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  #1  
Old 09-25-2006, 06:16 AM
Jengasan's Avatar
1971 280SE 3.5 (Celia)
 
Join Date: Jan 2006
Location: Scotland
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Question Smoke ! Lots of it !! HELP !!! One for the old timers

All

The following is going to be long and involved but I wanted to impart as much information as possible in order to paint a clear picture of the symptoms and circumstances. Over the last couple of days I had replaced most of the fuel lines and some vacuum lines under the bonnet (hood) of my '71 280SE 3.5 (M116.980 engine). In addition I had just received all 8 injectors back from having an ASNU clean and service (highly recommended before you buy new ones - if you can get then) which I duly refitted along with fresh injector seals. Doing the injectors was actually the original impetuous to do the job as some of the short hose connections from the fuel rails actually had blisters on them - 35 year old rubber and all that. Suffice to say that everything went back together nicely and the car, once warm, ran a treat and definitely felt like it was pulling even better than usual.

Now for the bad bit. I took it out for a spin to warm it through on Saturday (I have the classic hunting problem on a cold start - but that's a different story and one than can wait till later - I have a plan) and basically got caught behind a van doing about 50 mph on our motorway (limit 70mph) , the engine was now warm and I pulled out to over take - without mashing the throttle I might add, and happened to still be looking in the rear view when I see this massive blue/white cloud appear behind me - my first reaction was oh ***** !! I nursed her back to our house and parked her up for a think. I should add here that, as a matter of habit, I checked the oil the previous day when doing to fuel line work and it was spot on half way between the marks on the dip stick. I am also not aware that the car has ever burned any oil, but then I have only done about 2500 miles on her (Scotland is a summer only venue for these cars due to weather and road salt).

After calming down, I decided to try and narrow down the options. My first thought was of course a blown head gasket. I did the basics and checked the radiator for oil - none. I checked the oil filler cap for emulsified oil as well as the rocker cover breather on the right side bank - again none. I'm not yet totally familiar with the M116 but I suppose it could have ruptured through an oil way to the head into a cylinder - but that would be a head off diagnosis anyway I think. At this point I dipped the oil again - just over the bottom of the stick - not the minimum mark, the bottom of the stick - bl**dy hell ! That has to be way over a litre (quart ?) of oil in about 100 miles so what ever it is, it’s bad.

I though then, ok, maybe the rings are shot BUT as I said this is a new phenomenon and I am fairly paranoid about exhaust smoke. Surely rings is a wear issue and it would be a gradual 'getting worse' issue rather than the instant result viewed in the mirror, unless one or more broke of course. By the way she sounds fine, no rattles, thumps or hideous scrapping noises..

My other thought was valve stem seals. Again I don't even know what they look like on the M116 yet but I have my reasons. Obviously when I saw the oil consumption I was on here (the forum) in a flash searching for similar symptoms. All the blown gasket stuff I could find (though I may be just crap at searching on here) related to coolant loss and I also could not find a catastrophic ring failure. I did find some really weird and wonderful stuff - leaking brake servo (booster) allowing fluid along the vacuum line into the intake etc but that would not account for the oil loss and the brake fluid level is fine.

One post that caught my eye regarding valve stem seals was by Tomguy (I think) because he had an interesting theory regarding the angle the car was parked at. My drive is a fairly steep slope and I have noticed that (since the smokescreen incident) when cold, if I start her up there is no smoke what so ever for about the first 10 seconds, then a slowly increasing light blue haze develops into the belching. Logically using Tomguy's theory, the oil is draining away from the cam box area via the rear oil drain (car parked 'nose up' at about 15-20 degrees), when fired up we have to wait for the oil to circulate to the top end in sufficient quantity before seeing the smoke - it's a really tempting theory as I'm willing to do all the valve seals in preference to a full top end off job any day.

The thing that's really getting me however is the volume of the oil loss, I mean a full litre in 100 miles or less is massive. Surely a valve stem seal is not going to pass that volume ? Or is the 'sucking' of the piston maybe helping it drink ? Another point is that I pulled all 8 plugs, absolutely no oil on them at all. They all looked pretty good too - I was expecting pure black soot at least form a D' Jetronic car but they were all grey/brown though perhaps a little light (which is getting on for lean which would be frankly bizarre - but again let's not get into that now). It's therefore tempting to think that the stem seal on an exhaust is shot, allowing oil into the exhaust stream but not the cylinder, hence the clean plugs - but again, over to you far more experienced 'old timers' on here to shoot that one down (gentlemen - you may take 'old timers' as the compliment it was intended to be).

