Mercedes 5 cylinder diesels of the 1980's

Over the past 40 years, there have been a few vehicle models that stand out as excellent examples of superior design and engineering. Typically, they are models at the peak of a certain engine design. What also makes these vehicles sustainable? I used the following criteria for defining a sustainable vehicle:

Reliability – The fewer repairs and parts replacements, the more sustainable the vehicle. The longer they last, the fewer new vehicles have to be built to replace them.

Biofuel ready – Cars that can run on renewable biofuels are more sustainable. The more flexible they are for different fuel types the better.

Fuel Efficient – Vehicles that use less fuel are more sustainable. An extremely fuel efficient vehicle that will run on multiple biofuels is about as sustainable as you can get.

EMP Hardened – This is more of a preventive criteria for sustainability. In the event of an electro-magnetic pulse (EMP), vehicles that are not EMP-hardened will have all electronic systems permanently damaged and disabled. Any vehicles that use electronics would fail and be inoperable until new electronics are installed. I consider cars that are completely disabled to be a sustainability issue. Vehicles that can continue to run indefinitely even after any type of EMP are a more sustainable option. An EMP can be caused either by natural or Man-made sources. Severe solar storms or a nuclear explosion in the stratosphere are two possible causes of powerful EMP events.

There are certainly other criteria that could be used such as use of recycled materials in construction, the recyclability of components and the distance from where components are sourced and where the vehicle was manufactured vs. the destination of sale/usage. However, most auto manufacturers from this time period didn’t have any of this on their radar.

Here are my TOP THREE Sustainable Vehicles of the 20th Century:

1. 1981-1985 Mercedes Diesel Vehicles

2. 1993-1998 Dodge RAM 2500 Cummins Diesel Trucks

3. 1999.5-2003 Volkswagen TDI Vehicles with 5 speed Manual Transmissions

One of my Biodiesel Jetta TDI's

Half way through the model year in 1999, Volkswagen introduced a new body style of their Jetta with an improved “ALH” TDI engine.  When combined with the 5 speed manual transmission in any of the body styles, this drivetrain was extremely fuel efficient and very reliable.  This 1.9 liter direct injection diesel engine was available in the Jetta, Golf and Beetle body styles.

The average fuel mileage ranged from 45-50mpg without any special driving techniques or modifications.  The fuel system was very flexible and can be run on biodiesel with little modification.  Even though this is a direct injection engine, waste vegetable oil can be used as fuel if a heated, two tank conversion kit is installed that gets the injection temperature of the fuel up to at least 160*F.

Stay away from automatic transmissions.  They are prone to failure and are very expensive to repair or replace.

Pros

• Engines are extremely reliable
• There are lots of online resources for technical troubleshooting and inexpensive parts
• Extremely fuel efficient. Averages 45-50mpg without tuning or hyper-miling
• Can be run on biodiesel with little effort. Just replace the fuel return hoses with viton or another fluoro-elastomer hose.

Cons

• Interior and body parts are of low quality. Parts tend to break. The engine and transmission will outlast the body.
• Avoid autumnatic transmission vehicles. The auto transmission is prone to failure and is very expensive to repair.
• Timing belt and water pump MUST be replaced at recommended interval. Older models can be retrofitted to a 100k mile interval by replacing rollers, tensioners and all recommended auxiliary parts during timing belt change. Failure to service at recommended interval will cause timing belt failure and damage to head, valves and cylinders.
• EGR systems are prone to coking in the intake manifold and throttle body. They need to be cleaned when the Check Engine light comes on and is an EGR-related code. There are EGR deletion kits that prevent this but are not legal for road use.
• Vacuum hoses tend to harden with age and crack. They need to be replaced at around 100k intervals or when failure occurs.
• Cooling systems should be maintained properly and only VW pink coolant should be used. Switching to green coolant or mixing the two will cause issues for cooling system components.
• Injection system is electronic and is not EMP-hardened. There are mechanical injection pumps that can be retrofitted to make it EMP-hardened

