I am looking into buying a mercedes with the 350 6 cylinder turbo diesel. I know the old 5 cylinder models were the ultimate wvo engines, just wondering about the 6 cylinder? Is it IDI? Is it the same IP as the 5 cylinder? I know they had problems with the engine early on but this car has the new replacement engine that is supposed to be better.
Rusty

They call them rod benders.OK if engine was replaced with one with stronger rods.

Is it still the IDI and same IP as the 5 cylinder?
Rusty

Rusty,

What year? Compared to the cast iron fives, the six cylinders are less robust and use lower compression. The heads are made from alloys and will need to be replaced at 250,000 miles. Other than that, they are solid and reliable cars if maintained well. Signs of neglect are electrical components which don't work, vacuum lines which are brittle (do all the locks come up and down together? Does the engine stop smartly?) or cracked. Other points of failure in the older models are worn seats - refurbishing is expensive! - kaput rear defogs, antenna doesn't raise, suspension rubbers and motor mounts are inneed of replacement, etc...

Aloha!

quote:

Originally posted by rtarh2o:
Is it still the IDI and same IP as the 5 cylinder?
Rusty

Yes they are still IDI and tough Bosch inline IP. The 350s 3.5 liter engines are all rod benders even with new rods, they never solved the problem according to some. Mercedes started replacing the 3.5 with 3.0 when they failed under warranty. The 3 liter engines are also 6 cylinder, and don't have the rod bending problem, but they had a head cracking problem only in 1987 models with a #14 head. Which was solved on later model heads #16 and up (sold until 94), which are often put on 87 models making them very good engines. They don't need replaced unless they crack. The >#14 heads last much more than 250k miles regularly.

All of the 350 models used the redesigned >#14 heads, but I wouldn't ever get one because of the rod bender issue.

The 6 cylinder engines are more powerful, and far smoother and quieter than any of the 5. Another advantage is they used hydraulic lifters so they don't need the valves adjusted every 15k miles which is the recommended interval for the 5. I think the 3 liter 6 is the ultimate VO engine if they have the better head. I agree with many of the mercedes fans at http://www.mercedesshop.com/shopforum/forumdisplay.php?f=15 who claim they are the best car and diesel engine ever put in a car now that I have driven both extensively. The 3.0 are hard to find unlike the older models which are everywhere. And one with the >#14 head is even harder to find since they imported far less of them.

Here is a good article about them:
http://en.wikipedia.org/wiki/Mercedes-Benz_OM603

Sounds like what I am looking for. The car is actually a G Wagon so I can't be too picky about it, they are impossible to come by in this country. The engine is completely rebuilt so I am not too worried about it for a while. The guy sounded like he took every precaution to prevent the head from warping again and it is the replacement block and rods which I have heard were better? The main thing is the WVO, I am running a blend in my 6.2 Land Cruiser and it is running great but with the 6.2 it is too truck like for anyone in my family except for me, thus the more civilized Mercedes.
Rusty

The new head is the better kind. The new block is the same. Some say the rod bending problem is no better even on replacement 350s since no one ever discovered what was causing it, and MB switched back to the 3.0 engine.

The site I linked above has posts by people with replacement 350s with the "better" rods and still have had rod bending problems.

I have done it, sold my 6.2 diesel Land Cruiser and bought the G350DT Mercedes. So my question now is what method am I going to use blending in the Mercedes. As was mentioned this is the 3.5 liter which is basically a stroked version of the 3.0 liter 6 which as Sunwizard and others have mentioned is the ultimate WVO engine, this is the reason I have made the switch. I told myself if I ever found a turbo diesel G Wagon that I could afford I would buy it. I can't believe I am selling my Land Cruiser I have worked so hard on, especially since I have it running so well now, I must be crazy, but this is a deal I can't pass up!
Anyway, back the point. I have been running about a 70 wvo/30 diesel blend with a coolant heated filter. I tried using rug but had vapor lock problems with the heat. I like the idea of the heat, especially with the IP in the 6.2, I figure the shorter amount of time I could run the thicker fuel through it the better off I would be. The Mercedes inline IP from what I have read is much more tolerant of the thicker fuel. Should I do without the heat and blend with rug? I like this idea now that rug is under $2 again but is it the best thing? I still kinda like the idea of the heated filter but is it needed with the Mercedes? I guess I should mention that I make sure my WVO is really clean, I first put it in an upflow settling tank and from there into a centrifuge. After that it is pumped through a Goldenrod filter and into my tank. I mention this to let you know I am not using the heat because of fatty WVO.
Just when I sort of have it figured out with my 6.2 I am starting over again!
Rusty

quote:

Originally posted by rtarh2o:
Just when I sort of have it figured out with my 6.2 I am starting over again!

Rusty,

Congratulations! Not to worry, you can apply all of your blending theory from the Land Cruiser to your Benz hypothesis. If it has been well maintained, you might find the dieseling options a little more "flexible" but this is not to say that you can forgoe the normal Benz recommended servicing and concerns of biofueling (increasing oil changes to prevent oxidizing, etc.) Before you start thinning alternative fuels for your Benz I'd recommend that you get a baseline engine oil analysis and evaluate performance on ULSD first.

