S280 (2005) Undiagnosed smoking issue

[Alanfrank]

Hi, I have to confess, and apologise, that I have joined this forum in order to pick your collective brains as I have a real problem with my S280 and a number of mechanics have had to admit defeat. I have a 2005 W220 S class, petrol with an LPG conversion kit fitted, 98k miles.
I bought the car privately in September 2017 and it has driven like a dream until recently. One morning I started the car and noticed a huge plume of white / blueish smoke from the exhaust. The smoke stopped on driving but over the next few days things deteriorated, I started to notice a slight misfire then, intermittently the car emitted massive amounts of white / blue smoke, only for a second, but enough to make cars behind change lane in order to see where they were going ! I made an appointment with a local garage but on the way the car lost power, started to vibrate and produced a lot of smoke again. A diagnostic showed a misfire on no 2 and 5 cylinder, so the coil packs were replaced as was the air filter. On idle the car was then showing no faults, and drove fine for about 6 or 7 miles when the exact symptoms reoccurred. The mechanic recommended a local Merc specialist who had the car for the day but reported that they couldn’t find no fault with it !
The car continued to drive okay but I noticed that the smoke continued to be produced on acceleration after slowing down, taking a bend or negotiating a roundabout. That may sound nuts but it can’t be a coincidence as I could almost predict where it would happen on my regular routes. The car also started to use oil at a ridiculous rate, requesting a litre of oil after about 80/100 miles
I put the car in a different garage who did a compression test, and a ‘leak down’ test. I was told that the results were fine, all cylinders showing around 190/ 200, and all pretty much equal. The guy checked the bores and told me they appeared normal also. The guys at the garage said the smoke did have a smell of oil but that it was combined with a smell they did not recognise and had not smelled before. They even asked two mechanics from a rival garage nearby to smell the exhaust fumes and they were equally stumped. I was advised that the car had not been well maintained before I bought it and that the plugs were heavily coated in carbonised oil and the leads were in poor condition, all of which was identified during the compression test. They used flushing oil and changed all plugs and plug leads hoping that may solve the issue. After running the car on idle for 30 mins and a quick test drive, they reported that the car still smoked on start up but not when driven. I collected the car but after 20 mins the same issue repeated itself in exactly the same circumstances but was now lacking any real power. Once I arrived home I tried to rev the engine but even with my foot to the floor it would not go past 4000 revs.
As stated the car is drinking oil, but there are no obvious leaks on the driveway, it is not overheating, and is not losing coolant. I rang the mechanic and he simply said he did not know what the problem was.
The car itself is in fantastic condition ( engine aside)and I’d hoped to keep it for several years so I am reluctant to scrap it even though I only paid £2.5 k for it but none of the pros seem to be able to tell me what the problem is.
Can anyone help ?
Apologies for such a lengthy post but I thought if I am seeking your help then I should provide as much info as possible.
Thanks for your interest.

Regards
Alan

 

[Westheath]

Have the engine breather system checked out.
Could be a PCV (if fitted) valve gone faulty.
I'm more diesel orientated with Mercedes ....
but sounds like a crank case breather system problem
if
the LPG system been checked out
and the rest of the post is correct at the point of testing.

 

[Alanfrank]

Hi, thank you for your reply. The last garage I took it to ( who changed the plugs etc) is an LPG specialist. They are happy the LPG is not the issue as the smoking occurs on both petrol and LPG. I intend to take it back to them again later this week so will put your suggestion to them. The only possible suggestion they could come up with was a potential problem with the ‘oil scraper’ ring on the piston becoming seized and not clearing the cylinder but he admitted that was just a guess. Appreciate your time. Cheers.

 

[Westheath]

Ok
Forget the rings for the minute.......

MB call the PCV an Oil Separator.

I'm sure a petrol savvy MB member will be along shortly.

I don't want to lead you up the "wrong" garden path if you know what I mean.

