This document is uncontrolled when printed. Before use, check the
McLaren Knowledge Base website to verify that this is the current MTI
version.

Vehicles affected: All vehicles
Location: Chassis - Steering
Concern: Excessive noise from the power steering pump

Condition: Constant and/or when turning the steering wheel

Diagnostic Trouble Codes

N/A

Measure

All McLaren vehicles are equipped with an electronic pump to supply pressure for the
power steering and suspension system.

The pump is located at the front end of the vehicle, behind the luggage bin.
It is called EPHS upon MDS and within technical information.

The pump is operating at high speed, up to 5600 RPM, and is mounted upon rubber
Vibration Absorbent mountings.

The pump is also wrapped in a sound absorbing jacket to prevent unwanted noise
levels,

All EPHS pumps will generate a characteristic high frequency noise in operation,
however if this noise is determined to be too high the following should be verified.

= Make a comparison with another vehicle of the same variant, model year, and
software level.
= Verify if the complaint is excessive noise from inside or outside the cabin.

= Verify that once the fluid gets warm (for info the fluid will get warm after
approximately 5 minutes of pump normal operation or after 1 minute having the
steering wheel at full lock position) the pump goes into sleep mode (1000rpm) when
the steering is not being moved. If the pump does not enter sleep mode, check the
status of the steering angle sensor signal in the SAS actual values. If the value
fluctuates (should be O deg) it can indicate an issue the steering angle sensor inside
the MRM.

= Verify the condition of the pump’s mountings, check they are not twisted or in “Shear”
condition with split rubber - see image below.

= Verify no contact can be made between the pump and it’s mounting bracket - see
images below.

= Verify the installation of the noise isolation jacket.

Image below of incorrectly fitted noise isolation jacket.

Verify the jacket is not loose, Velcro tape must not be visible.

Correctly fitted noise isolation jacket

Ensure sealing of the HVAC distribution box to the bulkhead is correctly applied. If the
HVAC unit is not sealed to the bulkhead unwanted noise from EPHS can be heard
inside the cabin. See image below. Reseal using RTV sealer as detailed with SIS if this
issue Is present.

= Hydraulic system pipes should be correctly routed, clipped and secured together to
prevent clash and unwanted vibration / noise

= Ensure the electrical harness is routed correctly so that is not contacting the noise
isolation jacket of the pump. If the adjacent harness is not routed correctly it can
press upon the pump’s jacket, unwanted noise can transfer to the carbon tub,
Shortcutting the antivibration mountings

MTIl Updates Information

N/A

This document is uncontrolled when printed. Before use, check the McLaren
Knowledge Base website to verify that this is the current MTI version.