Hi,
Here is a description of how I changed my plugs on my '97 c240T. This is a simple enough job, which is made difficult by lack of working space. You need no special tools and it took me about 2.5 hours, going slow and taking pics. MB allows 1.7 hours for this procedure, and they do make a special tool for removing the plug leads. I used a spanner instead.
I have many pics, but the system is limiting me to 3 uploads. If there is a way around this please let me know.
First - weapons; plug socket, U/J, ratchet and two extensions. Hex key and 17mm spanner, flat screwdriver. 12 Platinum spark plugs (F8DPP332 from GSF in my case.)
Start with a cold engine. Cover the wings so you don't scratch them. The first job is to remove the engine cover which just lifts off. Move to the NS and undo the single nut holding the washer bottle in place, then lift it straight up and balance it on top of the NS inner wing, near the ABS box.
Now move to the offside, and locate the air filter box. It's black and it has four or five clips holding the lid on. Pop these clips with your finger. If you follow the path that the air takes you will come to the MAS, which is connected by two more clips. Pop these two clips, you may need a screwdriver for the lower one. Remove the airbox lid, clean the inside, and set aside. Remove the airfilter and set aside.
Next remove the MAS. There is a loom running to it, just unclip the harness and move it out of the way, then loosen the jubille clip with a flat screwdriver, or a small socket.
You now have a clear (ish) working space, but you still need to remove the coils. There are 3 coils on each side, fixed to the cam covers. Each coil feeds two plugs in one cylinder. All the HT leads are arranged in the same way - ie top lead is for the forwardmost plug. Each coil is attached by a single hex bolt - simply remove the hex bolt with a hex key. There is a small wiring connection to the engine loom, unclip this then remove the HT leads.
Removing the HT leads is a swine. They are tight, they've been there for a while, and you MUST NOT PULL ON THE LEADS. Only pull on the cap, which is mostly buried flush in the head. Take a 17mm open-ended spanner and use it to lever the caps off using the head as a fulcrum. This is how the MB special tool works. Persevere - this will take a long time and you will lose knuckle-skin. This is where you are saving £80-odd per hour!!
Remove all the coils and keep them in the right order. This is not vital but it is a good habit and I can't shake it.
Now for the plugs. I started with the NS front. Thats the easiest pot to work on, and it allows you to get a feel for how much force you are going to use. Just use the plug spanner in the normal way. You will need the short extension on most of the pots. There is very little room and you can't make much progress - 1/16th of a turn at a time!! The worst pot is the NS rear. You will need to drop the plug spanner down the hole, then the extension, then the U/J, then fit the ratchet! On some of the pots I found it best to use the shorty extension, but not to fully engage the extension into the U/J, to give an extra 2-3mm length. This was because the longer extension would not fit in. It is going to take a while to get the plugs out. Be patient. You may need a fair bit of force.
Once the plugs are out you can start fitting the new ones. I gapped mine all before starting - 1mm. Again, do the front pots first as they are easiest. This gives you the feel for the forces invloved before you start with the U/J and the fingertips! Fit the plug to the plug spanner, fit the extension and spin them in by hand. On the NS rear you 'll need to drop the plug in, then the extension. Each couple of turns in, spin them out half a turn, then keep going in. This will clean the threads in the head enough so you can spin them all the way down by hand. When they seat, you will need to torque them in. I did not use a torque wrench, there was no room for it. As a guide you can seat the plug then give it 1/8 to 1/4 turn and it will be fine. DISCLAIMER - I've been working on enginge for a long time and I can fit plugs without a torque wrench. If you don't use one and you strip the threads out of your heads, I won't pay for the repairs.
Once your plugs are all tight you refit the coils. I used the 17mm spanner to press the HT caps into place. Make sure they seat down fully. Refit the wiring connectors into the loom.
Hoover the airbox clean, refit the MAS and its wiring connector, then the air filter, the hoover the filter and the airbox lid. Fit the snap clips, then wiggle the lid and the pipework around to seat it, then last of all tighten the jubilee clip. Move the washer bottle back into place and fit the nut.
Check your tools to make sure you have retrieved them all. Now start the engine and check for ticking. If you hear loud ticking, locate it, then turn off the engine and re-seat the HT leads.
Congratulations. You don't have to do that again for 4 years, or 60,000 miles!
