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Smoking, burning, leaking oil behind and under the rear motor issues with pictures

10K views 43 replies 8 participants last post by  dmorgan1952 
#1 ·
As previously mentioned on my earlier posts regarding the oil burning/smelling/smoking and leaking under the rear bottom of the motor, here is the follow-up/update:

I put the Mercedes wagon on top the front two ramp giving me about 2 or so feet clearance while I was on the ground under the Mercedes. Got under the wagon and saw very clearly and not muddy or dirty transmission and the motor. No need to put in Gunk foam engine cleaner.


I then proceeded to put in the 1 oz oil dye in the oil crankcase. Start the motor and got off the ramps. I ran the motor for a few minutes then drove about 10 miles. Smoke was visible at the back of the Mercedes while driving as I saw the smoke coming out by looking through the rear view mirror. After driving and heading back home to put the Mercedes on the ramp, smoke was also visible under the passenger side door. Lift the hood, smoke (burning oil) was also visible underneath the rear motor near the EGR valve area.

Got the Mercedes back on the ramps again. Turned off the motor. Smelled burning oil and saw smoke near the EGR valve area again. Smoke also visible under the passenger door side. I waited for about an hour to cool off the motor. I then go under the motor to see if any leaks showing through the dye using the yellow glasses and the LED flashlight. Here are the pictures of the results below:

Here are the first group of 21 pictures (1-5) below (finally got a camera) showing before and after cleaning up using a rag. (Hope the pictures are not that bad since I am new in this situation). The next 5 pictures are in order on the next thread and thereafter until all the remaining pictures are included in this post. I just wish there is an easier way to post all pictures in the same thread.

Because all of the pictures were line up in the attachments and I could not figure out how to separate the pictures group in between with additional information/comments. I came up with the following:

First 21 pictures refers to before and after cleaning up the motor/transmission area.

The last pictures group of 11 were after putting the oil dye and running/driving the Mercedes and using the LED flashlight (purple spots areas) showing afterwards the oil leakage area. Notice the smoke coming out from the inside the hood area near the egr valve location near the rear motor as well as smoke coming out under the passenger side door.

Oil puddle on the cardboard just underneath straight down from the outer edge of transmission bell on the left/passenger side facing me. Oil leak could be from the above the transmission bell area and dripped down under, causing the oil puddle? I really cannot pinpoint where exactly the oil leak is coming from. I am guessing the rear seal (broken,torn, cracked?) is the culpit that goes in between the transmission gear to the rear motor.in addition, the oil pan gasket seems to be ok and I don't think that is the issue. I am tempted to drive the Mercedes to a mechanic who can actually (hopefully) spot the exact location where the oil leaking is coming from and give me the correct/right diagnosis. Anybody out there have any clues? Comments/feedback is greatly appreciated.
 

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#3 ·
here are the next 10 pictures of the first group (11-20). I just figured out the maximum number of pictures is 10 to upload.
 

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#5 ·
The last pictures group of 11 were after putting the oil dye

The last pictures group of 11 were after putting the oil dye (first 10 pictures)
 

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#6 ·
Finally the last picture of the second group with oil dye. In recap for those who missed the first thread:


As previously mentioned on my earlier posts regarding the oil burning/smelling/smoking and leaking under the rear bottom of the motor, here is the follow-up/update:

I put the Mercedes wagon on top the front two ramp giving me about 2 or so feet clearance while I was on the ground under the Mercedes. Got under the wagon and saw very clearly and not muddy or dirty transmission and the motor. No need to put in Gunk foam engine cleaner.


I then proceeded to put in the 1 oz oil dye in the oil crankcase. Start the motor and got off the ramps. I ran the motor for a few minutes then drove about 10 miles. Smoke was visible at the back of the Mercedes while driving as I saw the smoke coming out by looking through the rear view mirror. After driving and heading back home to put the Mercedes on the ramp, smoke was also visible under the passenger side door. Lift the hood, smoke (burning oil) was also visible underneath the rear motor near the EGR valve area.