Performance: Get a stopwatch or a watch with a seconds hand and measure your 0-62mph (0-100kmh) time on a straightaway. Go one way and then the other and divide the difference to account for road incline. This'll help you evaluate the relative power of your blend.

Efficiency: What's the mileage? Does the odometer and trip odometer still work? Don't reset it while in motion and it should continue to work. Use this to record and analyze your fuel consumption between town, highway and trips with heavy load. Also, especially with a used car, consider a coast down eval of the efficiency. UnwiredTools.com makes a good calculater, but this test will help to measure your potential mileage and pinpoint compromises between the chassis (drag, toe-in, etc) and the powertrain.

Off the top of my head I don't recall, but if your Benz uses fuel to lubricate the top end of the IP, you will want to consider a lubricity additive for ULSD. Just follow the fuel lines and see where they go. I add a liter of VO or motor oil with every other tankful when ULSD fueling (roughly one quart to forty gallons). When you do start thinning for this car, consider that it was designed for the much more lubricious Low-Sulfur diesel (yes, that's "LSD") fuels of its day.

Cold Summer and Winter Starting. Evaluate with and without waiting for the glow relay light to go out. See if going through two or three cycles makes a difference, but get to know how long it takes to turn over your cold engine. Smoke quantity and quality will depend on the previous days driving, ambient conditions (temp/dew point) and how long the car has sat (sun/shade/garaged?) On a warm day you should be able to turn over the cars engine within ten seconds without the glow plugs. Don't crank the starter for more than 30 seconds (allow it to cool if you crank it this long!), but the heat from the engine compression should be sufficient to ignite the fuel. This presumes normal maintenance and servicing of the ignition-charging system, fuel delivery and timing, aspiration and crankcase. Once this baseline is established it can be useful when analyzing your blends and their effect on cold starts - i.e. too thick, spray patterns, timing and the resulting conflagration, atomization, powerstroke and emissions are compromised and it will take longer to start.

Aloha!

p.s. not sure if your car has the impedence wires between the glows or heats them all at once with the parallel wiring, but on a dark quiet night with the car in Park, open the hood, then turn the key to the glow position. You will see the impedence wires glow, or if you have the parallel wiring, just count out the seconds - shouldn't take more than sixty of em - and wait until you hear the glow relay clunk out. When the wires stop conducting current to the glow plugs, they'll just stop glowing when the relay clunks out. It's a little hard to hear the "clunk" from within the cabin, but whichever wiring you have, it is useful to know how long the glow plugs will stay on without the relay light on the dash panel.

1978_300D, good information. I am thinking about flying out to get the car and driving it home, it is about a 1,200 mile drive so I should have plenty of time to get to know the vehicle. The engine was just rebuilt so everything should be good but it never hurts to check.
Rusty

Ok, I am buying the Mercedes G350DT. It is the 3.5 liter 6 cylinder diesel. I am wondering what I need to do to the engine before I start running a WVO blend. The engine is recently rebuilt so I am thinking more about fuel pump and filter. On my Land Cruiser 6.2 diesel conversion I ended up installing a Raptor fuel pump and a Grease Kings heated filter because I knew these would hold up well to the WVO. I am wondering how the Mercedes pump and filter work with WVO? I know the IP is supposed to be the best so I am not worried about that.I am also still trying to decide if I want to run it unheated and blend with RUG,or heat and blend with Diesel?
Rusty

Rusty,

Keep an eye on your see-thru pre-filter. I removed my stock 5 micron filter on my 617 (the 5 cylinder) and replaced it with a DavcoTec 234a heated filter/water separator. It uses coolant heat exchange and has an electric heating option, however, it is insufficient alone for VO fueling and far from optimal for 100% VO. I now have two "pre-filters" in the fuel line. One is just after the send line and the other is just prior to the fuel pump. I am thinking about putting a third in right before the return hard line. I like see-through

I forget if you already discussed this in these forums or not, but in addition to replacing the fuel lines (and possibly upgrading to DuPont's Viton - though I asked the parts folks at M-B and they said the fuel lines they sell are not Viton but are biodiesel safe. All I know is biodiesel ate away the rubber gasket on the tank neck of my 1978) I would consider removing and cleaning the entire tank. This will minimize any future likelyhood of your WVO blends loosening up any sludge from the last twenty years of diesel fueling. It won't stop the "fuel fungus" from getting introduced into your tank, but if you clean it first and keep her topped up (above 3/4 - especially when humidity and ambient dew point is reached regularly), this will minimize the moisture available in your tank for the cladosporium resinae to feed upon. Also, cleaning the tank now will help you to avoid the dreaded "Mercedes-Benz WVO enthusiast roadside break-in period" - by which I mean that most people who start fueling old benz's with lotsa VO end up on the side of the road with a fuel filter clogged from an onslaught of diesel sludge which has been loosened up by the VO.

