C400 Loss of Compression?
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From: Freeland, MI
2011 ML550, 2015 C400
C400 Loss of Compression?
Sent my CPO C400 (52k miles) into the dealer for another panoramic roof issue (third time the shade will need to be replaced) and asked them to look into why it has a little shake at idle. Noticeable, not terrible, but also not acceptable. Dealer calls last night wanting me to authorize a $480 diagnostic test due to the tech getting low compression across all cylinders. The further testing I was told would be to do an actual compression test by pulling the plugs and digging in a little deeper. Told them it was a CPO and they still insisted I had to authorize the potential charge if it comes back as something they won't warranty.
Anyone else have major issues with the 3.0 twin turbo? I'm surprised it could that serious since I've noticed no performance decline but there has been some oil consumption between changes.
Mostly creating this as a placeholder for whatever they find since there was little out there that returned from a search.
Anyone else have major issues with the 3.0 twin turbo? I'm surprised it could that serious since I've noticed no performance decline but there has been some oil consumption between changes.
Mostly creating this as a placeholder for whatever they find since there was little out there that returned from a search.
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C400
C400 here, no issues like that
if ALL 6 cylinders tested low compression that would be amazing.
if the compression check machine wasn't setup correctly and misread all 6 cylinders, that seams more likely to me.
and what exactly is the $480 diagnostic test? Is that a 4 hour diagnostic or...? I mean to go from a mild shake at idle (which could be a LOT of things) and jump directly to a blown motor? I mean...come on.
if ALL 6 cylinders tested low compression that would be amazing.
if the compression check machine wasn't setup correctly and misread all 6 cylinders, that seams more likely to me.
and what exactly is the $480 diagnostic test? Is that a 4 hour diagnostic or...? I mean to go from a mild shake at idle (which could be a LOT of things) and jump directly to a blown motor? I mean...come on.
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From: Freeland, MI
2011 ML550, 2015 C400
That's why I think it is bizarre. I called yesterday to check on it and they started the same speech I got Monday night, that the computer is showing low compression across all cylinders and that they need to "do a test where they take out the spark plugs." I've not had great luck with this dealer but they are the closest to me (40+ miles) and the next closest is another 45 minutes further. The car is still covered under CPO so I cannot possibly see how they find anything wrong that wouldn't be covered under powertrain, so it was more a "do whatever you need to do" decision.
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From: Freeland, MI
2011 ML550, 2015 C400
I made them confirm it was still under CPO coverage, which they did. The car has had numerous issues fixed since I have owned it, without any mention of me being responsible for any diagnostic fee.
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A gaggle of MB's
Call Mercedes Customer Care (800) 367-6372 with the Repair Order # from the dealership - and tell them you feel you are being asked to Pay-For-Diagnostic on a problem your dealer has detected during Service - frankly that's not Kosher - and frankly you are getting "hosed" "taken for a ride" pick whatever phrase you feel fits - you are being told "total bullsh*t" -
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Thread Starter
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From: Freeland, MI
2011 ML550, 2015 C400
Customer Care said it certainly is not unusual for a dealer to need authorization in case the problem is not covered by warranty (and they did confirm my CPO is good until 11/24 of this year). I guess I get that and Customer Care isn't involved with the dealer to really know what is going on so I'm going to let it go until we find out the problem, which I cannot image won't be warrantied.
The dealer however is a total nightmare. They scheduled me for this Monday, which I got a call that night needing to authorize diagnostics. Guess what has been done since then? Nothing at all. I literally was unable to get an advisor on the phone Tuesday night (when I would have expected some answers) or all day yesterday. They also ignored all voicemails left, so when I called again this morning to no answer and an offer of voicemail, I snapped on the receptionist and magically someone got on the phone. When pressed she admitted the car is sitting outside waiting for a tech to have time to look at it. Mercedes Customer Care said they will be contacting the dealer.