Got the Mercedes back on the ramps again. Turned off the motor. Smelled burning oil and saw smoke near the EGR valve area. Smoke also visible under the passenger door side. I waited for about an hour to cool off the motor. I then go under the motor to see if any leaks showing through the dye using the yellow glasses and the LED flashlight. Here are the pictures of the results below:

Here are the first group of 21 pictures (1-3) below (finally got a camera) showing before and after cleaning up using a rag. (Hope the pictures are not that bad since I am new in this situation). The next 3 pictures are in order on the next thread and thereafter until all the remaining pictures are included in this post. I just wish there is an easier way to post all pictures in the same thread.

Because all of the pictures were line up in the attachments and I could not figure out how to separate the pictures group in between with additional information/comments. I came up with the following:

First 21 pictures refers to before and after cleaning up the motor/transmission area.

The last pictures group of 11 were after putting the oil dye and running/driving the Mercedes and using the LED flashlight (purple spots areas) showing afterwards the oil leakage area. Notice the smoke coming out from the inside the hood area near the egr valve location near the rear motor as well as smoke coming out under the passenger side door.

Oil puddle on the cardboard just underneath straight down from the outer edge of transmission bell on the left/passenger side facing me. Oil leak could be from the above the transmission bell area and dripped down under, causing the oil puddle? I really cannot pinpoint where exactly the oil leak is coming from. I am guessing the rear seal (broken,torn, cracked?) is the culpit that goes in between the transmission gear to the rear motor.in addition, the oil pan gasket seems to be ok and I don't think that is the issue. I am tempted to drive the Mercedes to a mechanic who can actually (hopefully) spot the exact location where the oil leaking is coming from and give me the correct/right diagnosis. Anybody out there have any clues? Comments/feedback is greatly appreciated.
 

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#7 ·
Compiled a checklist for issues on the 1994 Mercedes Wagon

I wrote up a checklist for the mechanic, if I decide to send the Mercedes to a shop. Here it goes:

My 1994 Mercedes E320 wagon needs to be diagnose and/or check out on the follow areas:

1. Smelling burning oil and smoke locations. 2 or more possible locations of smoke are by the EGR Valve area on the exhaust manifold near the back of the engine and underneath the Mercedes on both the driver's side and passenger's side, possible by the exhaust muffler and/or front end of tail pipe. Determine what and where the source is coming from and the exact locations of smelling burning oil and why. Does the EGR valve needs to be replace? What else needs to be done to correct the above issues?

2. Check for all oil leaks and location of oil leaks. If there are any oil leaks, what needs to be done to correct the problems? Check the oil pan gasket, head gasket, front cover timing seal gasket, and transmission gasket. Also, check the rear seal, if possible from the transmission bell to the rear motor for leaks.

3. Check the wiring of the oil sender unit sensor near the oil pan plug. See if wiring connections and connectors are tight and not loose inside the oil sender unit sensor. Check/ inspect the wiring for torn, cracked, exposed wires. Check the voltage on the oil sending unit sensor wire. Also, check if the oil sending unit sensor is defective or not. Oil sending unit warning lights on the instrument cluster panel kept going off and on when driving. If there any problems with the oil sender unit sensor issue, what needs to be done to fix the problems?. Does the oil sending unit sensor unit need to be replace?

4. Check the oil pressure unit sensor, its connecting wire for loose, frayed, exposed wiring connector. Check the voltage on the oil pressure unit connecting wire. It is located in the front of the oil filter housing near the master brake fluid reservoir. On the instrument cluster panel, the oil pressure guage keeps fluttering up and down. Does the oil pressure unit sensor need to be replace?