 

[oigle]

I would agree with Westheath in that the PCV (oil separator) would certainly be worth checking. To happen so suddenly with no apparent reason would take rings out of the equation unless you have overheated it.
The vacuum in the inlet manifold would pull plenty of oil through the PCV if the valve malfunctioned and would smoke like hell after a throttle backoff with high vacuum. Not too hard to check and or replace.

 

[LostKiwi]

As above check the breather system. Also remove cam covers and check for blockages in the breathers on the cam covers.

 

[Alanfrank]

Westheath, Oigle, Lost Kiwi,
Again thank you for taking the time to respond. Not being particularly mechanically knowledgeable I have had to google / research the Pcv valve and from what I am reading the symptoms of a failed pcv do match what is happening with my car particularly the massive increase in oil consumption, general poor running of the car and the mechanic reported a lot of oily sludge when he removed the rocker box cover. They are classic symptoms of a failed pcv right ? Would the smoke emitted from the exhaust be white/ blue though? From some of the stuff Ive read the smoke is more likely to be black. Any thoughts?
It is my intention to ask the garage to change the pcv when I return it this week but thinking ahead, if this is the problem, would replacing it solve the problem or would it’s failure have caused other serious damage to the engine ?
Apologies for loading you up with further questions ?

 

[LostKiwi]

If the PCB is blocked and the crankcase is getting pressurised there are a couple of things can happen:
1. Oil gets pumped the heads and can't return due to pressure caught in the crankcase. This then gets pushed by pressure down the valve guides causing blue smoke and oil consumption.
2. Pressure in the crankcase pushes oil up past the rings causing blue smoke and oil consumption.
The symptoms you describe are very much aligned to blocked engine breathers.

 

[Alanfrank]

If the PCB is blocked and the crankcase is getting pressurised there are a couple of things can happen:
1. Oil gets pumped the heads and can't return due to pressure caught in the crankcase. This then gets pushed by pressure down the valve guides causing blue smoke and oil consumption.
2. Pressure in the crankcase pushes oil up past the rings causing blue smoke and oil consumption.
The symptoms you describe are very much aligned to blocked engine breathers.

That’s really helpful. Cheers? The pcv looks a relatively simple fix, would blocked breathers be a difficult job to unblock or would it be better to replace them?

 

[LostKiwi]

To be honest I'd replace the hoses as they've probably become brittle. Take the breather off the top of the cam cover and clean it out but beware they can be hard to reseal and are prone to oil leaks if not done right. Replace the PCV as well.

 

[Alanfrank]

I think I’ll get the mechanic to do that as I’d want it done properly and I’m not sure I would trust myself with a diy job unless it was very straightforward. Once again thank you and I’ll post to let you know if I make any progress or resolve the issue.
Cheers

 

[Alanfrank]

Good Morning guys, hit a bit of a snag here. Received a number of replies to my ‘smoking issue’ on an S280 2005 W220. All of your replies pointed towards the problem being the PCV valve and breather system. I have this morning contacted by MB main dealer to price up a new PCV only to be told that an S class W220 doesn’t have a pcv valve / oil separator. Now Im totally confused. Westmeath, Oigle, Lost Kiwi or anyone else can you advise ?
Thanks

 

[Alanfrank]

I would agree with Westheath in that the PCV (oil separator) would certainly be worth checking. To happen so suddenly with no apparent reason would take rings out of the equation unless you have overheated it.
The vacuum in the inlet manifold would pull plenty of oil through the PCV if the valve malfunctioned and would smoke like hell after a throttle backoff with high vacuum. Not too hard to check and or replace.

Good Morning,
Again thanks for your reply to my post. I don’t whether you have seen my latest update, but I thought it might be worth coming back to you directly as well as to the general forum. I contacted my local MB main dealer parts dept, in order to price up a new PCV. I was told that the s280 2005 model doesn’t have a pcv and that the job of a pcv is incorporated into the breather system whatever that means. I have to say the guy at the parts depot didn’t sound overly convincing. Any thoughts.
Thank you in anticipation.

