low oil pressure MERCEDES-BENZ ML350 1997 Complete User Guide

216 OperationAt the gas stationEngine oil level
More information on engine oil see “Engine
oil” (
page 218).Vehicle lighting
Check function and cleanliness. More in-
formation on replacing light bulbs can be
found in the “Practical hints” section
(
page 266).
Tire inflation pressure
More information on tire inflation pressure
can be found in the “Operation” section
(page 227).
!If you find that the brake fluid in the
brake fluid reservoir has fallen to the
minimum mark or below, have the
brake system checked for brake pad
thickness and leaks immediately. Noti-
fy an authorized Mercedes-Benz Light
Truck Center immediately. Do not add
brake fluid as this will not solve the
problem. For more information, see
“Practical Hints” (
page 245).

222 OperationEngine compartment
Screw filler cap2 back on filler neck.
More information on engine oil can be
found in the “Technical data” section
(
page 300) and (
page 301).
Transmission fluid level
The transmission fluid level does not need
to be checked. If you notice transmission
fluid loss or gear shifting malfunctions,
have an authorized Mercedes-Benz Light
Truck Center check the automatic trans-
mission.Coolant
The engine coolant is a mixture of water
and anticorrosion / antifreeze. To check
the coolant level, the vehicle must be
parked on level ground and the engine
must be cool.
!Excess oil must be siphoned or drained
off. It could cause damage to the
engine and catalytic converter not
covered by the Mercedes-Benz Limited
Warranty.
Warning!
G
In order to avoid any possibly serious burns:

Use extreme caution when opening the
hood if there are any signs of steam or
coolant leaking from the cooling system,
or if the coolant temperature gauge indi-
cates that the coolant is overheated.


Do not remove pressure cap on coolant
reservoir if engine temperature is above
194°F (90°C). Allow engine to cool
down before removing cap. The coolant
reservoir contains hot fluid and is under
pressure.


Using a rag, slowly open the cap approx-
imately ½ turn to relieve excess pres-
sure. If opened immediately, scalding
hot fluid and steam will be blown out un-
der pressure.


Do not spill antifreeze on hot engine
parts. Antifreeze contains ethylene gly-
col which may burn if it comes into con-
tact with hot engine parts.


227 Operation
Tires and wheels
Life of tire
The service life of a tire is dependent upon
varying factors including but not limited to:

Driving style


Tire pressure


Distance driven
Direction of rotation
Unidirectional tires offer added advantag-
es, such as better hydroplaning perfor-
mance. To benefit, however, you must
ensure that the tires rotate in the direction
specified.
An arrow on the sidewall indicates the in-
tended direction of rotation of the tire.
Checking tire inflation pressure
Correct the tire pressure only when tires
are cold.
Regularly check your tire pressure at inter-
vals of no more than 14 days.
If the tires are warm, you should only cor-
rect the tire pressure if it is too low for cur-
rent operating conditions.
A table on the fuel filler flap lists the spec-
ified tire inflation pressures for warm and
cold tires as well as for various operating
conditions.
!When the wheels are heavily soiled,
e.g. after driving through mud, clean
the inside of the wheels with a jet of
water.Warning!
G
Tires and spare tire should be replaced after
six years, regardless of the remaining tread.
!Keep unmounted tires in a cool, dry
place with as little exposure to light as
possible. Protect tires from contact
with oil, grease and gasoline.
Warning!
G
If the tire pressure drops repeatedly:

Check the tires for punctures from for-
eign objects.


Check to see whether air is leaking from
the valves or from around the rim.

303 Technical data
Fuels, coolants, lubricants etc.
Premium unleaded gasoline
Fuel requirements
Use only premium unleaded meeting
ASTM standard D 439:

The octane number (posted at the
p um p) m us t be 91 mi n. It i s an a vera ge
of both the Research (R) octane num-
ber and the Motor (M) octane number:
(R+M) / 2). This is also known as the
ANTI-KNOCK INDEX.
Unleaded gasoline containing oxygenates
such as ethanol, IPA, IBA and TBA can be
used provided the ratio of any one of these
oxygenates to gasoline does not exceed
10%; MTBE must not exceed 15%.
The ratio of methanol to gasoline must not
exceed 3% plus additional cosolvents.
Using mixtures of ethanol and methanol is
not allowed. Gasohol, which contains 10%
ethanol and 90% unleaded gasoline, can be
used.
These blends must also meet all other fuel
requirements, such as resistance to spark
knock, boiling range, vapor pressure, etc.
Gasoline additives
A major concern among engine manufac-
turers is carbon build-up caused by gaso-
line. Mercedes-Benz recommends only the
use of quality gasoline containing additives
that prevent the build-up of carbon depos-
its.
After an extended period of using fuels
without such additives, carbon deposits
can build up especially on the intake valves
and in the combustion area, leading to en-
gine performance problems such as:

