Ser05E500

Hi everyone. I am about to change the spark plugs on my 05 E500. I bought 16, Bosch 7422 plugs at autohausz.com for $4.37. Based on my readings these plugs are OEM replacement.

I have a couple of questions and need some assistance:

I think I have all the tools but am a bit concered if I should adjust the gap. These plugs are gapped as .040 as they come out of the boxs.

How tight should it be in lbs.

Any other tips will be greatly appreciated.

Thanks a lot!

Dan

MercFiveHundred

Dont gap the plugs. They are already gapped for you and .040 is correct. Wear mechanic's gloves if you have to save your hands.

I didnt use a torque wrench - just did it on feel.

shaunls1

to save you some trouble go down to the parts store and get a spark plug wire removal tool it looks like a pliers with a bent end and they should be ruber coated.
it was almost impossible to remove em with out it.

Efivehundred

It's a good idea to check the gap before installing them to assure they are gapped to spec.

lkchris

It's no longer 1956 and we're not talking 'merikun iron here.

Bosch plugs come pregapped in the box and have so for decades.

Have NEVER found one not properly gapped.

Efivehundred

So you check the gap? To have NEVER found one not properly gapped, one would actually have to check the gap.

Most have found they are gapped properly, some have found otherwise. It's so easy to check.

EHop

or use a 17mm wrench

vettdvr

I would agree but I would confirm the gap. I have bought plugs where the box was dropped and the plugs damaged with the gap being closed. It is better to check twice than remove for inspection once.

I also used the 17mm wrench but mine was straight not offset. It worked but a little of a pain. I recommend to twist the plug cap before trying to remove it to break the initial stick this will make it easier to pull off.

Also when installing you must really press the plug cap on to seat it. If not it will force jumping a large gap and could cause coil failure. So pick an easy one for the first removal and then look at he cap/ plug to see how it fits while it is all out.

You will also need 27 mm torq to remove the coil packs.

Note each wire is different make sure each coil pack goes back to the same position and each wire back to the exact plug.

When unplugging the coil pack use care not to break the lock tab on the plug in the coil. They are replaceable at about $2.00 each but not fun to wait on for delivery.

When you first break the plug loose, stop. I worked it back and forth about 1/8 turn to remove the carbon build up on the end of the plug. I also would remove until it would feel tight then turn to tighten to break the threads free. I never put the plug wrench on and just cranked one fully out for fear of pulling the threads out of the head.

I put a small amount of neverseize on the threads and silicon on the plug cap. I know there are those who will say NO to this,, but it is My car so I did it to make removal a little easier if I do this again.

Overall the plugs are relatively easy to change and if needing changing again I will do it myself.

Benz-O-Rama

Don't forget to add some dielectric grease to inside of your plugwire before you pop it on your plug.

Ser05E500

Thanks to everyone. I was able to change the spark plugs without any problems.

bigben320e

I do have a question, did you change your wires or just the plugs?

Reason is, the dealer (of course) is telling me I should change my wires also. Does anyone know what the recommended change interval is for the wires BTW?

Ser05E500

Based on my readings unless you are having problems with your wires you do not need to change them. I only changed spark plugs.

I know that changing spark plugs at the dealer costs around $500. Throw in wires and and someone said dealer quoted them $1900, I do not know how but that is just CRAZY!

BTW when I changed my spark plugs at 80,000, they were in very good condition. They have have lasted another $20,000 without problems.

vettdvr

I agree. I changed mine around 78,000 and they looked new. From what I have see each plug wire is specific to that specific plug and not a interchange with another wire. This exclusive set up is probably why the cost.

But I would say $1900 is a for plugs and wires.

Wildcat55

I am going to do the same this weekend, only I am using Bosch 9652 Iridium and my gap is .039. Maybe they are different because of plugs are different.

Wildcat55

Dan,

I don't want to throw you a curveball here but I just went thru this experience last week with identical car, only to discover by accident that I installed the wrong Bosch plugs myself. I had checked many resources for double iridium and all came up with the same 9652 plugs. However, since my engine light kept coming back on after a few short trips, I starting researching what could be possible causes. I went to the Bosch website only to find out that the 9652 was NOT compatible and after talking to two different technicians at Bosch, they both said 6702 was the ONLY plug to use. Said our car can't even use an iridium plug and that a double-platinum wasn't available either. You might want to confirm that before installing it with Bosch.

Also, it is nearly impossible to remove the ignitions coils without snapping the little plastic piece at the top. However, you will want to remove them as they are easy and makes reaching the plugs much easier. Be careful of the little screws and the T30 bit to remove coils as I dropped two of them never to be seen again. LOL.

While you are at it, you might want to change the wire as well since you are going to have them off. I installed NGK as I think they are considered the best.

Good luck.

Wildcat55

Update on the iridium plugs on 2005 Mercedes e500. My engine light has not come on in two weeks and the car seems to be running fine. I have called four Mercedes dealerships to confirm the iridium plugs would be fine to continue with them and could not get a direct answer, other than I should use what the OEM calls for (Platinum). Has anyone used anything on their similar model other than Platinum plugs?

tjts1

I use copper plugs. More conductive than iridium or platinum at a much lower price. Downside is I'll have to replace them more often. I can live with that. I don't need 100k mile spark plug intervals.

Wildcat55

Thanks for sharing. I am probably going to stick with my iridium until the light comes on again, then change out to the platinum that I have on standby.

Wildcat55

Engine light finally came on and replaced plugs with Platinum. Drove car 7 times and came on again. However, car is running normal at the moment with the engine light still on. I read where it could go off on its own after 50-100 miles. Since I have only driven less than 10, not sure what to do. New plugs and wires, along with new ignition coils on the two cylinders showing the misfire.

Any suggestions?

tjts1

Read the codes.

Broly

i used the 7422s yesterday since the plugs had not been changed for the life of the vehicle (currently 286000+ KM).

i actually was surprised the plugs inside were NGK and not bosch. i did a compression test and it turns out me M112 is very healthy (100+ reading on first crank for each piston!!).

removing the ignition wires with a plug plier was not fun at all. many times i debated quitting but i said **** that, as i imagined some hindu with his devious little smile relishing in any failure of mine.

new plugs are great!

Wildcat55

Thanks for the reply and that was the first thing I did. Says misfire on cylinder 4 and 7.