WEBSRFR

I had to take my car to the dealer because of the engine stalling which turned out to be the crank position sensor. They are replacing it under warranty.

Now they are saying that the spark plugs are also due to for replacement because the car is 5 years old and I don't remember seeing that as one of the services for the 40K mile service that we just had done 5 months ago.

How often should the spark plugs in this car be replaced and I'd really appreciate some guidance on cost. What is the typical cost for this?

The dealer quoted almost $550 and it seemed rather exorbitant!

edwinwalke

Looks like the service manual suggests to change the plugs at 91K or at 5 years. If it were me I would continue to run the plugs until it reaches the mileage to replace them or they cause a problem.

WEBSRFR

Thanks for the advice! I'm thinking that I wait until the 50K mile service at the end of this year to change the plugs, as the car only has about 43K miles now though I suppose the 5 year period called by the warranty is up.

What would be a fair price for a dealer or Indy to do this? I guess I should make sure they use the Bosch 7422 plugs?

If anyone feels this must be done now I'll do it as I plan to keep the car for a while...

PS: Is this the correct part for my car?

Flash Gordon

If you are handy with tools. It's not difficult to replace the plugs yourself. There are several threads that document the procedure. Because there are 16 plugs, it will take you about 2 hours since you have not done it before. You saw how cheap the plugs are in Amazon! I just did mine this past weekend.

Kwijibo

An E550 will only have 8 plugs and they are very easy to DIY. Just remove each coil, and the plug tips are staring directly at you. The previous two-plug-per-cylinder V8s were more difficult.

I used the NGK equivalents, you can choose from: NGK PLKR6A #5149 (6 heat range, which is what came installed in my car), NGK PLKR7A #4288 (7 heat range, which seems to be the current recommendation).

My owner's manual lists the correct plugs as NGK PFR5R-11 #4292, but those plugs were not even close to being correct. Wrong size, wrong reach, wrong thread pitch.

moosejaw

Mine were under an hour to install and that's for 16 of them

vettdvr

I changed all 16 plugs on my E500 at 85,000 miles. They looked new when pulled.

WEBSRFR

Sounds like I made the right call in not having this done at 5 years with only 42K miles. I think I'll wait for the 50K mile service to get this done and by then the car would be about 6 years old and from what I heard the spark plugs should be okay.

The dealer tried the scare tactic on me saying that the by now the spark plugs would be in really bad shape because it has been 5 years and if the engine breaks down because they are bad the warranty would not cover anything!

Unfortunately I am not handy with stuff like this and I don;t want to break anything. I got a call from my Indy to do this for $330 and that sounds much better than the dealer's quote of $550.

vettdvr

The plugs don't wear out in a car that isn't driven. I would push it to 80,000+ before changine if it were mine.

ozusa

There is little reason to believe that the plugs need changing at 40K. They can go roughly 90 - 100K.

If a dealer wants to change them earlier, have them pull one or two for you to prove they are in poor condition. (but you'll need to know what "poor" looks like by googling for a few pics)

WEBSRFR

Thanks for all your advice! Had I've not known any better I'd be out $550 by now

Efivehundred

How did they look at that mileage?

MB4tronic

Thanks for this thread, I am at ~60k and was going to this and the belt around 90k.

WEBSRFR

Does the 550 have a "belt?" I thought it was a timing "chain" that did not need replacement around 100K like a belt would...

ozusa

The belt referred to is not a timing belt. (timing is indeed done with a chain and is not externally visible). The belt referred to is for the water pump, power-steering and alternator and is on the front of the engine and plain to see.

ozusa

At 114K they still worked, most looked OK, some looked a little worn, but none were a disaster. Some of the wires didn't look very good, though, so I suggest changing those at the time you do the plugs.

Flash Gordon

Generally speaking platinum plugs last 100K. I just changed mine in the G35 when it hit 101K. My W211 plugs were replaced last week at 69K. The W211 is running and idling smoother. The MB was purchased in 11/2003 so the plugs were in there for a long time! The gap sure has widened when I pull them out, but they all look normal wear and tear.

Kwijibo

I did my E550 plugs at 90K. They "looked" okay but the gaps were huge, around 0.045". It was definitely time to replace.

vettdvr

If I remember correctly .045 is the correct gap for new plugs but remember the new plugs are set at the factory and NON-adjustable.

Kwijibo

My docs show 0.031" for E550, 0.039" for E500. But who knows? The owner's manual was incorrect for the E550 spark plugs, so these numbers could be wrong too!

My new plugs arrived gapped at 0.032", and I left the gaps alone.

Gersh320

I replaced mine at about 95k and 8 years. 2003 E320. They looked great, very little carbon too. I've had the car since 40k and have always used premium fuel. I keep the engine bay clean by wiping it down with each car wash. Dealership wanted over $370. I purchased all 12 from MB dealership in NE for about $65 and changed myself. Most difficult part was removing the wires in the back!!!!! I will let them go another 100k and replace the wires at that time. I noticed no improvement in power or mileage since the old ones were in such good shape.

WEBSRFR

Wow thanks again for everyone who chimed in and the great feedback about how these plugs are good to go much beyond the time frame my dealer wanted them replaced!

You guys should have heard him say how if I did not change the plugs right this minute at 42K miles and 5 years the engine may blow up and it will not be covered by the warranty... What BS... It seems the worse that can happen is that the car might misfire or might rough idle. And of course if I notice anything weird with the engine I'll have them changed immediately but my plan is to do it at about 6 years 50K miles just to be sure...

vettdvr

That really is alot of !@#$ from the dealer on the warranty. If you change the plugs at the recommend mileage from the service FSS you will find it should all be under warranty if your warrenty goes that long.

relinuca

FWIW, nobody has mentioned the importance of using an anti-seize compound when installing new plugs and proper torque loads. Small details like these are critical to such a DIY project.

relinuca

Flash Gordon

That's really given for those of us DIY.