Spark Plug Replacement - How to?
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From: Haubstadt, IN
20 GLS450
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Just following up on my original question with the results. Short answer is that there is a reason they charge so much for a plug change on the GLS450. All of the real effort is in getting to plug number 6, which is a pain in the butt. After disconnecting all of the obvious oil lines, the process included first removing the divert air switchover valve (#1), then the actuator (#2) for the turbo (not proper name), and then the intake air duct (#3) for the turbo before you could even begin to fight with the coil and plug in minimum space. Moving #2 required getting to the 2 bolts underneath the back right side only viewable with bore scope. Then the second bolt on the intake is not accessible from above or below easily and required removal of the wheel well which didn't help that much. I relearned how to use WIS/ASRA though, so I got something out of it. Short story is it may be worth it to have the dealer or experienced GLS x167 Mechanic do it unless you have limitless free time, all the proper tools, a good working knowledge of WIS/ASRA and a lot of luck. Plus be extra careful with the wiring harness which I read is very prone to cracking and breaking ($$). I will not do it again. Makes the LX 600 start to look awful nice... just saying 
Access to plug #6
Access to plug #6
Last edited by d.p; Jan 7, 2026 at 04:16 PM.
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2020 GLS450 (wife) / 2024 Ford Bronco (mine) / 2014 VW Tiquan (son)
It really is remarkable how poorly MB engineers come up with some of this stuff. Is there not one person on that entire team with the title of "Director: Common Sense Control"? It's like the front differential of the W212 4Matic. It's like they said...
"Give them a drain plug, but no fill plug, because I said so. Make them take the entire axle out to refill it!!"
Or, and this was a fun one on my old W212. "Das, the PCV should be replaced every so often to prevent oil leaks, so make sure you bury that F'r as deep as you can in the back of the engine!" Seriously, $45 part....$700 in labor to get to it.
This is one area where VW beats the other German brands. The PCV will prevent so many problems and they know it, so they literally put it directly on top of the engine all by itself. Just sitting there free and clear. Plugs? Easy as a lawn mower. About the only thing even marginally complicated on the 4Motion AWD system is to remember to pull the actuator motor out of the transfer case to clean the screen. Otherwise, it's simple as pie.
As I get older and my patience level for stupidity continues to shrink, stuff like this becomes even more important to me and I'm willing to sacrifice certain luxuries to have them.
"Give them a drain plug, but no fill plug, because I said so. Make them take the entire axle out to refill it!!"
Or, and this was a fun one on my old W212. "Das, the PCV should be replaced every so often to prevent oil leaks, so make sure you bury that F'r as deep as you can in the back of the engine!" Seriously, $45 part....$700 in labor to get to it.
This is one area where VW beats the other German brands. The PCV will prevent so many problems and they know it, so they literally put it directly on top of the engine all by itself. Just sitting there free and clear. Plugs? Easy as a lawn mower. About the only thing even marginally complicated on the 4Motion AWD system is to remember to pull the actuator motor out of the transfer case to clean the screen. Otherwise, it's simple as pie.
As I get older and my patience level for stupidity continues to shrink, stuff like this becomes even more important to me and I'm willing to sacrifice certain luxuries to have them.
Last edited by nc211; May 3, 2026 at 02:07 PM.
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It really is remarkable how poorly MB engineers come up with some of this stuff. Is there not one person on that entire team with the title of "Director: Common Sense Control"? It's like the front differential of the W212 4Matic. It's like they said...
"Give them a drain plug, but no fill plug, because I said so. Make them take the entire axle out to refill it!!"
Or, and this was a fun one on my old W212. "Das, the PCV should be replaced every so often to prevent oil leaks, so make sure you bury that F'r as deep as you can in the back of the engine!" Seriously, $45 part....$700 in labor to get to it.
This is one area where VW beats the other German brands. The PCV will prevent so many problems and they know it, so they literally put it directly on top of the engine all by itself. Just sitting there free and clear. Plugs? Easy as a lawn mower. About the only thing even marginally complicated on the 4Motion AWD system is to remember to pull the actuator motor out of the transfer case to clean the screen. Otherwise, it's simple as pie.
As I get older and my patience level for stupidity continues to shrink, stuff like this becomes even more important to me and I'm willing to sacrifice certain luxuries to have them.
"Give them a drain plug, but no fill plug, because I said so. Make them take the entire axle out to refill it!!"
Or, and this was a fun one on my old W212. "Das, the PCV should be replaced every so often to prevent oil leaks, so make sure you bury that F'r as deep as you can in the back of the engine!" Seriously, $45 part....$700 in labor to get to it.
