTION-
The strutassembly prevents the drive axle and wheel bearing
carrier
from dropping too far. Supporting the wheel bearing
carrierbefore disconnecting the strut mounting fasteners pre-
vents damage to the brake hose, parking brake cable and
drive axle
CV joints.

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400 Body-General
........................ General ........................... .40 0.2 Roof paddin~ 400-7
Body Assembly ................... .40 0.2
Body dimensions (in inches)
............ .40 0.2
Bodyshell
........................... 400-3
Exterior and aerodynamics
............. .40 0.3
Sport Wagon ...................... .40 0.4
Tailgate
............................ .40 0.5
Tailgate lock system
.................. .40 0.5
Rear wiper system ................... .40 0.6
Antenna and sound system ............ .40 0.6
Safety and Security Features ....... .40 0.7
Safety cage
......................... .40 0.7
Door locks and door handles
........... .40 0.7
.
........................... Seat belts 400-7
Airbags ............................ 400-8
Battery safety terminal (BST)
........... 400-9
Security
............................ 400-9
Interior Features ................... 400-9
............................. Seats 400-10
Instruments and controls .............. 400-10
Central body electronics
.............. 400-1 1
Heating and Air
Conditioning (IHKA)
............... 400-12

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Body-General
SAFETY AND SECURITY FEATURES
A number of new or improved safety and security features are
incorporated in
E39 cars.
Safety cage
4 The body safety cage is a continuation of an established
BMW concept for passenger protection. Tubular impact
structures built into the body provide protection against pas-
senger injury during front or rear impacts.
Door locks and door handles
4 The door handles allow easy door opening, but are secure in
accidents.
Electrical components in the locks are fully encapsulated and
cannot be picked easily. The door handles, latches and
loclc
assemblies offer reliability and security against theft.
Door position and
loclc condition are detected by hall sensors.
Roof padding
In addition to the side and head protection airbags, there is
supplementary padding at the roof pillars and along the roof
above the doors. This is positioned to present energy absorb-
ing
surlaces to passengers thrown around by side impact
forces.
Seat belts
Each front seat belt assembly has a height-adjustable anchor
at the 8-pillar.
An automatic pyrotechnic (explosive charge) tensioner tight-
ens the front belt at the buckle upon impact, snugging up lap
and shoulder segments of the belt. The tensioners are de-
signed to automatically tension the belts by about
2 inches
(55 mm) in the event ofa collision.
A force limiter puts an upper limit on the amount of iorce each
belt can exert on the passenger.