The dealer however is a total nightmare. They scheduled me for this Monday, which I got a call that night needing to authorize diagnostics. Guess what has been done since then? Nothing at all. I literally was unable to get an advisor on the phone Tuesday night (when I would have expected some answers) or all day yesterday. They also ignored all voicemails left, so when I called again this morning to no answer and an offer of voicemail, I snapped on the receptionist and magically someone got on the phone. When pressed she admitted the car is sitting outside waiting for a tech to have time to look at it. Mercedes Customer Care said they will be contacting the dealer.
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You are getting hosed...
1. A "little shake at idle" at 50K miles - I assume there was no check engine light/code ?
2. There is absolutely no way for a technician to diagnose "low compression all cylinders" - a technician can read a trouble CEL code "like misfire Cylinder 3" - and to eliminate a cylinder/valve problem test the compression on that cylinder - put a compression test for all cyclinder ? You will pay for that diagnostic - 90% it won't find a thing - and you're stuck with the bill
3. If there "was" a trouble code - find out what it was - and report back before you approve that "test compression all cylinders" - that's a rip off unless there is some other indication
1. A "little shake at idle" at 50K miles - I assume there was no check engine light/code ?
2. There is absolutely no way for a technician to diagnose "low compression all cylinders" - a technician can read a trouble CEL code "like misfire Cylinder 3" - and to eliminate a cylinder/valve problem test the compression on that cylinder - put a compression test for all cyclinder ? You will pay for that diagnostic - 90% it won't find a thing - and you're stuck with the bill
3. If there "was" a trouble code - find out what it was - and report back before you approve that "test compression all cylinders" - that's a rip off unless there is some other indication
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From: Freeland, MI
2011 ML550, 2015 C400
1. I had no check engine light.
2. From what I'm gathering from the advisor, who doesn't seem to know anything, is that the tech used some sort of computer diagnostic tool to determine that "compression is down on all cylinders." I assume this to be a relative compression test, which from what I'm seeing it is possible to get an idea if there is a bigger problem. It would probably be best if I spoke directly to the tech, but I'm not sure they'll let that happen. Their next step was to "run the boroscope to see what's going on" and to do a "manual compression test." This was supposed to be done on Monday night into Tuesday. I'm still not aware of them starting this test as the vehicle was put outside and no longer being worked on.
What I cannot understand is that if the car is reported and verified to have a shake and the relative compression test shows low compression and the car is under warranty, why it would even be suggested that I'm potentially liable for the diagnostic fee. My only thought is that they find no oil in the engine or that I did something malicious, voiding the warranty. They did say that if the problem was found to be warrantied I would not have a diagnostic charge.
I noticed nothing else wrong with performance. MPG hasn't changed. Power seemed to still be there. Never felt a misfire or bucking or anything to suggest something more severe is going on. Car has consumed a little oil though. Before the last oil change there wasn't even oil on the dipstick so it wouldn't surprise me if something odd is going on.
2. From what I'm gathering from the advisor, who doesn't seem to know anything, is that the tech used some sort of computer diagnostic tool to determine that "compression is down on all cylinders." I assume this to be a relative compression test, which from what I'm seeing it is possible to get an idea if there is a bigger problem. It would probably be best if I spoke directly to the tech, but I'm not sure they'll let that happen. Their next step was to "run the boroscope to see what's going on" and to do a "manual compression test." This was supposed to be done on Monday night into Tuesday. I'm still not aware of them starting this test as the vehicle was put outside and no longer being worked on.
What I cannot understand is that if the car is reported and verified to have a shake and the relative compression test shows low compression and the car is under warranty, why it would even be suggested that I'm potentially liable for the diagnostic fee. My only thought is that they find no oil in the engine or that I did something malicious, voiding the warranty. They did say that if the problem was found to be warrantied I would not have a diagnostic charge.
