1999 BMW 525i Workshop Manual

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11 3-3
Cylinder Head Removal and Installation
4 Rotary angle torque dial gauge
(Tool No. BMW
11 2 250100 9 120)
4 El2 Torx socket for cylinder head bolts
(Tool No.
BMW 11 2 250)
4 Crankshaft loclting tool
(Tool No.
BMW 11 2 300)
4 Camshaft locking tool set, 6-cylinder
/I (Tool No, BMW 11 3 240)
< Timing chain adjustable tension setup tool, 6-cylinder
(Tool No.
BMW 11 4 220)
>
Double VANOS adiustment date
4 Secondary sprocket setup tool for double VANOS
(Tool No. BMW
11 6 180)

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11 3-4
Cylinder Head Removal and Installation
4 Camshaft locking tools (cyl. 5-8), V-8
112442 112446 (Tool No. BMW 11 2 44211 1 2 44611 1 2 44311 1 2 444)
4 Camshaft loclting tools (cyl. 1-4), V-8
(Tool No. BMW 11 2 44511
1 2 44111 1 2 44311 1 2 444)
4 Timing chain adjustable tension setup tool, V-8
(Tool No. BMW 11 3 390)
Secondary timing chain tensioner loclting pin, V-8
(Tool No. BMW 11 3 310)
4 Hydraulic lifter securing plugs
(Tool No. BMW 11 3 250)
< Camshaft bearing cap tensioner (6-cylinder)
for
camshaft removal and installation
(Tool No. BMW 11
3 26011 1 3 270)
4 Secondary timing chain tensioner loclt set
(Tool No. BMW 11 3 29111 1 3 292)

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113-5
Cylinder Head Removal and Installation I
< Fuel line plugs
(Tool No.
BMW 13 5 281113 5 282)
4 Fuel line removal tool for quick-disconnect fittings
(Tool No.
BMW 16 1 050)
< Tensioning bracket (V-8)
(Tool No. BMW 11 7 380)
Compressed air fitting for testing VANOS operation
((Tool No.
BMW 11 3 450)
< Upper timing cover installation tool set, V-8
(Tool No. BMW 11 1 41 0)
Cylinder compression, checking
A compression gauge is needed to make a compression test.
For accurate test, the battery and starter must be capable of
cranking the engine at least
300 rpm, and the engine should
be at normal operating temperature.
NOTE-
Performing a compression test may cause a fault to set in the
ECM and may illuminate the Malfunction
Indicator Light
(MIL). The light can only be turned out using either
BMW
special service scan tools or an equivalent aftermarket scan
tool. Disconnecting the battery will not erase the fault memo-
ry or turn out the light. See OBD On-Board Diagnostics.

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11 3-6
Cylinder Head Removal and Installation
- Disable ignition system by removing DME main relay. See
610 Component Locations for relay location.
WARNING-
. The ignition system produces high voltages that can be fa-
tal. Avoid contact with exposed terminals and use
exfreme
caution when working on a car with the ignition switched on
or the engine running.
Do not touch or disconnect ignition
components while
the engine is running or being cranked by the starter.
Failure to remove the DME main relay or attempting to
disa-
bie the fuel andignition systems by other methods may result
in damaoe to the enoine control module
(ECM).
- - Remove plastic cylinder head cover(s)
,,I . ,. .*,.,,&- - Remove coil grounding straps.
I CAUTION-
I nition system components. I
- Remove coils.
- Remove spark plugs from all cylinders.
NOTE-
Check the spark plugs for oil deposits that may indicate poor
cylinder sealing, then set them aside in order. Used spark
plugs should be reinstalled in the same cylinder from which
they were removed.
4 Install compression gauge in first cylinder spark plug hole,
tight enough to form a good seal.
- With parking brake set, transmission in PARK or NEUTRAL,
and accelerator pedal pressed to floor, crank engine with
starter. Record highest value indicated by gauge.
NOTE-
* The compression gauge reading should increase with
each compression stroke and reach near its maximum
reading in about
4-6 strokes.
All cylinders should reach maximum compression in the
same number of
strolces. If a cylinder needs significantly
more strokes to reach
maximum compression, there is a
problem.

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. .- . --
Lr -- - - - -- Cylinder Head Removal and Installation I -
- Release pressure at compression gauge valve, then remove
gauge from spark plug hole. Repeat test for each cylinder
and compare results with values given in Table a.
Table a. Compression testing specifications
Minimum compression
6-cylinder
10-1 1 bar (142-156 psi)
V-8 12-14 bar (174-203 psi)
Maximum difference between
cylinders (all engines)
0.5 bar (7 psi)
- Compression readings may be interpreted as follows:
Low compression indicates a poorly sealed combustion
chamber.
0 Relatively even pressures that are below specification nor-
mally indicate worn piston rings
andlor cylinder walls.
Erratic values tend to indicate valve leakage.
Dramatic differences between cylinders are often a sign of
a failed head
gasket, burned valve, or broken piston ring.
- If readings are within specifications, reinstall spark plugs and
ignition coils.
NOTE-
Used spark plugs should be reinstalled in the same cylinder
from which they were removed.
Tightening torque Spark plug to cylinder head 25 Nm
(18 ft-lb)
lanition coils to cylinder head 10 Nm (7.5 ft-lb)
- Remainder of installation is reverse of removal. Be sure to re-
install all wires disconnected during test, especially ground
wires at coils and cylinder head cover (where applicable).
Wet compression test
To further help analyze the source of poorcompression,awet
compression test is the next step.
- Repeat compression test, this time squirt a teaspoon of oil
into each cylinder. The oil will temporarily help seal between
piston rings and cylinder wall, practically eliminating leakage
past rings for a short time.
- If this test yields a higher reading than "dry" compression
test, there is probably leakage between piston rings and
cylinder walls, due either to wear or to broken piston rings.
- Little or no change in compression reading indicates other
leakage, probably from valves.

