Mercedes-Benz Parts Catalog Mercedes-Benz Accessories Catalog Mercedes-Benz Technical Articles Mercedes-Benz Tech Forums
 
Follow Pelican Parts on Facebook Follow Pelican Parts on Twitter Follow Pelican Parts on Instagram Follow Pelican Parts on YouTube Follow Pelican Parts on Pinterest Follow Pelican Parts on Tumblr
  Search our site:    
View Recent Cars  |   Cart  | Project List | Order Status | Help    
 >  >
Mercedes Spark Plugs and Coils
 
Bookmark and Share

Pelican Technical Article:

Mercedes Spark Plugs and Coils

Steve Vernon

Time:

4

Tab:

$72

Talent:

**

Tools:

T-30 Torx driver, 5/16th spark plug thin wall socket extensions and universal joints

Applicable Models:

Mercedes-Benz ML320 (1998-03)
Mercedes-Benz W203 (2001-07)

Parts Required:

Spark Plugs

Hot Tip:

Work on a cold engine

Performance Gain:

Better mileage

Complementary Modification:

New air filter

Replacing the spark plugs on your Mercedes-Benz C320 is recommended routine maintenance. Mercedes recommends replacing the spark plugs on C320 models every 100,000 miles. With all the major engine design changes over the years, spark plugs now last up to three times as long as they did in years past. This is good and bad. It means you save money and time not having to service them so frequently, but run the risk of a spark plug seizing in the cylinder head. I suggest replacing your spark plugs every three years regardless of mileage. If the last time they were serviced is unknown, replace them right away. I don NOT recommend putting anti seize on the plugs.

You are going to have to remove the engine air ducts and covers to get access to them.

Remove each duct by compressing them towards the engine and slipping them off the air inlet.

With the ducts off remove the front engine cover. It pulls up and away from the engine. The cover is held on by five clips and will easily come off with hand pressure.

Next, you will need to remove the main engine cover that also houses the air filters. It is held on by four pressure clips. You can see the two at the front of the engine, to remove the housing lift it at the front of the engine and once the front clips release the rears (which you can not see) will release as well.

We are going to begin with the right side covers. You will be able to see the valve covers on top of the heads, they hold the coils.

Disconnect the individual wiring harnesses going to each coil, there are three of them. They simply squeeze in and pull out of the coil.

Use a T-30 Torx and remove the bolts holding the coil packs in place. With the bolts gone you can just swing the coils out of the way.

You do not need to remove the wires and boots from the plugs but now is a good time to take them off and clean them. The boots can be very tricky to remove and will take a little patience, especially the ones at the rear of the motor. The boots are on quite snug and you will need to use a 17mm open end wrench to place over the end of the boot and using the valve cover gently pry the boots off. If you want to make the job very easy Pelican sells the Hazet tool that is basically a specially bend open ended 17mm wrench that makes getting the boots off a ease and you can use them to help seat the boots when you reinstall them. Note: NEVER try and remove the boots by pulling on the wires, you will only end up ripping the wires from the boots!

Remember the while the coils are interchangeable the wires from each coil must go to the appropriate plug. With the coil mounted on the cover the "A" wire always goes to the forward plug. Carefully inspect the coils and wires for any fraying, cracking, drying or other damage.

There are twelve plugs on the C320 and some of the ones at the rear of the engine are more difficult to access, just get yourself a 5/16 thin walled socket along with a series of extensions and a universal joint and remove each plug. Take you time especially when installing the new plugs as you do not want to cross thread the openings in the cylinder heads.

Installation is the reverse of removal.

You will need to remove the two air inlet ducts (red arrows) as well as the front engine cover (yellow arrow) to get access to the air filter housing on top of the engine.
Figure 1

You will need to remove the two air inlet ducts (red arrows) as well as the front engine cover (yellow arrow) to get access to the air filter housing on top of the engine.

Remove each duct by compressing them towards the engine (red arrow) and slipping them off the air inlet.
Figure 2

Remove each duct by compressing them towards the engine (red arrow) and slipping them off the air inlet.

With the ducts off remove the front engine cover.
Figure 3

With the ducts off remove the front engine cover. It pulls up and away from the engine (yellow arrow).

The cover is held on by five clips (red arrows) and will easily come off with hand pressure.
Figure 4

The cover is held on by five clips (red arrows) and will easily come off with hand pressure.

Next, you will need to remove the main engine cover that also houses the air filters.
Figure 5

Next, you will need to remove the main engine cover that also houses the air filters. It is held on by four pressure clips. You can see the two at the front of the engine (red arrows).

