They Said it Can't be Fixed - A Journey to the Inside of a Mercedes Bluetec

Komodo said:

FJ40Jim said:

Not sure about the laws & emissions standards in your country, but in USA ...

There are of course requirements. Every second year we have to go to an approved workshop for a "EU-test" of the car. Among the tests are emissions, but I am not certain of the tolerance limits. However, earlier today I spoke to my former college who does the tuning, and he says that I can delete the EGR, the swirl flaps, and the DPF, and still not get any problems with the limits. Have not decided on the DPF yet, but at least the EGR and swirl flap goes out. 

 

It didn't go to limp mode when MAF is unplugged because MAF input is only used to trim the fuel map. It's common on the very similar VW TDI to reflash with a performance tune that deletes MAF input and relies only on MAP, IAT, RPM, TPS. 

Thank you very much Jim, this was exactly what I was wondering about! Not that I fully understand all this, but I have some more to get into (I am not a car mechanic, so the abbreviations has too be looked up...).

I can't help you with the Mercedes stuff, but:

MAF - Mass Airflow Sensor (as you know)

MAP - Manifold Air Pressure

IAT - Intake Air Temperature

RPM - Of course :)

TPS - Throttle Position Sensor

Basically, with a tune, instead of looking at the airflow (which on a diesel isn't a throttled/controlled amount like a on a petrol engine), it can look at the air pressure in the manifold with the intake temperature, and fuel according to what your foot is telling it to do relative to those two.    The MAF is really only to dial in/fine-tune the amount of fuel injected on a diesel, since you control the engine speed with the amount of fuel you're injecting.

On a gas engine where the throttle is literally throttling (choking off) the incoming air, the MAF (or equivalent) is really important to get good throttle response, because that lets the computer know how much air is coming down the tube, so it can get a bit ahead of it for injecting fuel.  Most of those won't run at all with an unplugged MAF, although some will but only allow, say, 2000 RPM or other failure modes, all of which are accompanied by pretty warning lights on the dash.

In reply to Komodo :

Welcome!  I can assure you that you speak (or at least write) my language far better than I can communicate in yours, so I have a great deal of respect for that.

I like the term "Monday Car".  I've not heard that before, but I may have to adopt it.

As far as unplugging the MAF sensors, I do not fully understand exactly what the computer is doing, but I think that what happens is that because there's no MAF signal, the computer goes into a "fail safe" table of some sort and stops trying to do EGR things.  Since it doesn't try to acutate the EGR valve, it doesn't blow the code that forces it into limp mode.  Now, why it won't go into limp mode with disconnected MAF sensors is a mystery to me.  You'd think that since it isn't doing EGR things at all, it would limp, considering that if it fails to do EGR things it goes into limp.  Maybe two different software development teams were working on those functions.

It's interesting that it ceased making bad noises, though.  I'd be curious to know if the noises would stop with the MAF sensors hooked up and the EGR installed but disconnected.  Or with the EGR installed and connected and all that with the variable pitch controller for the turbo unplugged.

wae said:

I like the term "Monday Car".  I've not heard that before, but I may have to adopt it.

"Monday Car" is an old expression in Norway. I guess its originally refers to that the workers had a bad hangover on Mondays, and did a lousy job building cars. Just a saying of course. But as we all know, before the CNC age, the tolerances on manufactured parts were a lot wider. And when you put together an assembly with parts that are in the wrong side of the allowed interval, the finished product may get very bad quality. So these days with modern production quality of components, Monday Cars should not be a topic. 

As far as unplugging the MAF sensors, I do not fully understand exactly what the computer is doing, but I think that what happens is that because there's no MAF signal, the computer goes into a "fail safe" table of some sort and stops trying to do EGR things.  Since it doesn't try to acutate the EGR valve, it doesn't blow the code that forces it into limp mode. 

Yes, this sounds logical for me to. 