So there you go….that's all the info I can think of to be relevant but I am open to suggestions and am particularly interested in similar experiences. I know you guys are more familiar with the M117 but that's only really a stroked version of the M116 so symptoms should be identical?

Your thoughts ?

Cheers

Alan

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  #2  
Old 09-25-2006, 09:03 AM
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Well I for sure have no idea

I am totally unfamiliar with your car and I am really just throwing this out because it was my experience with weird oil-burning. In my Fiat once the PCV hose got kinked and clouds of oil smoke poured out of the car because the increased crankcase pressure forced oil past the rings and pretty much every other seal.

Josh
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  #3  
Old 09-25-2006, 09:52 AM
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1L in 100mi is way more than valve stem seals I believe. With the angle I used to be parked at, the oil would sit in the head overnight rather than draining out, resulting in smoke about 5 seconds after firing, lasting for about 15 seconds (longer in the winter), leading me to believe it all accumulated in the exhaust.

I've heard reports of some m117's loosing a cam oiler (cracked with age? Cracked due to human error? Unsure why). Once that oiler is loose, if it happens to shoot oil in the top rear of the right valve cover (your driver's side), oil will travel through the breather hose into the intake. I think you can imagine what happens after that. Aside from this issue, I highly doubt it'd be a head gasket issue - I THINK the only oil pathway going from the block to the head is in the rear for the camshaft oiler tube. I'll double-check and make sure about what that small path between each cylinder is... If it's leaking from there I suppose it could be the issue but only 1 or 2 cylinders would be burning oil if this is the issue. I have never heard of catastrophic ring failure on these engines.
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  #4  
Old 09-25-2006, 12:21 PM
Jengasan's Avatar
1971 280SE 3.5 (Celia)
 
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Good point !

Tomguy

I hadn't even got to taking the air cleaner off for a look - I shall go and do this now (just home from work). I've never had the rocker covers off this engine as yet so there is a schance the cam oiler tube has let go. I'll fire it up with the breather disconneted and see what happens. Thanks too to you Kalpol, although I was going to say that these engines breath only through the cam boxes (as far as I know) I hadn't made the jump to Tomguy's suggestion - again thanks to you both...now let's go an see what the car thinks. I will post my results later after a spot of dinner.

Cheers

Alan
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  #5  
Old 09-25-2006, 04:30 PM
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1971 280SE 3.5 (Celia)
 
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Posts: 88
Update

Well guys, as reported I went out and pulled the air cleaner (which I had replaced about 2 weeks before the 'incident') and it was as clean as the preverbial whistle...damn. When running, the breathers certainly produce vapour but not beyond what I would expect..back to the drawing board. Strangely enough I took her out for a short spin this evening as the smoke didn't look as bad...yeah I checked the oil level again - all ok. Guess what...no smoke, or certainly so little that I couldn't see it out the rear view, it has been windy though. I was too chicken to really rev very hard so maybe this was just because the car wasn't really trying (50mph tops).

It also occured to me that I hadn't carried out the 'sludge in the oil filler cap' test when the engine was cold so I'm going to do that in the morning. I really need to pursue this till the end as it's making me very wary of driving the old girl too much lest I do serious damage.
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Old 09-25-2006, 05:28 PM
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Jengasan: Buy the oiler tube plastic bits for both sides of the engine. Even if you get them at the stealership they won't cost over $25. while you're at it, get new valve cover seals and crush washers. Take the valve covers off, make sure all your cam lobes are good. Take the oiler tubes off, take off all the old plastic bits, and clean the tubes well with "petrol", carb cleaner, or whatever you choose. Use the new plastic pieces and put them back together, then back on the cam towers. Make sure they all fit in snug.

