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Engine suddenly lost compression on 5 out of 6 cylinders


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ltwargssf
Novice

Mar 8, 2020, 2:44 PM

Post #1 of 15 (498 views)
  post locked   Engine suddenly lost compression on 5 out of 6 cylinders  

I have a 2008 Mercedes C300 v6 with the 3L m272. It been a very good car for the last 6 years and put over 275k on it. Yesterday, unfortunately, after accelerating to merge on the high way (I got pretty close to redline) the car gave me a check engine light and as I slowed down, I started misfiring really badly.

I had to stop and get the car towed since it wasn't drivable with the misfires.

I scanned for codes and it's only giving me misfire codes all cylinders with nothing else..

I have the Xentry, dealer level scan tool which can perform a compression test.

This didnt look good since 5 out of 6 cylinders had 100-110psi and cylinder 4 was the only one with 225psi. I did this 3 times and it appears 5 cylinders are down 100psi on compression.

My question is, how can a perfectly good engine just have 5 cylinder die at the same time. If it was just one or two, I would supect a bend valve/piston but what are the chances of all 5 ? The car never burnt oil.

Since the scan isnt giving me more then misfire codes, I dont know where to look next.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Mar 8, 2020, 3:10 PM

Post #2 of 15 (486 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

Pretty easy...... by jumping time (belt/chain) or even running low on oil.

PS, I deleted your duplicate question.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Mar 8, 2020, 3:11 PM)


ltwargssf
Novice

Mar 8, 2020, 3:12 PM

Post #3 of 15 (478 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

Oil is at the full mark which its always been. How would I go on inspecting the timing ? This is a timing chain, the car is high mileage on the original timing chian.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Mar 8, 2020, 3:17 PM

Post #4 of 15 (476 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

Yep, it was overdue.

You'll have to tear it down to check timing but if it did jump you are likely looking at replacing the engine as there will be bent valves.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



ltwargssf
Novice

Mar 8, 2020, 3:29 PM

Post #5 of 15 (466 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

These engines aren't really known for chain failure. There was no knocking sound, just misfires. Are you saying the chain skipped and damaged 5 different cylinders? I find that unlikely since it still starts and runs but misfires badly.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Mar 8, 2020, 3:34 PM

Post #6 of 15 (462 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

OK, you've got it all figured out. You don't need us.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



ltwargssf
Novice

Mar 8, 2020, 3:38 PM

Post #7 of 15 (458 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

Hey man, im just trying to figure out since this car never had engine problems in my 5 year ownership and over 150k+ i've driven it.. It was always smooth and I'm just trying to figure out how the chain could skip a tooth without throwing any camshaft codes.. There's 4 camshaft position sensors on the car and typically the computer would at least throw a code if the timing was off.. Like I said, all im getting is misfire codes on all cylinders and low compression..


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Mar 8, 2020, 3:46 PM

Post #8 of 15 (442 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

Like I said, you have your own opinions and don't need or want ours.

You haven't even done a real compression test yet so I don't trust those readings anyway. Electronic cranking compression is just relative compression.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



ltwargssf
Novice

Mar 8, 2020, 3:53 PM

Post #9 of 15 (436 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

What would the best way to approach this if it does indeed have bent valves? I will go get a compression gauge but if the timing is off and the valves aren't closing correctly, doing a leak down test at TDC could be a waste of time without first checking the timing right?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Mar 8, 2020, 4:01 PM

Post #10 of 15 (430 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

The leakdown test will only tell you if the valves are bent, not whether it is out of time and if the cams are out of synch with each other you may not even be able to do a leakdown.

If it has bent valves I think you would be looking at another engine as repairing it with that many miles would run into way too many problems.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



ltwargssf
Novice

Mar 8, 2020, 5:17 PM

Post #11 of 15 (409 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

Yes exactly, I would not repair it if the valves were bent but I am still very sceptical about the bent valves because when this happened, there was no metal to metal noise, as soon as I slowed down, that's when the engine just started misfiring. If I have bent valves on 5 cylinders, would that make a very noticeable knocking/tapping sound?

Thanks for your help


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Mar 8, 2020, 5:22 PM

Post #12 of 15 (407 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

No, it would not. All the damage would be done during the first revolution and nothing after that. We see this with bad timing belts all the time.

It depends on how far off the timing is. One tooth probably wouldn't make contact but would effect the compression on multiple cylinders but any more than that likely would bend valves.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



ltwargssf
Novice

Mar 9, 2020, 6:26 AM

Post #13 of 15 (374 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

Well got my compression gauge today and cylinder 4 is completely dead. Guess its time for a new engine. Thanks again for your help.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Mar 9, 2020, 6:28 AM

Post #14 of 15 (371 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

You're welcome, I'll close this now as solved.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Mar 9, 2020, 6:47 AM

Post #15 of 15 (364 views)
  post locked   Re: Engine suddenly lost compression on 5 out of 6 cylinders  

Late suggestion still closed/solved: " ltwargssf " Do the math sport. Residual value of what you have still has 275K + cost of so called new engine if that works out fine what's the new REAL value? Factor time lost now too plus knowing the rest of the car still has the 275K what horror could be next? Just to think about,


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