Buying Guide

• Most used VW’s from this era will have the check engine light on.  Take it to a chain store and have the codes read.  The problem is likely EGR or glow plug system related.  These are not hard or expensive to fix but you should adjust the buying price accordingly.
• Plan on replacing the timing belt and water pump immediately after purchase unless the previous owner can produce a recent invoice for replacement.  In this case, call the repair shop and find out what types of parts they used.  You can’t assume a 100k mile service interval unless you are certain these updates were performed during the last change service.
• Refer to online VW TDI sites for more technical troubleshooting.  Fred’s TDI Forum is a great resource for knowledge.  ID Parts or AutohausAZ are good choices for inexpensive parts.

Preventative Maintenance

• Change the oil every 7,500 miles with a full synthetic oil such as Shell Rotella T6 or Mobil-1 Full Synthetic (5W40)  Use good quality oil filters and replace o-rings during the oil change
• Service the timing belt and water pump immediately when service intervals are reached.
• Replace the fuel filter every 30k miles or as needed from dirty fuel
• If you suspect water in fuel, make sure to use the drain plug in the fuel filter to periodically drain off the water and contamination.
• Change the manual transmission fluid every 60-100k miles depending on usage
• If you have an automatic transmission, sell it. (changing the fluid could cause problems if it wasn’t serviced regularly)

In 2004, Volkswagen introduced a new diesel engine called the PD which used a high pressure fuel system and other modifications to the camshaft and valves.  They require special additives to the full synthetic oil and are prone to cam lobe failure.  Later TDIs from 2006 and on had more updates.  There is not enough information on these models to recommend.

NOTE: Volkswagen diesels built before 1999 are also very reliable and fuel efficient. However, there were some issues with head gaskets on earlier 1.6 diesel engines. If the cooling systems are properly maintained and the fuel injection system or turbo are not over-boosted, they are very reliable and fuel efficient.

Dodge RAM 2500 12 valve Cummins Diesel

In 1993, Dodge introduced an updated version of their Cummins 6BT 12 valve diesel engine that used a Bosch P-7100 mechanical injection pump.  When combined with the all mechanical 47RH hydraulic automatic transmission, buyers have the ultimate, bullet-proof work truck rated for 3/4 ton and 20mpg.

Later models introduced the 47RE electronic version of the automatic transmission that exposed the truck to typical issues with electronics on vehicles. (prone to failure after prolonged use and expensive to repair)

Vehicle Specifications

• 12 valve Cummins 6BT Engine
• Bosch P7100 Injection Pump
• 47RH Hydraulic Automatic Transmission (or 5 speed manual)

Pros

• Extremely reliable drivetrain with proper maintenance
• Bullet-proof mechanical injection pump
• All mechanical transmission with no electronics
• Compatible with biodiesel by replacing soft fuel lines with SAE30R9 fluoro-elastomer-lined high pressure fuel hose. This is available at most chain auto parts stores and is called, “high pressure fuel hose” Make sure to check the spec printed on the hose to make sure it is SAE30R9 (R6, R7 are not biofuel compatible)
• Can be run on refined, de-watered vegetable oil with a two-tank system where the oil is heated to at least 160*F before injection.
• Gets good fuel mileage/weight ratio. Averages around 20mpg for a non-tuned stock engine. This is almost twice the fuel mileage of the gas-engine version of the same truck.

Cons

• Killer Dowel Pin (KDP) One of the dowel pins that holds the timing cover to the front of the engine block tends to work its way out of the timing cover and falls out. It sometimes falls into the timing gears and destroys the gears and timing cover. This can be prevented by installing a KDP kit that keeps the dowel pin from falling out. There are several variations including one method that replaces a nearby bolt with a longer version and an egg-shaped offset washer that covers the dowel pin opening.
• Some models came with the 47RE automatic transmission. This is an electronic version of the original hydraulic 47RH transmission. It contains electronics so it is less reliable and is susceptible to failure from EMP.
• This is a direct injection diesel engine. Running it on vegetable oil with injection temperatures less than 160*F will cause coking on the rings and cylinder walls resulting in eventual engine failure.
• This is a heavy truck so suspension components are a point of failure and require replacement if used for heavy towing
• -Electric windows are not EMP-hardened so would fail from an Electromagnetic Pulse.

