low oil pressure AUDI S4 1998 B5 / 1.G Engine Manual

1415
SSP 198/49

Engine
Engine lubrication
The oil circuit of the 2.7-litre V6 biturbo engine largely corresponds to that
of the 3rd V6 engine generation.
In addition, the two exhaust gas turbochargers are supplied with
pressurised oil from the main oil gallery via a distributor piece. The oil is
returned directly to the oil sump.
The oil cooler was adapted to withstand the higher thermal stresses in
comparison with a naturally aspirated engine.A new feature of the biturbo is
the “integrated oil supply“ (see
next page).
to oil filter/oil cooler
Spring-loaded slipper
(chain tensioner)
Main oil gallery
Oil retention valves
Bypass valve
Filter element
Bearing cap
Oil groove
Oil temperature
sender
Oil pressure switch
Restrictor
Oil retention
valve
distributor piece

The oil circuit
A duocentric oil pump draws in the oil
through a coarse filter. Located in the
pressure chamber of the pump is a
pressure relief valve which protects
downstream components against
pressure peaks during cold starts.
The oil is fed to the oil filter via the oil
cooler. After passing an oil retention
valve, the oil flows through the filter
element. A bypass filter is connected in
parallel with the filter element.
The oil subsequently reaches the main
oil gallery. A branch line is routed to the
oil pressure control valve (clean oil
side).
The following components are supplied
with oil from the main oil gallery:
- the four crankshaft bearings
- the two exhaust gas turbochargers
via an oil distributor line
- the three pairs of piston spray jets via
a spray jet valve
- the cylinder head of cylinder bank 1
via an oil retention valve
The cylinder head of cylinder bank 2 is
supplied through a separate bore from
crankshaft bearing 2 via an oil retention
valve also.
First of all, the camshaft adjustment
valve is supplied with oil from the inlet
drilling in the cylinder head. After the oil
has passed by a restrictor, it is
channeled via the cylinder head main
gallery to the hydraulic valve tappets
and the camshaft bearings.
Exhaust gas turbocharger
Bypass filter
Oil pressure relief valve
from oil filter/oil coolerOil pressure
control valveInduction filter
Oil pressure relief valve
from oil filter/oil cooler
to oil filter/oil cooler

16
Engine
The component parts of the oil circuit
is integrated in the primary flow. By increasing
the capacity and optimising the flow
resistance, the entire oil flow can be routed
through the oil cooler. Unlike the V6 naturally
aspirated engine, a bypass is not required.
The oil cooler ......
contains an oil retention valve, the filter
element, a bypass filter and the filter bypass
valve. The latter has the task of maintaining
engine lubrication via the bypass filter if the
filter element becomes clogged up or if the oil
has a high viscosity.
The oil filter ......
opens up the oil flow to the piston spray jets if
the oil pressure is greater than 1.8 bar.
Reason: at low oil viscosity and low engine
speeds, the oil pressure would otherwise drop
below the minimum permissible level. That
aside, piston cooling is not necessary at low
engine speeds.
The spray jets valve ......
SSP 198/57

Oil pressure control valve
Oil pressure limiting valve
Chain guard

is an internal gear pump. It is attached to the
crankcase as a separate component.
The oil pump is designed in such a way that it
projects deep down into the oil sump and is
immersed completely in the engine oil when
the oil level is correct. This prevents the oil
pump running dry.
The oil pump, in combination with the
extremely short intake path, enables oil
pressure to build up more quickly and safely,
particularly during cold starts.
The oil pump is driven by the crankshaft by
means of a single chain.
A spring-loaded flat plate produces the
necessary tension.
A new feature of the oil pump is the chain
guard made from sheet steel. It encapsulates
both the chain wheel and the chain over a large
area.
This reliably prevents oil frothing and the
problems associated with this.
The oil pump ......

17
is a pressure relief valve. It is located inside the
oil pump housing and opens when the oil
pressure rises too high (cold start). If an
excessively high oil pressure builds up,
various component parts of the oil circuit (e.g.
oil filter, oil cooler) may be damaged. Also,
there is the possibility of the inlet and exhaust
valves opening or no longer closing, due to
“bulking“ of the hydraulic tappets. The knock-
on effect of this is that the engine can no
longer be started or cuts out.
The oil pressure limiting valve ......
regulates the engine oil pressure. It is
integrated in the oil pump housing. The oil
quantity “regulated“ by the oil pressure
control valve is fed to the suction side of the
oil pump.
This helps to optimise efficiency.
The oil pressure control valve ......
prevent the oil running out of the oil filter and
the cylinder heads and back into the oil sump
while the engine is stationary.
The oil retention valves ......
The “integrated oil supply“ ...
will also be adopted for all V6 5V naturally
aspirated engines.
Each camshaft bearing is supplied via a
drilling stemming from the cylinder head main
gallery.
The oil is fed along a bolt shaft in the bearing
cap to a transverse drilling.
A lubrication groove distributes the oil
throughout the camshaft bearing. It is no
longer necessary to run a pipe to the
individual bearing caps.
Advantages:
•
Fewer components
•
Quick and even oil supply
•
No additional installation work necessary
•
Lower cost
SSP 198/58