Now, why it won't go into limp mode with disconnected MAF sensors is a mystery to me. You'd think that since it isn't doing EGR things at all, it would limp, considering that if it fails to do EGR things it goes into limp.

That one is hanging in the air. (is that an expression? )

It's interesting that it ceased making bad noises, though. 

My guess is that the unplugged MAF sensors not only tells the EGR to take a brake, it also tells the swirl flap motor that it can rest for a while. This is of coarse only guessing, but after yesterdays experience I guess that the nois came from the swirl flap system, and that carbon buildup made it impossible for the motor to set the flaps in correct position, and it therefore was flapping back and forth. A friend of mine (experienced car mechanic) listened to the engine with a stethoscope, and was relatively certain that the noises came from the turbo, and not the engine it selves. But I am not convinced. The frequency did not correspond to a turbo in my ears (which are severely damaged). The sound was like "cho, cho, cho, cho", like a bad fan belt in frequency. 

But I will plug in the MAFs tomorrow and check. If the nois returns, I can not understand that it comes from the turbo. Unless, of course, the problem is that the VGT actuator is flipping and making that noise...

I'd be curious to know if the noises would stop with the MAF sensors hooked up and the EGR installed but disconnected.  Or with the EGR installed and connected and all that with the variable pitch controller for the turbo unplugged.

If I get time for this tomorrow, I will give it a try! At least weather should be nice 

And one more thing. When I spoke to "the tuner" yesterday he said that I can choose from blinding out the EGR with a metal sheet, or remove the whole EGR valve and the EGR cooler. In the last case I have to install a tube or something to replace that part of the cooling circuit, and of course blind off the other side of the cooler where the exhoust gas goes into the blending chamber. Any thoughts about that? I my eyes it would be an advantage to get rid of the entire cooler. 

Well, I officially have 50k miles on my rebuild job:

I've got a few other things to deal with before I get in there and figure out what's up with the front air and to deal with the O2 sensor.  What's kind of funny is that when I woke up on Monday morning this week, my plan was to go over to a local dealer and try to buy a fully loaded used QX80.  It was a beautiful Hermosa Blue with a Wheat interior, a color combination that is my weakness.  But that activity will have to wait until I've found a job and in the meantime, I'm going to have to keep der Scheißwagen trundling along.

In reply to Komodo :

It seems like getting the cooler completely blocked off and sealed up would be quite a job.  I wonder how feasible it would be to thread the coolant and oil ports and put plugs in them.

wae said:

In reply to Komodo :

It seems like getting the cooler completely blocked off and sealed up would be quite a job.  I wonder how feasible it would be to thread the coolant and oil ports and put plugs in them.

I have never had these parts apart, so I don`t know. But as I see it, the EGR cooler is basically a regular heat exchanger, where the exhaust gas coming from the EGR is cooled with water. Two ports in, two ports out. So my thoughts where to bypass the water in- and out with a tube or a hose. But when I delete the EGR valve (no matter if the valve is left in the car og removed permanently), the gas part is blocked, so there should be no reason not to block the ports in both ends. I am more uncertain whether the liquid part could be blocked, or if the water flow is essential for other functions in the cooling system. Therefor the bypass tube. 

You mentin oil ports, not quit certain what you mean by that. I think there are some differences in the EGR valve on my old ML from your newer GL, but does it have oil ports? 

If you look 24:43 min. into this video, there is a water hole at right beside the big hole to the EGR. That water port is not in my car. My EGR does not have a gascet either, it only has a thin O-ring. So it should be easy to turn a plug to blind off that hole with an O-ring. 

If you look 23:31 min. into this video, you see three of the ports on the cooler. The water port on the manifold in the left part of the picture should be easy to convert to a hose nipple either by a flange, or as you propose to thread up the port with a suitable tread dimension. The gas port could be blinded with a flange, but also with a plug if the hole is circular. In the front the gas port of the exchanger goes into the mixing chamber (if I have understood the assembly correctly. That port should be easy to blind off with some sort of a plug. I have a lathe in the garage, so I can make a plug as a copy of the end of the pipe. 

