C55 AMG - carbon build up
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2005 C55 AMG
C55 AMG - carbon build up
Hi Guys
My car developed a rough idle when running at full running temperature.
Searching the net, I was hoping for a quick fix, by way of cleaning the throttle body, but unfortunately this was not to be, in my case...
The valves in cylinders 7 and 8 are suffering from excessive carbon build up, to the point that the valves are unable to seat properly, hence the rough idle.
So, the heads must be removed and everything de-coked etc , then put back together - a very unhappy surprise.
Prior to purchasing the car, I researched the model extensively and couldn't find any issue around carbon build up, so pretty gutted to learn that I will have to spend around $6K to sort the issue {only paid $13K for the car - done 165,000kms}
It has had 7 owners prior,so I suspect some of them may have driven the car too "soft" or shorter distances.
Just curious to know if anyone else has suffered the same issue, and what sort of a result did you experience after the repair?
walnut blasting not an option unfortunately as the carbon is in the seats/cylinders as well
Best regards Rowan
My car developed a rough idle when running at full running temperature.
Searching the net, I was hoping for a quick fix, by way of cleaning the throttle body, but unfortunately this was not to be, in my case...
The valves in cylinders 7 and 8 are suffering from excessive carbon build up, to the point that the valves are unable to seat properly, hence the rough idle.
So, the heads must be removed and everything de-coked etc , then put back together - a very unhappy surprise.
Prior to purchasing the car, I researched the model extensively and couldn't find any issue around carbon build up, so pretty gutted to learn that I will have to spend around $6K to sort the issue {only paid $13K for the car - done 165,000kms}
It has had 7 owners prior,so I suspect some of them may have driven the car too "soft" or shorter distances.
Just curious to know if anyone else has suffered the same issue, and what sort of a result did you experience after the repair?
walnut blasting not an option unfortunately as the carbon is in the seats/cylinders as well
Best regards Rowan
Last edited by Rowdog; Sep 15, 2023 at 05:09 PM.
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2005 C55 AMG
Quoted by a local after market Mercedes service agent
Bit of an update. Had another Servuce agent I’ve used previously comment on the issue and reckons he’s developed a system for a top of cylinder clean so will stop in and get him to have a look. Fingers crossed?! Cheers
Bit of an update. Had another Servuce agent I’ve used previously comment on the issue and reckons he’s developed a system for a top of cylinder clean so will stop in and get him to have a look. Fingers crossed?! Cheers
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asdas
Sounds strange. If I were you I would remove the spark plugs to cylinders 7 and 8 and take a look inside the cylinders yourself with a borescope. They can be had for relatively cheap on Amazon. There's a reason why excessive carbon buildup rarely occurs on our port injected cars. If the valves are unable to seat properly, why would you only notice the problem when fully warmed up?
On the other hand, rough idle is probably the most common complaint with M113 cars and there's a list of usual culprits that you can search for that I would make absolutely sure aren't your issue before taking off the head to clean. I would even try running some seafoam or other top end cleaner through the system before taking off the head after confirming the presence of excessive carbon buildup myself.
On the other hand, rough idle is probably the most common complaint with M113 cars and there's a list of usual culprits that you can search for that I would make absolutely sure aren't your issue before taking off the head to clean. I would even try running some seafoam or other top end cleaner through the system before taking off the head after confirming the presence of excessive carbon buildup myself.
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C55 AMG
Check engine light on? Carbon build up and rough running sounds like EGR stuck open. Not sure why only 7 and 8 would be affected. Cheap boroscope camera is a great idea. Pull spark plugs and have a look inside 7 and 8. Suggest the cell phone attachment type on Amazon. They are cheap and you might be able to snake it in to see valves.
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2005 C55 AMG
Sounds strange. If I were you I would remove the spark plugs to cylinders 7 and 8 and take a look inside the cylinders yourself with a borescope. They can be had for relatively cheap on Amazon. There's a reason why excessive carbon buildup rarely occurs on our port injected cars. If the valves are unable to seat properly, why would you only notice the problem when fully warmed up?
On the other hand, rough idle is probably the most common complaint with M113 cars and there's a list of usual culprits that you can search for that I would make absolutely sure aren't your issue before taking off the head to clean. I would even try running some seafoam or other top end cleaner through the system before taking off the head after confirming the presence of excessive carbon buildup myself.
On the other hand, rough idle is probably the most common complaint with M113 cars and there's a list of usual culprits that you can search for that I would make absolutely sure aren't your issue before taking off the head to clean. I would even try running some seafoam or other top end cleaner through the system before taking off the head after confirming the presence of excessive carbon buildup myself.