5. Check the oil pump to see if the oil pump is working ok.

6. Check transmission fluid level in the dipstick and leaks if any. Engine needs to be running to get accurate reading level on the transmission dipstick. If found to have a leak on the transmission fluid, what needs to be done to correct the issue? If no leaks are found and the transmission fluid level on the dipstick is low, how much extra transmission fluid needs to be fill until appropriate transmission fluid level on the dipstick is ok?

7. Check the transmission pan for leaks, stripped bolts, etc. and the transmission pan gasket. Does the transmission pan gasket and filter needs to be replace?

8. is the head gasket in good shape? Check for any signs of leaking oil on the head gasket area, especialy the rear end of the engine. Does the head gasket need to be replace?

9. Check the shifting gears for hesitation issues, especially the drive and reverse shifts. Very loud changing gear shifts. What is the issue, if any, and how can that be fix?

10. Check the fuel pressure regulator. Is the fuel pressure regulator ok or defective and needs to be replace?

11. Check the engine compression. Is the engine compression ok?

12. Check for vacuum leaks near the throttle body, intake manifold areas using a "smoker" through the vacuum lines to detect leaks and if so, should see smoke coming out of the vacuum lines. The Mercedes have high idling issues.

13. Take pictures using my camera of the oil leaks locations after finding the correct diagnosis as well as burning oil smell and smoke. In additon, take pictures of the vacuum leaks, if any,

14. Any other areas that needs to be check that are not in this checklist?

15. What would be the estimate total cost of diagnosis on the above issues?

16. What would be the estimate total cost including labor and parts, if needed, on the above issues that needs to be repair?

Anyone out there have any comments/feedback?
 
#8 · (Edited)
Did you change the valve cover gasket already? The rear has two semi-circle gaskets that are susceptible to leaks if the VC gasket doesn't sit flush with them.

One way to check if you have gasket leaks is if your idle does NOT change if you open the oil filler cap. This is provided you do not have any vacuum leaks elsewhere (i.e. Vacuum tubes and connectors downstream of the throttle actuator and MOT purge valve). These M104.99 engines need good crankcase vacuum to idle properly.

Your engine should be pulling a vacuum through your crankcase at idle. Think of your crankcase as a big PCV valve, which is why this engine does not have a PCV valve. Oil should not be leaking at idle, but during acceleration and partial to full load when crankcase is at positive pressure.

Oil should also not leak via valve cover with engine off and sitting still as the oil drains back down to the pan. Oil level should also not touch the Max line on the dipstick. It's best to keep midway max and min.

If oil is leaking above the oil pan with engine off and parked overnight, you may have crankcase seal issues.


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#9 ·
Sorry about the delay in responding due to the weather. Mercron, thanks for your last response/comments, especially regarding to the PVC valve comment. I thought there was a PVC valve on 1994 Mercedes E320 wagon. I could not find a PVC valve on the engine area until you explained that the crankcase and/or the engine is actually a "PVC valve" in disguise. So, there is no PVC valve on the engine, afterall. Good to know. Excellent comment!! For that, I really appreciated it and clears up the confusion in regards to the PVC valve issue!!

Yes, the valve cover gasket was earlier removed and replaced with a new one along with the two semi circle gaskets (so-called half moon grommets/gaskets) that goes back on the rear of the engine above the cylinder head (in addition to the new 6 rubber sealers that goes on the valve cover holes where the spark plugs goes in).

I fired up the Mercedes (non ASR) this morning. At first, high idling around 1300 and settled down around 800 rpm. Warmed up to normal temperature range of around 82c to 85c. I then removed the oil crankcase cap and went back inside the Mercedes to checked the idling showing around 800 rpm and not fluttering.

In addition, I did a comparison check on the other 1994 Mercedes E320 wagon (with ASR) I have as well. I fired up the engine and warmed up to normal temperature range of around 82c to 85c. With the oil crankcase cap off, the rpm reading shows around 700 rpm and not fluttering, In addition, I noticed the o ring on the oil cap is missing. Switch oil caps on the other Mercedes (non ASR). same idlng results, no fluttering.


