6.0L Power Stroke Problems, Part 2: EGR

• February 11, 2021
• Story By
  Mike McGlothlin

While some of you might’ve been surprised at our listing the oil cooler as the 6.0L Power Stroke’s biggest problem in Part 1, none of you will be surprised with its runner-up issue: the exhaust gas recirculation (EGR) system. From a stuck EGR valve to a plugged or leaking EGR cooler to overtaxed engine coolant, the 6.0L is a hot mess in terms of its NOx-fighting components. Like a lot of things with the 6.0L Power Stroke, many EGR-related issues can be avoided with proper (and frequent) maintenance. However, with some problems surfacing in as few as 20,000 miles, plenty of owners find themselves both surprised and frustrated with the EGR system’s lack of service life.

So was it inadequate hardware from the factory or the average truck owner’s lack of regular maintenance that made the 6.0L’s EGR system so notorious for failure? Below, we’ll explain why it’s likely a mixture of both.

The EGR Valve

Located at the front of the intake manifold, the EGR valve directs cooled exhaust gases back into the intake stream of the 6.0L Power Stroke. It utilizes two valves, connected via a common shaft, to allow exhaust gases to enter the intake air stream. Over time, the shaft and valves become inundated with carbon accumulation (a mixture of soot, oil vapor from blow by and other deposits) and eventually suffers from sticking issues. When the valves stick open or closed, poor drivability, smoke, low power, rough idle and hesitation occur. Navistar and Ford attempted to correct the sticking EGR valve issue on the 6.4L (the engine that followed the 6.0L) by including a unit with a much stronger DC motor for more forceful actuation.

Codes & Cleaning

When the EGR valve seizes at or near the open position, the 6.0L’s powertrain control module (PCM) will throw a check engine light (CEL) with a P0402 code. When the EGR valve sticks at or near the closed position, a scan tool will pull up a P0401 code. The general consensus in many 6.0L Power Stroke circles is that regular cleaning of the EGR valve should be performed every other oil change or once a year, but certainly no more than 20,000 miles. In fact, many EGR valves begin to stick within 20,000 miles.

Cracked EGR Cooler

Roughly 90-percent of all EGR cooler failures are the result of a plugged oil cooler starving them of coolant, hence the reason we spotlighted the oil cooler as the 6.0L’s single biggest deficiency in Part 1. With a lack of coolant supply making it to the EGR cooler, its ability to drop the temperature of the exhaust gases that need to reenter the intake tract is reduced significantly. When enough heat builds in the EGR cooler this is what you get: a ruptured internal core. Also known as a “cracked” EGR cooler, at this point coolant is allowed to enter the exhaust stream (and even the intake in some cases), which culminates in excessive white smoke out the tailpipe.

Two Different EGR Coolers (Early Vs. Late)

When an EGR cooler fails with the oil cooler in good working order, it’s often due to the EGR cooler plugging up with carbon. No different from the EGR valve, the EGR cooler acts like a carbon trap in the 6.0L engine. Over time, an insurmountable amount of carbon deposits accumulate internally, hampering exhaust flow. Early style coolers, which were round (’03, right) tend to last much longer before plugging up, which is primarily due to their larger, circular internal exhaust passageways. The later, square style EGR cooler is more notorious for clogging (’04-’07, left) thanks to its smaller exhaust passages.

A Taxed Engine Cooling System

Even without coolant supply being restricted or cut off due to a bad oil cooler, the 6.0L’s EGR cooler is extremely hard on coolant. This is because it is the coolant’s job to drop the temperature of the exhaust gases entering it from as much as 1,200 degrees F to 300 degrees F by the time it leaves it, roughly 12-inches later. Here, you can see where coolant leaves the oil cooler and also where it enters the EGR cooler. For comparison’s sake, Ford and Navistar added two EGR coolers to the 6.4L.

Coolant Flushes Should Be Performed Regularly

Without a doubt, the antifreeze in the 6.0L Power Stroke lives a very hard life. Being in constant indirect contact with 1,000-plus degree exhaust gases via the EGR cooler takes its toll, and the coolant begins to break down in a fairly short amount of time. This breakdown often contributes to the plugged oil cooler scenario we discussed in Part 1, where gel-like debris becomes lodged in the narrow passageways of that heat exchanger. Ford recommends flushing the 6.0L’s cooling system after the first 100,000 miles (or five years) and then every 45,000 miles (or three years) after that, but doing it every 20,000 to 30,000 is a much better idea, especially for engines in full emissions compliance.

Your Engine Oil Suffers, Too—So Pick A Good One

Being that EGR brings so much exhaust back into the engine, it stands to reason that a higher soot particle count appears in the 6.0L’s engine oil. This high soot content isn’t good for an engine oil that not only lubricates bearings and operates at 20-70 psi, but that also actuates the fuel injectors on the high-pressure oil side of the equation to the tune of 3,600 psi. This is why you should always run a high-quality oil in any emissions-compliant 6.0L Power Stroke and change it like clockwork every 5,000 miles (Ford’s severe duty recommendation). We recommend a synthetic 5W-40 engine oil for better cold-weather and injector performance, which we’ll touch on later in this series.

EGR & Diesels: A Dirty Business

Life isn’t just hard for the EGR valve and EGR cooler on the 6.0L Power Stroke, but rather anything and everything in the path of exhaust gases. This excessive carbon buildup on the end of an intake air temperature sensor occurred within 20,000 miles. The same thing happens within the intake manifold and even the cylinder heads, with airflow slowly becoming more and more restricted with time. As the buildup accumulates, engine performance and efficiency is gradually reduced.