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Discussion Starter #1
Good evening guys,

I'm not sure if anyone else has had this issue, mine has been going on for some time. I have a 1997 S600 which had been running great for a long time. I used it for work and drove it daily about 100 miles. One day my check engine light came on nad it has not turned off since ( that was 2 years ago). A few weeks after it first happened I noticed reduced power especially when I get aggressive. Got so bad the car would only "limp" home. After the mechanic looked he said I "melted" the cats. Not sure if that is the literal assesment but they were plugged solid. The only code it was throwing out was O2 sensor so we replaced everything and it was good for a while. About 6 months later and 2 new sensors (I had him change them again since it was the only code showing up after 3 months) she clogs the cats again. Now I'm getting mad, so I fixed it again but now I can tell it has to be something else. She will idle rough at stops occasionally and if I hit the gas hard I get a large blue smoke cloud. The blue smoke seems to fit because she is consuming a lot of oil (1qt per 1000 miles synthetic) but no leaks.

HELP!!!!
 

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My only suggestion is, if the temp was so bad, that it so called melded the cats, what the hell was the back pressure and the temp of the motor, it could be many things and most times its a process of elimination, dont think of the worst things like deformed oil rings becase of overheating, hopefully its something simple like a bad gass supplier, stuffed gas filter, fuel regulator, intermittent coil out, plug or plugs failure, .
The first thing I wold do is take it to a service shop that has a history and good reputation ask some of the members here that are in your area, that may cost you a little more now, but in the long run save you money as you will be told, and shown , then know.
Cheers Mate EJ
 

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How many miles on the car? What code were you getting exactly?

Blue smoke and oil consumption without a leak? Certainly it must be burning it in the cylinders. How is it getting in the cylinders? Either from the top (through the valves via getting past the valve guide and valve stem seals) or from the bottom (past the piston rings). A compression and leakdown test may be able to pinpoint a piston ring problem. One valve guide test is to run the engine to high rpm, then let off the throttle suddenly to produce a high intake vacuum situation, and then see if smoke appears from the tailpipe under this high vacuum situation. You want the transmission to be in 1 not D so that it won't upshift on you. You need high rpm without going 100 mph, and someone else will probably need to drive behind you, or maybe it can be done in an open parking lot with an observer standing outside the car. Anyway, if the valve guides are worn and/or the seals are not sealing well, the high intake vacuum will suck oil past the guides and seals and cause oil smoke from the tailpipe.

You might pull the spark plugs and have a look at them. Buring significant oil may foul the plugs and give you more confirmation that you're burning oil.

One other possibility, I suppose, is oil passing to the throttle body from the PCV system. You can pull the PCV hoses off the throttle bodies and look to see if there is major oil signs in the hoses and where the hoses enter the throttle bodies.

I'm not completely sure what to think about melting the cats. I'm not sure how much oil has to get to the cats to cause a meltdown like that. My thoughts are that burning 1 qt per 1000 miles wouldn't be enough oil to cause cat meltdown. (I think I'm correct in saying that 1 qt per 1000 miles is "in spec" for Porsche's current flat-6 engines according to the owner's manuals. Don't quote me on that however. Most engines do not burn that much.) I think a better guess to the problem might be overly rich running (too much fuel) rather than oil causing the cat meltdown, but the O2 sensors and MAF sensors are responsible for ensuring that doesn't happen. Perhaps it's worth replacing the O2 sensors and MAF sensors.

I have a question. When you say you fixed the catalytic converters, what did you do? Did you replace them? new ones, used ones? Just curious.

Brett
 

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I know that if the car is dumping lots of unburnt fuel into the cats that can ruin them, you're not running very rich are you? One thing you might consider is that until you get this problem sorted remove the cats and weld in some pipe so as not to ruin anymore.
 

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Discussion Starter #5
How many miles on the car? What code were you getting exactly?

