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Pelican Technical Article:

Vacuum Pump Replacement

Steve Vernon

Time:

3 hours3 hrs

Tab:

$300 to $500

Talent:

***

Tools:

17mm Crawfoot, 19mm wrench, 6mm, 5mm Allen

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Vacuum pump, gasket

Hot Tip:

Clean the bolt heads before removing

Performance Gain:

Better running motor

Complementary Modification:

Change fuel filters

The Mercedes diesels from 1980 to 1985 have an engine driven vacuum pump. This pump performs several vital functions on your vehicle; it helps brake the car by providing vacuum pressure to the brake booster, it controls the door locks and some climate control systems as well as being the key to getting your engine to shut off. If you are having problems in any one of these areas the first thing you should do is check the vacuum pump.

As these cars age, the vacuum pumps begin to fail at a high rate. Unfortunately at the time of writing this article, rebuild kits are no longer available--which means replacing the pump unit. The pump is located on the left front of the motor and depending on whether you have a self-leveling suspension or not, this will determine what components you need to remove to replace the pump.

Over the years your car may have been serviced by multiple people including previous owners and this can lead to parts replaced with different size fasteners and hardware. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches. If something is different on your vehicle please let us know and share your info to help other users. If you have any questions or comments or even a different procedure you would like to share, please leave it below and remember to include your vehicle information.

The vacuum pump (red arrow) is located on the left front of the engine.
Figure 1

The vacuum pump (red arrow) is located on the left front of the engine. To replace it you will need to remove the fan and shroud as well as loosening the power steering pump to remove the belt. Please see our articles on these procedures for additional assistance.

Our project 300TD has the Self Leveling Suspension and the SLS pump (red arrow) stopped us from being able to loosen and remove the vacuum line on the vacuum pump (yellow arrow).
Figure 2

Our project 300TD has the Self Leveling Suspension and the SLS pump (red arrow) stopped us from being able to loosen and remove the vacuum line on the vacuum pump (yellow arrow). If you do not have the SLS pump you can simply use a 17mm Crawfoot and 19mm wrench and remove the line.

Because of the SLS pump we need to first remove the vacuum line after the power steering pump--using a 17mm Crawfoot and 19mm wrench (red arrow).
Figure 3

Because of the SLS pump we need to first remove the vacuum line after the power steering pump--using a 17mm Crawfoot and 19mm wrench (red arrow).

Check the fitting when they are separated for any corrosion as they do need to hold a vacuum and sometimes the fittings can fail.
Figure 4

Check the fitting when they are separated for any corrosion as they do need to hold a vacuum and sometimes the fittings can fail. Next use a 6mm Allen and remove the hard mount attached to the fuel filter mount (red arrow).

Move back to the pump and remove the six 5mm Allen bolts.
Figure 5

Move back to the pump and remove the six 5mm Allen bolts. Make sure the bolt heads are clear of any oil, dirt and debris before attempting to break them loose, you absolutely do NOT want to strip these bolt heads.

With the pump and line loose, we could move it around to separate the vacuum line from the pump and remove it from the engine (red arrow).
Figure 6

With the pump and line loose, we could move it around to separate the vacuum line from the pump and remove it from the engine (red arrow). Make sure to clean and inspect the mounting area around the pump on the block and always install a new gasket. Installation is the reverse of removal.

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