Other than that, I would have a professional shop with an old Benz certified mechanic take a look at the undercarriage (especially bushings and other rubber components) and align the steering and balance the tires. This will increase your miles per gallon. How old are the tires and when were they "rotated"? I put rotated in quotes cause likely you don't "rotate" them like most American cars where you switch left and right sides. Benz's usually just switch front to back, no left right swaps.

What color are the brake, coolant and power steering fluids? If the brake fluid is dark brown, You might consider a full brake service job (lines, pads, rotors) as this indicates neglect. Likely you won't have brake pads which are worn too thin, but old brake fluid is extremely water-attracting and can become unsafe in emergency braking situations. Look around the brake reservoir also and see if the paint has been corroded away by brake fluid. Signs of neglect and sloppy work. If the power steering fluid is also opaque, replace it - making sure to pump out all the old fluid. Also, what color is the coolant? I am pretty sure that you are required to use the orange stuff. The green stuff doesn't have the correct pH range and will compromise the internal heat exchange in the cabin and other ACC (automatic climate control) functions.

I would very hesitantly assume that the glow relays are good on a rebuilt engine, but it never hurts to check! You might also want to ask if the motor mounts and shocks were inspected and/or replaced? Is yours a turbo (did they make a non-turbo wagon?) If so, was the ALDA set with the rebuild?

Aloha!

Hey Rusty,

I have a '91 350SDL. BIG W126 body. Man I love that thing.

Anyway same engine as yours. I run a WVO, K1, Acetone, Turpentine, Diesel Kleen blend. Runs great. Well the 3.5 did till it bent the rod @ 240K miles. Now the 3.0L runs great on it. Cold starts can be rough at 20F but it does start and runs great!!! Got 15K on the 3.0L now.

HTH,
Shane

Finally got the Mercedes on Saturday. I plan to run a couple tanks of diesel through it just to see how everything is doing (it is a recently rebuilt engine) then start blending. So far I love it!
I don't have an easy source for Kero so I am going to use a diesel/rug blend unless I can find some winter diesel (probably not likely in Texas) I am thinking about 75%WVO/15%diesel/10% rug in an unheated stock system, how does that sound?
Rusty

I have a 97 E300D and temps get down in the 30's at night. I'm running 10gal WVO, 1.5gal K1, .8gal RUG and 3gal #2 diesel. My car is stock (no heat). Keep an eye on the RUG, I tried to bump up the RUG to 1.5gal and the car REALLY didn't like it. This will be my first winter with the car so my mix could change if needed. K1 went up to $6/gal so I'll just add more diesel if needed. I was adding 6oz of turpentine but that stuff was adding about $.40 per gallon so no more of that.

quote:

I am thinking about 75%WVO/15%diesel/10% rug in an unheated stock system, how does that sound?
Rusty

Hey Rusty, your mix sounds pretty conservative to me. It will be interesting to find out how your Mercedes 350 6 cyl turbo diesel runs on the blend. Where abouts in Texas are you? Panhandle, west, coastal? I am in Amarillo, and the temps can get pretty cold here. It has already been down in the low 20s.

I am in northeast Texas on the border of Arkansas, pretty mild temperatures here but it is supposed to get down to the low 30's tonight and tomorrow night. I might add a little WVO to my next tank (maybe 50%) and see how it does, I am guessing I probably won't notice much difference (at least I didn't in my 6.2) except for the smell which I miss! I will try adding a little rug since kero is hard to find and up my blend to the ratio mentioned above. Possibly in the summer I will try move WVO.
What are most running in their Mercedes?
Rusty

Hello Rusty, I have been speculating that an 80/20 VO/RUG blend would run fine on most autos year round, except the tundra. So, reading about many blending experiments and their results helps to hone that theoretical blend formula.

As incomprehensible as it may be, You need to revise your speculation or add another exemption.

20% RUG is far too much for my Mercedes in summer here. It runs rough, loses significant power and creates vaporization issues. It is NOT an appropriate blend for at least 6 months of the year.

I also believe one all year round blend that suits most cars would be a completely flawed theory and extremely bad advise to recommend such a thing.
Locations that have a wide temperature variance will automatically rule out any possibility of a " 1 size fits all" blend for many vehicles let alone the myriad of different engines and the differences in the way they operate.

By the time you revise your speculation to make it at all accurate and add in all the exceptions, it is going to be far easier to come back to the commonly suggested advise of adjusting one's blend to suit the vehicle and conditions at the time.

Good points about seasonal blending. With my 6.2 I ran about 75WVO/25Diesel in the hot months of the Summer. By the time I sold it a few weeks ago I was running about 50WVO/50Diesel. I quit using RUG because I had a heated system and started experiencing vapor lock. Running wise I couldn't tell much difference and it always started fine. I plan a similar thing with the Mercedes and will probably eliminate most of the RUG in the Summer months.
Rusty