Cylinder head main gallery
Transverse drilling

prevent “flooding“ of the cylinder heads. At
high engine speeds, an excessively large
amount of oil enters the cylinder heads and
has to be returned to the oil sump via the oil
return drillings. The restrictors reduce the oil
flow and thereby ensure that return flow takes
place.
The restrictors ......

30
SSP 198/07

Engine
The crankcase breather ...
...comprises a distributor piece, a pressure
limiting valve, a non-return valve and the
associated hoses.
The oil vapours and “blow-by“ gases from the
cylinder heads and the crankcase converge in
the distributor piece.
The pressure limiting valve and the non-return
valve control the return of these vapours and
gases to the engine, depending on the intake
manifold pressure.
Vacuum in intake manifold:
The oil vapours and “blow-by“ gases return
via the non-return valve in the intake manifold.
charge pressure in intake manifold:
The oil vapours and “blow-by“ gases return
via the pressure limiting valve in the air
distributor.The pressure limiting valve limits the vacuum
in the crankcase. If the vacuum in the
crankcase exceeds a defined value, the
diaphragm is drawn over the connection
against the force of the spring and closes the
connection. The valve is designed in such a
way that it allows a small quantity to pass
through when closed. This prevents the engine
oil being drawn into the intake tract and has no
adverse effects on engine breathing.
Distributor piece
Pressure limiting valve
Non-return valve
The term “blow-by“ gases refers to
the gases which escape from the
combustion chamber past the piston
rings.
Connection
Diaphragm
Air distributor
to air
distributor
from
distributor
piece

62
Functional diagram
Components:
F Brake light switch
F36 Clutch pedal switch
F47 Brake pedal switch
F96 Altitude sender (integrated in engine
control unit)
G2 Coolant temperature sender
G6 Fuel pump
G28 Engine speed sender
G31 Charge pressure sender
G39 Lambda probe (cylinder bank 1)
G40 Hall sender (cylinder bank 2)
G42 Intake air temperature sender
G 61 Knock sensor (cylinder bank 1)
G62 Coolant temperature sender
G66 Knock sensor (cylinder bank 2)
G70 Air mass meter
G79 Accelerator position sender 1
G108 Lambda probe (cylinder bank 2)
G163 Hall sender (cylinder bank 1)
G185 Accelerator position sender 2
G186 Throttle valve drive (electric throttle
control)
G187 Angle sender 1 for throttle valve drive
G188 Angle sender 2 for throttle valve drive
G235 Sender 1 for exhaust gas temperature
G236 Sender 2 for exhaust gas temperature
J17 Fuel pump relay
J220 Motronic control unit
J338 throttle valve control part
K132 Warning lamp for electric throttle
control
N Ignition coil, cylinder 1
N30 Injector, cylinder 1
N31 Injector, cylinder 2
N32 Injector, cylinder 3
N33 Injector , cylinder 4
N75 Solenoid valve for charge pressure
control
N80 Solenoid valve for activated charcoal
canister
N83 Injector, cylinder 5
N84 Injector, cylinder 6
N122 Output stage (cylinder bank 1)
N128 Ignition coil, cylinder 2
N158 Ignition coil, cylinder 3
N163 Ignition coil, cylinder 4
N164 Ignition coil, cylinder 5N189 Ignition coil, cylinder 6
N192 Output stage (cylinder bank 2)
N205 Camshaft adjustment valve 1 (cylinder
bank 1)
N208 Camshaft adjustment valve 2
(cylinder bank 2)
N249 Divert air valve for turbocharger
Z19 Heater for lambda probe
Z28 Heater for lambda probe 2
I To dash panel insert
II To dash panel insert (warning lamp)
Additional signals
1 CAN-high (automatic gearbox)
2 CAN-low (automatic gearbox)
3 „Set/decelerate“ signal for cruise
control system
4 “Off“ signal without cancellation for
cruise control system
5 “On/Off“ signal with cancellation for
cruise control system
6 Resume/accelerate“ signal for cruise
control system
7 Road speed signal
8 Immobiliser/diagnosis signal
9 Air conditioner compressor “On/Off“
signal
10 Coolant temperature signal
11 Engine speed signal
12 Fuel consumption signal
Colour codes:
Input signal
Output signal
Positive
Earth
Bidirectional