I noticed nothing else wrong with performance. MPG hasn't changed. Power seemed to still be there. Never felt a misfire or bucking or anything to suggest something more severe is going on. Car has consumed a little oil though. Before the last oil change there wasn't even oil on the dipstick so it wouldn't surprise me if something odd is going on.
Last edited by kkoepp31; Sep 20, 2019 at 07:21 AM.
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I understand you're frustration - at the same time - each post of your's has a bit of "added info":
1. YES - for specific years of the new C-Class - there have been "wrist pin issues" that have lead to premature engine failure - and there have been incidences of "excessive oil consumption" due to manufacturing defects with the cylinder rings - which in turn lead to premature wear/scoring of the engine cylinders.
2. When these dudes mention "Boroscope" that is the instrument that gets inserted into the cylinder thru the pulled plug - to examine the condition of the piston and condition of the cylinder wall - which is followthru on the "excessive oil consumption"
3. There is "NO" computer diagnostic to detect "low compression" whether for one cylinder or all cylinders - the ONLY compression test is to pull the plug and do a "mechanical" pressure test with a gauge
4. If these guys are being "legitimate" - then this has way less to do with the "shake" (except as a 2nd less major symptom) and much more to do to identify the problem that could be causing your excessive oil consumption - and YES this could be a major problem that will require up to replacement of your engine - which if it goes that far SHOULD BE a warranty repair.
You haven't mentioned getting a Check Engine Light (CEL) and you have mentioned seeing the LOW OIL LIGHT (which is strange since you report you had zero oil showing on the dipstick - I guess at some point the full story might eventually come out
1. YES - for specific years of the new C-Class - there have been "wrist pin issues" that have lead to premature engine failure - and there have been incidences of "excessive oil consumption" due to manufacturing defects with the cylinder rings - which in turn lead to premature wear/scoring of the engine cylinders.
2. When these dudes mention "Boroscope" that is the instrument that gets inserted into the cylinder thru the pulled plug - to examine the condition of the piston and condition of the cylinder wall - which is followthru on the "excessive oil consumption"
3. There is "NO" computer diagnostic to detect "low compression" whether for one cylinder or all cylinders - the ONLY compression test is to pull the plug and do a "mechanical" pressure test with a gauge
4. If these guys are being "legitimate" - then this has way less to do with the "shake" (except as a 2nd less major symptom) and much more to do to identify the problem that could be causing your excessive oil consumption - and YES this could be a major problem that will require up to replacement of your engine - which if it goes that far SHOULD BE a warranty repair.
You haven't mentioned getting a Check Engine Light (CEL) and you have mentioned seeing the LOW OIL LIGHT (which is strange since you report you had zero oil showing on the dipstick - I guess at some point the full story might eventually come out
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From: Freeland, MI
2011 ML550, 2015 C400
I did not mention seeing the Low Oil Light, and I never have seen it come on. In fact when I sent the car in to have other problems addressed I only mentioned a slight shake at idle. Only noticed a lack of oil on the dipstick when performing the last oil change, which is the only one I have ever done on this car. Prior to that all service work was performed by the dealer because it was included in the CPO plan. I was never told of any oil consumption from the dealer so I do not know how long it has been happening.
The last time of spoke to the dealer, on Thursday, was their first mention of the boroscope in addition to the full compression test. This was after my call to Mercedes Customer Care, who I assumed got in touch with the dealer to figure out what is going on. They claimed they were doing everything they could to either start the diagnostic Thursday night or Friday. As of yesterday afternoon I know the car had not yet been moved inside from the parking lot, so it won't be until Monday before they maybe, or maybe don't, start working on it. My frustration is growing but it seems there is little I can do.