This is one area where VW beats the other German brands. The PCV will prevent so many problems and they know it, so they literally put it directly on top of the engine all by itself. Just sitting there free and clear. Plugs? Easy as a lawn mower. About the only thing even marginally complicated on the 4Motion AWD system is to remember to pull the actuator motor out of the transfer case to clean the screen. Otherwise, it's simple as pie.
As I get older and my patience level for stupidity continues to shrink, stuff like this becomes even more important to me and I'm willing to sacrifice certain luxuries to have them.
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2020 GLS450 (wife) / 2024 Ford Bronco (mine) / 2014 VW Tiquan (son)
Oh I would disagree on VW. Perhaps not “VW”, but Audi certainly is. Just like Lexus is to Toyota. Same engines, gear boxes, nuts and bolts for majority.
some of MB is easy, which is always the head scratch with MB. Why make one thing super easy, while making two others hard that should be even easier? That is MB.
some of MB is easy, which is always the head scratch with MB. Why make one thing super easy, while making two others hard that should be even easier? That is MB.
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Oh I would disagree on VW. Perhaps not “VW”, but Audi certainly is. Just like Lexus is to Toyota. Same engines, gear boxes, nuts and bolts for majority.
some of MB is easy, which is always the head scratch with MB. Why make one thing super easy, while making two others hard that should be even easier? That is MB.
some of MB is easy, which is always the head scratch with MB. Why make one thing super easy, while making two others hard that should be even easier? That is MB.
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'21 AMG53 wDPP & ARC, 19 GLC300 - Former-03 C240,2 ML BlueTecs,20 GLE450 E-ABC,15 Cayenne D,17 Macan
I don't know which might be harder to work on, but the VW group mild hybrids are Belt-driven starter generators, while the Mercedes SUVs have ISG's, inline starter generators.
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2020 GLS450 (wife) / 2024 Ford Bronco (mine) / 2014 VW Tiquan (son)
We've not gotten into repair territory on the GLS yet, but on the W212 with the 3.5 V6 in the 4matic arrangement, everything seemed to be difficult to get to. The 4Matic made it hard for the transmission mounts, which were crammed up too close to the exhaust which accelerated their wear. The front diff could only be refilled by removing the front passenger side axle. The PVC was packed into the rear of the engine, requiring dismantling of other items to dig it out. That sort of stuff. I think the plugs were likely easy to get to, and the cam magnets were also an easy one. I know my shop basically had the front of that engine removed and put back together in matter of hours for some notable repairs / leaks that it suffered from, so that didn't seem too complicated. I do agree, several items are smartly located for ease of maintenance. But others, definitely leave you scratching your head as to why in the heck did they do that.
I know my guys were cursing about the plugs on our GLS as well when we did them at 50k. In particular #6. But compared to the W212, as they said, it was like working in a warehouse of happiness vs a whorehouse of anger.
I know my guys were cursing about the plugs on our GLS as well when we did them at 50k. In particular #6. But compared to the W212, as they said, it was like working in a warehouse of happiness vs a whorehouse of anger.
Last edited by nc211; May 5, 2026 at 05:42 PM.
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2017 GLE350 4MATIC
I feel like MBs are the easiest to work with among the 3 German luxury brands. At least according to one of my mechanic friends. Perhaps tight packaging is a German luxury thing? Technically Volkswagen is not a luxury brand so maybe that is why. Anyways, thanks for commenting.
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From: SW Ontario Canada
2020 GLS580, 2023 Corvette Z06
Plug change on GLS580
Does anyone know the procedure to replace the plugs on the 580 V8? I am concerned the dealer will not do a good job and check for dirt in the plug area before removing the plug etc. Any information I have seen so far about this job on other models indicated it is a difficult job so I am hesitant to do it myself. How many hours would the dealer charge?
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'21 AMG53 wDPP & ARC, 19 GLC300 - Former-03 C240,2 ML BlueTecs,20 GLE450 E-ABC,15 Cayenne D,17 Macan
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From: unbegrenzt
2017 GLE350 4MATIC
Cayenne S. The same engine is used in several Audi models and the lower tune version is used in the Volkswagen (brand) Touareg.
Touareg today is sadly not available in the North American market. I would be driving one today and would have pocketed alot of savings vs. the Porsche, if VW continued with the Touareg instead of the garbage which is the Atlas.
Touareg is a best buy in the class because it is on a near-exotic capable platform (Urus), selling for Volkswagen prices.
Touareg today is sadly not available in the North American market. I would be driving one today and would have pocketed alot of savings vs. the Porsche, if VW continued with the Touareg instead of the garbage which is the Atlas.