This will give you much raised confidence in your valvetrain's lubrication. If it's a periodic issue with leaking then this will resolve that as well. Safety of mind is worth the few bucks IMO. You really should clean those oiler tubes if they're old. Not doing so can result in this:

Clean those camshaft oilers... PLEASE!
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  #7  
Old 09-25-2006, 08:11 PM
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recently my 74 450sl threw its power steering belt off whilst driving on the interstate. i had no spares or tools and had to call a towing service. the tow truck was the sort that the bed tilts down on, and the car is winched onto the bed, then the bed is lowered. as my car was being pulled up the steep incline oil began running out from under it. the driver said every time he loads an old mercedes he has this problem. i don't know if this will relate to your oil issues or not, just thought i would pass it along.
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  #8  
Old 09-26-2006, 05:03 AM
Jengasan's Avatar
1971 280SE 3.5 (Celia)
 
Join Date: Jan 2006
Location: Scotland
Posts: 88
Update the 2nd

First off I just posted this in the wrong place - so here goes for a second attempt (I'm glad you guys don't know what I do for a living as this could get embarrasing) anyway.......

Bad news guys........checked the oil filler cap this am and there is a little white in there...not a lot, in fact the least amount I have ever seen in a 'suspected gasket blow' situation, but it's there.......damn. I still don't get the oil consumption though ??? All this means is that the head gasket is allowing coolant into the oil, bad enough I suppose. Oh well, this just means that the poor old thing is going to bed for the winter a bit earlier than expected this year.

Interesting reading on the cams and oiler tubes, suffice to say that since the top is coming off she'll be getting all new plastic and rubber parts involved....this is going to cost me Unfortunately Fastlane can't ship to Scotland so the stealership (good one Tomguy!) may be in profit again this year. So by my calculations this means.....head gaskets for boths sides (I see no point in waiting for the other one to go), ascociated inlet and exhaust gaskets, plenum rubber seals, valve stem seals, rocker box cover seals and crush rings and I may change the cam chain guides.....I'll do a tretch test first but I'm hoping the chain doesn't need done too or I'll start to get complaints about 'it's not worth it' from the other half

As a last ditch attempt at getting another couple of weeks motoring I'll be getting a very experienced mechanic friend to give me a second opinion, he's just back from holidays over your side of the pond so he's going to love me when I turn up at his place with the merc and a downturned mouth.

Any way, as usual thanks to all for your imput, at least we tried to keep the heads on !

Alan

P.S. There is actually no way I'd ever abandon her over money....if you think they are rare over there, they are practically none existent over here in Scotland
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  #9  
Old 09-26-2006, 05:51 AM
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I am not sure if the oil filler cap diagnosis is reliable on determining gasket failure. The engine air space is big and specially in cold climates condensed moisture may gather in there if the engine is not heated all the way (short rides). Are you loosing coolant or is there bubbling of coolant when the engine is running. A cylinder pressure test may also be a good idea.

Another thought: is your car auto transmission, if yes have you checked that auto fluid level. It may be possible the your gearbox vacuum modulator valve leaks auto oil through the vacuum tube into the intake of the motor. Check if the vacuum tube is clean and not oily. It would not explain your motor oil consumption though
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Last edited by Tomit1; 09-26-2006 at 06:11 AM.
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  #10  
Old 09-26-2006, 08:42 AM
Jengasan's Avatar
1971 280SE 3.5 (Celia)
 
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Location: Scotland
Posts: 88
Interesting points Tomit1

I have to admit that I am not 100% convinced myself, mainly due to the fact that any blown gasket I've seen (though not on these engines) has produced a oil filler cap like a yoghurt tub, and there has been oil in the coolant. In answer to your question, there is no oil in the coolant that I can detect and I do not seem to be losing any or producing any jacuzzi effects. The radiator cap looks a bit dodgy actually so I'll change it, but I like to check fluid levels regularly so I don't think its going down.

Re the cylinder pressure test, I am hoping to con my mechanic friend into doing one for me, though I am presently unsure if he has the correct equipment to do so, a compression test at the very least will be done.

The car is indeed an auto transmission, and to be honest I never gave the tranny a second thought.....guess what I'll be doing tonight. Having said all of that, Tomguy and others have scared me enough to get at least the rocker covers off and the cam oiler tubes cleaned etc so I've ordered some bits for that today...it would be REALLY nice not to have to do the gaskets though as it would prolong my motoring this year.

