5 Symptoms of a Bad EGR Cooler (and Replacement Cost)
If you’re the owner of a diesel or otherwise heavy-duty truck, you’ve likely heard concerning stories about EGR cooler failures from other drivers. But would you know how to spot the symptoms if that component failed today?
Whether you’ve owned diesels all your life or are new to diesel engines, recognizing the signs of a bad EGR cooler early can help you avoid catastrophic engine damage and unexpected downtime. While replacement isn’t cheap, ignoring the issue could be far worse.
What Is an EGR Cooler?
An EGR cooler is a water/air heat exchanger that cools recirculated exhaust gasses before they are reintroduced into the intake stream for further combustion. EGR coolers are found most predominantly on diesel-powered vehicles, as well many heavy-duty trucks.
The EGR system as a whole, is part of a vehicle’s standard emissions equipment, as mandated to meet applicable compliance standards. This system allows a certain percentage of spent combustion gasses to be redirected into an engine’s intake stream for dilution with fresh intake air, prior ultimately being combusted yet again.
Purpose
The purpose of an engine’s EGR cooler is to reduce the temperature of these redirected combustion gasses, prior to being dosed downstream. Engine coolant is circulated through the EGR cooler, removing heat from exhaust gasses through radiant measures.
Location
The location of an engine’s EGR cooler can vary radically from one vehicle to the next. However, in most cases, this component is found inline between an engine’s turbocharger and EGR valve.
In some applications, the EGR valve can be found bolted to the rear of a truck’s engine, yet in others, affixed along the side of the block or mounted to the valve cover itself.
Bad EGR Cooler Symptoms
A number of symptoms often accompany the failure of an engine’s EGR cooler, some of which are more prominent or easily noticed than others. Quick recognition of these symptoms can speed up the diagnostic process and eventual repair.
#1 – White Exhaust Smoke
Perhaps the most common symptom of EGR cooler failure is a noticeable or persistent discharge of white smoke or steam from a vehicle’s exhaust. This occurs when coolant is introduced into a vehicle’s exhaust stream.
The smoke typically appears thicker and whiter than normal exhaust vapor, especially when the engine is warm. It’s particularly noticeable during acceleration or when the engine is under load.
#2 – Unexplained Coolant Loss
Going hand-in-hand with the symptom above, it is also relatively common to notice reduced coolant levels that appear otherwise unexplainable. This results from the continuous introduction of coolant into a vehicle’s exhaust stream.
You may find yourself needing to top off the coolant more frequently than usual, even though there are no visible leaks under the vehicle. This coolant loss often starts gradually but can become more severe as the failure progresses.
#3 – Engine Overheating
It’s also not uncommon for an engine to experience overheating in the event of an EGR cooler failure. This occurs when exhaust gas temps are unable to be regulated before being reintroduced into the intake tract. As a result, combustion temperatures rise as well.
The overheating might start intermittently, typically under heavy load or during highway driving, but can become more frequent over time. Your temperature gauge may fluctuate erratically or show steady high readings even in normal driving conditions.
#4 – Pressure Within Cooling System
You might also notice that your vehicle’s cooling system has become pressurized when EGR cooler failure occurs. This comes as the result of exhaust gasses being introduced into the cooling system. In severe cases, you might even notice that coolant begins to surge out of the coolant overflow tank.
This pressure can be particularly noticeable when removing the radiator cap (which should ONLY be done when the engine is completely cool). You might hear a distinct hissing sound from the coolant reservoir, or notice the coolant reservoir hoses are unusually firm to the touch.
#5 – Illuminated Check Engine Light
In some cases, a vehicle’s check engine light might be Illuminated as EGR cooler failure takes place. This occurs when irregularities in exhaust gas temperatures trigger the storage of one or more active diagnostic trouble codes or faults. The longer the issue at hand persists, the more likely it is that a fault will be registered.
