If you haven't already done so, use the BMW ETK (on realoem.com) for your car and VIN number to be sure what your X5 should have. One alternative to suggest, the factory pressure cap on my 2002 X5 3.0 diesel, it's rated at 1.4 bar. Part number is 17 11 1 742 232.

Note that later BMW E30 (facelift from memory) had a specific low pressure cap as part of a US market recall to minimize blown heater cores and the resulting scalding / burning a driver's right shin from the gush of hot coolant. Research this a bit, but from memory it was rated under 1 bar.

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2002 Euro X5 (E53) 3.0 diesel (M57)
5 speed manual with UUC short shifter.
Pre-xDrive NV125 transfer case (chain & gears).
Factory Xenon headlights, Spyder LED tail lights
Updated vortex crankcase breather.
Motorsport dead pedal, factory fire extinguisher, factory first aid kit, factory F&R mud flaps, factory PDC

Bilstein B6 shocks F&R
Redline oil has replaced "lifetime" fluids (F&R diff, manual transmission, transfer case and P/S).
Dimple magnetic drain plugs in all compartments.