To remove the housing lift it at the front of the engine and once the front clips release the rears (which you can not see) will release as well (red arrows).
Figure 6

To remove the housing lift it at the front of the engine and once the front clips release the rears (which you can not see) will release as well (red arrows).

The two red arrows show the valve covers on each side.
Figure 7

The two red arrows show the valve covers on each side.

We are going to begin with the right side cover.
Figure 8

We are going to begin with the right side cover. You will be able to see the valve covers on top of the heads; they hold the coils (yellow arrows). The breather hose is located just above the coils (red arrow).

Disconnect the three individual wiring harnesses going to each coil (red arrows).
Figure 9

Disconnect the three individual wiring harnesses going to each coil (red arrows). They simply squeeze in and pull out of the coil. You can see how filthy the valve covers are in this picture.

NOTE: This step is optional.
Figure 10

NOTE: This step is optional. I did it for additional space and harness cleaning. Next remove the crankcase breather hose from the breather cover (red arrow). If the hose is fairly new it should slide off. If the hose is original or old there is a very good chance it is dry and brittle and you are going to damage it and need to replace it. Do yourself a favor and order new hoses before you start this job. 

Use a T30 and remove each bolt from the three coil packs (red arrows).
Figure 11

Use a T30 and remove each bolt from the three coil packs (red arrows).

Remove the wires and boots from the plugs, the boots can be very tricky to remove and will take a little patience, especially the ones at the rear of the motor.
Figure 12

Remove the wires and boots from the plugs, the boots can be very tricky to remove and will take a little patience, especially the ones at the rear of the motor. The boots are on quite snug and you will need to use a 17mm open end wrench to place over the end of the boot (red arrow) and using the valve cover gently pry the boots off.

If you want to make the job very easy Pelican sells the Karlyn tool (part # 2771Z-INT) that is basically a specially bend open ended 17mm wrench that makes getting the boots off (red arrow) an ease and you can use them to help seat the boots when you reinstall them.
Figure 13

If you want to make the job very easy Pelican sells the Karlyn tool (part # 2771Z-INT) that is basically a specially bend open ended 17mm wrench that makes getting the boots off (red arrow) an ease and you can use them to help seat the boots when you reinstall them. Note: NEVER try and remove the boots by pulling on the wires, you will only end up ripping the wires from the boots!

Remember that while the coils are interchangeable the wires from each coil must go to the appropriate plug.
Figure 14

Remember that while the coils are interchangeable the wires from each coil must go to the appropriate plug. With the coil mounted on the cover the "A" wire always goes to the forward plug.

There are twelve plugs on the C320.
Figure 15

There are twelve plugs on the C320. Some of the plugs at the rear of the engine are difficult to access, you will need a 5/16 thin walled socket along with a series of extensions (red arrow) and a universal joint and remove each plug. Take you time, especially when installing the new plugs as you do not want to cross thread the openings in the cylinder heads. Remember work on a cold engine, a hot engine causes the metal to expand, making the removal of the plugs difficult and it also causes the metal to become "softer" making cross threading easier.

Here is a picture of an old plug (right side) and a new one side by side.
Figure 16

Here is a picture of an old plug (right side) and a new one side by side. You can clearly see how the electrode on the old plug has worn away (the rust doesn't help either).

Bookmark and Share
Comments and Suggestions:
Sue Comments: The car is: Mercedes w203 C240;
please may you confirm the information below ?
Torque spark plugs to 24.4 Nm 18 ft-lbsame as BMW E90 motors.
Thank you
September 2, 2016
  Followup from the Pelican Staff:
I don’t have that info.



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
 
Sue Comments: Figure 10: Please, Why we should remove the crankcase breather hose from the breather cover red arrow ???
September 1, 2016
  Followup from the Pelican Staff: If it is not in your way, do not remove it. it may have to do with the wiring harness and moving it aside. - Nick at Pelican Parts  
Richard t. Comments: Where is the number 3 coil
February 13, 2016
  Followup from the Pelican Staff: On what vehicle? - Nick at Pelican Parts  
phil Comments: does the ML320 use a 5/8 or 5/16 socket for the spark plugs?
July 1, 2015
  Followup from the Pelican Staff: Should be 9/16. That is a typo. - Nick at Pelican Parts  
Bekim Comments: Hey Nick, what is the proper amount of torque to be given to the new plugs? Thanks!
May 30, 2015
  Followup from the Pelican Staff: What vehicle? - Nick at Pelican Parts  
Francis Comments: I plan to replace the spark plugs and plug wires on my 2002 Mercedes C320. Please advise where to locate the 4 wires that are longer than the other 8?
Thank you.
May 30, 2015
  Followup from the Pelican Staff: Replace one wire at a time, matching the old wire lengths to the new ones. - Nick at Pelican Parts  
John Comments: Hi, I'm new here and I may need some coils for my 2000 CL K3 20. My mechanic said one or more may be bad. What would you suggest as a labor charge to check those coils and how long should it take? I'm retired and must keep my costs low.