The idling is still the same as before. That means either one or both gaskets and vacuum lines are leaking. Correct? If so, how and where can I find the leaks source? Could it be the rubber o-ring on the inside crankcase oil cap (non ASR) and/or inside oil dipstick o-ring both defective and need to be replace? What about the Mercedes with ASR missing o ring as well? Does it make any difference? Use a smoker to detect vacuum leaks?

When I remove the oil crankcase cap from the other Mercedes wagon that is in good running idling and use it on the current Mercedes that was having issues. No difference, same results on the idling rpm. So I assume both oil crankcase caps are good and not an issue for vacuum leaks. The same results applied as well as swtiching both oil dipsticks. Sorry if I had to repeat myself.

What I discovered when switching both the oil dipsticks and both the oil crankcase caps, the two wagons have the same idling rpm.


Also, I made an appointment on March 15th to have the oil leaks diagnosis using the checklist as a guide previously mentioned earlier in this post/thread. Will follow up/update on this and stay tune.
 
#10 · (Edited)
Did you replace the 12 rubber grommets that seal the bolts of the valve cover gasket as well? These should be torqued to 10NM.

You would need to trace all vacuum lines coming off the intake manifold. These include:

1. EGR/Air pump switchover valve line,
2. Manifold pressure sensor line,
3. Fuel pressure regulator line,
4. Purge valve line from throttle body,
5. Vacuum supply line going behind the brake booster.
6. Transmission modulator line from top of intake manifold to the auto transmission.

There is an emissions diagram on the front assembly of your car by the driver headlight.

Also, check the U shaped rubber connector behind the EGR switchover valve for deterioration.


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#11 ·
Oil caps and dip sticks have nothing to do with idle rpm or vacuum of any sort. Also, ASR/non-ASR, has nothing to do with idle.

It seems to me that you are chasing approximately 100 rpm. At this point, I'd suggest getting out and driving the car for several days. If you have some open highways you can get up to 70-80 mph for a sustained time, do it. After a week or so of normal use, let's see where you are.
 
#12 ·
Jayare, thank you for your clarification on the oil cap and oil dipstick issues in regards to the vacuum leaks. As for driving on the highway so the idling will be "settling in" to normal idle, it would be quite some time for that to happen because of the current oil leaks issues I am now having. However, I will keep this issue update as I am progressing along to resolve the oil leaks issues. Stay tune.
 
#13 ·
mercron, Thanks for your latest comment in regards vacuum lines/leaks issues. I appreciated it. Yes, I replaced the 12 rubber grommets (new) that seal the bolts of the valve cover gasket.

Also, thanks for the trace list of all vacuum lines coming off the intake manifold in addition to the U shaped rubber connector behind the EGR switchover valve for deterioration. I make sure to add those to the checklist when I go to the mechanic next week. Afterwards, I will report my findings on this thread. Stay tune.
 
#14 ·
It's all a process of problem elimination until you solve it. On my E320, once I sorted my vacuum leaks I could hear change in idle when I take off the oil cap without checking the tachometer. It would change too once I put it back on.

But Jayare is right. Drive the car to let things settle. The ECM will adapt to any repairs you made after several trips. I think it's between 10 to 19 trips.


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#15 ·
mercron, thank you for your latest post and clarifying the issue of the vacuum leaks as well.

I just received an email from the shop that was going to do the oil leaks issues as well as other things on the updated checklist. I was informed that the owner had stated that he will not be able to work on my Mercedes. No reason or explanation given as to why he declined to diagnose the oil leaks among other issues as well.

I am tempted to do this work on my own. The problem is trying to find and locating the source and location of the oil leaks. Even though, I already tried the oil dye and using the led flash light to pinpoint oil leaks location, I got mixed results and not clearly finding the source and location of the oil leaks. So I ordered a 5M 7mm Endoscope Waterproof Snake Borescope USB Inspection Camera that can connect to my laptop and I could put the camera under the Mercedes while running and hopefully will show some area of the leaks as well as the source of burning and smoking oil. I will follow-up/update on this as soon as I get the camera.
 
