Why Some US Toyota Owners Are Swapping Their Engines For a Mercedes Diesel

Mercedes OM617 diesel engine after installation in a 1989 Toyota 4runner.

Why Some US Toyota Owners Are Swapping Their Engines For a Mercedes Diesel

While the number of shade-tree mechanics in the USA may be dwindling rapidly due to the increasing complexity of the modern automobile, there are still quite a few vehicle owners who like to tinker with their cars. In the United States, some of the more sophisticated tinkerers are replacing the gasoline engines in their older Toyotas with a used Mercedes diesel engine. Here’s why it’s happening, and what anyone thinking about making this kind of swap needs to think about.

Why Swap a Gas Motor for A Diesel?

Toyota is well-known in the United States for quality and reliability, and an older Toyota gasoline engine is no different. Even if an older engine breaks down, there are plenty of older OEM Toyota parts available online, so there’s really no reason to swap a gas for a diesel as far as reliability is concerned. In fact, we have to look off-road to find the answer.

The late 80′s and early 90′s Toyota 4Runner and Toyota Tacoma are incredibly popular off-road vehicles in North America, mostly because of their world-class reliability combined with their factory-tough off-road ability. Yet the weak-point of these older 4Runners and Tacomas is that their relatively small 4 cylinder gas engines lack low-end torque.

For this reason, many older 4Runner and Tacoma owners are swapping their Toyota gas engines for 4 or 5 cylinder diesels from the Mercedes 240D and Mercedes 300D. The engine from the 300D – also known as part of the OM617 Mercedes diesel family – is particularly desirable because it can often be found with a turbocharger. However, any older Mercedes diesel will offer more of the low-end torque that off-road enthusiasts favor than the stock Toyota gasoline engines.

Another popular reason that people swap out Toyota gasoline engines for Mercedes diesels has to do with a desire to be “green,” or environmentally friendly. Older Mercedes diesels can be configured to run on bio-diesel (there are quite a few commercial kits available), and running on bio-diesel is something that is very important to many vehicle owners.

Finally, older Mercedes diesel engines are well-known for reliability (500k+ kilometers of use isn’t unheard of) and they’re fairly inexpensive in the US. A used Mercedes 300D or 240D with 200k kilometers of use can be purchased for as little $500 US, and then the diesel engine can be harvested while the rest of the vehicle is sold for spare parts.

Mercedes OM617 diesel engine after installation in a 1989 Toyota 4runner.

 

What’s Involved In A Mercedes Diesel -Toyota Truck Engine Swap?

The short answer is, a lot more work than one might think. First, you have to think about how the engine is going to mount to the engine bay as well as how it will attach to the transmission and/or how you’ll make the Mercedes transmission attach to the Toyota transfer case.

Next, you’ll need to think about connecting Toyota’s engine management systems (everything from throttle cables to oil pressure sensors) to the MB diesel. Making fuel and cooling systems work together can be a challenge too, many Toyota owners elect to use as much of the stock Mercedes diesel engine system as possible to minimize complexity.

Finally, you’ll need lots of time to adapt the MB diesel to work around it’s new home. The bell housing and oil pan usually need to be modified to work within the constraints of the suspension system and frame mounts, for example.

However, despite all the effort required to make this swap, the rewards can be excellent. An early 80′s OM617 turbo-diesel has much more low-end power than a 1990 Toyota 22R – 180 lb-ft at 2400 RPM vs. 187 lb-ft at 3,400 RPM – and that steeper torque curve makes a big difference off-road. Add in the incredible reliability of the Mercedes diesel and the uniqueness of the swap, and Toyota truck owners who take the time to make the swap have something they can be very proud of.

About The Author: Jason Lancaster works with ToyotaPartsCenter.net, a website dedicated to providing cheap Toyota parts online.
Photo: Courtesy of “defiant4wd’s” PhotoBucket album.

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