Shop Tour: American Diesel in Southern California


The heart and soul of the diesel market lies about 1,500 miles away our offices. Being located out of Southern California, we don’t have the most diesel-friendly population in the land, so it’s cool to find a local shop like American Diesel (AD) just up the road and learn just how active the culture is – despite the opposition from our soft-headed representatives in Sacramento.


Magnets on the tool chests add quite a bit of character to AD.

As with all vehicles, diesels circulate through AD for a variety of reasons, whether the work involves upgrades or repairs. It’s one thing to banter and bicker about the differences of the various diesel platforms on the Internet; it’s another thing to actually see with our own eyes how differently these engines function in the real world, and accept them for their strengths and limitations. To put it another way, manufacturers and commenters can boast all day long about their brand, but sooner or later, they all wind up at a place like AD for service.

Our recent tour of the shop gave us an inside look at the lively and varied usage of diesels amidst the Inland Empire, as we counted 10 different vehicles being serviced while we were there. From consumer-grade drivers to construction workers to contractors, customers have found all sorts of uses for their Ford, GM, and Mopar trucks, and AD has the skills, resources, and passion to keep them chugging along for miles to come.

Sitting down with Robert “Junior” Schuman, we were given the full scope of what American Diesel is, both as a business and as a place of restoration. All of the customers’ trucks have stopped working, but their time is not up yet if AD has anything to say about it.



The whiteboard in the break room reminds everyone to stay involved in shop cleanliness.

How long has American Diesel been around?

IMG_7894Robert Schuman: My dad and I started this company back in 2006, so about 10 years ago. I’ve been here since day one. We used to be a mobile service with a service truck, and then our first actual shop was about 1,250 square feet. I started out as a minor tech in the back, doing brakes and oil changes, and moved on to engine overhauls within a couple of years. Over the years, I’ve done the Big Three numerous times, and gotten into working on Caterpillar, Kenworth, and Peterbilts too.

We’ve been in this current building going on 2½ years, and it’s our third shop. It’s 10,000 square feet with nine employees. Most of our work goes toward regular trucks like Duramaxes and Power Strokes, but on rare occasions we will take on a tractor-trailer, too.

IMG_7783 What is the full list of services that AD can perform?

RS: We can do anything – brakes, oil changes, transmissions, differentials. The good way to put it is we do anything but tires and paint and body. We’ll do some mild fabrication stuff because every truck out there has something you have to fabricate, whether it’s bracketry for fuel pumps or gussets for tubing or something. We’re always fabbing something, especially when it comes to exhaust work.

The shop seems incredibly busy. How many trucks, would you say, come in here on a monthly basis?

RS: On average, we have 40 to 50 trucks in some stage of rebuild or restoration here in the shop. Lately, our scheduling has been able to stay about a week out on work coming in. We do get the emergency stuff that gets towed in. We try to throw that into the mix of everything that’s been scheduled.


What does the typical customer need done to his vehicle?

IMG_7787RS: We have plenty of standard jobs like replacing injectors and springs, and that affects all the American diesel mills we see. We do a lot of transmission services and head gasket jobs on the 6.0-liter Power Strokes, and head gasket or rocker issues on the 6.4-liter Power Strokes. I’ve got three head gasket jobs lined up for 6.7-liter Cummins motors. We do gas cars, too. Timing belts, oil, brakes, all that stuff. We do a variety of everything

What is AD looking to do in 2016? What are some initiatives?

RS: One big thing right now is a 7.3-liter Power Stroke motor that we’re going to use for drag racing. We have hopes to make it generate over 1,500 horsepower and 2,000 pound-feet of torque. It will go into a 1994 F-250 and be used to smash the competition at diesel drag racing events here in California and elsewhere, and we’d like to get it entered into the Diesel Power Challenge next year. Business-wise, I think we’re doing great right now. I just want to keep the momentum going, keep the flow to where it’s manageable. And we want to stay on top of the latest developments in the diesel market.

IMG_7788 Interesting. So, do you have thoughts on the current and future developments in the diesel market?

RS: The Cummins Titan makes me curious and a little worried, too. Everyone thinks that they’re going to have the same power as they would in a three-quarter or one-ton truck. Putting that much power and torque in a motor and sticking it in a half-ton is going to make people overconfident, especially where the brakes are concerned. Those brakes and that frame, in a heavy-duty towing situation, just aren’t going to pass muster. I think people are going to have some serious accidents. I mean, we’re doing big-time upgrades to trucks already designed to tow 10/15/20,000 pounds, and here’s this Titan that is probably rated to tow 5,000 to 6,000 pounds – it will lead to trouble.