Blue smoke and oil consumption without a leak? Certainly it must be burning it in the cylinders. How is it getting in the cylinders? Either from the top (through the valves via getting past the valve guide and valve stem seals) or from the bottom (past the piston rings). A compression and leakdown test may be able to pinpoint a piston ring problem. One valve guide test is to run the engine to high rpm, then let off the throttle suddenly to produce a high intake vacuum situation, and then see if smoke appears from the tailpipe under this high vacuum situation. You want the transmission to be in 1 not D so that it won't upshift on you. You need high rpm without going 100 mph, and someone else will probably need to drive behind you, or maybe it can be done in an open parking lot with an observer standing outside the car. Anyway, if the valve guides are worn and/or the seals are not sealing well, the high intake vacuum will suck oil past the guides and seals and cause oil smoke from the tailpipe.

You might pull the spark plugs and have a look at them. Buring significant oil may foul the plugs and give you more confirmation that you're burning oil.

One other possibility, I suppose, is oil passing to the throttle body from the PCV system. You can pull the PCV hoses off the throttle bodies and look to see if there is major oil signs in the hoses and where the hoses enter the throttle bodies.

I'm not completely sure what to think about melting the cats. I'm not sure how much oil has to get to the cats to cause a meltdown like that. My thoughts are that burning 1 qt per 1000 miles wouldn't be enough oil to cause cat meltdown. (I think I'm correct in saying that 1 qt per 1000 miles is "in spec" for Porsche's current flat-6 engines according to the owner's manuals. Don't quote me on that however. Most engines do not burn that much.) I think a better guess to the problem might be overly rich running (too much fuel) rather than oil causing the cat meltdown, but the O2 sensors and MAF sensors are responsible for ensuring that doesn't happen. Perhaps it's worth replacing the O2 sensors and MAF sensors.

I have a question. When you say you fixed the catalytic converters, what did you do? Did you replace them? new ones, used ones? Just curious.

Brett
Very informative, thank you. I will try the test and let you know. I will take her close to redline and let off the gas to see what happens. The blue smoke happens only when I hammer it, it hesitated for a second then dumped a big blue cloud but did not continue to do it. I have a feeling the cats and oil may be seperate problems, we have replaced 6 O2 sensors already and they seem to be functioning normally. I have heard many times running lean can cause my cat problem. I have heard if there is any damage to the wiring of the O2 sensors it can cause a false code or tell the car its lean or rich even if it's not. The car has 112,000 on the clock and I believe we are using new cats each time. my concern with the oils is that it started consuming more when the problems started, before it was a QT per 3000 miles. Again may be unrelated but I need this engine to last until I can afford to swap it for the 2006 V12 which installed with tranny and everything is close to 30k. Did I mention it's a show car?
 

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Discussion Starter #6
I know that if the car is dumping lots of unburnt fuel into the cats that can ruin them, you're not running very rich are you? One thing you might consider is that until you get this problem sorted remove the cats and weld in some pipe so as not to ruin anymore.
I was actually thinking the same thing! I have a friend that owns a muffler shop and he can do it but I want to see if I can figure this out. If not were going straight pipe V12!!!:D
 

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Very informative, thank you. I will try the test and let you know. I will take her close to redline and let off the gas to see what happens. The blue smoke happens only when I hammer it, it hesitated for a second then dumped a big blue cloud but did not continue to do it. I have a feeling the cats and oil may be seperate problems, we have replaced 6 O2 sensors already and they seem to be functioning normally. I have heard many times running lean can cause my cat problem. I have heard if there is any damage to the wiring of the O2 sensors it can cause a false code or tell the car its lean or rich even if it's not. The car has 112,000 on the clock and I believe we are using new cats each time. my concern with the oils is that it started consuming more when the problems started, before it was a QT per 3000 miles. Again may be unrelated but I need this engine to last until I can afford to swap it for the 2006 V12 which installed with tranny and everything is close to 30k. Did I mention it's a show car?
We would enjoy some pics if it's a show car. Let's see what you've done, so we can all make fun of it. Just kidding...

