Cooling System
The coolant pump shell is integrated in the timing cover. The pump wheel is still driven by the auxiliary unit's transmission.
The coolant pump pumps coolant through the cylinder block, and also cools the cylinder head, cylinder sleeves, spark plug wells, intake ducts and fuel injection nozzles.
The coolant flows in at the coolant pump and passes through a number of channels before it collects and then flows out to the thermostat housing. If the thermostat housing is closed, the coolant passes via the by-pass channel directly to the coolant pump to then circulate through the cylinder block again.
For the turbocharged engine, the task of the cooling system is to supply the turbocharger with coolant.
Coolant pump and drive gear
Engines B6324S4/B6324S5/B6304T (does not apply to XC90) are equipped with EHPAS (E lectro H ydraulic P ower A ssisted S teering) instead of a conventional belt-driven servo pump. This means that drive of the coolant pump changes. With a belt-driven servo pump drive of the coolant pump takes place via a clutch on the servo pump. To drive the coolant pump, a belt pulley of reinforced plastic has been added and the attachment for the belt pulley on the coolant pump has been changed, which means that the pump is driven directly by the auxiliaries belt. To further reduce weight the coolant pump's housing is made of aluminum instead of steel, as before.
The fastening bolts for the coolant pump are longer since the coolant pump's flange is slightly thicker due to the change of material. Same gasket as before is used.
Alternator/clutch
The belt pulleys on alternator and intermediate shaft have improved surface treatment.
On the alternator shaft between alternator and intermediate shaft there is a clutch with a freewheel (one-way clutch) at each end. The function is to filter the engine's different irregular shape and thus avoid gear rattle/noise in the geartrain.
In connection with introduction of EHPAS (electric servo pump), the belt-driven servo pump with its heavy steel belt pulley is discontinued as well as the clutch for the coolant pump. The reduced rotating moment of inertia means more freewheeling, primarily when idling.
To reduce/avoid wear, the drive gears' outer ring (against the one-way clutch's friction band), are treated with nitride.
AC bracket
The AC compressor's fastening bracket is simplified. Earlier solution with a main bracket and three separate stays, is replaced by a modified bracket which has the front reinforcement stay integrated and a new fastening point in the transmission. The change means, except that the fastener assembly has 9 fewer bolts, that the installation method becomes easier and there is no longer a need for any special tools when assembling.