Applying anti-seize to spark plugs


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Tools you will need:

1) T-30 screwdriver or socket bit
2) 5/8 spark plug socket
3) 8" extension
4) 4" extension (or creative equivalent)
5) ratchet for above
6) torque wrench (optional)

Supplies you will need:

1) high temperature anti-seize, pure nickel is best, although I impulse-bought and went with what my local Napa had in stock
2) medium strength thread lock

On a difficulty scale of 1 to 10, I'd give this job a rating of 3. It took me about 2 hours working in no particular hurry.
(For me, 1 corresponds to checking the air pressure in tires, 5 -- replacing brakes shoes, and 10 -- installing a cylinder head)


1) The Sprinter M272 3.5L V6 gasoline engine has individual coils for each spark plug. They are at the top of the engine and unmistakable. To access the spark plugs, remove the two T-30 bolts holding the coils in place. The coils will need to a little wiggling/encouragement and will come free of the spark plugs with a satisfying pop sound. The T-30 bolts have thread lock applied at the factory and will need firm pressure to remove. A ratchet will be no problem. Using a screwdriver is possible as well, but takes a really determined force.


2) Once the coil is removed it can hang down below the access ports to the spark plugs. Note, you do NOT need to remove the wires that go to the ignition coils. No connectors were separated in the entire procedure.


3) With the 5/8 spark plug socket and the 8" extension, insert into the access port and use finger pressure to securely seat socket onto the spark plug bolt head. Attach ratchet to extension and unthread. There have been multiple reports of threads stripping out of the aluminum cylinder head when removing the glow plugs on the diesel M642. One suggestion has been to let the engine heat up a little before removing the glow plugs. I did not do this myself for the spark plugs, but it was a warm day and my engine only had about 2 years and 15k miles on it. I still felt a surprising amount of sticktion breaking the seal. I would suggest anyone doing this procedure on a much older engine to warm-up the engine a little before removing the spark plugs.


4) With a clean rag wipe out all the accumulated crud from the threads and apply a thin coating of anti-seize. The spark plug threads should still be evident and no anti-seize should be on the tip of the spark plug itself. Carefully wipe-off any excess that may have smeared past the first thread. I found it most handy to leave the spark plug in the socket and hold it by the extension.

5) Reinstall the spark plug using your fingers to turn the end of the extension to hand-thread the spark plug finger-tight. Torque spark plug to spec. (I'll follow-up with more discussion on torque in the next post.)


6) Reinstall coil by pushing it firmly down onto the spark plug, applying thread lock to the T30 bolts and tighten firmly.


7) Repeat steps 1-6 for the next cylinder.

As might be guessed from the first photo, the passenger side was super-easy to access and work on. The driver's side has the brake booster and master cylinder as well as the jump-start port and cable obstructing access. It took much more finesse, and I'll have some thoughts and suggestions concerning it in the next post. Good luck and please let me know if you decide to do this job as well. Thanks.


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The driver's side is not nearly as easy to access as the wide-open passenger's side. There's the brake power booster and master cylinder, jump-start cable, and the washer jug gets in the way just enough to be annoying. Fitting the torque wrench in there took the most finesse, but I was able to make it work for all 3 cylinders.


The brake booster and master cylinder are completely in the way of accessing the rear-most cylinder. You will need a T-30 on a ratchet drive to remove the coil bolts as the power booster will be completely in the way. Also, you will need about 4" of extension to remove the spark plug. 8" is too much to fit. I didn't have a 4" extension so made due by splicing together a universal, a 3/8 to 1/2 drive converter, and then 1/2 to 3/8 drive converter. I'm a little embarrassed by it, but it got the job done. Barely.

On the middle cylinder the master cylinder is just enough in the way require using either a 4" extension or a universal joint on the 8". Lacking a 4", I opted for the universal joint.


For the front cylinder, the 8" extension will work. In fact, the 4" would be too short as there is something immediately forward of the spark plug access and you need to be above it with your ratchet. Sorry no picture.

Concerning the torque spec, I couldn't find a definitive number prior to starting the job. I did use my torque wrench to measure four of the spark plugs and they all took 19 ft-lbs of torque to "break the seal". I also measured the threads with a digital mic and they are 12mm (11.89 to be exact). The directions on anti-seize are to reduce the torque by 1/3. 1/3 less of 19 gives a torque of about 13 ft-lbs. I started out using that, but it seemed not very tight. I decided to increase it to 15 ft-lbs which is firmly in the middle of the range of internet conventional wisdom and felt much more secure. If you don't have a torque wrench, I can say 15 ft-lbs feels tight but not with any strain. Hold the ratchet in the middle of the handle, don't try too hard and you'll probably be plenty fine. Good luck.

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