The last time of spoke to the dealer, on Thursday, was their first mention of the boroscope in addition to the full compression test. This was after my call to Mercedes Customer Care, who I assumed got in touch with the dealer to figure out what is going on. They claimed they were doing everything they could to either start the diagnostic Thursday night or Friday. As of yesterday afternoon I know the car had not yet been moved inside from the parking lot, so it won't be until Monday before they maybe, or maybe don't, start working on it. My frustration is growing but it seems there is little I can do.
are you sure there is anything wrong with the car? did you research what oil level usually reads on these cars? did you check it since switching the oil yourself? how many miles elapsed?
the guy above you is referencing c300 problems when you have a c400. there are maybe 2 or 3 actual issues on these forums with this particular engine. you might want to search/ x post this in the appropriate section where others actual have this engine - the c43 forums (this is just a detuned version).
the guy above you is referencing c300 problems when you have a c400. there are maybe 2 or 3 actual issues on these forums with this particular engine. you might want to search/ x post this in the appropriate section where others actual have this engine - the c43 forums (this is just a detuned version).
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From: Freeland, MI
2011 ML550, 2015 C400
Compression test revealed two cylinders that were low. I guess a Mercedes rep has authorized taking a cylinder head off to troubleshoot. Probably won't be complete today, but hopefully will get news tomorrow.
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The good news is they identified the issue - and so you know - each step of the way forward will need to be approved by MBUSA - when this whole process is done you might have a fresh engine under warranty !
Keep the beat !
Keep the beat !
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From: Freeland, MI
2011 ML550, 2015 C400
Well, here we are, a week later and my call to the dealership yesterday was not answered and my message was not returned. From a worker I know at the dealership it sounds like the manifold is now off and so is a valve cover, but nothing is yet known and nobody is currently doing anything to it. Two full weeks in the shop and still not close to a diagnosis. Extremely frustrating and I'm wishing I could lemon law this thing...
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Where this is at can be frustrating - MBUSA/diagnosis tells the teller to do #1 - report back with photo's - and dealer has to wait for MBUSA approval to do step #2 - report that back - etc/etc.
The good news is the process ultimately will identify what needs to be done - and from what you shared ultimately it could be a new engine under warranty.
Keep the beat !
The good news is the process ultimately will identify what needs to be done - and from what you shared ultimately it could be a new engine under warranty.
Keep the beat !
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2017 Mercedes C63s
I drive a C400 as well, and no issues. I would take it to a mechanic that specializes in European cars, they would be cheaper but yet give you the quality that you want. $500 for a test is outrageous, I got a buddy that can do that for like $100 for labor.
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From: Dallas, TX
2015 Mercedes-Benz C300 AMG-Sport Package
Hm I have a 2015 C300 and also been having a slight jerk/shaking at idle but no check engine light. Its only noticeable because it doesn't happen constantly. Its hard to believe its something like low compression on the engine though. I'm out of warranty so I'm hoping its not something major.
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From: Freeland, MI
2011 ML550, 2015 C400
Still have not heard from the dealer about my car, although some kid did call on Monday saying they want the loaner back because it has been leased. I told the kid they brought this vehicle to me and can send someone with a replacement. Said he would need to talk to an advisor and they would call me back. Haven't heard a word since. From another dealership employee I have heard that my car is still sitting there with the head off but nothing has been done in at least a week.
I'm beginning to think I need to at least pursue damages and I have spoken to a lemon law attorney that will take the case. The complete lack of care by the dealership has me overboard at this point.
I'm beginning to think I need to at least pursue damages and I have spoken to a lemon law attorney that will take the case. The complete lack of care by the dealership has me overboard at this point.
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From: Sarasota, Florida
2023 E450 Cabriolet, 2019 F150 Platinum, 2014 Dodge Challenger R/T
Absolutely do not give the loaner back without getting another one....
Audi tried to grab my loaner after they had my car for a month...
1 of many reasons i will never buy another Audi.
Audi tried to grab my loaner after they had my car for a month...
1 of many reasons i will never buy another Audi.
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2017 Mercedes C63s
This is crazy, even with loss of compression, I would think that itll take up to a week to fix max. My buddy had bad compressions on 6/8 cylinders and it took him 5 days to order the parts he needed and get it done.
