Mercedes MBE 900 Diesel Engine - Changing Thermostats

MBE 900 Diesel Engine Specs:

Configuration: inline 6

Displacement: 7.2 Liters
(439 cu in)

Bore: 4.17 in (106 mm)

Stroke: 5.35 in (136 mm)

Weight: 1,362 lbs (618 kg)

Electronics: DDEC® VI

Compression Ratio: 18:1

The local Mercedes dealer recommended to replace thermostats and coolant every two years on the MBE 900. Coolant breaks down over time and becomes acidic chowing down on gaskets and engine parts. On a conventional and pusher bus this is an easy operation. Three bolts and upper rad hose is all it takes to get to the thermostats.

The two thermostats come with a split o-ring that fits around the edge of the stat and nestles nicely into the bore of the thermostat housing. Below is a short video of a Mercedes MBE 900 diesel engine idling in a pusher bus. These engines come with  EGR and DPF (Diesel Particulate Filter) systems to control emissions. Check out how the emissions are controlled using these components Right Here.

Diesel Engine Mechanic Tips

Here are some diesel engine mechanic tips I've learned over the years. I want to keep them basic so anyone can follow them. Keeping things simple and following these tips will pay off in the long run. If you are thinking you don't have time just think about the consequences if you neglect these basic areas on your diesel engine.

1. Always keep the intake air clean with proper filtration and check the inlet piping and hoses for deterioration.
   
2. Make sure fuel filters are replaced consistently according to manufacturer's specs. (probably the most overlooked mechanical solution)
   
3. Adjust the engine valves at least once a year or depending on how much mileage accumulated.
   
4. Check the coolant for proper protection and replace every 2 years to prevent deterioration. Coolant breaks down and becomes acidic eating away at gaskets and castings.
   
5. Check turbocharger and exhaust system for leaks to prevent power loss. Check the turbo shaft for wear or any indication of contact with the housing.
   
6. Make sure charge air cooler does not have any leaks to prevent power loss. Turbo boost drops substantially with any core leakage in the cooler.
   
7. Check fuel lines for looseness or damage to prevent air entering the fuel system. Air in the fuel causes hard start & no power problems.
   
8. Replace coolant thermostats every 2 years. A thermostat that is stuck open or closed causes overheating or cold running conditions.
9. Load test your batteries every fall to give you an indication of their state of charge. Being prepared before winter starts is a good habit to get into.
10. Check your block heater as well, which goes without saying how vital it can be when you are on the road and parked far away from any mechanical assistance.
    

I hope these basic Mechanic Information Tips have helped you. I have seen a lot of preventable break downs because one or more of these checks have not been made. It's preventive maintenance that should be followed to save you headaches down the road.

Thomas HDX Pusher Radiator Modification

In 2 of our new Thomas HDX Pushers we had rocks go through the radiator core. This was caused by an opening at the side facing the right rear dual wheels. Here the repair has been made by the rad repair shop using epoxy. The radiator has an aluminum core with plastic tanks.
[click picture to enlarge]




All that has to be done is to bend a piece of sheet metal to ninety degrees and use a 2 foot square mudflap strategically placed in front of the radiator.







Mount the sheet metal to the bus body with sheet metal screws and position the mudflap as low as possible for better protection.




















So far we've had no more incidents and hopefully this modification will fix the problem. It's a good days work to re and re the radiator so anything to improve the situation and avoid another core failure is well worth a try.

Advantages of LPG and CNG in Diesel Engines

The vast majority of diesel engines in service today use solid injection and the information below relates to that system. In the diesel engine, only air is introduced into the combustion chamber.

The air is then compressed to about 600 pounds per square inch (psi), compared to about 200 psi in the gasoline engine. This high compression heats the air to about 1000 degrees Fahrenheit. At this moment, fuel is injected directly into the compressed air.

The fuel is ignited by the heat, causing a rapid expansion of gases that drive the piston downward, supplying power to the crankshaft. In Diesel's manuals, he described the supply of compressed gas into the cylinder to promote the final burn. It is now possible to fumigate the air intake with a small quantity of LPG/CNG.

The now air-gas mixture is compressed as above, and when the diesel ignites, the small quantity of gas ignites as well, causing a more rapid and more complete burn of the diesel. Most diesel engines waste between 30 and 15% of the diesel fuel, so by burning the near total amount of diesel consumed on each stroke, the mechanical effect is to improve the torque curve by as much as 28%.

The net outcome of applying gas into diesel is improved fuel economy via better torque at the driving wheels resulting in fewer gear changes, and greatly reduced exhaust emissions.

Advantages of the diesel engine are numerous. It burns considerably less fuel than a gasoline engine performing the same work. It has no ignition system to attend to. It can deliver much more of its rated horsepower on a continuous basis than can a gasoline engine. The life of a diesel engine is generally longer than a gasoline engine. Although diesel fuel will burn in open air, it will not explode unless compressed.

Some disadvantages to diesel engines are that they are very heavy for the horsepower they produce due to the required heavy design, and their initial cost is much higher than a comparable gasoline engine.

Recommended: Diesel Engine Repair Manuals

Diesel Coolant-What Color Should You Use?

Diesel Coolant has changed over the years and the most apparent difference is the various diesel coolant colors available on the market, there's green, red, purple, blue, orange etc. So what do all these colors signify?

In my part of the country the authority on coolant is a company called Recochem who manufacturers coolant, this is what they have to say.

Both packaged and bulk heavy duty diesel engine coolants will be transitioned from green to purple by June 1, 2007. The change of color will not affect the performance of the coolant. Green and purple coolants can be mixed and will perform to specs.

Four Types Of Diesel Coolant Are Described below:

• Green coolant [Ethylene Glycol] needs to be pre-charged with DCA4 & tested regularily with proper test strips provided by Fleetguard.
• Purple & Pink [Ethylene Glycol] coolant is a conventional heavy duty fluid that is already precharged to specs. no treatment is required.
• Blue colored coolant is a Propylene Glycol that is the equivalent of the purple and pink mixture.
• Red has Organic Acid Technology and meets one or more of the OEM [original equipment manufacturer] specs. for International, Caterpillar, Detroit and Mack diesel engines.

Labeling close to the coolant fill tank is advisable so mixing doesn't occur with the acception of the green and purple diesel coolant.