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  #1  
Old 12-12-2009, 01:04 AM
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If you're gonna pull your engine....

what would you do while you have it out?


my dear old vehicle has 2 major problems: a bad exhaust manifold gasket and a bad rear main seal leak. it could be that there are other oil and exhaust leaks but until i fix that rear main seal and replace the exhaust gasket (along with tightening all of the loose exhaust bolts), figuring out what else is leaking is going to be nearly impossible. i have tried lots of different things, including the turbo return pipe and the air filter/turbo fittings. but the darn thing still leaks and smokes like an incontinent, farty old lady. a lot of that oil leaking is happening where the engine meets the transmission, and a lot of the smoking is coming from the place where the engine meets the exhaust manifold.

so, i have accepted that i need to pull the engine and replace that rear main seal and the exhaust manifold while i'm at it.

this is going to be something of an undertaking so i am wondering what you all would do if you were in my position and were removing your engine from your mercedes. are there any other seals or replacements that you would do while you have it out?

a big part of the reason that i bought an old diesel was because i live on a sailboat that i plan to someday sail around the world. back when i was light-duty commercial underwater diver, i used to have engine problems on my little 2 stroke motor that propelled my work-skiff. when i had those problems, my first response was to sit down and cry. not very effective. i realized that if i was going to someday own a bigger sailboat and sail it around the world, i would have to develop a more useful response to engine trouble. my mercedes has given me the chance to learn about diesel engines in an environment where breaking down meant a long walk home over land, not a near-death experience in the middle of the pacific. this was a wonderful decision on my part. i have learned from all of my stupid mistakes and am now more capable of fixing things on my diesel than many people who have sailed around the world. much of the work that i have had to do was due to my own stupidity but over time, that stupidity has worn itself out and i find myself a lot smarter and a much better engineer than when i began. i owe a lot of that learning to reading the posts on this board.

working on my mercedes has taught me a lot of important mechanical lessons. one of which is to not fix things if they aren't broken. so i don't want to open any unnecessary cans of beans. that being said, i respect the wisdom of a lot of the people on this board. if there are things that you think i should do when i have the engine out, i want to know what they are. i have a place to work on it and i wouldn't mind digging deep and doing some good deeds for a vehicle that has served me well and tolerated my learning process.

Thanks in advance for any responses,
Sasha

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Old 12-12-2009, 03:38 AM
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Sasha,
I think I would be doing the job in 2 parts. I wouldn't pull the engine. Before starting CLEAN EVERYTHING! First I would do the manifold. Maybe you dont need to have the manifold/turbo/plumbing right out of the car.
It may be easier to pull the transmission back enough to get at the back of the motor. It may be possible to do the seal then. Maybe some one can comment on my suggestion. I assume it is feasible. If its not some one will say so.
Good Luck!!!!
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1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
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  #3  
Old 12-12-2009, 06:42 AM
t walgamuth's Avatar
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That is good advice...the main seals rarely are a problem. I'd look for a leak elsewhere after cleaning it really well.
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..I also have a 427 Cobra replica with an aluminum chassis.
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Old 12-12-2009, 09:47 AM
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Sasha,
A couple more thoughts. Going on from the last post of twalgamuth. Its much easier to find leaks on a clean engine. They are much better to work on as well.
The bottom of the bell housing is the lowest point at the back of the motor. Just about any leaking oil will end up there. I have never had to replace a rear main seal on a diesel engine unless the crankshaft was taken out.
When I have had to cure an oily engine, I start at the top. The oil from the leak will always move down. The smoke you mention maybe from oil leaking out of the cam cover gasket and being heated by the exhaust/ turbo. That will produce plenty of smoke. I have had to replace a few of them. It would be a good time to set your tappets if they haven't been done lately. Oil leaks from there tend to find their way towards the back of the motor and onto the exhaust manifold. If bad enough it then runs down the back of the motor and so looks like a rear maim leak.
The exhaust manifold gasket could cause exhaust noise if it is leaking. I have used some wet cloth to hold against the gasket to see if its leaking. With a motor that is not too hot the wet cloth will dampen the exhaust noise and you can determine exactly where the leak is. It may also be in the expansion piece just after the turbo or between the manifold and the turbo.
You don't say how many miles the car has done. If it has done a lot, it would be worth checking to make sure the motor is not breathing excessively. Simply disconnect the pipe that runs from the top of the cam cover to the air cleaner while the engine is running and has been running for a while and if smoke comes out of it like a steam train it would be a sign of possible ring trouble/ very worn motor. The pressure build up that occurs with this problem will make it near imposible to cure oil leaks.
I hope this is of use. Is the underside of the car wet with oil? Is there oil spots showing on the back of the car? How much oil is on the ground after the car has been parked over night?
Let us know if any of this doesn't make sense.
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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving
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  #5  
Old 12-12-2009, 09:58 AM
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I've heard the rear main seal can be done by pulling the tranny back and dropping the upper pan and lowering (not too far) the crankshaft. You're trading ease of access for quality of access to the engine tho, probably easier to get it right on a stand.