But, I would think a puff of smoke when you go wide open throttle is nothing to worry about. You might just be blowing some soot out of the muffler with the high air flow rate. As I understand, the computer over-enrichens the mixture at wide open throttle as well, to eliminate the possibility of lean running at max power (That would be a major disaster.). You might just have excess fuel blowing out, too. If it were my car, I would perform the closed throttle test to see if I could determine if there is valve guide leakage. I would check spark plug condition to determine if they are fouling excessively or fouling unevenly indicating a more serious problem with one or more cylinders specifically. And barring any other serious symptoms, I would simply continue to drive it and more carefully monitor oil use and leakage to make sure oil loss isn't from leaking. I'm no expert, but I have read that one should begin to ponder engine rebuild when oil consumption gets up to around 1 qt in several hundred miles.

Again, I really don't know what to say about melting the cats. And, again, I'm no expert, but I'm not so sure how a lean running condition leads to cat problems. Lean running does lead to hot running and engine troubles from that, but I don't see cats melting. The cats get hotter when they work harder to burn unburned fuel from the engine. Lean running means there isn't any excess fuel left in the combusted mixture, so I don't see how that affects the cats... Unless the hotter exhaust gasses from the lean running engine are still hot enough downstream to affect the cats.

Well, here's a possibility. The rough running may be due to a misfire (or no fire) at one or more spark plugs. That lack of fire then dumps excess fuel into the exhaust and cats. For such a serious rough running condition, I would expect the OBDII system to throw misfire codes. Not sure why it wouldn't... bad sensors perhaps... but, then I think it should throw codes for bad knock sensors. Anyway, your misfiring and rough running may be due to bad ignition coils. Usually, one gets a cylinder specific misfire code, and that points you in the right direction of which one to change. Without that knowledge, I'm not 100% sure how to identify bad ignition coils except to check them for open circuit, which would certainly be a bad coil, and check them for physical damage (cracks in the housing or sealing materials, bad contacts for the spark plugs). May be worth the investment for 12 new ones.

Do you know exactly what OBDII codes you're getting?

Brett
 

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Updates?
 

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Discussion Starter #9
Not much, I tried running it up to 6000RPM and letting go of the accellerator quickly and no more smoke or anything like that but i know by the sound that whatever is wrong is not fixed yet. She will run a little rough at idle still si it is really frustrating. Time to switch the engine to the Newer twin turbo V12 and be done with it!!:surrender:
 

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Not much, I tried running it up to 6000RPM and letting go of the accellerator quickly and no more smoke or anything like that but i know by the sound that whatever is wrong is not fixed yet. She will run a little rough at idle still si it is really frustrating. Time to switch the engine to the Newer twin turbo V12 and be done with it!!:surrender:
I thought I misread your other post but youre gonna swap the V12 BiTurbo to the W140?!? :eek:
 

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I thought I misread your other post but youre gonna swap the V12 BiTurbo to the W140?!? :eek:
Yes sir, that is the idea. It all started about 18 months ago when I was attempting to get the Renntech 7.3 conversion done and they weretelling me that they may not have all the available parts due to the age of the car 1997. So I started researching alternatives because really wasn't thrilled about spending 50+ thousand dollars for only 75 hp or so anyway. Called Mercedes and got a quote for a new engine, tranny and brain for under 40k. Found a shop in LA who will put it in under 5 grand and make sure it works perfect too. With a 1700 upgrade I can have 775 lb ft of torque as well so it was a no brainer. By the way Mercedes would offer the full warrenty too.
Now that the economy is tough I'm going to go back and see if I can get a better price or try a local dismantaling yard. Los Angeles has more S600s than anywhere other than the middle east so when I get the package down to 20-25 grand it's going in. It will be lighter, better weight distribution, and much more powerful. I will do a build post when I get closer to d day but I'm finishing a lowrider first that is taking up a lot of my time.
 