Does the vacuum modulator have a rubber diaphragm by any chnage and can this rupture ? I'll be down there anyway as I've been replacing all the old rubber hoses and I believe that there is short section on the end of the metal take off pipe from the manifold. As for the bit it's self, can the diaphragm be replaced or is it a new modulator ? If so are we talking big bucks ?

I'll let you know what happens.

Alan
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Old 09-26-2006, 08:58 AM
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It is a good idea to change the oiler plastic parts on the cam, if never done before.

the modulator has a rubber diaphragm that may break. It has to be changed I think the whole thing, cost about 60 euros over here from MB dealer.
Take of the plastic cap off where the vacuum tube goes and if it is oily, then it leaks and can produce irregular smoke from the exhaust.
It takes 5 min to replace it, just make sure the inner piston is at the same length as the old one as here you adjust the smoothness of the gear changes (if too smooth the gear may slip and that is no good).
I just had a case like this, although I have only experience in the 116, 123 and 107 chassis.
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  #12  
Old 09-26-2006, 01:23 PM
david s poole
 
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smoking

i think i may have your solution.when you serviced the injectors i bet you didn't change the oil.you had a serious case of oil contamination with gasoline[petrol to you]and when engine got warm enough gas in oil wants to burn and oil with it hence the smoke.pull dipstick and see if the oil is pulling away from the edges of the stick.this should confirm it but seen it before on same year car.
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  #13  
Old 09-26-2006, 02:59 PM
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1971 280SE 3.5 (Celia)
 
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Exclamation David S & Tomit1

Gentlemen

Progress....most interesting. I'll do these in reverse order so bear with me.

David S - you are absoutely right, I hadn't changed the oil as I was hoping to do so after diagnosing my 'hunting on idle' problem (I'm awaiting delivery of the Bosch manual/book on the d-Jetronic system). I just dipped the oil and you are again absolutely right, the oil is pulling way from the edges, looks kind of bubbly and weird too. What I don't get is that I do not remember seeing this before having the injectors done. I had them serviced really as a by product of wanting all the feed hoses (fuel rail to injector) changed as a couple of them had blisters in the casings...not good at 29psi. Also the car did not smoke prior to the incident mentioned above (that I noticed anyway)...I cannot deny the evidence in the oil though. How is it getting into the combustion chambers ? is it just straight blow past the rings ? I'm a little confused as to the mechanism here...but see below for another twist.

Tomit1 - The first thing I did when I got home tonight was dip the ATF, which appeared to be at normal(ish) level, though I confess I did it engine off and in Park. However I then got under the car and got a bit of a surprise. I had thought that the vacuum line to the transmission modulator would end in a rubber hose but it is actually all metal with a banjo fitting. I have never seen a banjo on a vacuum fitting before and had to convince myself I was looking at the right part - suffice to say I'm convinced as it couldn't be anything else (i.e. it wasn't a cooler line etc). I undid the banjo and sure enough there was "oil" in there. Now it may be ATF but it was fairly filthy to say the least and the stuff on the dip stick was clean as you would expect. I presume though that any trace of ATF at all inside this banjo means that the modulator is indeed shot and I need a new one ? (ruptured diaphragm as discussed).

All - This is pretty interesting isn't it. When I bought the car the PO did tell me he was a 'body' man and that although I would probably find a better one mechanically, I would not find a better example in the body department. I have to confess I think he was right because although I seem to be having my fair share of mechanical woes right now, at least I'm not trying to track down rare sheet metal and spending hours with a welder. I think by the time I'm done I'll have replaced about all the service parts which I suppose is no bad thing. I've just added a tranny modulator and a tranny service kit to my list in the previous post

Anyway, I'll post the next installement when I get the bits and fit them, I might even take some pictures if you think it's relevant. As always, many, many thanks to all for the input and advice.

A
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  #14  
Old 09-27-2006, 12:30 AM
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AT Modulator diaphram

I have a 1963 that had a blown AT modulator diaphram. The symptoms were similar to yours. Lots of smoke on original start and acceleration after lengthy idle. Vacuum was sucking the AT dry over time. Diaphram replacement part was $20 and car has been smoke free since. Hope yours is as simple.
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  #15  
Old 09-27-2006, 12:46 PM
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smoking

ok but change the oil first.the other is minor compared to the engine oil.

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