Two Decades Ago, Ford Killed Its Legendary 7.3 Power Stroke And Replaced It With An Engine People Still Hate Today

In 2003 Ford began phasing out one of the greatest truck engines of all time. The 7.3-liter Power Stroke served as a reliable workhorse for years, but now it was time for truck buyers to get more power and cleaner emissions. The 6.0-liter Power Stroke launched that year and punched out more power, but also started to punch out wallets with expensive problems. What could have been a beloved follow-up is still hated by many today, and used truck prices reflect it. But was the 6.0-liter Power Stroke really that bad? Let’s take a look.

Diesel truck fans have a list of engines often considered to be the greatest of all time. We aren’t talking about just one brand, either. Fans of Ford, Chevrolet, and Dodge all have their faves, and that’s not even getting into the mills from outside of America.

Proponents of Dodge still love the 5.9-liter Cummins 12-valve straight-six turbodiesel and the fact that these engines will probably continue to work after the heat death of the universe. The folks in love with the General dig the 6.6-liter Duramax LBZ turbodiesel V8 for its ability to produce truckloads of power without the complications brought on by modern emissions systems. People are still paying near-new prices for these trucks even though it’s been nearly two decades since they were in production.

If you’re loyal to the Blue Oval, the Navistar/Ford 7.3-liter Power Stroke is a legendary engine. It’s been over two decades since the last 7.3 was built, yet enthusiasts continue to pay tens of thousands to own an example of one of greatest diesel engines of all time. Sure, a stock 7.3-liter doesn’t make a ton of power compared to today’s trucks, but these are engines that can last longer than the metal bodies in which they’re packaged.

Such status has escaped its successor, the 6.0-liter Power Stroke.

In theory, the 6.0 had the right ingredients to rise to stardom. The new engine had to comply with stricter emissions, but it still made more power out of the factory than its predecessor. Unfortunately, the 6.0 Power Stroke would encounter a long list of issues and give tuners even larger headaches. The 6.0 carries such a reputation today that it’s sometimes called the “6.Blow” and you can sometimes find newer trucks with the 6.0 selling for cheaper than an older truck with a 7.3.

But how did things get this way?

A Great Start

To get an understanding of why enthusiasts were so disappointed in the 6.0, let’s look at what came before.

The Ford 7.3-liter Power Stroke started life with a different company and with a different name. Our readers with experience in heavier trucking are familiar with the Power Stroke as the Navistar T444E. These engines served as the backbones of fleets for decades. If you were a driver in the 1990s or, heck, even today, there’s a chance your streets were plowed by a truck with one of these engines. If you were a kid like I was, you started each day with the familiar clackety sound of a DT466E or a T444E in the yellow school bus that picked you up. T444Es found homes in everything from box trucks to garbage vehicles.

Navistar used to be known as International Harvester, and the company’s history is filled to the brim with machines built for work. International Harvester’s roots were in the 1800s with reapers, but the company helped change farming in only 1905 with its first tractor. The famous Farmall tractor would come later in 1924. International Harvester’s colorful history includes feats such as the Cub Cadet lawn tractor, as well as light duty on-road vehicles like the Travelall, the Travelette, and the Scout.

International Harvester’s impact on diesel started in 1932 with the impressive McCormick-Deering TD-40 TracTracTor crawler tractor. The 461 cubic inch four-cylinder engine in this beast got around the problem of cold diesel hard-starting by first slurping up gasoline before switching to diesel.

International Harvester was even one of the first American companies to put a diesel engine in a light-duty pickup truck. 1963 through 1968 model year C-1100 to C-1300 IH trucks could be had with diesel power, making them what some call America’s first factory-built diesel-powered light-duty trucks.

In the early 1980s, right around when the International Harvester name departed from light-duty on-road vehicles, Ford embarked on a journey for a new kind of diesel truck. The diesels of the era were not like the powerful trucks of today, but engines that got better fuel economy than their gasoline counterparts. In at least one case, going diesel even meant giving up on power. Ford felt there had to be a better way. The Blue Oval believed it was possible for diesel engines to evolve from thrifty powerplants to ones that delivered a kind of capability, durability, and power never seen before.

At the same time, International Harvester was looking to build a diesel engine for an automaker with a lineup of pickup trucks. General Motors was already married to Detroit Diesel, but Ford turned out to be a great marriage partner. Ford wanted power and International Harvester wanted to deliver.