Warm-up hesitation


Unstable idle


Knocking / pinging


Misfire


Power loss
Do not blend other specific fuel additives
with fuel. This only results in unnecessary
costs and may be harmful to the engine
operation.
!To maintain the engine’s durability and
performance, premium unleaded gaso-
l i n e m u s t b e u s e d . I f p r e m i u m u n l e a d e d
is not available and low octane fuel is
used, follow these precautions:

Have the fuel tank only partially
filled with unleaded regular and fill
up with premium unleaded as soon
as possible.


Avoid full throttle driving and abrupt
acceleration.


Do not exceed an engine speed of
3000 rpm if the vehicle is loaded
with a light load such as two per-
sons and no luggage.


Do not exceed
2/3 of maximum ac-
celerator pedal position if the vehi-
cle is fully loaded or operating in
mountainous terrain.

Shift-Lock, Function

See SHIFT
-LOCK FUNCTION.
Park Pawl Interlock, Function

See PARK PAWL INTERLOCK, FUNCTION
.
Steering Lock Interlock, Function

See STEERING LOCK INTERLOCK, FUNCTION
.
Survey Of System Components, Automatic Transmission, Location/Task/Design/Function

See SURVEY OF SYSTEM COMPONENTS, AUTOMATIC TRANSMISSION,
LOCATION/TASK/DESIGN/FUNCTION.
Automatic Transmission, Function
Automatic transmission 722.6 is an electronically controlled 5-speed transmission with a lockup clutch in the
torque converter.
The ratios for the gear stages are achieved by three planetary gear sets. The 5th gear is designed with a step-up
ratio as an overdrive.
Shifting is initiated electronically. The gears are shifted by the corresponding combination of three
hydraulically actuated multi-disc clutches and two mechanical freewheels.
Basically automatic transmission 722.6 with electronic control offers the following advantages:
Reduced Fuel Consumption
Improved Shift Comfort
More Favorable Gear Steps As A Result Of 5 Gears
Enhanced Life And Reliability
Reduced Servicing Costs
The electrohydraulic control unit is bolted onto the bottom of the transmission housing. The end of the
transmission is formed by an oil pan made of sheet steel.
The oil pressure for the converter lockup clutch and center multiple-disc clutch is supplied via holes in the input
shaft. The oil pressure to the rear mulitiple-disc clutch is routed through the output shaft. The lubricating oil is
supplied and distributed by additional bore holes in both shafts. All bearing points of the gear sets as well as
freewheels and shift elements are supplied with lubricatin
g oil. NOTE: Transmission Without Touch Shift 722.6 In Model 163.

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1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662
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Operation
If the piston (B1a) on multiple-disc brake B1 is subjected to oil pressure, it presses the internal and external
discs of the disc set together. See Fig. 44
. The front sun gear (v1) on the housing is locked via the internal
multiple-disc carrier (B1c). the front planetary gears (V2) roll on the front sun gear (V1).
If the rear multiple-disc brake (B2) is engaged via the piston (B2a), then this presses the disc set together. The
center sun gear (M1) is locked against the housing via the internal multiple-disc carrier (B2c). The center
planetary gears (m2) roll on the center sun gear (M1).
If the center multiple disc brake (B3) is engaged via the piston (B3a), then the rear planetary gear carrier (H3)
and the center hollow gear (M4) are locked. When the center multiple-disc brake (B3) is engaged the direction
of rotation reverses.
Multi-Plate Clutch, Location/Task/Design/Function

