Murphy’s Law
by George Murphy
Vacuum Filters Revisited
In diesels from 1984 and earlier, if the line from the vacuum pump to the air cleaner is fouled with engine oil, the vacuum pump diaphragm may be leaking. If so, engine oil will eventually migrate throughout the vacuum systems in the car, causing the rubber parts to rapidly deteriorate. If you see oil dripping from the ignition steering lock switch in your diesel, the vacuum pump diaphragm may be leaking or the engine shutoff actuator on the injection pump may be leaking (and the engine may not shut off). The lubricating oil in a diesel engine can eat away the rubber parts in the brake booster, door lock actuators, vacuum cruise-control actuator, and climate-control flap actuators. So it is a good practice to check the system from time to time.
Starting with 1985 diesel models, a small filter was installed in the vacuum takeoff from the brake booster line. It is recommended that this filter be retrofitted to earlier diesels as it serves as a monitor of vacuum pump integrity, and, if the pump internals should fail, it prevents engine oil from reaching vacuum consumers in the car – climate control, door locks, and so forth. Now, if the diaphragm in the vacuum pump should begin leaking, oil will be clearly visible in the filter, alerting you to the problem and preventing oil from entering the vacuum systems.
This small inline transparent air filter should be installed in two locations. One can be installed in the vacuum line that connects to the T in the brake booster line – see diagram. Simply cut the rubber vacuum line about an inch from the T and insert the filter. The filter paper cone in the strainer should “point” to the vacuum source – the vacuum pump. The arrow on the filter should point toward the vacuum consumers – cruise control, climate control, door locks, and so forth. 
In this manner, any oil migrating from the vacuum pump will show up on the outside of the fluted paper cone.
It’s also a good idea to put one in the vacuum shutoff line connected to the injection pump shutoff actuator. If the actuator internal diaphragm should rupture, the filter will prevent oil from reaching the ignition shutoff switch. In this case, the arrow should point away from the shutoff actuator (see diagram).
The filter is part no. 000 078 06 56; the connector hose to use is part no. 117 078 03 81.
Power Steering Leaks, Take 2
Updated Service Bulletin for ML-Class Models 163.154/157/172/174/175, Model Years 1998 - 2004
A number of 1998-2004 ML-Class cars have been plagued with power-steering hose leakage. MBUSA issued a Service Bulletin initially in May 2003. If you missed it, more recently MBUSA issued an updated Service Bulletin (Campaign No. 2003040005, October 2008) to replace the affected power-steering hose and hose clamp.
This second bulletin was reissued to cover vehicles that were previously repaired without the latest repair kit and repair instructions. The revision also covered vehicles that were not included in the previous recall campaign.
The 2008 recall campaign involved replacement of the low-pressure power-steering hose and clamp on certain vehicles that were previously repaired without the latest repair kit. MBUSA had determined that on approximately half the vehicle, repairs under the previous recall may have been performed with a method that makes the car susceptible to future power-steering fluid leaks or disconnection of the low pressure power-steering hose.
In addition, MBUSA attempted to contact approximately 15,000 owners who did not respond to the 2003 owner notification or who were not included in the initial 2003 campaign.
These vehicles were to be repaired again with the latest service instructions and with a parts kit designed to eliminate the potential for future leakage. Dealers will replace the lower power steering hose and clamp in all affected subject vehicles.
If you own an ML built between 1998 and 2004, and are not sure whether your vehicle has been repaired with the kit specified in the 2008 recall campaign, contact your M-B dealer with your VIN and ask if the appropriate corrective repairs have been made on your car.