Common trouble codes related to EGR cooler issues include:
- P0401: EGR Flow Insufficient
- P0402: EGR Flow Excessive
- P0404: EGR Circuit Range/Performance
- P2457: EGR Cooling System Performance
- P2459: EGR Cooling System Performance – Flow Detected With Valve Closed
- P0405/P0406: EGR Sensor Circuit Low/High Input
In addition, you might see temperature-related codes such as P0217 (Engine Coolant Over Temperature) or P0128 (Coolant Thermostat Temperature Below Regulating Temperature). These codes can help pinpoint the exact nature of the failure and guide diagnostic efforts.
EGR Cooler Replacement Cost
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The exact cost associated with EGR cooler replacement can vary considerably between various makes and models of vehicles. The reason behind these price fluctuations can be attributed to differing replacement parts costs and variables in complexity of replacement, thereby impacting overall labor costs.
Generally speaking, you can expect to pay between $1,000-$3,500 to have your vehicle’s EGR cooler replaced. In many cases, this cost is roughly 50% parts related to 50% labor relayed, in nature.
Is It Safe to Continue Driving?
Continuing to drive with a failing EGR cooler is not recommended and can lead to severe engine damage. While you might be tempted to make a quick trip to the shop or finish your current route, doing so puts your engine at significant risk.
When an EGR cooler fails, it can introduce coolant into the combustion chamber or allow excessive heat into the intake system. This can result in:
- Hydrolocked engine (if too much coolant enters cylinders)
- Severe engine overheating
- Damage to turbocharger components
- Increased wear on internal engine components
- Potential catastrophic engine failure
If you notice symptoms of EGR cooler failure, the safest course of action is to have your vehicle towed to a repair facility. The cost of a tow is significantly less than the potential expense of major engine repairs or replacement.
If you absolutely must drive the vehicle a short distance, keep an eye on the temperature gauge closely and stop immediately if the engine begins to overheat or if white smoke increases significantly.
What Causes an EGR Cooler to Fail?
The most common cause of EGR cooler failure is overheating and thermal stress. An engine’s EGR cooler must prove capable of managing extremely high temperatures for prolonged periods of time. Therefore, anything capable of compromising an EGR cooler’s cooling capacity can lead to significant stress and failure in time.
Poor quality or contaminated coolant is the mortal enemy of EGR coolers, as the unit’s small internal passages can easily become clogged, leading to an overall reduction in cooling capacity.
Likewise, low coolant levels or air pockets within the cooling system can also quickly destroy even the most heavy duty EGR cooler. A lack of flowing coolant through an EGR cooler often leads to warping and internal cracking of the cooler itself.
Yet another cause of EGR cooler failure is carbon fouling within the cooler’s exhaust passages. This fouling leads to blockages that ultimately cause “hot spots” of increased thermal stress. If serious enough, these blockages can even cause significant increases in cooler temperatures.
Cleaning vs Replacement
A common argument is whether to replace an EGR cooler or to have it professionally cleaned. While there is a case for both, most professionals now agree that the replacement of a questionable EGR cooler is the best method to ensure proper repair. In fact, there are many cases when EGR cooler cleaning is considered ineffective.
Cleaning of an EGR cooler is ineffective when internal failure has taken place, allowing the barriers between a cooler’s exhaust/coolant passages to fail. Under these circumstances, replacement is the most viable option.
The only cases in which EGR cleaning is considered satisfactory are those cases in which carbon fouling has clogged the cooler’s exhaust passages. Nonetheless, even after cleaning, there is little guarantee that hot spots have not been generated, or that warping has not taken place.
Bad EGR Cooler vs Blown Head Gasket
Many often find it difficult to discern between a failed EGR cooler and a blown head gasket, when diagnosing issues pertaining to coolant loss and white-colored exhaust discharge. This stems from the fact that both failures are known to present similar symptoms, making it difficult to pinpoint the culprit.
One obvious symptom that would point to a failed head gasket, over a faulty EGR cooler would be the mixing of oil with coolant or coolant with oil. These two liquids do not share passages in the EGR cooler, making a blown head gasket the most likely culprit.
The presence of oil intrusion into the coolant system is most evident in the cooling system’s overflow tank, while coolant-contaminated oil takes on a milky consistency.
If ever in doubt, remove the EGR cooler and have it pressure tested with specialty equipment at a professional radiator shop. If the cooler itself passes this test, and all other common symptoms are present, there is probable cause to suspect head gasket failure.
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