#17 ·
I went to see a guy who works on radiator repairs. He was abled to pinpoint the cause of the oil leak. He spotted the oil leak/dripping oil by above the EGR valve on the passenger side end of the valve cover, just where the bolt on the side that goes in the bracket. In a way, it makes sense because when the oil is dripping, the oil leak landed on the exhaust manifold area (hot), causing the smelling burning oil and smoke. He told me to do this:

1.The valve cover end bolt maybe loose located the end of the valve cover on the passenger side. I was told to cleaned up with the engine degreaser and tighten the bolt and see if that is the problem resolve where the oil leak is coming from.

2. He also checked under the carriage on the passenger side door and saw no leaks above and below the head gasket area and/or other areas near the transmission and/or engine. The area looks clean. In fact, the head gaskets are in good shape. That is good news, no head gasket leaks!!

3. If the leaks continue where he suspected where it came from the bolt on the valve cover after tighten the bolt as describe above number 1, it is possible the valve cover is warp and possibly need a new valve cover replacement along with new valve cover gasket as well.

4. To determine if the valve cover is warp, remove the valve cover and place the valve cover on a flat surface like a table. Tilt the valve cover while it is on the flat surface/table to make sure it is straight/flat and not bouncing. Also, see if the bottom ends is flat and cannot see through on the other side of the valve cover while on the flat surface. If there is an opening, then the valve cover is warp and needs to be replace along with new valve cover gasket.


Will follow up on this and report my findings as soon as the weather gets warmer!!!

Anyone out there can relate or share this experience? Does this make any sense at all?
 
#18 ·
Just make sure you torqued the valve cover bolts to 10NM. I doubt the valve cover is warped since it's been bolted on the cylinder head all this time. My guess is the VC gasket is not properly sealing in that corner or the half moon gaskets haven't sealed properly with the gasket. You may want to look with a telescopic mirror around that area. Note that the engine is a slanted 6 so any leak in the rear valve cover will drip down the transmission dipstick corner.


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#19 ·
Time to pull off the cam cover/valve cover. The gasket is resilient and can be reused if undamaged. What you need to look for is proper seating of the gasket and also look for any oxidation or corrosion that may have taken place on the actual cam cover/valve cover itself in the area where you and the mechanic spotted the leaking. You want to make sure this cover is 100% before chasing any other causes. This will give you a chance to confirm whether or not the half moon gaskets are in their proper place as well.

And PS: glad to hear you don't have a head gasket leak to contend with.
 
#21 · (Edited)
for the details on crankcase ventilation on the 104.99x engine, see page 4 of this PDF, http://new.freescruz.com/.priv/W124/w124CD1/Program/Engine/104/01-0400.pdf



its fairly complicated and clever.


And It's very effective at keeping the engine clean as can be seen in my M104.995's like-new valve train with 228k miles on it.



Of course the previous owners' maintenance schedule and choice of oil and filter may have something to do with it as well.

PS. Here's another interesting article on the M104 crankcase ventilation and vacuum although it applies to the W210 body so the idle control valve and PCV valve doesn't apply. Also, there is no need to use an adhesive to glue the VC gasket into place.

http://www.pelicanparts.com/techart...eaks/09-ENGINE-Fixing_Common_Vacuum_Leaks.htm




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#22 ·
Stripped threads inside the holes on the top head

tuttebenne, LeftCoastGeek, mercron, thanks for your latest posts.

Here is the latest update:

My Mercedes is still having burning smoke and smelling oil in the back of the rear engine area. I checked the valve cover bolts and four of the bolts were loose, two on the each side in the rear engine area. Tightened two bolts on the valve cover on the rear engine area on each side of the exhaust manifold and the intake manifold area.