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113-8
[cylinder Head Removal and Installation 1
Cylinder leak-down test
The most conclusive diagnosis of low compression symp-
toms requires a cylinder leak-down test. Using a special
tester and compressed air, each cylinder, in turn, is pressur-
ized. The rate at which the air leaks out of the cylinder, as well
as where the air leaks out, can accurately pinpoint the magni-
tude and location of the leakage.
Before attempting any repair that requires major engine dis-
assembly, use a leak-down test to confirm low compression.
~YL~NDER HEAD REMOVAL AND
~NSTALLATION (M52 ENGINE)
WARNING-
Due to rislc of personal fnjur~: be sure the engine is cold be-
fore beginning the removal procedure.
Cylinder head removal and installation is a time consuming
repair procedure requiring multiple special
service tools.
Read the entire procedure before beginning the repair.
This procedure includes the following steps:
Cylinder head, removing,
M52 engine
Cylinder head, installing,
M52 engine
Cylinder head, removing, M52 engine
- Disconnect negative (-) cable from battery in luggage com-
partment.
CAUTION-
Prior to disconnecting the battea read the battery discon-
nection cautions in 001 General Cautions and Warnings.
-

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11 3-9
Cylinder Head Removal and Installation
< Remove left and right interior ventilation ducts (left shown):
Release ventilation filter cover latch (A) and remove cover.
Release plastic locking tab
(6) or release locking tabs on
top of duct (later models).
Rotate duct counterclockwise to unlock from bulkhead and
remove (arrow).
Disconnect electrical connector from hood switch
(C).
Release spring lock (D).
Slide filter housing away from inner fender to remove.
Removal of right side ventilation duct is similar.
Remove rear bulkhead panel: Remove rubber sealing
gasket (arrow).
0 Remove 3 mounting clips (A).
Remove
4 retaining screws (6).
Lift out panel.
< Remove complete air filter housing:
Loosen
intake duct hose clamp (A) at throttle assembly.
Loosen clamp and remove idle control hose from
~ntake
duct (6) and disconnect Idle speed control valve electr~cal
harness connector.
Disconnect
electr~cal harness connector (C) from mass alr
flow sensor.
Remove air filter housing mounting screw (D).
Disconnect vent tube
(E).
Loosen air intake duct clamp (F).
Carefully lift air filter housing out of engine bay.
4 Remove positive battery cable and intake manifold cover:
Remove protective cover from positive (+)jumper post (A).
Loosen and remove battery lead mounting nut.
Remove battery lead and push down through intake mani-
fold.
Remove trim caps (arrows) from fuel injector cover.
Remove cover hold down fasteners and lift off cover.

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113-10
Cylinder Head Removal and Installation
4 Working above engine, disconnect the following:
Vent line from cylinder head cover
(A).
. Oxygen sensor connectors (B).
Electrical harness connector from VANOS solenoid
valve
(C).
Electrical harness connectors at throttle valve position
switch
(D), ASC valve position switch (E), fuel injector har-
ness
(F) and vent valve (G).
CAUTION-
Be sure to mark oxygen sensor harness connectors so that
they can be reassembled correctly Do not interchange con-
nectors.
4 Where applicable, remove schraeder valve cap (arrow) from
air connection on fuel rail. Using a tire chuck, blow fuel back
through feed line using a brief burst of compressed air (max-
imum of
3 bar or 43.5 psi).
WARNING-
. Fuel in fuel line is underpressure (approx. 3 - 5 bar or 45 -
75 psi) and may be expelled. Do not smoke or work near
heaters or other fire hazards. Keep a fire extinguisher
handy Before disconnecting fuel hoses, wrap a cloth
around fuel hoses to absorb any leaking fuel. Catch and
dispose of escaped fuel. Plug open fuel lines.
- Always unscrew the fuel rank cap ro release pressure
;n the tank before working on the tank or lines.
Disconnect fuel lines by sliding locking collar in (arrows) and
pulling lines apart.
NOTE-
BMW uses three styles of fuel line connections; a one-time
use
clamp; a locking fitting that uses BMWspecial tool 16 1
050 to release; and a quick release sleeve (above) that dis-
connects the line when depressed.