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Discussion Starter #1
Maybe it's me or maybe it's not but I just started w140 diesel, let it warm up for a minute and then i drove off. When leaving my street there's a hill and the car moved up with no problems. I was actually impressed but confused because when i came back home i took a different route and went up a hill and it lacked that same power. I had it floored and it would hold the speed but slowly decrease. Any ideas?

Please don't tell me i'm another victim of the rod-bender!
 

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There are many reason why the power could fall off, I would get a fault code read out before anything
 

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Vacuum issue

Maybe it's me or maybe it's not but I just started w140 diesel, let it warm up for a minute and then i drove off. When leaving my street there's a hill and the car moved up with no problems. I was actually impressed but confused because when i came back home i took a different route and went up a hill and it lacked that same power. I had it floored and it would hold the speed but slowly decrease. Any ideas?

Please don't tell me i'm another victim of the rod-bender!
RodBender will still run pretty well typically, just consumes oil at a very high rate (quart every 1-200 miles).

Very complicated vacuum system (egr, turbo, shifting, electrical vacuum engine shutoff) on the w140 cars with a few more wrinkles versus previous diesels. I am going to be working on this in the next couple weeks and post. I've got two of these right now, so I am hoping to get some good intel on how to deal with these cars. Right now both of mine do not climb highway hills the way I would like. I recall blowing through the mountains of west virginia in top gear in the past. Neither car does that and you are left flooring the car and having the slow decrease when you are up against steep truck lanes. I will be making a simple code reader and we will see if the engine codes identify any problem vacuum transducers. For now, check all your vacuum lines for cracks, disconnections. My new car will have all new lines when I get done. Always have these thoroughly checked out. In the past, I've had multiple turbos put in my car when the issue was vacuum related.
 

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Put a boost gauge inline on the manifold to make sure you still have turbo.

The diesel module on these cars will shut down turbo if it senses some problem with airflow i.e. EGR inop etc. If vacuum isn't being maintained to the turbo waste gate then there's a problem somewhere, and it's all controlled by the mess of transducers behind the passenger headlight.

good luck
 

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Pass headlight transducers

Put a boost gauge inline on the manifold to make sure you still have turbo.

The diesel module on these cars will shut down turbo if it senses some problem with airflow i.e. EGR inop etc. If vacuum isn't being maintained to the turbo waste gate then there's a problem somewhere, and it's all controlled by the mess of transducers behind the passenger headlight.

good luck
Yep. That was what got mine going.
 

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Thanks... I'm hoping to work on the car towards the end of the year when I take some time off of work. Does anyone have a diagram of the vacuum lines? i'm not much of a hands on person for forgive the stupid questions.
 

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Thanks... I'm hoping to work on the car towards the end of the year when I take some time off of work. Does anyone have a diagram of the vacuum lines? i'm not much of a hands on person for forgive the stupid questions.
If you go to page 12 of this transmission diagnostic guide:

http://w126.pp.ru/akp722.pdf

Ignore the reference in the document to C220 etc, the vac diagram is for 300SD / S350 cars.

You should be able to sort it out with this.

good luck
 

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Five diagrams and more

Does anyone have a diagram of the vacuum lines? i'm not much of a hands on person for forgive the stupid questions.
Be careful what you ask for. I've been hunting for these recently. ShutoffDiag.jpg is very blurry, but has a legend very much like OM603971vacuum.pdf. The diagram on pg.12 of transmission diagnose is identical, but has a different legend. Of course, the infernal part numbers don't match with this, and of course they call things different things in the diagrams. I probably ought to put this posting somewhere else, but I'll clean that up when I am done playing with this.

I believe the key shut-off switchover valve is one of several parts that make this car a little different from other diesels which means your neighborhood diesel expert will probably mess it up. I believe all three switchover valves are the same part number. I am getting ready to tear into this so you might ask for an update around christmas time. I am playing with two cars right now so it should be interesting. Going to try making a $20 code reader.

If you want to replace all the lines and connectors with new. I've got a couple recent orders I could post. This is my first foray into the guts of this area. If you want it done right sometimes its best to do it yourself. I figure when these things fail down the line I can keep on top of them.
 

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Discussion Starter #9
Be careful what you ask for. I've been hunting for these recently. ShutoffDiag.jpg is very blurry, but has a legend very much like OM603971vacuum.pdf. The diagram on pg.12 of transmission diagnose is identical, but has a different legend. Of course, the infernal part numbers don't match with this, and of course they call things different things in the diagrams. I probably ought to put this posting somewhere else, but I'll clean that up when I am done playing with this.

I believe the key shut-off switchover valve is one of several parts that make this car a little different from other diesels which means your neighborhood diesel expert will probably mess it up. I believe all three switchover valves are the same part number. I am getting ready to tear into this so you might ask for an update around christmas time. I am playing with two cars right now so it should be interesting. Going to try making a $20 code reader.

If you want to replace all the lines and connectors with new. I've got a couple recent orders I could post. This is my first foray into the guts of this area. If you want it done right sometimes its best to do it yourself. I figure when these things fail down the line I can keep on top of them.
Thank you!
 
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