Touareg is a best buy in the class because it is on a near-exotic capable platform (Urus), selling for Volkswagen prices.
Last edited by chassis; May 18, 2026 at 12:03 PM.
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From: unbegrenzt
2017 GLE350 4MATIC
We've not gotten into repair territory on the GLS yet, but on the W212 with the 3.5 V6 in the 4matic arrangement, everything seemed to be difficult to get to. The 4Matic made it hard for the transmission mounts, which were crammed up too close to the exhaust which accelerated their wear. The front diff could only be refilled by removing the front passenger side axle. The PVC was packed into the rear of the engine, requiring dismantling of other items to dig it out. That sort of stuff. I think the plugs were likely easy to get to, and the cam magnets were also an easy one. I know my shop basically had the front of that engine removed and put back together in matter of hours for some notable repairs / leaks that it suffered from, so that didn't seem too complicated. I do agree, several items are smartly located for ease of maintenance. But others, definitely leave you scratching your head as to why in the heck did they do that.
I know my guys were cursing about the plugs on our GLS as well when we did them at 50k. In particular #6. But compared to the W212, as they said, it was like working in a warehouse of happiness vs a whorehouse of anger.
I know my guys were cursing about the plugs on our GLS as well when we did them at 50k. In particular #6. But compared to the W212, as they said, it was like working in a warehouse of happiness vs a whorehouse of anger.
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2017 GLE350 4MATIC
Brake fluid replacement is a breeze.
Brake pads and rotors with fixed calipers are a breeze. Easier than floating calipers on many MBs.
Spark plugs are about the same amount of effort as the M276. Not super easy but not impossible.
Cams can be removed with the engine in the car.
T/case oil change is a breeze. A bit less space under the car vs. W166 and I assume V167 but the job is doable.
PCV/OVS components are directly accessible on top of the engine, easy to replace.
Yes, I am talking about the EA839 2.9TTV6. It has iron sleeves which makes the engine desirable from a longevity/reliability point of view. No crummy plated or etched cylinder walls.
Last edited by chassis; May 18, 2026 at 12:16 PM.
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'21 AMG53 wDPP & ARC, 19 GLC300 - Former-03 C240,2 ML BlueTecs,20 GLE450 E-ABC,15 Cayenne D,17 Macan
@chassis Thousand dollar oil changes! And I thought my $350 oil change was high.
No wonder you hate MB. You were taken advantage of, big time!
But you point out something that's been eating at me. I've been wanting to change my camshafts without removing the engine.😀 Guess I need a Cayenne.
No wonder you hate MB. You were taken advantage of, big time!
But you point out something that's been eating at me. I've been wanting to change my camshafts without removing the engine.😀 Guess I need a Cayenne.
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Joined: Dec 2019
Posts: 32,642
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Cayenne S. The same engine is used in several Audi models and the lower tune version is used in the Volkswagen (brand) Touareg.
Touareg today is sadly not available in the North American market. I would be driving one today and would have pocketed alot of savings vs. the Porsche, if VW continued with the Touareg instead of the garbage which is the Atlas.
Touareg is a best buy in the class because it is on a near-exotic capable platform (Urus), selling for Volkswagen prices.
Touareg today is sadly not available in the North American market. I would be driving one today and would have pocketed alot of savings vs. the Porsche, if VW continued with the Touareg instead of the garbage which is the Atlas.
Touareg is a best buy in the class because it is on a near-exotic capable platform (Urus), selling for Volkswagen prices.
Edit: To be fair mazda also didn't bring the CX-60 to North America, so there is that....
Last edited by W205C43PFL; May 18, 2026 at 01:21 PM.
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I tackled this the other day and ended up just doing 1-5 and said **** it to #6. I have a friend that owns a shop that I am going to more than likely do that one. Even 1-5 aren't all that easy to get to, have to remove the turbo heat shield and move the oil line to get to 3-4-5 as they are buried between the head and those shields.
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From: Fleriduh
W212 E63S Wagon - GSL580 - E63 - E350 - C300
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From: Colorado
'21 AMG53 wDPP & ARC, 19 GLC300 - Former-03 C240,2 ML BlueTecs,20 GLE450 E-ABC,15 Cayenne D,17 Macan
All we know is that you couldn't do the job without hiring a mechanic.
They are required to provide a fixed estimate, which you probably shouldn't have approved if you didn't like the charge.
Sometimes special knowledge and special tools can be expensive.
They are required to provide a fixed estimate, which you probably shouldn't have approved if you didn't like the charge.
Sometimes special knowledge and special tools can be expensive.
