Hi All
I posted another topic around a week ago about sudden blue smoke from my 12/1977 350SE, which had been standing as well as started and stopped many times for quite a while during some body repairs. Also, I believe it has been standing as well for a long time, before I bought it in Germany and brought it up to Denmark in March this year.
The engine is the original in the car (checked the datacard) and it has done 327.000 km, and I don't believe it has been renovated - at least I have no documentation to show it has. In any case, it is smoking a lot less now and I cannot see any noticeable oil consumption on the oil pin, even though it does give a puff of blue smoke at de-accelleration on the highway exit and at warm starts, where it is also more difficult to start.
So, I decided to do a compression test to get a first impression of the condition of the engine.
The compression test was done with the following comments/details:
- the engine is a M116.985 - European version with 1st generation K-jettronic, before the upgrade in 1978.
- did it with cold engine, as I did not fancy getting burn marks from the exhaust manifold trying to dig out the spark plugs!
- fuel pump relay disconnected
- plug removed from ignition coil
- full throttle when cranking
- measurements taken after 5 strokes of the needle on the gauge
- did not do a wet compression test, as I did not see any low compression readings
- spark plugs have not done more than about 4-500 km max.
Results: (1-4 left side standing in front of the car with 1 closests - 5-8 right side with 5 closests)
Cylinder 1: 170 psi - spark plug white
Cylinder 2: 174 psi - spark plug white
Cylinder 3: 170 psi - spark plug white
Cylinder 4: 177 psi - spark plug white
Cylinder 5: 179 psi - spark plug wet with oil
Cylinder 6: 177 psi - spark plug white
Cylinder 7: 164 psi - spark plug white
Cylinder 8: 166 psi - spark plug white
I have attached two pictures, showing the typical white spark plug, which all look about the same, as well as nr. 5 which was wet with oil.
Nr. 5 is wet with oil, but compression is the highest of them all. So I am puzzled, and I would like to hear your opinions.
So what do you think is the verdict here? ???
Thanks,
Christian 8)
Hi Christian,
Your description of smoke when decelerating (long downhill then accelerating again) corresponds perfectly to valve seals. Either too hard or worn.
I had an engine that did that. To test this theory back then, I added a quarter of heavy/dense/high viscosity oil additive. The one you find at any auto store. Brands vary but Winns or STP would do.
If after adding the additive blue smoke disappears or diminishes significantly, you have in fact valve seals that need to be replaced. The additive is not a permanent solution but rather a mean to test the valves theory. It treats the seals so they can seal better, but the condition will come back eventually.
Also, I have seen engines smoking like that when too much oil is added by accident. As with the valve seals theory the smoke is bluish and not black or white.
If you find in fact is the valves, you are in a best-case scenario, rather than for example a broken ring, etc.
Good luck.
Robert
Quote from: revilla on 09 August 2020, 05:02 AM
Hi Christian,
Your description of smoke when decelerating (long downhill then accelerating again) corresponds perfectly to valve seals. Either too hard or worn.
I had an engine that did that. To test this theory back then, I added a quarter of heavy/dense/high viscosity oil additive. The one you find at any auto store. Brands vary but Winns or STP would do.
If after adding the additive blue smoke disappears or diminishes significantly, you have in fact valve seals that need to be replaced. The additive is not a permanent solution but rather a mean to test the valves theory. It treats the seals so they can seal better, but the condition will come back eventually.
Also, I have seen engines smoking like that when too much oil is added by accident. As with the valve seals theory the smoke is bluish and not black or white.
If you find in fact is the valves, you are in a best-case scenario, rather than for example a broken ring, etc.
Good luck.
Robert
Thanks Robert, very good input and suggestion. Do you have a specific brand or type you can link to, so that I can the right stuff in my local auto-store?
About the broken ring theory: Wouldn't I see a combination of the oil-wet spark plug AND a low compression reading, if this was the case, especially when doing the compression testing with a cold engine?