But that was just some thougts, I don`t know if it is doable. 

And then a short update on the ML.

Yesterday I took out the ECU and delivered it to the tuning guy. He will put in a program he called "Eco", which should make the car run more economically, but also give it 10-15% more torque and power. 

But before I removed the ECU I did some more testing. First I drove a little trip with the MAFs unplugged, just to ensure that the noise was gone, and that it did not go into limp. And it didn`t. Then I plugged in the MAFs. The noise returned immediately, and after a coupe of kilometers it went into limp mode. I then unplugged the EGR valve (as you proposed WEA), and the car behaved similarly as with the MAFs unplugged. No problem, no lamps in the dashboard. But I got a feeling that the torque curve was somewhat different from when the MAFs were unplugged. Got a feeling that it lacked torque between 1400 and 2000 rpm, and that I had to press the pedal in the floor to make it accelerate. Then it went very high up in revolutions before it shifted down. Might just be a feeling though. 

At least I pulled out both the MAFs and the EGR, and the behavior was similar as when only one was unplugged. I did not have the time to unplug the turbo though, so that question still hangs in the air. 

At this point I am quite certain that the noise comes from either the swirl flap system, or the VGT system on the turbocharger. It was a big relief that as well the noise as the limp mode disappeared when I followed your advise to unplug the MAF sensors. This tip alone was worth reading the whole tread! It brought me a big step further in my troubleshooting. So thank you very much one more time! 

Here are two short cuts of the noise. It comes in low speed, and is present aproximotley between 1400 and 1900 rpm. 

First video 

Second video

At last I have one more question for you. The rubber parts on the underside of the engine cover are worn out. Does any of you know what they are called? I have seen a Youtube clip where a guy replaced those rubbers, but I have not found a place to buy them. The cover is totaly loose on top of the engine. 

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Edit:

Now it came in a message from the tuner. The ECU is done already, so just to come and get it. Will be exiting to see if the car runs fine with the EGR unplugged, and without fault codes. Yesterday when testing I got 11 fault codes... 

Short update on the ML.

Installed the ECU, plugged in the EGR and MAF sensors, deleted all of the fault codes, and took it for a ride. The car was now completely different to drive! Suddenly the gear shifts was smooth, and the torque was again even through the revolution register. And even better, after several kilometers of driving, there is no fault codes on the scanner  

But of course, I have to replace the turbo, and will do a job with cleansing the intakes, removing swirl flaps, and all that stuff. But now I will stop to pollute WAEs wonderful thread. At least until I have some new questions 

By the way, I found the rubber for the engine cover on Aliexpress if any of you need those.

In reply to Komodo :

Pollute away!  I like to think of this as an opportunity for group therapy.

Okay, so here is where I need to admit an embarrassing fact:  Not only can you speak my language better than I can speak yours, you can also speak my language better than I can speak my language.  You said EGR cooler.  I was thinking oil cooler.  So, yes, I think you're absolutely on to something in being able to remove that.  I agree that a bypass tube is probably the best way to go about that.

What I don't know, however, is what the benefit would be to removing the EGR and blocking it off versus just making sure it's shut and then tuning it out.

That noise is really weird, though.  It sounds like something in the driveline banging around, but it doesn't correlate to road speed or, really, even to engine speed.  I'd wonder if it were an accessory, but if it goes away when you unplug the MAF, that's even weirder.

The noise is accompanied with a high pitch turbo whine. I think that banged up turbo needs replaced ASAP. I'm concerned it will fail catastrophically, sending shrapnel into the intake or into the oiling system.

wae said:

In reply to Komodo :

Pollute away!  I like to think of this as an opportunity for group therapy.

Okay, so here is where I need to admit an embarrassing fact:  Not only can you speak my language better than I can speak yours, you can also speak my language better than I can speak my language.  You said EGR cooler.  I was thinking oil cooler. 

