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  #1  
Old 06-29-2015, 02:39 PM
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Join Date: May 2013
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w108 - Engine Smoke - Can you tell cause from video?

Perhaps you can weigh in on the cause of engine smoke.
Here are 2 videos I made to help:
part 1 - before start walk around - http://youtu.be/nRr-KT2fPDQ
part 2 - running and smoking - http://youtu.be/rzUaq0Izy20

The car starts and sounds great, but once it's warmed up, it develops moderate/heavy smoke in the engine bay and the cabin fills with a good amount of smoke/fumes.

Here's what I think are the possible causes could be, let me know what you think:

A) Exhaust manifold to downpipe (over torqued, under torqued or misaligned)
B) Exhaust/Intake gasket (leaking)
C) Valve Seals - leaking oil
D) Leak at injector value / copper crush gasket - burning fuel
E) Head Gasket - coolant steaming
F) Other

The smoke is not easy for me to identify - it's not bluish and there is little smoke out of the tail pipe. It doesn't seem like steam either nor do i detect a sweet smell.

I suspect it's exhaust leaking from the downpipe connection (A). I did recently replace the exhaust system from downpipes back. They are custom stainless steal downpipes I purchased used. I used new oring gaskets inside/between downpipe and the mainfold and new 10.9 bolts/nuts to secure it all. I am not too confident in alignment or torque. Manual says "Hex Bolts or nuts from exhaust pipe to exhaust manifold - 2.5 kpm". That's 18 ft lbs which isn't much torque at all. Also the joint seems a bit like a wobble socket extension. If this is the problem, I'm not sure how to correct it.

A bit more background in case it helps.
-1972 280 SE 2.8L, but has a 1970 280se 2.8 engine and trans. I've done a lot of work transplanting the engine. Donor engine didn't seem to smoke before transplant.
-This car hasn't been road tested yet.
-The Manifold and gasket to head is original.
-I've pulled, swapped and cleaned the injectors. They are all spraying nicely. I reused the metal washer/gaskets.
-Valve cover gasket was replaced
-All valves adjusted to spec
-installed pert ignit 2 with coil. New plugs, newish wires/dist cap.
- timing has not been checked
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  #2  
Old 06-29-2015, 03:50 PM
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Location: Middle Haddam, CT
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Best guess is that some fluid is leaking on some part of the exhaust system.
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Berfinroy in CT
Present vehicles:
1973 300 SEL 4.5
1959 Rolls Royce Silver Cloud I
Past vehicles;
1958 Bentley S 1
1976 ex-Max Hoffman 6.9
1970 300SEL 2.8
1958 Jaguar MK IX
1961 Jaguar MK IX
1963 Jaguar E-type factory special roadster
1948 Plymouth woody
1955 Morgan plus 4
1966 Shelby GT350H Mustang
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  #3  
Old 06-29-2015, 05:33 PM
Jub Jub is offline
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I was looking at frame 1:08 on first video, it looks like your head gasket isn't seated tightly...oil (is your oil running low)?

Are any of your fluids running low? I recently bought a older mercedes which smoked terribly (no one could figure out what is was)...turns out it was brake fluid leaking onto exhaust resonator. The clue though, was the fluid kept running low (and everytime was at stop light (ie, compressing brake), would start to smoke.
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1972 Mercedes Benz 280
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  #4  
Old 06-29-2015, 06:27 PM
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I think the video looks like a bit of an odd reflection at 1:08 (near the first injector). I don't see the head gasket from that angle, you'd have to go under the intake/exhaust to see that line. You can see the valve cover gasket, but I didn't see anything wrong with it.

I did just do a brake overhaul - replace the master cylinder, rebuilt all calipers, replaced all flex lines. The brakes seem to work good and no drop in fluid or leaks detected (but again, I haven't taken it on a road test yet, as I'm still not confident in the car). Per suggestion, I did pull the brake vacuum line off and stuck some cardboard down to see if there was any fluid (indicating a MC gasket leak). It was totally dry.

I'm getting a suggestion for either valve seals (which I think may be an easy job that I can do and probably needs it anyway), or the auto trans modulator (which I have no idea about and will need to research how/why this may cause this smoke and how to test and fix.

Last edited by Danxp; 06-29-2015 at 07:36 PM.
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  #5  
Old 06-29-2015, 09:31 PM
Jub Jub is offline
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Sorry...Valve cover gasket (thinking and typing at same time). I once put mine back on and pinched at one end and saw smoke right around manifolds. It caused an extremely slow oil leak (enought to cause smoke out of the bay).
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Current:
1971 Mercedes Benz 250 (Euro Spec)
1972 Mercedes Benz 250 (US Spec)
Past:
1972 Mercedes Benz 280
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  #6  
Old 06-30-2015, 11:02 AM
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Location: Middle Haddam, CT
Posts: 251
Valve seal failure smoke would come out the exhaust, not under the hood. I"ve been there.
__________________
Berfinroy in CT
Present vehicles:
1973 300 SEL 4.5
1959 Rolls Royce Silver Cloud I
Past vehicles;
1958 Bentley S 1
1976 ex-Max Hoffman 6.9
1970 300SEL 2.8
1958 Jaguar MK IX
1961 Jaguar MK IX
1963 Jaguar E-type factory special roadster
1948 Plymouth woody
1955 Morgan plus 4
1966 Shelby GT350H Mustang
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  #7  
Old 06-30-2015, 12:52 PM
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Join Date: May 2013
Posts: 15
I think you are correct about the valve seals might not be the issue exactly for the reason you stated.

Today I focused a bit on the transmission as a possible cause. Since I haven't road tested it, I wasn't able to get the tranny up to operating temp to properly check the fluid level. I deliberately went under the level as I ran through the gears with the car cold and then checked the level with it in park and running - but again the fluid was cold. I have since added about a half quart of atf to get it to the bottom of the dipstick indicator. Anyway, this didn't resolve the smoke. It still smokes up pretty quickly.

If this was an exhaust leak (from the downpipes not being properly seated), I would assume it would smoke immediately upon start. The fact that it needs to warm up a bit before smoking is pushing me back to the theory that the trans modulator being an issue. I do have similar transmission (from a 72 280se) that I could pull that module off of and put on this trans (a 70 280se). I'm hoping it a simple 5 minute job. Not sure if they are interchangeable and I hope I don't need to drain fluid, adjust it etc

Any other thoughts or suggestions are welcome. thanks.
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  #8  
Old 07-02-2015, 10:58 AM
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So it went it the shop yesterday. I should hear back soon and I'll update you on the issue/fix.

thanks.
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  #9  
Old 07-07-2015, 06:42 AM
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Join Date: Jun 2004
Location: brisbane,Qld.Australia
Posts: 2,059
It looks like trans fluid smoke to me. Or...oil leaking from the timing chain tensioner and getting blown back onto the manifolds. How much running has the engine done since you installed it? It's not oily finger prints on the pipes is it?
it's idling a bit fast too. 800 RPM at running temperature is what it should be. get your shop to check the injection pump cold start thermo for correct action and the throttle linkage for correct correlation.
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