First came the indirect injection diesel engine, but trucks in the 1994.5 model year and beyond got something special: the mighty 7.3, which brought direct injection, computer control, and more. From my retrospective:

One key component to the 7.3-liter Power Stroke and the Navistar T444E is the HEUI system, which stands for Hydraulically Activated, Electronically Controlled Unit Injector. It’s a complicated computerized system that uses pressurized oil to fire the engine’s injectors. HEUI technology made its debut in 1993 by Caterpillar and Navistar teamed up with the former to provide the technology to the T444E, Power Stroke, and another famous engine, the Navistar DT466E straight-six turbodiesel.

A lot is going on in the HEUI system, so I’ll try to simplify it. A low-pressure lift pump sends 40 to 70 psi of fuel to the injectors in early Power Strokes. Later 7.3s send 60 to 65 psi of fuel. The powertrain control module commands an injection event and the injector driver module triggers the injector solenoids. When this happens, the solenoid pulls an internal poppet valve off of its seat, allowing high-pressure oil into the injector. That oil comes courtesy of a high-pressure oil circuit charged by the high-pressure oil pump. The HPOP sends high-pressure oil into the injectors, which forces a piston in the injector down, lifting a nozzle. This pressurizes the fuel in the injector. The nozzle then opens and 3,000 psi of fuel pressure multiplies to 21,000 psi of fuel pressure in the cylinder.

All of this happens with computer and electronic control, allowing for the control of injection events independent of what the crankshaft is doing. HEUI is able to provide peak pressures under a variety of conditions, helping to keep power up, fuel consumption down, and emissions down as well. Some quirks come with HEUI, such as the fact that you technically cannot run it out of oil. The system requires a minimum amount of oil. A 7.3-liter Power Stroke holds some 15 quarts of oil. Once you run it below 7 quarts or so, the HEUI system just won’t have enough oil to permit an engine start.

HEUI joins forces with six head bolts per cylinder, a Garrett turbocharger, forged connecting rods, and a fluid-to-fluid oil cooler to provide high performance and a lifespan that could outlive you. Later examples of the 7.3 got a wastegate for the turbo and an air-to-air intercooler. There was also a brief moment between 2001 and 2003 when powdered metal con-rods were used.

As I said earlier, the 7.3-liter Power Stroke is known for relative bulletproof reliability in stock form. Tuners have also found the engine to be receptive to taking on more power, too.

A New Engine

Unfortunately, the 7.3 was built for a different era.

By the early 2000s, diesel engines were ramping up in power, leaving the old reliable Navistar engine in the dust. GM truck buyers got to enjoy 300 HP and 520 lb-ft of torque from a 6.6-liter Duramax LB7 V8. Meanwhile, Ram buyers got a 5.9-liter Cummins straight-six with 305 HP and 555 lb-ft of torque. Ford buyers? Well, the best they got from a stock 7.3 was 275 HP and 525 lb-ft of torque, assuming a manual transmission. Power fell to 250 HP with an automatic.

Times were also changing. As Motor Trend notes, regulations for 2003 would have required Ford to equip the aging mill with exhaust gas recirculation, which would have put the 7.3 even further behind the competition. Navistar and Ford decided that the best way forward was to build an all-new engine with the power to compete and the emissions to keep the feds happy.

The International Truck and Engine Corp. decided to take a high-tech approach with this new engine. As Fleet Owner reported in 2002, several improvements were implemented:

The key to the VT 365’s increased performance, despite tighter emission controls, rests on several components. First is the Electronic Variable Response Turbocharger (EVRT), which provides improved throttle response and peak torque capability at lower rpm levels. Second, it is equipped with Electro-Hydraulic Generation Two (G2) fuel injection technology, which is based on a low-pressure common rail fuel system. Finally, Intuitive Shift controllers allow for smoother driving to compensate for the use of cooled Exhaust Gas Recirculation (EGR) technology, which cuts oxides of nitrogen (NOx) emissions.

“The VT 365 has four valves per engine cylinder, compared to two valves per cylinder in the T-444E. That gives the VT 365 better air-flow capability, which translates into better acceleration for drivers especially in stop-and-go environments,” says Mark Wildman, International’s field service manager.

The G2 fuel system uses high-pressure injectors developed jointly by International, Sturman Industries and Siemens Diesel Systems Technology to more efficiently manage fuel consumption. Higher injection pressure combined with four valves per cylinder increases performance and fuel economy while lowering emissions.

But that wasn’t all, as the 6.0 iron block V8 was physically a different engine. The 6.0 featured an oil cooler and high-pressure oil pump integrated into the block, helping the engine earn a more compact size than the outgoing 7.3-liter engine. Navistar’s continued changes by relocating the gear train to the rear of the engine and reinforcing for the bottom end. The crankshaft main and rod bearing surfaces were treated to an induction-hardening process and the crankshaft itself was held in place with a plate.