Also I was getting a misfiring and then changed a catalytic converter. It's smoothed out the engine. Can a catalytic converter actually throw a code for the ignition? How can I know for sure.
December 18, 2014
  Followup from the Pelican Staff: I wouldn't know how much they charge, as labor rates vary. I would call a few local shops for estimates. The catalytic converter may have been damaged from the misfire.

Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
 
jay Comments: Got a 1999 clk 320 its barely moving don't know if the cat converter or the plugs or the mass air flow, where do I start?
June 14, 2014
  Followup from the Pelican Staff: Start by checking exhaust back pressure. - Nick at Pelican Parts  
jay Comments: How many plugs are in a clk 320 1999
June 14, 2014
  Followup from the Pelican Staff: 12 - Nick at Pelican Parts  
Adrian Comments: Brilliant instructions! I found that when inserting the new plugs, to use your fingers on the 16mm tool first before attaching the shifter. That ensures you seat the plug properly and don't cross thread. Additionally the space in the engine bay is very tight and I found a 75mm extender was the best tool to attach to the 16mm thin wall tool for plug removal. I found it pays to give the boots on each of the coils a good wipe down as well. Be careful with the wire attachment that plugs into the top of each coil. While they should just clip off, they are likely to have aged a little and become brittle. Finally once the plugs have been inserted and you're reattaching the coil boots, be sure to use the 17mm open head shifter to gently press the boot over each plug. They will be snug but then click into place when sufficient pressure is applied. Again don't pull or push on the wires attached to the boot of the coils!
April 29, 2014
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
Noah Comments: Sorry, there was a typo in the previous post: "then," not "than."

Also, on that engine the breather/valve covers have been leaking oil for quite a while-that should be addressed as well.
April 21, 2014
  Followup from the Pelican Staff: Thanks, got it. - Nick at Pelican Parts  
Noah Comments: To me, the old spark plug looks like a conventional, i.e. non-spec spark plug for these engines. Conventional copper spark plugs would normally need to be replaced after 30k miles or so. Platinum spark plugs last twice as long, Iridium spark plugs three-four times as long, i.e. about 100k miles. If less miles are driven per year, than changing spark plugs every three years is overkill. Every five-six years would be a prudent and conservative approach.
April 21, 2014
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
sert Comments: you guy are the best of the world.
April 19, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Ace Comments: On a C230 Kompressor 1999, how can I tell which one is #2 coil? That's the one my code reader says is bad.
February 22, 2014
  Followup from the Pelican Staff: This will be the coil over cylinder #2. Cylinders 2 and 3 are on the same bank, at the front of the engine. - Nick at Pelican Parts  
DOUG Comments: HOW TO TEST THE COIL AND WIRES SINCE THEY ARE OFF? WHY NOT PUT ANTI-SIEZE ON PLUG? PLUGS SHOWN ARE COMPLETELY DIFFERENT STYLE, BUT SHOULD NEVER BE WORN THAT MUCH. WHAT PLUG IS BETTER? WHAT IS GAP?
June 12, 2013
  Followup from the Pelican Staff: I suggest you buy a service manual to answer in detail, the wide variety of questions you have.
-whunter-
 
Jim Comments: Good tutorial! I did this job yesterday on my 2001 SLK320.
Using a 4 inch long socket extension would also help in removing the plugs. Also, I used low-strength thread locker compound on the Torx bolts holding the coil packs, as they should not be over-tightened or risk stripping the threads in the valve covers.
June 9, 2013
  Followup from the Pelican Staff: Glad it was helpful. I agree, for best results low strength thread lock compound is needed on those screws.
-whunter
 

  Search our site:    

View Cart & CheckOut | Project List | Order Status |  Help    

 

[Home] [Customer Service] [Shopping Cart] [Project/Wish List]
  [Privacy Statement]  [Contact Us] [About Us] [Shipping] [Careers]

Copyright © Pelican Parts Inc. -    DMCA Registered Agent Contact Page

Page last updated: Fri 12/9/2016 02:29:35 AM