However, another two of the bolts (one of each side of the intake side and the other bolt on the exhaust side) were still not able to be tighten. I feared the inside thread holes on top of the cylinder head inside threads are stripped. I thought the issue was resolved by putting in helicoils. When I removed the two bolts that were not tightened, I saw helicoills still attached on the end of each bolt below the bolt cover/sleeve. See the attached photo below. The 2 blue circles on the inside valve cover indicates the locations of the stripped threads on the top of the clyinder head.

It seems the helicoils are not doing its job. If I go ahead and retread again and using helicoils at a greater size hole, I believe it will crack the head since the top of the clyinder head thread hole is rather small on its width size.I have three options:

1. Take off the valve cover and using JR Weld and fill in the two holes using a syringe and dowel to push in the mixture to make it solid and tight. After 24 hours to dry, use a threaded drill bit and drill inside the hole. The trick is the drill have to be very straight going down on the new thread hole so the new rebuild thread will work on the valve cover bolts.

2. Someone wrote "Clean the holes out make sure they are clean and without any oil inside or the repair wont work. Fill the holes with plastic metal.Push the bolt in and let it set for a day.Then unscrew the bolt , Then ,clean the top of the hole flush.These are very low torque and if you over do it they will strip out in normal circumstances . I think 9nm to lock up . Put some hylomar blue on the gasket as well as you refit it. Also keep it all clean, or bits might get in to the oil"

Is plastic metal as described above referred to Bondo® Plastic Metal, 5 ounce, Plastic Metal seals?

3. The other option is I am trying to avoid (most costly and time consuming process) and that is to replace the head on top of the engine block with another head that have no issues on the inside threaded holes.

As for the three choices above, it seems that number 2 is the better choice. Any comments/feedback/advice is greatly appreciated.
 

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#23 ·
A better view/image of the head with red circles showed the stripped threads location

Mercron your picture of the head without the valve cover in your post #21 is excellent. My picture of the valve cover showing upside down with the blue circles showing the holes is rather crude. So I use your image and made red circles to show exactly where the female threads are stripped and probably caused the leaking oil and burning smoke. I hope you don't mind using the cropped picture to show the locations (in red circles)
 

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#24 ·
No problem. Hope it helps you. I thought that the cylinder head would be tougher to strip than the valve cover. But maybe someone over tightened the bolts due to a hardened rubber grommet. Out of your three choices, it looks like no 2 is the best for now.


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#26 ·
Right now I am putting on hold on this bondo thread stuff. I wanted to explore other options other than the ones mentioned earlier.


See attached photos below of the 2 bolts with helicoils that were removed. Notice the 2 bolts are the same size M6 x 65 with washer:

in regards to the type of form a thread inside the hole on top of the head. Should I use Loctite 442-28654 4.80ml Form-A-Thread Stripped Repair Kit or Bondo® Plastic Metal, 5 ounce, Plastic Metal seals? Does it make any difference? Any other brand of form a thread that would work on repairing these particular threaded holes on top of the head?

What about replacing with a longer Helicoils with the same size bolt M6 x 65 that will fit on the bolt?

How about using a longer bolt than the current size M6 x 65 to replace using a longer or shorter helicoils without fracturing the top head hole thread? Can that be done and if so how much longer of the bolt size M6 x 65 that could possibly work?

if using a form a thread, where should the application goes? Inside the hole? On the bolt? Would putting on form a thread on the outside or inside of helicoils would work?

How about using a longer bolt size to replace the current size bolt? Would that work without damaging/fracturing the area around the bottom/top hole of the thread? If a longer bolt is advisable, what length should it be? Would using a longer helicoils or the same helicoils that I have now would work better with a longer bolt size? Sorry about repeating myself. Just to explore what are my best options at this point.

Any comments/feedback/advice is greatly appreciated.
 

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