Vauxhall Workshop Service and Repair Manuals

New components for DOHC-0 petrol engines

From April 2003, all DOHC-0 petrol engines will be using several new components, some of which were already used on the 1st generation of DOHC-0 petrol engines, namely the Z 10 XE and Z 12 XE up to MY 2004 and then on the Z 12 XE from MY 2004. They will also feature on the new members of the 2nd generation of DOHC-0 petrol engines, the Z 10 XEP and Z 14 XEP from MY 2004, from start of production.

The main reason for using these new components is a new timing case supplier, namely SHW.

Overview of new components

As these components cannot be randomly interchanged, it is extremely important that the following component descriptions and service instructions are read and followed.

Timing case

The new timing case from SHW will replace the previous Pierburg component from MY2004 and has already been fitted to the Z 10 XE and Z 12 XE engines during MY 2003.

Difference between the two versions when not installed:

Note the following features to distinguish between the two versions when not installed:

• "Pierburg" lettering on the old version
• "SHW" lettering on the new version
• Different sealing areas where coolant pump is installed
• New design (SHW) does not have groove for coolant pump gasket

Differences when installed:

One clear way of distinguishing between the two versions when installed is the new coolant pump, which will be described in greater detail in the "Coolant pump" section.

1 Old timing case from Pierburg 5 "SHW" lettering 2 Sealing faces for coolant pump (old version) 6 Sealing faces for coolant pump (new version) 3 Groove for coolant pump gasket (old version) 7 New timing case from SHW 4 "Pierburg" lettering

•  Service:
The timing case including all associated components, can be replaced.

SHW: Unrestricted use for all model years

Pierburg: Can be used up to MY 2004

Coolant pump

All engines in the DOHC-0 series that have the new SHW timing case also have a new coolant pump.

The main feature of the new coolant pump is that it does not have a flange in the upper section where the coolant temperature sensor and the coolant connection are located.

1 Coolant connection 4 Coolant pump - old design 2 Coolant temperature sensor 5 Coolant pump - new design 3 Flange

Another feature which distinguishes the old and new coolant pumps is the pump gear which is metal on the new version and plastic on the old. The new pump gear also has a completely different shape.

The new coolant pump gasket is a flanged metal gasket which, in contrast to the rubber gasket on the old design, does not need a groove in the timing case.

•  Service:
The new coolant pump and coolant pump gasket must not be installed into the old Pierburg timing case; likewise the old coolant pump and coolant pump gasket should not be fitted into the new SHW timing case.

1 Coolant pump (old design) 4 Gasket (new design) 2 Pump gear (old design) 5 Pump gear (new design) 3 Gasket (old design) 6 Coolant pump (new design)

Thermostat

Corsa-C and Astra-G vehicles with DOHC-0 petrol engines fitted with the new coolant pump, and thereby the new timing case, also have a new thermostat, recognised from the smaller 23 mm valve disc.

This thermostat has already been in use on the Z 10 XE and Z 12 XE engines from April 2003. At this point, these thermostats still had the old part number 90 570 620. Where this was the case, the thermostat had a mark in the form of a white dot on the outside of the housing.

The reason for using the new thermostat with a smaller valve disc is the different coolant pump housing design.

To improve flow to the thermostat and the thermostat's control performance, an additional partition wall has been inserted where the thermostat is located in the coolant pump housing.

For space reasons, it was not possible to use the old thermostat with the larger disc.

A similar thermostat with a disc diameter of 23 mm, has already been in use on the Agila since the start of production.

Therefore, the previously installed thermostat can continue to be used unrestricted on Agila vehicles.

1. New coolant pump housing (thermostat flange mounting) 2. Partition wall in coolant pump housing 3. New thermostat 4. New disc with diameter of 23 mm

1. Old coolant pump housing 2. Old thermostat 3. Large disc (Corsa-C, Astra-G)

•  Service:
Under no circumstances should old thermostats with large discs be installed in the new coolant pump housing, recognised by its additional partition wall.

The new thermostats, with the smaller diameter, are compatible and can be used on all variants.

Cylinder head cover

The 4-cylinder engines of the 2nd generation DOHC-0 engine series, the Z 14 XEP, and the 1st generation Z 12 XE have a modified cylinder head cover which can be fitted to both the new SHW timing case and to the old Pierburg timing case

The reason for the modification is the insufficient gap between the old cylinder head cover, the coolant hose for throttle valve pre-heating and the coolant temperature sensor wiring harness plug.

The cylinder head cover on the 3 cylinder engines is not affected by this change as the problem of an insufficient gap does not arise here.

•  Service:
The old cylinder head cover must not be installed in combination with the new SHW timing case.

1. Old 4-cylinder engine cylinder head cover without recesses 2. New 4-cylinder engine cylinder head cover with recesses

Oil pump

All engines in the DOHC-0 series that have the new SHW timing case also have a new oil pump.

The new friction-optimised oil pump has a greater delivery rate and differs from the old oil pump as follows:

1 New external rotor 4 Relief on old internal rotor 2 New internal rotor 5 Old external rotor 3 Old internal rotor

•  Service:
Components of the new oil pump must not be installed in the old Pierburg timing case; likewise components of the old oil pump should not be installed in the new SHW timing case.

Like on the old design, when installing the external rotor ensure that the side with the chamfer going round the outer diameter is facing into the timing case.

The rotor recess (gap between rotors and upper edge of timing case) is measured with a straight-edge and a feeler gauge - permissible axial clearance is (0.020 ...0.065) mm on the new version, whilst it is (0.035...0.070) mm on the old.

1. External rotor 2. Chamfer

Oil pump cover

All DOHC-0 petrol engines that have the new oil pump, and thereby also the new timing case, also have a new oil pump cover.

The new oil pump cover is no longer made of steel but of aluminium and is attached by means of 6 socket-head cap screws instead of countersunk screws.

•  Service:
The new oil pump cover and new fastening screws must not be fitted to the old Pierburg timing case; likewise the old oil pump cover and old fastening screws must not be fitted to the new SHW timing case.

The specified tightening torque for the new fastening screws is 8 Nm, as on the former design.

1 Old oil pump cover 3 New socket head cap screw 2 Old countersunk screw 4 New oil pump cover

Oil pressure regulating valve

The oil pressure regulating valve has an different spring with a total of 13.5 instead of 12.5 turns. This has increased the opening pressure of the oil pressure regulating valve. Overview of part numbers: New spring - oil pressure regulating valve, part number: 55 354 283 Old spring - oil pressure regulating valve, part number: 90 529 547 •  Service: The new springs with 13.5 windings can only be installed in the SHW timing case. The old springs with 12.5 windings must only be installed in the Pierburg timing case. The new seal ring of the seal plug is now made of copper instead of aluminium, but can be used on all DOHC-0 engines. Plunger, pins and seal plug have the same design and can therefore be used on all versions of the DOHC-0 engine, both 1st and 2nd generation. 1 Piston 4 Seal ring 2 Spring 5 Seal plug 3 Pin