Cheers,
Christian
Yes Christian, you would see that in combination. But also, all valves seals might not be at the same level of deterioration/hardness. So your wet spark plug could be explained by just 1 bad seal. But of course, if you end up replacing the seals (still available BTW) you want to replace them all at once.
As far as brands, I have used Wynns in the past with success. But other brands might do as well. Read the label before buying, because you want to test the seals theory, it should specifically say it reconditions rubber joints/seals.
Good luck.
https://www.misteroil.fr/fr-fr/shop/product/970/wynns-engine-oil-stop-leak-professonal-formula?gclid=EAIaIQobChMI1O3BlPON6wIVw7LVCh3ZBwNiEAQYBSABEgIK0_D_BwE
Guys, don't forget that the valve stem guides are also very suspect here. It's not always just the valve stem seals.
Quote from: revilla on 09 August 2020, 05:30 AM
https://www.misteroil.fr/fr-fr/shop/product/970/wynns-engine-oil-stop-leak-professonal-formula?gclid=EAIaIQobChMI1O3BlPON6wIVw7LVCh3ZBwNiEAQYBSABEgIK0_D_BwE
Thanks a lot!! :-)
New development this afternoon, where it was very hot (for Denmark), reaching 32C.
After a small drive at low speed and standing at idle with temp. reaching 90-95C on the meter, the oil pressure dropped down to 1.0 bar and even slightly below. Could also register a slight growling sound from the engine, when pushing on the gas in D at crawling speed. And during all this it was smoking blue smoke and smelling very badly!! :(
By thy the way, I am running a standard semi-synthetic 10W40 engine oil.
Are these bad signs for this engine, despite the high compression readings yesterday?
I am worried about pouring money into the engine to replace eg. valve stem seals or worse, if the engine is basically "a dead horse"!
Thanx,
Christian
Might be time to take the valve cover off and inspect. As Aarons points out it could also be a valve guide dropping. Inspect first and then perhaps remove one head.
As long as the oil pressure went back up with engine speed I would not worry about that yet.
Quote from: rumb on 09 August 2020, 04:47 PM
Might be time to take the valve cover off and inspect. As Aarons points out it could also be a valve guide dropping. Inspect first and then perhaps remove one head.
As long as the oil pressure went back up with engine speed I would not worry about that yet.
Thanx for the advice. Unfortunately, I cannot do this myself and workshop charge a fortune to do any work on the engine. So just trying to get as much input from you guys, before I start spending money on that old high-mileage engine. :)
Understandable Christian. If it was my engine I would invest 10€ in the oil additive to confirm whether it's the valves stem seals/guides (thanks Aaron for clarifying).
Cheap, easy and non invasive.
Quote from: Berggreen on 09 August 2020, 02:29 PM
Quote from: revilla on 09 August 2020, 05:30 AM
https://www.misteroil.fr/fr-fr/shop/product/970/wynns-engine-oil-stop-leak-professonal-formula?gclid=EAIaIQobChMI1O3BlPON6wIVw7LVCh3ZBwNiEAQYBSABEgIK0_D_BwE
Thanks a lot!! :-)
New development this afternoon, where it was very hot (for Denmark), reaching 32C.
After a small drive at low speed and standing at idle with temp. reaching 90-95C on the meter, the oil pressure dropped down to 1.0 bar and even slightly below. Could also register a slight growling sound from the engine, when pushing on the gas in D at crawling speed. And during all this it was smoking blue smoke and smelling very badly!! :(
>>>snip<<<
Thanx,
Christian
Just to be 100% clear: Are you saying that the oil pressure suddenly dropped when you were driving slowly? Or is oil pressure of 1 bar only at idle or at slightly higher speed, say 1200 rpm? Bad sign if it's that low during actual driving, even if slow. As soon as you touch the gas pedal it should go up.
Plugs show that the engine is running way too lean, that is why it is overheating. Fix that first. Those compression figures are very good for a cold engine.