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Yes sir, that is the idea. It all started about 18 months ago when I was attempting to get the Renntech 7.3 conversion done and they weretelling me that they may not have all the available parts due to the age of the car 1997. So I started researching alternatives because really wasn't thrilled about spending 50+ thousand dollars for only 75 hp or so anyway. Called Mercedes and got a quote for a new engine, tranny and brain for under 40k. Found a shop in LA who will put it in under 5 grand and make sure it works perfect too. With a 1700 upgrade I can have 775 lb ft of torque as well so it was a no brainer. By the way Mercedes would offer the full warrenty too.
Now that the economy is tough I'm going to go back and see if I can get a better price or try a local dismantaling yard. Los Angeles has more S600s than anywhere other than the middle east so when I get the package down to 20-25 grand it's going in. It will be lighter, better weight distribution, and much more powerful. I will do a build post when I get closer to d day but I'm finishing a lowrider first that is taking up a lot of my time.
Good luck getting everything to fit. Quite an undertaking. But, all it takes is time and money. If you've got both of them, go for it. Will be interesting to follow.

By the way, did you ever get the fault codes that were associated with the check engine light?

Brett
 

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Good luck getting everything to fit. Quite an undertaking. But, all it takes is time and money. If you've got both of them, go for it. Will be interesting to follow.

By the way, did you ever get the fault codes that were associated with the check engine light?

Brett
Well that is the easy part per my mechanic. We need to fab up custom motor mounts and tranny mounts but the engine itself will swim in the compartment that the original V12 sits in. Mercedes has done all the work for me designing the monster that is the W140 V12!!!!!

The fault code is always the same, O2 sensor. I've replaced too many and I am really just over it. She drives and it costs about 700 every 6-12 months so once more maybe before I swap the engine and I wont even have to deal with it.
 

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Been reading your posts.. Just curious as to how the power is at the moment?? Just something to consider , if the timing has jumped just enough you will have mixture problems along with a rough idle and lack of power that can be confused with plugged cats..(seems strange you would go through 2 sest so soon dut to an 02 sensor)
I would look down that road before completely giving up.. Although I beleive you have to pull the valve covers which is no small job..

Just a thought for the offering.

Best wishes.
 

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I think you have two problems here, what is your fuel economy like ? Do all the things Brett suggests, additionally I would take the dipstick out and check for blow by ie compression in the sump.
Lets know what you come up with !
 

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If mine ever goes....

6.3 V8 500+ is the most logical choice for a swap.

Mbz has put them into almost everything they sell.
 

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Discussion Starter #17
Been reading your posts.. Just curious as to how the power is at the moment?? Just something to consider , if the timing has jumped just enough you will have mixture problems along with a rough idle and lack of power that can be confused with plugged cats..(seems strange you would go through 2 sest so soon dut to an 02 sensor)
I would look down that road before completely giving up.. Although I beleive you have to pull the valve covers which is no small job..

Just a thought for the offering.

Best wishes.
Yeah, I see where your going but it was plugged cats. The same thing always happens, she starts to sound a little different, a few weeks later I start to notice power loss, a few months after that she in limp mode any time I even try to get over 3000 rpm. Sucks, but hey now I don't really want to find the problem so I'll have an excuse for the swap!
 

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6.3 V8 500+ is the most logical choice for a swap.

Mbz has put them into almost everything they sell.
Weeeeell, I wouldn't say it's the logical choice sInce I have a V12 to put a V8 in but reliability and parts wise I see your point. It would prob. be much more practical. With that being said, who really buys a V12 anything to be practical!
Plus 500 horsies in a car this heavy just doesn't blow my skirt up you know! I need closer to 700 to make her sing. Got a few buddies with lambos and such and I think I can take them. Gonna put little stickers on the side like the old WW2 pilots did when they took out Nazis! (don't worry, they will be removable!)
PS I just painted her (myself) and I'm going to put a little so
ething up for everyone to enjoy, or hate depending on taste! Just have to go to the stealership to get some of the little plastic clips I broke when removing the lower exterior panels from the doors. Be on the lookout it should be sometime next week!
 

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Any luck on finding a motor/tranny/etc donor yet?

Are you going for the 5.5TT or the 6.0TT?

Granted, the latter is exclusively for AMG models so it'll be tougher to find, whereas the former can be found of cheap and sell the rest of the car to offset the costs.

Best of luck mate :)
 

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Sounds like you are having a cylinder thats not firing which is why you are dumping gas.
 
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