Powdered-metal connecting rods also made a return in the 6.0. These rods were panned during their short life in the 7.3, but they found a good home in the 6.0 engine. As DrivingLine explains, the 7.3’s engine revved low and submitted a lot of torque to the rods. The 6.0 revs more and the rods live an easier life. Reportedly, the rods in the 6.0 are known for durability.

International called this engine the VT365, and it was sold with horsepower ratings as low as 175 HP to as high as 230 HP. Torque peaked at 620 lb.-ft. Ford’s application of this engine (which could be found in lots of other machines) was called the 6.0 Power Stroke, and it went even further, hitting 325 HP and 560 lb-ft of torque in 2004 model year Super Duty trucks.

On paper, this engine was great. It put Ford back into the diesel truck power wars, and its EGR system satisfied emissions regulations. The variable geometry turbo was also great, allowing for hard power early on and throughout the powerband. Unfortunately, problems started getting reported in 2003 while these engines were still new.

What Went Wrong

There are a number of issues that plagued the 6.0 engine during parts of its life. Thankfully, time heals a lot of wounds, and there are now solutions to the engine’s infamous issues.

Perhaps the biggest problem with the 6.0 and the VT 365 comes from the engine’s torque-to-yield head bolts. The bolts are a sizable 14mm, but there are only four bolts per cylinder, compared to the six bolts per cylinder found in the 7.3. Unfortunately, the cylinder pressure under the head is a lot, and has been found to stretch the stock bolts, leading to an eventual blown head gasket. Reportedly, this happens most often with modified engines, but has happened with stock engines as well.

As I said before, there is a fix for this, and it’s tossing the factory head bolts in the trash and replacing them with stronger studs (above), hopefully putting blown gaskets in your rearview mirror.

While blown gaskets are an infamous problem with the 6.0, it’s not the only source of headaches. The oil cooler is another problem child. It’s located at the front of the lifter valley and integrated into the block itself. This cooler is a critical component because it cools the oil that runs the high-pressure oil pump, the oil that runs the injectors, the oil that cools the turbocharger, the oil lubricating the engine, and the oil cooling the EGR cooler. That’s a lot of important parts that depend on the oil cooler.

Sadly, the 6.0’s oil cooler is known for plugging up, which has a cascading effect of allowing the oil in all impacted components to reach dangerous levels. The resulting temps can kill expensive components and cause a catastrophic failure. DrivingLine notes that around 90 percent of 6.0 EGR cooler failures start with a plugged oil cooler. The remedy to this problem is installing a coolant circuit filtration system, which should catch nasty particles before they plug the oil cooler.

Still, if you’re unlucky, you may find yourself replacing the high-pressure oil pump. Or more. This is a big deal because you need high-pressure oil to activate the fuel injectors (per Ford: “The 6.0L Power Stroke Diesel Engine utilizes a hydraulic injection system where high pressure engine oil is used to compress diesel fuel. The fuel injector is used to precisely control the delivery of the fuel into the combustion chamber”). Unfortunately, the HPOP is located at the back of the engine under a cover and the turbo. The cab covers much of the engine, but an HPOP replacement can happen without removing the cab. It’s just a task that can take a backyard wrencher several hours.

Since we’re talking about oil, let’s look at the injectors. Oil pressurized as high as 3,600 PSI enters the injector through an electronically-actuated spool valve. The oil-actuated injector fires fuel into the cylinder at 26,000 PSI, 5,000 PSI better than the outgoing 7.3 engine. There are a lot of parts that can fail related to the injectors. You need low-pressure diesel fuel, a 48-volt, 20-amp coil to operate the spool valve, and high-pressure oil that hopefully isn’t blazing hot. Screw one or more of these up, and the injector can fail.

Somehow, we’re still not done with issues yet. Next, we have the fuel injection control module (FICM), the computer responsible for opening and closing the spool valves and thus, getting fuel to the cylinders. This module is the one sending 48-volt pulses to the coils and while its lower than the 100 to 120 volts utilized by the 7.3, any low-voltage problems with the truck could cause running issues. Additionally, the FICM itself is known for eventually failing.

All of this sounds scary, but for some people it’s worth it. In 2020, I owned a Ford E-350 van with a 6.0-liter Power Stroke.