Nice yarn BTW
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  #6  
Old 12-12-2009, 10:51 AM
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Concur with the other advice. Clean everything up and get a good diagnosis before removing. That being said, it's my understanding that the rear main seal is in two halves and the bottom half can be replaced with removing the engine, by removing the upper oil pan. Not having done it myself I can't confirm this. But it does stand to reason that the lower half of the rear main seal is more likely to leak than the upper half.
Like the sailboat part.
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1977 300d 70k--sold 08
1985 300TD 185k+
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  #7  
Old 12-12-2009, 11:26 AM
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Sasha.

I like your post. I had similar reasons for getting my first diesel MB, to learn something! Though I have no plans to sail around the world, yet, I did grow up around boats.

I look forward to reading about your progress.
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  #8  
Old 12-12-2009, 02:26 PM
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I know of more than one 617 that leaked oil from one of those ball bearing jobs used to plug the oil galleries near the rear crank seal. Make sure it's the rear crank seal leaking before you pull the engine apart.

Sixto
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  #9  
Old 12-12-2009, 02:33 PM
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Follow up before work is done.

Thank you! Those were very detailed responses so I have some detailed questions:

" I wouldn't pull the engine. Before starting CLEAN EVERYTHING!"

Man, I have. I have used some serious gallons of simple green - and it has been done several times. I know that my cam cover does leak but could this really be causing all of the mess I see? I know that everything flows downward so technically, it is possible. But I have put on new gaskets and the cover doesn't seem inordinately warped. I have checked it with a straight edge ruler.


"First I would do the manifold. Maybe you dont need to have the manifold/turbo/plumbing right out of the car."

That is true, the engine doesn't need to be out to do the exhaust manifold. I was just using it as a way to make me feel better about doing 2 big jobs - i.e. if i have the engine out, it will be easier to do the manifold gasket. Since I am not a real mechanic, I have learned to move slowly and think things through and usually do one job at a time, even if it takes longer because then I have one can of worms open at a time and it simplifies my troubleshooting. BUT, if I have the engine out, it will be easier to do the manifold gasket at that time which I can accept as being a rational workflow combination.


"It may be easier to pull the transmission back enough to get at the back of the motor. It may be possible to do the seal then."

OK, this is something that I haven't researched lately but is part of my task list this weekend. Back when I was worried that I might have to replace those rear main seals, I remember finding that a) you had to pull the whole engine to do it and b) it is actually a very common problem (reference a later post that suggested that this was not the case). Any perspectives and/or links to similar work would be appreciated. I really do remember people commenting that this was a common and frequently necessary repair so if I'm wrong, god and mercedes shop, please help me to right my wrong thinking.


"I have never had to replace a rear main seal on a diesel engine unless the crankshaft was taken out."

OK, I will take note of this. Kent Bergsma over at ************** seems to think it is a frequent problem.


"The smoke you mention maybe from oil leaking out of the cam cover gasket and being heated by the exhaust/ turbo."

This is true, too. Like I said, my engine compartment is a mess right now. The cam cover gasket has been replaced.


" It would be a good time to set your tappets if they haven't been done lately"

If you mean a valve adjustment, that has been done with no improvement. If you mean something else, please let me know and I will do it.


"I have used some wet cloth to hold against the gasket to see if its leaking. With a motor that is not too hot the wet cloth will dampen the exhaust noise and you can determine exactly where the leak is. It may also be in the expansion piece just after the turbo or between the manifold and the turbo."

OK, I will do this test on Monday or Tuesday.

"You don't say how many miles the car has done. If it has done a lot, it would be worth checking to make sure the motor is not breathing excessively. Simply disconnect the pipe that runs from the top of the cam cover to the air cleaner while the engine is running and has been running for a while and if smoke comes out of it like a steam train it would be a sign of possible ring trouble/ very worn motor. The pressure build up that occurs with this problem will make it near imposible to cure oil leaks."

I will do this check on Monday or Tuesday, as well. The care has about 200K miles on it and it starts at the first crank of the engine. It starts and runs remarkably well (even with one screwed up hard fuel line which is entirely my fault and going to be replaced as soon as I get the part from peachparts or the junkyard (if i can find one by monday).


"Is the underside of the car wet with oil? "

soaked. that is what is giving me so much trouble finding the leak. i have tried cleaning it and then idling it for long periods. that rear main seal area is the first to show areas of oil.