Ha ha, thanks And no, removing the oilcooler doesn`t make much sense  

So, yes, I think you're absolutely on to something in being able to remove that.  I agree that a bypass tube is probably the best way to go about that.

What I don't know, however, is what the benefit would be to removing the EGR and blocking it off versus just making sure it's shut and then tuning it out.

Have not decided yet, I`ll see what I end up doing. But as you say, removing the EGR probably does not help much. Not sure if it is any point to remove the EGR cooler either, I just thought it would be an advantage to simplify the system. We`ll see, what is most important is to make the car more reliable. 

That noise is really weird, though.  It sounds like something in the driveline banging around, but it doesn't correlate to road speed or, really, even to engine speed.  I'd wonder if it were an accessory, but if it goes away when you unplug the MAF, that's even weirder.

Yes, it`s weird. But now I have tried to unplug both the MAFs and the EGR several times, and the result is consistent; the noise disappears, and it does not go into limp. I can not anything but guess, but I can not see other reasons than the swirl flap system or the VGT system on the turbocharger. 

Anyways, the tuning and reprogramming of the ECU seems to be a success, and tomorrow I will start to demount parts. 

------------

FJ40Jim:

Unfortunately my hearing is permanently damaged on both ears, so I only hear the scraping noise. I do not hear the turbo whine you describe, but my daughter mentioned it. But I have got my hands on a used turbo that seems to be in good condition, so it will defiantly be replaced. It is actually the most important reason that I will do this job now. The secondary reason is to remove the swirl flaps and clean the manifold and the ports, and the third reason is to replace oil cooler seals and a few other service parts, like waterpump, generator pulley, belt tensioner etc. 

It's been really cold in Ohio of late. The OM642 has started up no problems. The cold idle seems very rough, especially when first dropped into reverse. I think that might be frozen liquid filled engine mounts. It becomes normal after 10minutes of operation.

The biggest cold weather problem staring me in the face (quite literally) is the LCD dash display. It seems to have developed a string of dead pixels. Anybody know if this is permanent or maybe will resolve itself after things get warmer in a month?

In reply to FJ40Jim :

That's interesting...  Mine kind of acts the same way.  A little noisy and rough for a bit and then it smooths out but only when it's stupid cold like it's been lately.

That looks very different from the dead pixels I've seen before...  I'm a bit concerned that it might not come back for you.

wae said:

In reply to FJ40Jim :

... but only when it's stupid cold like it's been lately.

What temperatures are you talking about? 

Komodo said:

wae said:

In reply to FJ40Jim :

... but only when it's stupid cold like it's been lately.

What temperatures are you talking about? 

Okay, fine, we're only talking about around 15°-20° which is around -9° Celsius.  But to me anything under about 80° is starting to get cold so....

We've had a few overnight lows of -20C and highs of -12C. Today it will warm up to -7 and the low will be -11C. The ML lives in a garage, but it's not heated or insulated, and it faces north, so it is very cold. We went on a little trip yesterday, total drive time about 4 hrs. During the drive the bad spot slowly moved up the display. The total area of bad pixels stayed about the same, so the defect was repairing itself while slowly percolating upwards. Hopefully it will continue heading up & off the display.

Okay, fine, we're only talking about around 15°-20° which is around -9° Celsius.  But to me anything under about 80° is starting to get cold so....

I see, then we have had the same temperature as you lately. -12 at the most, but mostly around -4. Today it is warm again (+5), and the forecast says no more cold weather in a couple of weeks. That suites me fine, because the Leaf is an icebox compared to the ML. But we live by the coast, so it is seldom very cold here. Not every year we see -20. 

But out of curiosity, do you use both Fahrenheit and celsius, or was it just out of politeness for a European? I understand that you still hold on to the imperial measuring system with inches, gallons etc. (really hard for us Europeans to understand )

I hope to have the ML on the road again soon, but today I had a little setback. Mounted the turbo, but forgot to put the cable harness back first  So I had to remove the turbo to put the harness down in the wally... I know the steel gaskets are for one time use, but after a consultant with a friend I decided to try to remount the turbo with the same gaskets. As he said, they have not been warm yet... 

