Hi everyone,

First time poster here. 2017 C63s. Really need help. Check engine light came on yesterday, had the car towed to nearby shop, full diagnostic report below.

In short — when i had new spark plugs installed back in 1/23 they weren’t installed / torqued properly and now have caused cylinder damage. Out of warranty by THREE months. They told me cylinder replacement would be a $7000-8000 job. Any advice on how to navigate this situation?

Finding: Note prior to any work being performed engine fluids were checked, we found engine oil was full and also the coolant was full. Note upon start up there was an engine noise heard. Scope and scan was performed we recorded P0300 "Engine misfire detected", P0306 "Misfire cylinder #6 detected", freeze frame and data pids were reviewed code P0300 and P0306 set at engine startup.
It was determined to gain access to the #6 cylinder which required removal of the air intake, filter assembly, and some other items. Ignition coil was removed and immediately an issue was found, when the coil was removed the spark plug from cylinder #6 came out with it, there was a hole in the spark plug boot and the spark plug electrode tip was missing "Burned off", also of note there were thread pieces from the cylinder head on the loose spark plug. Spark plug threads were inspected in the cylinder head and they are missing/damaged and will no longer accept a spark plug and allow it to be torqued down correctly. Note for reference The #5 spark plug was removed, we found it was loose "Note not torqued down correctly", this is the most likely cause for what happened to cylinder #6 spark plug. If the spark plug is loose exhaust gases pass thru the treads, causing it to overheat which gives it a torch affect and can cause spark plug electrode to burn off and damage to the threads in the cylinder head.

Note the other spark plugs will need to be checked to see if they are loose. Ignition coil on cylinder #6 should be replaced Concerns we have, there are no threads in cylinder #6 that will allow us to insert a compression tester to test the compression, we can hear compression when engine was running but this can be misleading. Research of TSB's, recalls and common failures was performed, nothing related to the spark plugs blowing out of the cylinders was found

Recommendation: Concerns we have, there are no threads in cylinder #6 that will allow us to insert a compression tester to test the compression, we can hear compression when engine was running but this can be misleading. Research of TSB's, recalls and common failures was performed, nothing related to the spark plugs blowing out of the cylinders was found. Need to some how repair the threads in cylinder head "Position #6" this will require special repair kit and there will be no guarantee it works and or if there is already compression issues in that cylinder, only other option would be cylinder head replacement which would be quite and extensive repair. Suggested to inspect the rest of the spark plugs and replace if original. Need to advise the customer of what was found, see if they have any type of extended warranty or if there is any manufacture warranty left. Recap spark plug blew out of the #6 hole, coil is damaged and should be replaced, need to try and repair the #6 spark plug threads, need to check compression on that same cylinder, need to check all the other spark plugs for proper torque and replace if original. Note compression was checked in cylinder #6, we could not seat the compression fitting due to missing treads so it was held in place manually, we recorded 80 psi but please note fitting had leakage so the actual compression is most likely higher, next compression from cylinder #5 was tested, we recorded 100 psi but the compression tester tool was not seated "This was done on purpose to allow leakage past the fitting", readings are fairly close so it is possible the #6 cylinder is going to be ok if the treads can be repaired.

 

Don't know if this will help. But last month and after having my MB 5 year Service that included Spark Plug change suddenly on a perfectly running car the check engine light came on (30,000 miles). Initallly I believed these misfires happened right after I gassed up.
Drove to the MB dealership and initial diagnosis cylinders 5 and 6 misfired. They had my car for 2 weeks and did a overnight road test to insure the Check engine light did not come back on. see photos below what steps were perforned. They replaced ignition coils and spark plugs 5 & 6.
Note: MB will replace ignition coils regardless of warranty up till 100,000 miles.
Currenty my the car is running great.
. Maybe a MB Dealership AMG tech.will have a different approach. I have the MB extended warranty but SM

stated all will be cover by the 100,000 mile ignition coil coverage not my extended warranty.

 

I can't find anything about this online. Can anyone provide any links on this?

 

I'm really sorry to hear about this. You can try a goodwill warranty request because it's only out by 3 months but I doubt it'll be accepted as spark plug indexing is important with our cars and can cause problems.

Who did the plugs? What plugs were used? Their fault and they should be paying/fixing.

 

same thing happened to me how did you end up fixing it

 

well if plug threads damaged and cannot be re-tapped the head has to be removed and you can try helicoil insert but that could cause issues to head casting.

For sure fix is new head but I would have head sent to the best engine rebuilder/machine shop you can find in your area and ask them if they can fix and how.

 

I hope the TE has solved his problem two years later.

The problem is that many mechanics have no knowledge
of the subject matter AND no respect for their customers' property.

 

I had this happen to an extended warranty customer of mine... new motor needed on his E63 AMG.

Trenton O. Gibson
tgibson@highline-autos.com
Highline Autos
Direct: 602.909.9216
Office: 480.348.0777

 

Do the spark plugs of the M177 engine tend to come loose,
or is this more a case of sloppy workmanship?

Good notice from Jonny - about the plugs and
the special situation (plug/angle etc) .
Best way to go 100% for sure is only new c- head in my mind ( not to fix by cnc shop like 100% oem).