"Is there oil spots showing on the back of the car? "

Yes, lots. When I researched this before, I was guided towards the turbo return pipe but that is now new and heavily sealed with silicon.


"How much oil is on the ground after the car has been parked over night?"

5 - 6 inch puddle but if left for a month, the puddle only grows to about 10"



OK, thanks for holding my hand in this endeavor. I have read lots of posts and tried to get a lot out of them but I am currently at a standstill and would be grateful for good advice.

Sasha
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  #10  
Old 12-12-2009, 07:55 PM
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Sixto mentioned ball bearing jobs used to plug the oil galleries near the rear crank seal. Anyone know the name of the part that he is talking about?

Sasha
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  #11  
Old 12-12-2009, 09:30 PM
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Sasha,
200k miles suggests the car is only young, it shouldn't have blow- by (breathing problems).

I had a look at your other posts, oil leaks are a real thorn in your side! I hope they are not an equivalent to a leaky boat! We don't want you spending "6 months in a leaky boat, trying to stay afloat"!!( that's from a well known pop song in Australia, LOL).
You show great patience. I assume you fixed the leak on the turbo oil return line completely.

Tappets adjustment is valve adjustment.

You need to fix the cam cover leak first. Assuming the cam cover gasket is reasonably new. Wash the gasket and the edge of the cam cover in petrol or spray degreaser and let it dry, then fill the groove in the gasket that goes on the cover with RTV before you put it on the cam cover, wipe off any excess RTV especially on the inside of the cover. Then clean the surface on the head where the gasket sits with petrol and place a continuous bead of RTV all the way around that surface of the head. Then put the cover back on and tighten it down. Leave it over night before starting the engine, That should fix the leak. i am sure you have found by now that oil on surfaces will stop RTV from sticking. I have had to do this several times on my both 300d's over the years & I am about to do it to my 250TD, I think the oil is running down the groove and running over at the back onto the exhaust manifold, only a couple of drops a day but I can smell it when the car first warms up.

I once had oil drops on the back of my car but it was caused by over filling the auto, the excess fluid just flowed out the trans breather when it was warm. That is not your problem though.

I once had oil leak from the back of the motor, I think oil had collected in a cavity some where. I had the car parked on a very steep hill pointing up hill. Is your car parked on a hill? If so try parking it pointing down hill if you can.

I would be a useful investigation to try and see inside the bell housing. in particular the fly wheel/ ring gear. If the main seal was leaking, there would be oil every where in there. Its a PITA to do, but removing the starter motor would allow you to see if oil is being thrown around off the crank shaft from a seal leak.

You mention in a previous post that you are topping up about a quart of oil every 400 miles. That's about what my old car was using at 800,000 miles. Makes me think that most of yours is leaking.

I hope you have had a very close look around the base of the oil filter housing. Its possible that there is a leak from a pipe joint or gasket.

Is there much oil dripping from the bottom of the sump? If you regularly park the car facing down hill and the rear main seal is the problem, then the oil will still be leaking from the bottom of the bell housing. If it drips from the sump or further forward on the motor, then it may not be a rear main seal.
Hope that helps. Its good that you are seeking advice from many people, none of us know it all & we have not seen the car.
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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving
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  #12  
Old 12-12-2009, 10:40 PM
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Quote:
Originally Posted by sashal View Post
Sixto mentioned ball bearing jobs used to plug the oil galleries near the rear crank seal. Anyone know the name of the part that he is talking about?
In EPC Section 01 = Engine Housing; Subsection 015 = Cylinder Crankcase, Cover, Gasket Kit; Item 62 = Ball, Oil Passage, Rear; Part Number = N 005401 517000; Qty = 2.

I have no idea how to replace such a plug.

Sixto
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  #13  
Old 12-12-2009, 11:11 PM
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Driven in w/ a hammer and a drift I think. Not sure how they come out.
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82 Benz 240 D, Kuan Yin
12 Ford Escape 4wd

You're four times
It's hard to
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  #14  
Old 12-12-2009, 11:26 PM
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I had a major oil leak on my wifes 81 SD that I thought was the rear main. Turned out to be the gasket between the oil filter housing and the block. We had oil covering the bottom of the car all the way back to the bumper.Not a easy job but doable, hardest part was breaking loose the oil cooler lines. Hope this helps. Rick
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Old 01-13-2010, 08:16 PM
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update

Thank you all for your replies. I haven't had a whole lot to reply since I haven't had a whole lot of time or space to work on my car. As of right now, I have worked on the valve cover gasket leak and removed the exhaust manifold. I am going to try to get the exhaust/intake and turbo back on to the car tomorrow and do another cleaning and oil check on Friday.

As of right now, I have found enough small leaks that I want to take care of them before I assume it is the rear manifold. I always like threads that post a conclusion and promise to do that.

Sasha

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