Buying Guide

• Look for 47RH transmission
• Look for Bosch P7100 injection pump
• Have compression checked on engine
• look for oil leaks at front timing cover for possible KDP issues
• Ask if KDP has been repaired
• Check condition of oil
• Check condition of transmission fluid (burn smell is bad)
• Check Suspension for wear. (lift front end and shake wheels)  This shouldn’t stop you from buying but will help you adjust the buying price and plan for near term repairs.

Preventative Maintenance

• Change the oil every 3-5K miles depending on usage. Use name-brand 15W-40 oil(Shell Rotella, Chevron Delo, etc.) and good quality oil filters.
• Replace fuel filter every 30k miles with good quality replacement filters.
• Change the transmission fluid and filter every 30k miles (drop pan to change filter)
• Adjust transmission bands every 60k miles for best performance
• Change rear diff fluid every 60k miles
• Flush cooling system every 2 years

Late in 1998, Dodge introduced a new 24 valve Cummins 6BT engine with a new injection pump design.  Unfortunately, the new injection pumps were very sensitive to fuel pressure.  If the lift pump stopped providing enough fuel pressure, the injection pump would completely fail and require rebuild or replacement.  This problem was so common that kits were developed to retrofit the older Bosch P7100 injection pump to the newer 24 valve diesel engine.

Mercedes 5 cylinder diesels of the 1980's

By the early 1980′s, Mercedes had hit the pinnacle of design and engineering with their 4 cylinder and 5 cylinder diesel engines.  The cast iron heads were bullet-proof and the pre-combustion chambers made them the perfect engine for using alternative fuels like waste vegetable oil.  Both the manual and automatic transmissions were also built strong and seldom had issues as long as they were maintained properly.

Models

240D, 300D, 300CD, 300SD, 300TD

Pros

• 5 cylinder diesel engine is legendary and is one of the best engines ever built
• Both automatic and manual transmissions are extremely reliable with proper maintenance.
• Cars are luxurious with very comfortable seating and ride
• Engine runs on biodiesel
• Engine runs on vegetable oil either with one or two-tank systems. Heated two tank systems are the most reliable and will prolong engine life and reliability compared to blending in one tank.

Cons

• Climate, locking and control systems are vacuum-actuated. Vacuum lines become brittle and crack with age. This causes vacuum leaks and failure of control systems. Vacuum systems can be repaired but troubleshooting and repair is tedious
• Hydraulic suspension on the 300TD wagon tends to fail with age and is expensive to repair or replace. If it fails, the system can be retrofitted to regular shock absorbers. This is the recommended repair method to avoid future expensive repairs.
• Leather seats tend to crack and split with age. The MBTex vinyl is more durable
• Dashes crack with age and wood laminate trim tends to peel
• Parts are expensive. Cars that were not maintained properly can cost thousands of dollars to restore. Your best bet is to learn how to fix the cars yourself. There are many online resources for technical knowledge and inexpensive parts.

Buying Guide

These cars are 30 years old now and many of them were not maintained properly by second and third owners.  If you are mechanically inclined, these are great cars to fix up and run as a primary vehicle.  If you are not mechanically inclined, you will spend thousands of dollars paying a German repair shop to keep one of these running.  Keep that in mind when choosing this as your source of transportation.

Here are a few items to look for:

• Watch out for transmissions that slip in and out of gear.  They will likely need to be rebuilt
• Excessive white, grey or black smoke could be a sign of serious engine issues.  White smoke could mean a blown head gasket, grey smoke could indicate excessive engine wear and black smoke could indicate problems with the fuel injection system.  Proceed carefully and make sure you are familiar with proper diagnosis before buying a vehicle with one of these issues.
• An inoperable Air Conditioning system could be a simple vacuum leak or a more serious problem requiring major component replacement.  Research diagnosis methods online and verify the issue before buying a vehicle with inoperable air conditioning especially if you live in a region where AC is not just a “comfort option” but mandatory.

