I just performed most of my 30k maintenance yesterday a little early (I'm just shy of 28k miles). Most people with a hemi and the know how opt to change their own plugs. The parts are really really cheap. The labor is insane because it takes TIME to swap 16 plugs. Most shops will take 2 to 3 hours minimum - probably more if the engine isn't cool. Average price on the labor at most shops for a hemi's plug swap would run 250 to 350 u.s. dollars. Here's what I can tell you:
Do NOT attempt to change your plugs without first buying a magnetic spark plug socket (5/8" for the stock plugs in a hemi). I bought a duralast from autozone - worked well, but wished it was just a quarter inch longer as it didn't completely engulf the nut portion of the socket.
You will need 16 (yes, 16!) new plugs. I opted to go with the stock Champion 570's rather than "upgrade". Two reasons: some people (not all though) with hemi's have reported issues with precious metal plugs not always firing, and the harder metals in upgraded plugs despite all their hype and cost don't outperform copper which actually conducts electricity far better - the precious/harder metals only mean you don't have to change your plugs as often (The only exception to this is silver plugs as silver conducts better than copper - but you'd have to change plugs just about every oil change if you used silver).
The stock plugs are your run-of-the-mill copper champion 570's (CHA 570 or RE14MCC4), and are typically suggested to be changed out every 30k miles. Gap spacing should be 0.045. Spacing on the new plugs should be darn close to dead on, but I noticed some variation on the 16 I bought, so I'd recommend passing a gap tool through all of them just to check. If in the US, they should only be a couple bucks and change each.
You should also pick up a tube of dielectric grease if you don't have some laying around the garage.
I would also suggest picking up an assortment of wobble socket extenders. A pair of value pack type kits with 3 or 4 different lengths each comes in extremely handy.
You'll need a torque wrench that goes down to 13 ft-lbs.
Here's how it is done:
1. Wait until your Jeep is more or less room/outdoor/garage temperature (so, do it in the morning before you drive anywhere). These hemi's are hot and take forever to cool off. Not having to worry about where to rest an arm while cramming yourself headfirst under the hood is definitely nice.
2. Remove the oil cap.
3. Pull up on the shroud/engine cover (the big pretty plastic and metal cover that proudly displays that you've got a Jeep with a Hemi under the hood), it should pop up and free fairly easily, then pull it forward until you've got it clear and set it aside.
Now that you've exposed your engine, here is what you should see. To the right and left of the plastic manifold are 8 coils (one per pair of plugs) held in by two bolts each. Each coil is a black box roughly 2 inches by 3 inches and about an inch and a half tall. Each has a connector on it with two wires that go into harnesses that run the length of the engine on each side. Attached underneath each coil (what you can't see yet) are a pair of spark plug boots with a spring in them (the spring is the contact b/w the coil and the spark plug). Below the boots are the plugs.
4. Disconnect each coil's electric connection. (Pretty simple, squeeze the tab on the connector and pull - should pop right off by hand without having to pry at all).
5. Find the correct socket, get your wobble extensions ready, and start unbolting a coil. You don't need to back them all the way out. You should feel a change once all the threads are out of the block and the only remaining threads are in the coil. No biggie if you take them all the way out - just be careful not to drop them.
6. Pull the coil out from the block. This will take some force as the boots have a nifty built-in sealing mechanism (instead of a gasket or o-ring) that makes a small vaccuum when you try to get it started out. The boots should remain attached to the coils and pull straight out easily once you get it started. The boots are soft flexible rubber, so if you've got to do some turning and twisting a bit to get past wiring and hoses - you should be fine.
There are now two holes exposed where the coil used to be. Trust me, there are spark plugs down there.
8. Slowly lower your magnetic socket down a hole, but before you lose sight of it down the hole, attach a 3" wobble extender (on the passenger side you can already have it attached for most of the plugs, on the driver side though it's a two step process as the socket plus extender attached just won't clear the wires and hoses and fuseboxes etc).
9. Carefully get on the plug and back it out. (On the driver's side, you'll likely have to dissassemble your socket extenders as you pull it out in order to clear all the obstacles.)
10. Place a little dielectric grease on the tip of the new plug you're going to install. (I call it the tip...the part that seats into the bottom of the boot, NOT the part with the gap where the spark occurs).
11. Put the spark plug in the spark plug socket, then lower it into place just like you did to remove it. You don't want to just drop it into the hole as it could possibly break the ceramic.
12. Torque it to 13 ft-lbs. Try for no more and no less. Hemi plugs don't have the forgiving ring b/w the threads and the seat that your lawn mowers typically have that allow you to rule of thumb it. These plugs are "tapered" and require a specific torque. The spec calls for 13, go for 13 - though typically +/- 1 ft-lbs is acceptable.
13. Repeat steps 11 and 12 for the remaining plug in the pair.
14. Take your tube of dielectric grease and put a dab of it inside the end of each boot.
15. Put the coil back on.
16. Re-attach the electric connector on the top of the coil, and repeat the process for the rest of the plugs.
17. The shroud/engine cover goes back on the same way it came off, just in reverse.
If you're normal, you're looking at a couple hours minimum. If you're good and/or have a friend that can prep everything for you while you bust your knuckles, you can do an entire side of the engine at one time and possibly knock it out in under an hour.
As for oil, 5w-20 is necessary for your MDS (the system that drops down to four cylinders under little load and constant rpm) to function as expected (basically cutting on/off as you pass up 65 mph). After draining my pan and dropping the filter and letting them drip for a beverage or two, it took 7.6 quarts in my case to hit the dipstick dead center.
Most the rest of a 30k maintenance is "inspect this that or the other and top off/replace/repair if needed" in addition to the regular oil and filter change/air filter change/tire rotation. I've got a K&N, so I just pop it out, knock out the dried out bits of insects we tend to suck up here in the south, and shop-vac'ed the remaining insect and leaf debris from the lower portion of the filter housing. Though I've been lusting after an easy way to get rid of the gigantic resonator/plenum from the intake, so an AFE 54-10242 is on order. I noticed some rust already forming on the stock muffler, resonator, and pipes - so I figure it's as good a time as any for me to swap it out for the Magnaflow 16665. I had my brakes checked not too long ago for a stupid squeel that just refuses to go away while idling on the break going through drive through fast food places - was told they look brand new. Once the two new "performance" items are in and ready to be bolted on, I'll go ahead and do my tire rotation, and take a look at all the rubber under the vehicle for any cracks or dry-rot. That just about covers everything under the sun for a 30k maintenance. About the only thing I did besides the standard 30k maintenance was to seafoam my engine as I was forced to use 10% ethanol gas for the last 27k miles until a zero-ethanol place opened up nearby. I did this prior to the plug swap and oil/filter change.
2008 Commander LTD, 5.7L Hemi, AFE Cold Air Intake, Magnaflow Cat Back exhaust
Last edited by chriscavell; 08-14-2011 at 04:45 PM.