Yeah, They did a pretty thorough inspection {3 hrs} - I thought it may have been the EGR, or the throttle body myself - they took photos within the cylinders and you can see a very thin, but obviously stubborn line of carbon, in the seats of the cylinder head {apparently pitted}
Took the car for a long drive yesterday,{120kms} and kept the revs over 3K - it still drives fantastic, with no noticible loss in power anywhere across the rev range - car was idling fine for most of the trip - only when the traffic came to a crawl, did the rough idle reappear - definately something related to heat.......
Anyway - I'll be getting a second opinion this week, with my usual mechanic, and go from there - quoted $7k to remove and clean the heads etc
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C55 AMG
Check all the small diameter vacuum hoses at the front and rear of engine. Also check oil breather hoses. Rubber may be rotten and leak when hot. Vacuum leak will cause rough idle.
EDIT ADD: This is from when I had a E430. Coils would show cracks on the back side of the plastic housing. I replaced 4 that had cracks and the engine ran smoother. Something is going on with 7 and 8. Check everything.
EDIT ADD: This is from when I had a E430. Coils would show cracks on the back side of the plastic housing. I replaced 4 that had cracks and the engine ran smoother. Something is going on with 7 and 8. Check everything.
Last edited by Socal Sam; Sep 16, 2023 at 10:15 PM.
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asdas
Yeah, They did a pretty thorough inspection {3 hrs} - I thought it may have been the EGR, or the throttle body myself - they took photos within the cylinders and you can see a very thin, but obviously stubborn line of carbon, in the seats of the cylinder head {apparently pitted}
Took the car for a long drive yesterday,{120kms} and kept the revs over 3K - it still drives fantastic, with no noticible loss in power anywhere across the rev range - car was idling fine for most of the trip - only when the traffic came to a crawl, did the rough idle reappear - definately something related to heat.......
Anyway - I'll be getting a second opinion this week, with my usual mechanic, and go from there - quoted $7k to remove and clean the heads etc
Took the car for a long drive yesterday,{120kms} and kept the revs over 3K - it still drives fantastic, with no noticible loss in power anywhere across the rev range - car was idling fine for most of the trip - only when the traffic came to a crawl, did the rough idle reappear - definately something related to heat.......
Anyway - I'll be getting a second opinion this week, with my usual mechanic, and go from there - quoted $7k to remove and clean the heads etc
At about 100k miles, you should closely inspect all the soft parts and really are due for an overhaul of all the soft parts. As has been mentioned, rubber shrinks/hardens/degrades over time and if any of it was ever disturbed, high likelihood of them being compromised. Replacement of literally ALL the rubber intake/vacuum/ventilation hoses and seals in the engine bay is surprisingly not that expensive in parts costs.
Also, if your engine/transmission mounts are going bad/never been replaced, you might notice normal things occurring more as vibration than you otherwise would, and it may seem abnormal, ie, EGR valve operation introducing exhaust gases into the intake tract, which is essentially a controlled vacuum leak. Even though it's controlled, it still changes the way your engine runs. You might read here or there or be told that EGR is supposed to be closed at idle, but EGR control is more nuanced than that. With bad engine mounts you can also notice more distincly when the coolant thermostat opens and how the engine responds around 87C if you're at idle when it happens. Our engine mounts typically need replacement every 50-60k miles, so if your car's first set were replaced around 50k miles ago and you're at 100k....
So take your time and eliminate the more likely potential causes of rough idle.
Last edited by brauhaus313; Sep 17, 2023 at 04:19 AM.
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2005 C55 AMG
Thanks Bud
Yes, tranny and engine mounts all been replaced within the last 12 months, I have the car regularly serviced regardless of mileage, very particular about all items being kept in good condition - all breather hoses replaced etc {only does 6500km a year - weekend car}.I drive the car very "honestly" so want it maintained correctly so it can take the pain I give it - ha ha
Most of the typical oil leaks have been sorted and alternator replaced.
I've asked for the photos but I haven't received them yet.
Very interested to get my typical mechanics feedback {unavailable at the time of diagnosis} - will see if he can inspect this week, and he claims to have a particular method for top of cylinder cleaning.
If it can be proven that I'm not damaging engine components with the rough idle, I think I'll just get him to do 1 or 2 cylinder cleans, and just keep enjoying the car as is - I don't have $7K to invest at the moment, on a car that cost me $13K {NZD}
Yes, tranny and engine mounts all been replaced within the last 12 months, I have the car regularly serviced regardless of mileage, very particular about all items being kept in good condition - all breather hoses replaced etc {only does 6500km a year - weekend car}.I drive the car very "honestly" so want it maintained correctly so it can take the pain I give it - ha ha
Most of the typical oil leaks have been sorted and alternator replaced.