Preventative Maintenance

1. Change the oil and filter every 5k miles with brand name (Shell Rotella, Chevron Delo, etc.) 15W40 oils and quality filters
2. Change the primary and secondary fuel filters every 30k miles or as needed due to poor fuel quality.
3. Change the auto transmission fluid and filter every 30k miles
4. Invest in a set of wrenches for adjusting valves.  This should be done every 60k miles.  Change the valve cover gasket when adjusting the valves.

In 1986, Mercedes introduced a new diesel engine with an aluminum head.  Aluminum is prone to crack when overheated and these engines were not exempt.  They also had problems with connecting rods in the 3.5 liter diesel engine in the 350SDL. By the early 90s, electronic controls replaced vacuum systems which are prone to failure and expensive to repair like most other contemporary gas and diesel engines.

NOTE: Mercedes has always built extremely reliable diesel vehicles before 1985. Therefore, choosing a diesel vehicle built before 1981 is also a good choice. The 300SD is the most powerful of these cars since it has a turbo. Most other pre-1981 Mercedes diesels are normally aspirated and do not have as much power. However, some will arguer that the non-turbo diesels are a better choice due to a less complicated combustion system.

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My 1970 Mercedes 220D Veggie Car

As part of my “no nonsense” series on bio and alternative fuels, I covered biodiesel and straight vegetable oil (SVO) and waste vegetable oil (WVO) diesel conversions.  Since I believe in experimenting first-hand with topics I discuss, a few years ago, I worked with a local company to convert a restored 1970 Mercedes 220D to run on vegetable oil.  I have had one other veggie car before “Helga” the Mercedes and you can read about the “Veggie Ranger” conversion on Greasology.org.

Restored Vintage Mercedes 220D Diesel

Why did I pick an old Mercedes?

Even though the first diesel engines built by Rudolf Diesel in the late 1800′s ran on plant oils, modern diesel engines are far removed from those first engines.  They use direct injection with high pressure common rail fuel systems with computerized injection and timing.  They use sensors everywhere that expect a fuel that has the same viscosity and cetane rating as diesel fuel.  They are also not very tolerant to water in the fuel

Helga the Veggie Mercedes interior

The 2.2 liter, indirect-injected, mechanical diesel in the Mercedes 220D is much closer to the first diesel engines and is a much more forgiving and tolerant engine for burning alternative fuels.  There are no computers or sensors.  Combustion occurs in a “pre-combustion” chamber off the side of the main cylinder (there are four of them).  This helps prevent carbonization of the piston rings in the cylinders since unspent fuel is carbonized in the pre-combustion chamber instead of in the cylinder.  This is very important for diesel engines that are run on vegetable oil.  It is common for veggie fuel to enter the combustion chamber at lower than optimal temperature which causes the fuel to be sprayed in a less than optimal pattern.  This causes some of the fuel to carbonize on the walls of the combustion chamber.  In modern diesel engines, fuel is injected directly into the cylinder.  Therefore, the carbonization occurs on the head of the piston and eventually on the walls of the cylinders.  This causes carbonization on the piston rings which eventually fouls them causing breakage and a dead engine.

Helga's Converted Engine Bay

There are some sophisticated and well-designed vegetable oil conversions such as the Frybrid and Vegistroke conversions that are designed to perform on modern, direct injection diesel engines but still require a very careful fuel preparation system.  This is a highly debated topic in the Grease Community but my recommendation would be to go with an older indirect injection diesel engine if you want to experiment with veggie fuel.

Helga's Veggie Fuel Tank

How Does the Conversion Work?

