ACtion Magazine - September/October 2013 - (Page 14)

Ford’s hydraulic cooling fan by Jacques Gordon T he 3.9-liter Ford AJ35 engine is actually a Jaguar V-8 built in Ohio. It was used in the 2000-06 Lincoln LS and 200205 Ford Thunderbird (Ford owned Jaguar from 1989 to 2008). One unusual feature is the hydraulically-driven engine cooling fan. The hydraulic motor is powered by a dedicated pump. Fan speed is controlled with a pulse-width-modulated (PWM) pressure control valve mounted on the pump. Two special fault codes are associated with this engine: P1258 (cylinder head over temperature) and P1299 (cylinder head overtemperature-protection activated). In addition to the normal coolant temperature sensor, there is a cylinder head temperature sensor (CHT) on the left head. If CHT exceeds the programmed limit, the PCM’s over-temperature-protection program will warn the driver and alternately disable fuel injectors to pump fresh air through the engine cylinders. The engine will continue running at reduced power and even for a limited period at full power/wide-open-throttle, but if temperature continues to climb, the PCM will disable all the injectors. There is a lot of inaccurate and/or incomplete information about this engine in aftermarket information sources, often because the information shown is for the V-6 engine also used in these models. If your service information shows only electric cooling fans or does not show the hydraulic pump in the drive belt routing diagram, keep looking. A common failure mode is that the fan runs even when the engine is cold, indicating a leaking pressure control valve. Commanding full duty cycle on that valve should make the fan run at full speed. If not, check the fluid level. If the fan runs at full speed all the time, this may be due to cylinder head overheating even though the instrument panel gauge shows normal coolant temperature. Also, if the CHT sensor fails, the scan tool will show a substitute value. Check resistance of the CHT sensor against the resistance/temperature chart. A stuck heater control valve will generate A/C fault codes and may even cause the engine to overheat. Thermostat failure is also common, and so is a cracked thermostat housing; replace both at the same time. This cooling system is very difficult to bleed, and air in the system can cause local or intermittent overheating and odd cooling fan behavior. A vacuum cooling system filler tool solves that problem. Ford’s Failure Mode Effects Management (FMEM) is a control strategy that lets the PCM continue operating the engine if any sensors fail. The PCM will substitute a fixed value and that number may be shown on the scan tool. If the sensor begins to operate within limits again, the PCM returns to the normal engine operating strategy. All FMEM sensors display a 14 ACTION • September/October 2013 sequence error message on the factory (or enhanced) scan tool. The message may or may not be followed by fault codes when attempting Key On Engine Running (KOER) self-test mode.

Table of Contents for the Digital Edition of ACtion Magazine - September/October 2013

ACtion Magazine - September/October 2013
Contents
Outlook
Freeze Frame
Virtual View
Leonard’s Law
Cooling Corner
Member Profile
News & Updates
Special Update on R-1234YF
Technician’s Operating Procedure
Emergency Business Plans
Association News
Quick Check
New Products & Services
Last Watch

ACtion Magazine - September/October 2013