And 1.0 bar at 95 degrees is fine.
1.0 bar at idle that is.
Quote
Just to be 100% clear: Are you saying that the oil pressure suddenly dropped when you were driving slowly? Or is oil pressure of 1 bar only at idle or at slightly higher speed, say 1200 rpm? Bad sign if it's that low during actual driving, even if slow. As soon as you touch the gas pedal it should go up.
I did not really observe the oil pressure when driving, but I believe it was at max.. It was just at the end, when the temperature went up that I saw the pressure drop from the normal warm engine level of around 1.5 bars and then down to 1.0 and even a little below.
Quote from: Lance on 10 August 2020, 09:16 PM
Plugs show that the engine is running way too lean, that is why it is overheating. Fix that first. Those compression figures are very good for a cold engine.
Great, I am happy to hear the compression readings are at least ok.. And do you agree to my procedure with 5 strokes of the needle? I was worried that I maybe had generated false high readings with 5 strokes, because if I did more, I did not see that the pressure level was increasing more.
Agree...the spark plugs, apart from the oily one, are very white. However, initially I was associating this to the fact that I have done less than 500 km with these plugs. Maybe they need some more km, before I can determine if the mixture is too lean. What do you think?
Sorry, I am a newbie with these M116 engines and K-jetronic injection systems. How do I regulate the full range mixture? Doing so, I guess I have to adjust the idle mixture afterwards to compensate. Or?
I have two 280SL w113s as well, and on these cars I know all the tricks to adjust the mixture on the old BOSCH injection pumps. But I am still a novice on the K-jettronics, but eager to learn! ;)
Thanks for your input and help - much appreciate it. :D
Christian
Quote from: Berggreen on 11 August 2020, 06:14 AM
Agree...the spark plugs, apart from the oily one, are very white. However, initially I was associating this to the fact that I have done less than 500 km with these plugs. Maybe they need some more km, before I can determine if the mixture is too lean. What do you think?
The only way to check properly is hooking up an exhaust gas analyser, and checking for CO% while mixture is adjusted at the distributor.
CO should be ~1.5% to 2.5%
In summary we have a hi mileage engine returning to service after a long sleep. It was blowing oil like crazy and now seems to be settling in as it's getting some use. Of course the valve stem seals are going to be dry and cranky: they might come good. The compressions are curiously impressive: espec for a cold engine . Industry practice is of course on a warm motor...be interesting to see the diff. Theoretically the comp would be a bit higher when warm. One wonders how much a carbon build up is contributing to these impressive figures.
I don't feel the mixture is too lean looking at the new plugs.
What does intrigue me tho is no 5...the odd one. This appears to be a plug not firing.........I would expect a near regular miss on this cylinder . ..but this has not been reported. If this plug is only 500 kms old something weird is going on. It appears to me to be more of an electrical gremlin than a plug so fouled it can't fire. OR you have a leaking injector.
On the matter of mixture.......in K jetronic this is determined by fuel control pressure. We're only interested in hot values at road speeds ..3.4 to 3.8 bar. BUT you need a test kit to determine this.!
Adjusting the fuel flap richness screw is only really relevant to idle/fast idle values and is really emission control centric.
As the story is evolving the cracked ring theory is losing ground ...
btw hot idle oil press at 750 rpm in the wet sump V8's on fresh-ish oil should be 1.5 bar minimum at 80/85. deg C.
I think on a hot day your engine was running a bit hot might be more to do with the cooling system's age than a lean mixture scenario.
Sort out no 5...keep driving! See what develops. ::)
Quote from: Randys01 on 14 August 2020, 12:45 AM
In summary we have a hi mileage engine returning to service after a long sleep. It was blowing oil like crazy and now seems to be settling in as it's getting some use. Of course the valve stem seals are going to be dry and cranky: they might come good. The compressions are curiously impressive: espec for a cold engine . Industry practice is of course on a warm motor...be interesting to see the diff. Theoretically the comp would be a bit higher when warm. One wonders how much a carbon build up is contributing to these impressive figures.