On the flipside, there’s the EcoDiesel. It seems to be a great little motor. I haven’t really seen a lot of them so far, just a couple of oil changes and preventative maintenance. The few guys that are coming out with performance modifications show that the EcoDiesel has real potential.

GM has the 2.8-liter Duramax. It’s a Duramax, it’s an Isuzu …


Not a big fan of Duramaxes?

RS: I hate them. I despise them. I work on them all the time. There are a lot of things that I see that make me want to smack the engineering team, because it just doesn’t make sense. They make decent horsepower up until you get to the 500 mark, they run the common rail system which is a good system because, you know, Ford and Ram switched over to it. They seem to work real well, but in my opinion, they’re aggravating. For example, to pull out a turbocharger on a Chevy 3500, it takes close to 20 hours. You have to remove the transmission and front suspension; I mean, the amount of work that has to go into it is just ridiculous. Compare that to a 6.0-liter Power Stroke which, in the same amount of time, I can have out of the truck, torn down, and ready to go back together for a head gasket repair.

The Shop


If talking with Schuman was intriguing and eye-opening, it was something else to walk out into the shop and see it packed to the brim with trucks of all makes in assorted states. We took a walk around the floor and got the story on a few of them.


This late model Ram 2500 was in the shop for excessive boost readings.

First up was a 2010 (or newer) Ram 2500, which had mods aplenty for use as an off-roader. AD did much of the performance-related work, including twin fuel injection pumps, a FAST fuel system, a compound turbo setup, ARP studs, valve springs, injector nozzles, gauges, intercooler and piping – all of this was done in a matter of three to four weeks.

The truck was in the shop to have its head removed, possibly addressing a head gasket issue that the owner had been noticing. One of AD’s technicians, Harley, stated that it was pushing 78 pounds of boost, where it should have been in between 10-20 pounds.


The 1996 F-250 “Project Resto-Truck” had a crack in the front cover on the engine.

Next was a 1996 F-250, affectionally called “Project Resto-Truck.” As Schuman told us, it belonged to a customer who had been meticulously restoring the truck in his garage for the past two years. “Every bolt, every bushing, everything’s been replaced from front to back and top to bottom,” said Schuman. The rebuilt 7.3-liter Power Stroke, despite looking very clean, had over 300,000 miles on it and had recently cracked its front cover, causing coolant to gush out and onto the ground.

AD was tasked with replacing the front cover while also maintaining its near-factory-fresh theme. “It’s very rare for me to see a 7.3 do this,” commented Schuman. “I’ve only seen one other 7.3 do this, in fact. Normally, these motors are incredibly strong and powerful. This guy just had a dose of bad luck.”


A water-sprayer truck lost the use of its reverse gear. Its transmission was sent out for service.

A water-sprayer truck was also in for some tinkering. It had been used at a local material yard recently and was unable to go into reverse. The AD crew had removed the transmission from the truck and sent it to a nearby transmission center for inspection.

“While we have that out, we’re going to remove the clutch and resurface the flywheel,” said Schuman. “We don’t know the exact cause of the reverse failure, since it can be set off by slamming the shifter into reverse, letting the clutch out without fully disengaging the gear, there are a lot of different variables.”

Closing Thoughts


In our short time traipsing through American Diesel, we were quite impressed with the level of activity and attention we got to see. This was a group of guys that had the passion and drive to keep diesel trucks happy and healthy.

IMG_7870“What we’re about, we’re here for the customer, whatever they want to do,” said Junior. “Our motto is, ‘I’ll never sell you anything you don’t need, but I’ll sell you anything you want.’ We’re not here to gouge anybody. When someone comes in and wants to make more power, I’m not going to sit there and sell them a compound turbo system or 100hp injectors. In everything we do, we try to match what the customer uses their vehicles for.”

It’s a hearty sentiment to adhere to, and one that puts the customer first – definitely a good sign for any business. Find out more about AD on its website, and stay tuned to Diesel Army for more news, videos, and other hard-hitting diesel content.


About the author

David Chick

David Chick comes to us ready for adventure. With passions that span clean and fast Corvettes all the way to down and dirty off-road vehicles (just ask him about his dream Jurassic Park Explorer), David's eclectic tastes lend well to his multiple automotive writing passions.
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