Here is a description of how I changed my plugs on my '97 c240T. This is a simple enough job, which is made difficult by lack of working space. You need no special tools and it took me about 2.5 hours, going slow and taking pics. MB allows 1.7 hours for this procedure, and they do make a special tool for removing the plug leads. I used a spanner instead.
I have many pics, but the system is limiting me to 3 uploads. If there is a way around this please let me know.
First - weapons; plug socket, U/J, ratchet and two extensions. Hex key and 17mm spanner, flat screwdriver. 12 Platinum spark plugs (F8DPP332 from GSF in my case.)
Start with a cold engine. Cover the wings so you don't scratch them. The first job is to remove the engine cover which just lifts off. Move to the NS and undo the single nut holding the washer bottle in place, then lift it straight up and balance it on top of the NS inner wing, near the ABS box.
Now move to the offside, and locate the air filter box. It's black and it has four or five clips holding the lid on. Pop these clips with your finger. If you follow the path that the air takes you will come to the MAS, which is connected by two more clips. Pop these two clips, you may need a screwdriver for the lower one. Remove the airbox lid, clean the inside, and set aside. Remove the airfilter and set aside.
Next remove the MAS. There is a loom running to it, just unclip the harness and move it out of the way, then loosen the jubille clip with a flat screwdriver, or a small socket.
You now have a clear (ish) working space, but you still need to remove the coils. There are 3 coils on each side, fixed to the cam covers. Each coil feeds two plugs in one cylinder. All the HT leads are arranged in the same way - ie top lead is for the forwardmost plug. Each coil is attached by a single hex bolt - simply remove the hex bolt with a hex key. There is a small wiring connection to the engine loom, unclip this then remove the HT leads.
Removing the HT leads is a swine. They are tight, they've been there for a while, and you MUST NOT PULL ON THE LEADS. Only pull on the cap, which is mostly buried flush in the head. Take a 17mm open-ended spanner and use it to lever the caps off using the head as a fulcrum. This is how the MB special tool works. Persevere - this will take a long time and you will lose knuckle-skin. This is where you are saving £80-odd per hour!!
Remove all the coils and keep them in the right order. This is not vital but it is a good habit and I can't shake it.
Now for the plugs. I started with the NS front. Thats the easiest pot to work on, and it allows you to get a feel for how much force you are going to use. Just use the plug spanner in the normal way. You will need the short extension on most of the pots. There is very little room and you can't make much progress - 1/16th of a turn at a time!! The worst pot is the NS rear. You will need to drop the plug spanner down the hole, then the extension, then the U/J, then fit the ratchet! On some of the pots I found it best to use the shorty extension, but not to fully engage the extension into the U/J, to give an extra 2-3mm length. This was because the longer extension would not fit in. It is going to take a while to get the plugs out. Be patient. You may need a fair bit of force.
Once the plugs are out you can start fitting the new ones. I gapped mine all before starting - 1mm. Again, do the front pots first as they are easiest. This gives you the feel for the forces invloved before you start with the U/J and the fingertips! Fit the plug to the plug spanner, fit the extension and spin them in by hand. On the NS rear you 'll need to drop the plug in, then the extension. Each couple of turns in, spin them out half a turn, then keep going in. This will clean the threads in the head enough so you can spin them all the way down by hand. When they seat, you will need to torque them in. I did not use a torque wrench, there was no room for it. As a guide you can seat the plug then give it 1/8 to 1/4 turn and it will be fine. DISCLAIMER - I've been working on enginge for a long time and I can fit plugs without a torque wrench. If you don't use one and you strip the threads out of your heads, I won't pay for the repairs.
Once your plugs are all tight you refit the coils. I used the 17mm spanner to press the HT caps into place. Make sure they seat down fully. Refit the wiring connectors into the loom.
Hoover the airbox clean, refit the MAS and its wiring connector, then the air filter, the hoover the filter and the airbox lid. Fit the snap clips, then wiggle the lid and the pipework around to seat it, then last of all tighten the jubilee clip. Move the washer bottle back into place and fit the nut.
Check your tools to make sure you have retrieved them all. Now start the engine and check for ticking. If you hear loud ticking, locate it, then turn off the engine and re-seat the HT leads.
Congratulations. You don't have to do that again for 4 years, or 60,000 miles!
