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Replacing Your Oil Pump on your Mercedes-Benz
 
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Pelican Technical Article:

Replacing Your Oil Pump on your Mercedes-Benz

Steve Vernon

Time:

3 hour3 hr

Tab:

$338

Talent:

**

Tools:

13mm, 17mm wrench, 13mm socket and extension, flathead screw driver, 5mm Allen key

Applicable Models:

Mercedes-Benz W126 (1981-91)

Parts Required:

New oil pump

Hot Tip:

Check your chain and rail

Performance Gain:

Peace of mind over your oil pressure

Complementary Modification:

Oil and Filter

Proper oil pressure is crucial to your engines life. Your oil is the life blood of the engine and must be maintained at proper temperatures and pressures for the engine to function properly and last. The most important component of your engines oiling system is the oil pump.

The pump on the W126 is located on the front of the engine and is driven by a chain and sprocket driven from the front of the crank shaft. The lower part of the pump sits in the bottom of the oil pan and picks up the oil the has re-circulated down into the pan, and while there is a screen on the oil pick up debris and contaminants can get into the pump and destroy it over time. While the Mercedes-Benz W126 are not known for oil pump failures, they are know as one of the easiest oil pumps to replace. If you are going to be ordering your parts in advance, it is a good idea to plan on replacing the chain while you are in there.

You don't want to get everything apart and find out you can't put it back together for want of a chain.

Begin by safely lifting and supporting your Mercedes-Benz W126, please see our article on safely lifting and supporting your car.

Next drain your motor oil. You do not need the engine or oil to be hot as you are going to be taking the oil pan off which will give you plenty of opportunity to really clean the gunk out of the bottom of the pan.

With the oil drained remove the 20 5mm Allen-head screws holding the lower pan to the bottom of the front of the engine. Some of these screws might also hold the transmission cooling lines. I like to leave one screw on each corner with a little threat still in the engine case; this will help you remove the pan without having it fall off and spill oil everywhere.

You can now see the oil pump and the three 13mm bolts that hold it to the block along with the 13mm bolt holding the chain sprocket on.

Remove the 13mm bolt holding the sprocket to the pump.

Next remove the three 13mm bolts holding the pump to the case. Tilt the pump towards the rear and using a flathead screwdriver slip the chain sprocket off the front of the pump.

With the sprocket off the pump you can lower the pump out of the motor. Check that the new sprocket has the same amount of teeth as the old one. If the sprocket is heavily worn or damaged it is a good idea to replace the chain while you are in there. The new chain will have an open link, you will need to find the link on the old one a disassemble it. It is a really good to attach the new chain to the old and then hand turn the engine over until the new chain is securely on the crank sprocket.

Use a 13mm wrench and remove the drain plug and drain the oil from the car.
Figure 1

Use a 13mm wrench and remove the drain plug and drain the oil from the car.

With the oil drained remove the twenty 5mm Allen head screws (red arrow only one shown) holding the lower pan to the bottom of the front of the engine.
Figure 2

With the oil drained remove the twenty 5mm Allen head screws (red arrow only one shown) holding the lower pan to the bottom of the front of the engine. Some of these screws might also hold the transmission cooling lines. I like to leave one screw on each corner with a little threat still in the engine case, this will help you remove the pan without having it fall off and spill oil everywhere.

You can now see the oil pump and the three 13mm bolts (green arrows) that hold it to the block along with the 13mm bolt holding the chain sprocket on (red arrow).
Figure 3

You can now see the oil pump and the three 13mm bolts (green arrows) that hold it to the block along with the 13mm bolt holding the chain sprocket on (red arrow). Note: we preformed this work on an engine that had suffered a catastrophic timing chain failure, you will should not see the main timing chain hanging from the lower part of the motor!

Remove the 13mm bolt (red arrow) holding the sprocket to the pump.
Figure 4

Remove the 13mm bolt (red arrow) holding the sprocket to the pump. You are going to slip the sprocket off the locating pin (yellow arrow) in a minute.

Next remove the three 13mm bolts (red arrows) holding the pump to the case.
Figure 5

Next remove the three 13mm bolts (red arrows) holding the pump to the case.

Tilt the pump towards the rear (red arrow) and using a flathead screwdriver slip the chain sprocket off the front of the pump (green arrow).
Figure 6

Tilt the pump towards the rear (red arrow) and using a flathead screwdriver slip the chain sprocket off the front of the pump (green arrow). With the sprocket off the pump you can lower the pump out of the motor. Note: we preformed this work on an engine that had suffered a catastrophic timing chain failure, you will should not see the main timing chain hanging from the lower part of the motor!