I've asked for the photos but I haven't received them yet.
Very interested to get my typical mechanics feedback {unavailable at the time of diagnosis} - will see if he can inspect this week, and he claims to have a particular method for top of cylinder cleaning.
If it can be proven that I'm not damaging engine components with the rough idle, I think I'll just get him to do 1 or 2 cylinder cleans, and just keep enjoying the car as is - I don't have $7K to invest at the moment, on a car that cost me $13K {NZD}
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I must say I have never herd of a carbon build up on a modern car. My guess is that the 7 previous owners did not use the correct fuel and they drove many short trips and never took the car over 4k rpm.
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C55 AMG
Starting to think a rogue mechanic is fishing for an easy $7k. 7 and 8 cylinder not sealing because of dirty valve seats is fishy to me especially if engine still makes power. Compression check would be conclusive. One last thought from experience on another brand. While replacing intake manifold, I cleaned injectors and fuel rails. Car idled much better afterwards. Could be something as simple as injector cleaning or replacement. Could also be intake manifold that has been fouled by EGR muck and engine oil from breather.
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2005 C55 AMG
Can you post the photos? Still doesn't make sense why even on the same drive it would idle fine for most of the trip and then idle rough intermittently if the valves aren't seating all the time because of carbon buildup. Plus no misfire codes for 7/8? Doesn't make sense.
At about 100k miles, you should closely inspect all the soft parts and really are due for an overhaul of all the soft parts. As has been mentioned, rubber shrinks/hardens/degrades over time and if any of it was ever disturbed, high likelihood of them being compromised. Replacement of literally ALL the rubber intake/vacuum/ventilation hoses and seals in the engine bay is surprisingly not that expensive in parts costs.
Also, if your engine/transmission mounts are going bad/never been replaced, you might notice normal things occurring more as vibration than you otherwise would, and it may seem abnormal, ie, EGR valve operation introducing exhaust gases into the intake tract, which is essentially a controlled vacuum leak. Even though it's controlled, it still changes the way your engine runs. You might read here or there or be told that EGR is supposed to be closed at idle, but EGR control is more nuanced than that. With bad engine mounts you can also notice more distincly when the coolant thermostat opens and how the engine responds around 87C if you're at idle when it happens. Our engine mounts typically need replacement every 50-60k miles, so if your car's first set were replaced around 50k miles ago and you're at 100k....
So take your time and eliminate the more likely potential causes of rough idle.
At about 100k miles, you should closely inspect all the soft parts and really are due for an overhaul of all the soft parts. As has been mentioned, rubber shrinks/hardens/degrades over time and if any of it was ever disturbed, high likelihood of them being compromised. Replacement of literally ALL the rubber intake/vacuum/ventilation hoses and seals in the engine bay is surprisingly not that expensive in parts costs.
Also, if your engine/transmission mounts are going bad/never been replaced, you might notice normal things occurring more as vibration than you otherwise would, and it may seem abnormal, ie, EGR valve operation introducing exhaust gases into the intake tract, which is essentially a controlled vacuum leak. Even though it's controlled, it still changes the way your engine runs. You might read here or there or be told that EGR is supposed to be closed at idle, but EGR control is more nuanced than that. With bad engine mounts you can also notice more distincly when the coolant thermostat opens and how the engine responds around 87C if you're at idle when it happens. Our engine mounts typically need replacement every 50-60k miles, so if your car's first set were replaced around 50k miles ago and you're at 100k....
So take your time and eliminate the more likely potential causes of rough idle.
Hi Brauhaus
Quick update
What a difference a second opinion makes!
My typical mechanic, was happy for me to pop in at short notice - ran a diagnostic then and there - everything in order, apart from slightly low oil, and an issue with my alarm unit - otherwise nothing showing up - all services free of charge!
Commented the other Agent I went to were "absolute Rogues" , and presented to tell me some facts {not stories} about them - very disappointing.
Told him I had been running it with a fuel cleaner additive for the last 4 days, and suggested I keep doing it for 2 more tank loads {got some liqui Moly on order}, to see if the idle still persist {it has definately dissipated since adding the additive}
The upshot being, I'm feeling positive about the future of my baby {agreed with me, that if the valves weren't seating it would be running rough all the time?!}
Cheers!
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