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1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662
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Fig. 46: Multi-Disc Clutch, Function
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Operation
Front Multiple-Disc Clutch (K1) - If the piston (K1a) on the front multiple-disc clutch (k1) is subjected to oil
pressure, it presses the internal and external discs of the disc set together. See Fig. 46.
The front sun gear (V1) is connected to the front planetary gear carrier (V3) via the external multiple-disc
carrier (K1b) and the internal multiple-disc carrier (k1b) and the internal multiple-disc carrier (K1c). The front
planetary gear set is thus locked and turns as a closed unit.
Center Multiple-Disc Clutch (K2) - If the center multiple-disc clutch (K2) is engaged via the piston (K2a), the
piston compresses the disc set Via the internal multiple-disc carrier (K2b) and the center planetary gear carrier
(M3) on which the internal discs are seated, the front hollow gear (v4) of the front planetary gear set is
connected to the center hollow gear (M4) of the center planetary gear set. The front hollow gear (V4) and the
center hollow gear (M4) move at the same speed as the drive shaft (1).
Rear Multiple-Disc Clutch (K3) - If the rear multiple-disc clutch (K3) is engaged via the piston (K3a), then
this compresses the disc set. The center sun gear (M1) of the center planetary gear set is connected to the rear
sun gear (H1) of the rear planetary gear carrier via the external multiple-disc carrier (K3b) and internal multiple-
disc carrier (K3c). The center sun gear (M1) and the rear sun gear (H1) move at the same speed.
Upshift/Downshift Solenoid Valve, Location/Task/Design/Function

2001 Mercedes-Benz ML320
1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662
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lockup clutch (p-KUB) depending on the control pressure in converter lockup clutch (p-S/KUB). See Fig. 80.
Depending on the working pressure in the converter lockup clutch (p-KUB) the converter lockup clutch (KUB)
is:
Engaged
Disengaged
N slip mode
In the lower position of the converter lockup clutch regulating valve (27) lubricating oil (p-Sm) flows through
the torque converter and oil cooler (65) into the transmission (converter lockup clutch depressurized). In its
regulating position (slipping, torque converter lockup clutch pressurized), a reduced volume of lubricating oil
(p-Sm) flows through the annular passage (27a) bypassing the torque converter and passing direct through the
oil cooler (65) into the transmission. The other part of the lubricating oil (p-Sm) is led via the restrictor (a) into
the torque converter for cooling the converter lockup clutch (KUB).
R/P Lock, Location/Task/Design/Function

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1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662
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Task - The ETC control module (N15/3) determines the instantaneous operating condition of the vehicle and
controls all gearshift sequences taking into account the ease of shifting and the driving situation. This involves
receiving, converting and transmitting various digital and analog signals. See Fig. 96
.
It receives operating data in the form of input signals from:
Starter Lock-Out Contact (Y3/6S1)
RPM Sensor 2 (Y3/6N2)
RPM Sensor 3 (Y3/6n3)
Transmission Oil Temperature Sensor (Y3/6B1)
In addition there is a connection via the engine compartment bus to the:
Instrument Cluster (A1)
ME-SFI Control Module (N3/10) or CDI Control Module (N3/9)
The solenoid valves for the modulating and shift pressure and for the gear changes are actuated by the ETC
control module (N15/3).
The pressure required is calculated from all input signals, adjusted to the torque to be transferred. The following
information from other systems is then processed.
ME-SFI Control Module (N3/10) or CDI Control Module (N3/9):
Engine Torque
Engine Speed
Accelerator Pedal Position
Gear Shift
Engine Status
Electronic Selector Lever Module Control Module (N15/5):
Kickdown Switch (S16/6)
Selector Lever Position P/N
Traction System Control Module (N47):
Transmission Ratio
Speeds
Instrument Cluster (A1):
Selector Lever Position/Shift Range

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Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Task - The ETC control module (N15/3) determines the instantaneous operating condition for the vehicle and
controls all gearshift sequences taking into account the ease of shifting and the driving situation. See Fig. 97
.
This involves receiving , converting and transmitting various digital and analog signals.
Input signals:
Starter Lock-Out Contact (Y3/6S1)
RPM Sensor 2 (Y3/6N2)
RPM Sensor 3 (Y3/6N3)
Transmission Oil Temperature Sensor (Y3/6B1)
Kickdown Switch (S16/6)
Gear Recognition Switch (S16/10)
Output signals:
Reverse/parking lock valve
Input and output signals:
Datalink connector (X11/4)
In addition there is a connection via the engine compartment bus to the:
ME-SFI Control Module (N3/10) or CDI Control Module (N3/9)
Traction System Control Module (N47)
Transfer Case Control Module (N78)
The solenoid valves for the modulating and shift pressure and for the gear changes are actuated by the ETC
control module (N15/3). The pressure required is calculated from all input signals, adjusted to the torque to be
transferred.
The following information from other systems is then processed:
ME-SFI Control Module (N3/10) or CDI Control Module (N3/9)
(Y66/1)
Selector lever position P/N to the engine control module (ME-SFI) (N3/10) (only on detection of the
selector lever position "P" or "N" on the transmission range recognition switch (S16/10) and at the starter
interlock contact (Y3/6s1)).
Traction system control module (N47):
Wheel speeds

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