This photo shows the oil pump out of the motor.
Figure 7

This photo shows the oil pump out of the motor.

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Comments and Suggestions:
Papa Roy Comments: Pelican team, I have had the clanking oil pump failure sounds and oil pressure total failure. Vehicle is W 124 class / Mercedes 260e, well care for at 225,400 miles. After a replacement cat converter and oil service I passed smog check!Then a week after the engine made a suction sound recovered briefly then the chartering started just 2 miles from home, turned around back and its parked. Yes I have good to advanced mechanical skills water pump, lifters and some minor engine work. I'm up to the task on the oil pump replacement. I do need you tech notes on the removal & repair. I have used your articles on many repairs to my vehicles. I am a US Service Veteran, with excellent, complete helicopter combat repair & recovery tactical field repaired flyable status... this Mercedes is my daily driver & classic shape! Help me, coach me to success!
April 16, 2016
  Followup from the Pelican Staff: First check oil pressure to see if it is out of spec. The issue could be the oil pump or a timing chain.

We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
Homer Comments: how about w140 1992 400se oil pump replacement?
January 6, 2015
  Followup from the Pelican Staff: We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
arcticbenz Comments: I have a 1988 560 SEL. Do these instructions apply. What would be the cost of the pump, pan gasket, timing chain cover gasket, timing chain and rail.
would I have to pull the motor to change timing chain?
December 29, 2014
  Followup from the Pelican Staff: I am not the best with costs or part numbers:

Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.


This tech article applies to:
Mercedes 560SEC (1986-1991)
Mercedes 280SE 4.5 (1972-1973)
Mercedes 280SEL (1972-1973)
Mercedes 300SEL (1971-1973)
Mercedes 450SC (1973-1980)
Mercedes 450SEL (1973-1980)
Mercedes 560SEL (1986-1989)
Mercedes 500SEC (1984-1985)
Mercedes 280SE 3.5 (1971-1971)
Mercedes 450SLC (1973-1980)
Mercedes 500SL (1980-1989)
Mercedes 500SLC (1986-1991)
Mercedes 350SL 4.5 (1972-1972)
Mercedes 450SL (1973-1980)
Mercedes 380SEL (1980-1985)
Mercedes 380SE (1979-1985)
Mercedes 380SEC (1982-1983)
Mercedes 420SE (1985-1991)
Mercedes 420SEL (1985-1991)
Mercedes 420SEC (1985-1991)
Mercedes 500SEL (1984-1985)
Mercedes 350SE (1973-1980)
Mercedes 350SEL (1973-1980)
Mercedes 380SLC (1981-1981)
Mercedes 350SL (1971-1980)
Mercedes 380SL (1981-1985)
Mercedes 350SLC (1971-1980)
Mercedes 280SE 3.5 (1971-1972)
Mercedes 280SEL 3.5 (1971-1971)
Mercedes 300SEL 3.5 (1969-1972) - Nick at Pelican Parts
 
Leonard Comments: Do I need to remove the engine to replace the oil pump on a 1977 450Sl? I changed to 40 weight oil and oil pressure is good. The car is driven very little. What should oil press be at idle? I did this as oil pressure was very low at idle with 10W30 oil
December 14, 2014
  Followup from the Pelican Staff: I bet it does. I however don't h ave a repair manual for that vehicle to check.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
chris Comments: how about GL320 cdi
June 17, 2014
  Followup from the Pelican Staff: Wedon't currently have that tech article. If we get the chance to perform the repair we will be sure to document it. - Nick at Pelican Parts  
em Comments: I do not think it is accurate for you to include the 560SL as among the applicable models for this DIY instructions. It is a lot more complex to drop the oil pan for a 560SL as it requires dropping the front subframe first before the oil pan can be removed. I think we expect a lot more from a professional site like pelican for a more accurate information.
November 20, 2013
  Followup from the Pelican Staff: Thanks for the feedback.
- Nick at Pelican Parts
 
brian Comments: what about an 83 SEL 500? The part is the same as the part listed for the 84 and 85, how different would the replacement be from these instructions?
July 25, 2013
  Followup from the Pelican Staff: Sorry, 1983 would be a EURO model.
My best guess working from WIS data; Barring unknown EURO or Grey market variations, it should (be the same) work.
- whunter
 

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