Helga has a coolant-heated, two tank system with a looped return.  There are two parallel fuel systems that connect before the injection pump on the supply side and after the injection pump on the return side.  It was designed by Rob del Bueno of Vegenergy Fuel Systems and installed by Dezso Gavaller.  Rob is an experienced resource in the biofuel industry and is the star of the VegMyRide Instructional DVD on converting a diesel vehicle to vegetable oil.  You can order the video direct from Rob if you want a copy (link coming soon).  It includes all of the conversion fuel diagrams including the system installed in Helga.  Here is a brief description of the system:

1. A custom-welded tank with an integrated heat exchanger.  Coolant from the engine is looped through the heat exchanger welded into the tank to heat the vegetable oil.
2. Hose on hose (HOH) fuel lines from the fuel tank to the heated fuel filter. The coolant lines that take engine coolant to and from the engine are wrapped together with the vegetable oil fuel line as it runs from the tank to the fuel filter.  This keeps the fuel heated from the tank to the fuel filter
3. Coolant-heated fuel filter on the vegetable oil side of the fuel system. The head of the filter is a coolant-based heat exchanger that also uses waste heat from the engine to heat the oil coming from the fuel tank.
4. Arctic fox inline coolant-based heat exchanger. This is the last point of heating the fuel before it flows through the valve and into the injection pump.  Coolant that leaves the engine is at its hottest point so it flows first through the arctic fox, then through the fuel filter and then onto the fuel tank through the HOH lines to the tank.
5. Switching valves. One switches the fuel source from diesel to vegetable oil.  The second valve switches between returning diesel to the diesel tank and looping the return back into the fuel supply line.  The loop is used when the system is running on vegetable oil and during the diesel purge process.

How do I Operate the System?

When you first start the engine, the fuel system should be set to diesel and return. (there are two switches)  the engine is cranked and warmed up on diesel fuel.  Once the engine reaches operating temperature, both switches are flipped to the right simultaneously switching the fuel system to veggie and the return to a looped return.  You can now drive on veggie until you’re approaching your destination or you start to run out of vegetable oil.  When you are a few minutes from your destination, you need to begin the diesel purge process.  Flip the fuel selection switch back to diesel but leave the return switch on looped return.  Diesel enters the fuel system and return loop diluting the vegetable oil until it is almost completely diesel fuel.  This is usually about 1-2 minutes in Helga when driving on the highway at 65mph.  Once the system is purged, the return switch is flipped back to diesel return.

Helga's Veggie System Control - diesel/veg on left, return on the right

Pro’s and Con’s?

My overall experience with this car was positive.  However, I was very meticulous in doing research on the right vehicle, picking a well-designed conversion and performing proper filtration and dewatering of the fuel.

Pro’s

• Once I had the operating procedure down, the system was easy to operate.
• I used approximately 90% vegetable oil fuel on my 80 mile daily commute to and from work.
• I didn’t have any vegetable-oil related problems with the vehicle or fuel system during the year and a half that I used Helga as a daily commuter
• I only replaced the veggie filter one time during the time I owned her.
• The exhaust smells like french fries.
• There is no particulate in the exhaust so it doesn’t bother folks with breathing issues like asthma.

Con’s

• The conversion cost around $1700 installed.
• Fuel acquisition from restaurants is competitive, time consuming and messy
• Fuel preparation is messy and time consuming
• Most diesel mechanics won’t work on your veggie car or truck

Overall, I enjoyed running my two veggie vehicles and didn’t have any issues with the conversions or driveability.  However, they were well-designed and I took the proper precautions and procedures when preparing the vegetable oil for use.  I also perform most of my own vehicle maintenance and would consider myself an advanced “shade tree” mechanic.  I would not recommend veggie cars to someone that is not mechanically-inclined unless you find an installer that will provide all of your vehicle maintenance for you.

For more information on using vegetable oil as a diesel fuel, see the following “NotPetroleum-approved” internet sources:

Greasology.org

InfoPop SVO forum

Frybrid Forum

Vegistroke site

If you’re interested in doing your own vegetable conversion, here’s a great instructional video that steps you through converting a vintage Mercedes to Vegetable Oil.