I don't feel the mixture is too lean looking at the new plugs.
What does intrigue me tho is no 5...the odd one. This appears to be a plug not firing.........I would expect a near regular miss on this cylinder . ..but this has not been reported. If this plug is only 500 kms old something weird is going on. It appears to me to be more of an electrical gremlin than a plug so fouled it can't fire. OR you have a leaking injector.
On the matter of mixture.......in K jetronic this is determined by fuel control pressure. We're only interested in hot values at road speeds ..3.4 to 3.8 bar. BUT you need a test kit to determine this.!
Adjusting the fuel flap richness screw is only really relevant to idle/fast idle values and is really emission control centric.
As the story is evolving the cracked ring theory is losing ground ...
btw hot idle oil press at 750 rpm in the wet sump V8's on fresh-ish oil should be 1.5 bar minimum at 80/85. deg C.
I think on a hot day your engine was running a bit hot might be more to do with the cooling system's age than a lean mixture scenario.
Sort out no 5...keep driving! See what develops. ::)
Thanks Randy, you hit it spot on and thanks for all your good advice!! :)
I have arranged with my mechanic to do the following, as a start:
1) Change the valve stem seals - I have them and they did not cost more than 70-80 EUR for a full set.
2) Change all injectors in the same process. Also cheap parts - around 120 EUR for a full set.
3) Change the thermostat - maybe also the radiator as it looks old and worn. Which thermostat do you advice to use?
4) Change spark plugs to NGK BP6ES plugs. Mostly because the current plugs are BP6E plugs, and I can't get a replacement 6E plug for nr. 5! :(
5) Maybe change the engine oil to a 15W50 semi-synthetic instead of the 10W40 currently in the engine.
Then let's see where that brings me!
What do you think?
Thanx,
Christian 😎
Ps: I have been offered a replacement M116.985 engine from a 350SLC, which has done only 160.000 km. I have agreed to buy it as a spare to either use as spare part donor or to install, if things go sour with the original high mileage engine. The replacement is furthermore from 1981, but still with K-jetronic, thus it is of the second generation 985s with 205 HP against the early 985s with only 195 HP currently installed in the car. Replacement even has the aut. gearbox attached to it as well as the K-jetronic system. So it seems like a good deal for 1000 EUR delivered from Germany to Denmark - where shipping alone is around 250-300 EUR. :)
Nice to have a spare complete engine on hand but of course we need to get a definitive position on the existing.
1. proceed with the valve stem seals.
2. try a new thermo
3. just get a new plug for no 5. Even another brand for the purposes of the exercise.
4.Replace all injectors
5. don't worry about different oil...so long as what's in there is reasonably new.
I suspect:
- the valve stem seals will curb a lot of the smoking problem
-the thermo will make little diff but is good insurance to swap in a new one.
-new injectors are probably well overdue and can be reused in a better motor if this one doesn't improve
: but in conjunction with a new plug in 5 should present as a clean plug in a few 100kms of running.
Make sure your electricals are all good for all 8 cylinders..No 5 odd appearance could be due to no spark as much as leaking injector.
Quote from: Randys01 on 14 August 2020, 12:45 AM
hot idle oil press at 750 rpm in the wet sump V8's on fresh-ish oil should be 1.5 bar minimum at 80/85. deg C.
The manual says anything down to 0.5bar on hot idle is within acceptable limits, as long as it jumps to max as soon as RPM is increased.
Interesting..I've scanned my ref material many times and never seen it articulated in these terms. I've seen it written whereby they allude to low oil pressure at idle but no value ever stated.
Perhaps I should have said. "You want to see 1.5 at 750 at 85." Anything less- whilst within limits- would concern me...you will note the 750 rpm caveat. Yes sometimes hot idle will be less..hot day..in Drive at the lights..rpm sags to 500. Hot oil press will fall to 1 bar.
I've never seen less and don't want to.!