It had 287,000 miles on its odometer and came with a stack of service paperwork. Big ticket items included four injectors replaced before I bought the van and a turbo perhaps 50,000 miles before that. Oh yeah, that’s another problem I didn’t note. The Garrett GT3782VA turbo in these engines sometimes got gunked up with corrosion and carbon, leading to sticking. Some mechanics remove the cab from above the 6.0 engine to make replacing the turbo and heads easier. Lack of easy access is another downside to these trucks.

Yet, my van, which was stock, still drove on its original head gaskets and even still had its emissions equipment intact. It got 18 mpg with me behind the wheel — good compared to my friend with a stock 7.3 Power Stroke that got 13 mpg on a good day. Sadly, the van was detuned compared to Super Duty trucks and made 235 HP and 440 lb-ft of torque. But it still made that glorious diesel soundtrack so I didn’t care one bit.

I then drove the van thousands of miles without issue before a team of drug enthusiasts took it upon themselves to turn my van into a “science lab.”

Does The 6.0 Engine Still Suck?

I mentioned some “bulletproofing” tactics above, but there are others. Some owners replace the variable geometry turbo with a fixed geometry turbo, conduct more frequent flushing of the oil cooling system, and clean the EGR system.

Some believe that a 6.0 can be a reasonably reliable engine if it’s left stock and you’re anal with your maintenance. This is a departure from the 7.3, which can seemingly take all kinds of abuse all day every day. But, if you’re the kind of person who drives a stock truck, you may not get burned by a 6.0. It sounds like bulletproofing is a must if you want to send power to the heavens. Either way, it doesn’t hurt to spend some extra cash to zap known issues.

So, is the 6.0 a bad engine? It seemed like it was when it was new. Today? I suppose that depends on who you ask. Some still despise the engine. I was one of the people who wasn’t burned by this engine, but then again I didn’t own it for long and it was detuned in a van. Other people may not be so happy with their experience. It may not be the engine for you if you want to beat the daylights out of the truck or want to put down 700 HP at the wheels without some extensive work. Some searching of the web shows you can get newer 6.0-equipped trucks for a similar price to older 7.3s with more miles.

There is good evidence in favor of the 6.0 being a bad engine. In addition to the failures, and I didn’t even list all of them, Ford was sued over the engine’s problems. As USA Today reported, Ford knew something was wrong:

Ford initially denied a problem existed, then claimed there was insufficient evidence to prove the claim and finally maintained the company wasn’t aware of the extent of the diesel engine problem. Internal emails written by upper level management shattered the Ford defense.

One email presented during trial was dated five months before Margeson purchased his truck. John Koszewnik, Ford’s North American diesel division director, wrote on Feb. 5, 2006, that warranty repairs on the 6.0L engine were running “as high as $5 million a month” and added Ford would not invest in an engine upgrade. Two hours later, according to court records, Koszewnik warned people not to forward his email.

Mike Frommann, the Ford warranty manager, emailed his colleagues warning that the diesel engine could lead to a class action lawsuit if its cylinder pressure specifications went public. He wrote in an email to colleagues dated July 13, 2006, “I recommend we delete all these emails.”

But it got even worse, from USA Today:

By February 2007, warranty repair costs on the engine exceeded $400 million, including more than $227 million to fix fuel injectors and more than $182 million on turbochargers, which was the largest repair rate ever seen for any Ford engine. This information was taken from an affidavit by one of Ford’s own officials in a lawsuit it filed against Navistar. Despite this testimony, Ford later denied engine problems when it was being sued over the Navistar engine.

The appeals court affirmed there was “adequate evidence of intentional concealment of these problems by Ford to the detriment of consumers.”

The article goes on to note that Ford was not only sued in a class action, but six individual owners sued as well. Charles Brian Margeson was awarded $214,537.34 plus legal fees while five others collectively won $10 million against Ford.

In terms of sales, I could not find data that breaks the Power Stroke off on its own, but Ford continued to sell nearly a million F-Series trucks a year through the Power Stroke’s run of 2003 to 2007 in trucks and through 2010 in vans. While the engines were problematic, it seemed people just kept buying them, anyway.

I suspect that the 6.0 Power Stroke will continue to be passed on by enthusiasts as the years go by. The 7.3 Power Stroke can still be found in plentiful numbers while Ford’s newer Power Strokes are known for better reliability. I mean, I got to haul 40,000 pounds with a 6.7 Power Stroke last year, something a stock 6.0 could only dream about. If you’ve owned a 6.0-liter Power Stroke, I want to hear more. Did it treat you well? Or did you want to sue Ford over its issues?

Images: Manufacturers, unless otherwise noted.
Top graphic fireball: Jag_cz/stock.adobe.com