Have also some more things left, among other tings generator pulley, water pump, filters, oil, etc. Folding my hands, and praying for the best...

In reply to wae :

The older I get, the more I respect Bob Poling wearing a heavy onesie work suit at rallycrosses, even in the summer.

Of course, I always seem to work with a bunch of polar bears who whine how hot it is when it's 70F out.

In reply to Komodo :

I can't speak your language, but I can at least do the math so you don't have to!  I prefer my fasteners to be metric, but I can only really think in inches, pounds, miles, and such.

That whole garbage with that wiring harness running under the turbo inlet is one of the most infuriating things about the OM642.  If they had simply routed that differently, they could take significant time off the R&R for the swirl motor.  And I want to say there was something else that would be easier to do if the harness wasn't stuck under the turbo, but I can't recall what it could have been at this point.

I think you'll be fine re-using those particular gaskets.  Getting the turbo connected to the exhaust and the EGR is a real pain, though.  I do not envy having to do it any more than absolutely necessary!

Pete. (l33t FS) said:

In reply to wae :

The older I get, the more I respect Bob Poling wearing a heavy onesie work suit at rallycrosses, even in the summer.

 

Of course, I always seem to work with a bunch of polar bears who whine how hot it is when it's 70F out.

One of the most insidious things about winter is how I find myself getting conditioned to be all excited about how "warm" it's going to be next week when it gets up to 40.

wae said:

In reply to Komodo :

I prefer my fasteners to be metric, but I can only really think in inches, pounds, miles, and such.

Thank you, that`s very interesting! In this part of the world the metric system is learned from birth, so it`s given for us. I think most Europeans shake their head of the imperial measuring system with all the fractions of inch etc. Inches was common here also earlyer, but was faded out between the 50s and the 60s. The only thing we use inch/feet for now is in plumping (threads on fittings) and the length of a boat  

I think you'll be fine re-using those particular gaskets.  Getting the turbo connected to the exhaust and the EGR is a real pain, though.  I do not envy having to do it any more than absolutely necessary!

Thank you once more, I feel that my stomac is starting to calm down a bit now  I of course agree about the bolting connection, but I found out a pretty simple way to do it the last time yesterday. I will put in some pictures in the end if you don`t feel that I am spamming your thread to much. 

But now it is nearly 9 am here in Norway, so it is time for a cup of coffee and get into the icebox (a white Leaf...) and go over to the garage. I have no place to work indoors on the ML, but was so lucky that a friend offered me to use his garage. Fully isolated, warm, bright, and a lot of tools  

It took me two days to read this absolute E36 M3 show of a thread while I've been sick. You guys are genuinely insane.

In reply to Komodo :

That brings up something I've wondered about....  Sockets.  Around here, sockets come in 4 common attachment sizes: ¼ inch, ⅜ inch, ½ inch, and ¾ inch.  So if I'm holding my impact gun I might ask for the ½" 19mm socket to remove some lug nuts but when I'm using the "regular" ratchet to take off a fender, I'd ask for a ⅜ 10mm.

What nomenclature do you use to differentiate between the different sizes of sockets?

accordionfolder said:

It took me two days to read this absolute E36 M3 show of a thread while I've been sick. You guys are genuinely insane.

...but in a good way, right? 😁

They cover it all here, in a humorous way - they call it 12.7mm (that's a 1/2"), 9.5mm (it's actually measured at 9.525m or 3/8), and 6.35mm drive (spoilers, it's 1/4"). So it's all the same, just different. "A Rose by any other name..."

wae said:

accordionfolder said:

It took me two days to read this absolute E36 M3 show of a thread while I've been sick. You guys are genuinely insane.

...but in a good way, right? 😁

lol, all I'll say is: I applaud your tenacity! ;)