 

[Alanfrank]

Good Morning,

To be honest I'd replace the hoses as they've probably become brittle. Take the breather off the top of the cam cover and clean it out but beware they can be hard to reseal and are prone to oil leaks if not done right. Replace the PCV as well.

Again thanks for your reply to my post. I don’t whether you have seen my latest update, but I thought it might be worth coming back to you directly as well as to the general forum. I contacted my local MB main dealer parts dept, in order to price up a new PCV. I was told that the s280 2005 model doesn’t have a pcv and that the job of a pcv is incorporated into the breather system whatever that means. I have to say the guy at the parts depot didn’t sound overly convincing. Any thoughts.
Thank you in anticipation.

 

[Alanfrank]

Have the engine breather system checked out.
Could be a PCV (if fitted) valve gone faulty.
I'm more diesel orientated with Mercedes ....
but sounds like a crank case breather system problem
if
the LPG system been checked out
and the rest of the post is correct at the point of testing.

Good Morning,
Again thanks for your reply to my post. I don’t whether you have seen my latest update, but I thought it might be worth coming back to you directly as well as to the general forum. I contacted my local MB main dealer parts dept, in order to price up a new PCV. I was told that the s280 2005 model doesn’t have a pcv and that the job of a pcv is incorporated into the breather system whatever that means. I have to say the guy at the parts depot didn’t sound overly convincing. Any thoughts.
Thank you in anticipation.

 

[Xtractorfan]

I do have a suspicion that your valve guide seals may be shot..if smoking on the overrun after putting the foot down then that's a good pointer to oil seeping thru' past the valves, and being sucked into the engine. then burnt when the accelerator pedal is floored.

 

[Alanfrank]

XTractorfan,
Thanks for that. As Im a non mechanic could you advise if that requires a full engine strip down ? I am being advised by some that it would work out cheaper to swap the whole engine rather than rebuild it.
Regards
Alan

 

[LostKiwi]

Here is a parts diagram which looks the same for all M112 2.8 V6 engines:
http://mb-teilekatalog.info/view_Su...alog=19X&model=112920&group=14&subgrp=030#158

The PCV is called a connector and is 158.
I suggest you replace parts 140, 146, 152, 170 and 158. It may be wise to get a couple of the connectors 164 as well.

Part 140 is the full load breather whereas all the rest is the partial load breathers.
Parts 140, 146 and 170 all connect to a unit bolted to the top of the camshaft cover. These can clog and should be unbolted and cleaned out, resealed and refitted. NB - they can be a hassle to get to seal again as there is no gasket - just a sealant.

 

[Westheath]

Yea I did say in my first post in here " PCV (if fitted) "

And to check the breather system as it may be incorporated along the line
somewhere.

Here is a parts diagram which looks the same for all M112 2.8 V6 engines:
http://mb-teilekatalog.info/view_Su...alog=19X&model=112920&group=14&subgrp=030#158

The PCV is called a connector and is 158.
I suggest you replace parts 140, 146, 152, 170 and 158. It may be wise to get a couple of the connectors 164 as well.

Part 140 is the full load breather whereas all the rest is the partial load breathers.
Parts 140, 146 and 170 all connect to a unit bolted to the top of the camshaft cover. These can clog and should be unbolted and cleaned out, resealed and refitted. NB - they can be a hassle to get to seal again as there is no gasket - just a sealant.

 

[Alanfrank]

Yea I did say in my first post in here " PCV (if fitted) "

And to check the breather system as it may be incorporated along the line
somewhere.

Hi, yes you did add that caveat, I realise that. Others have said similar so it looks like this may well be the issue. I intend to replace all af the breather pipe system and keep my fingers crossed that it does the job. If not it looks like I could be looking at a replacement engine unfortunately. One of the reasons I bought the Merc was because I’d heard people say the engines are bulletproof and will run forever ! Unfortunately, it appears that isn’t always the case.
Thank you for your interest and assistance anyway.
Cheers
Alan