Let's have an in-depth discussion about the 2.2 SKYACTIV-D engine found in most modern Mazda cars, such as the one in my 2015 Mazda 6 III (GJ, facelift). There is a lot of information about overheating and head gasket issues, but specific details and root causes are often lacking. Buckle up, it's going to be a long story.
How it started: The vehicle mentioned above has 160,000 km mileage with an excellent service history and no major issues. Oil changes were done every 20,000 km (which is too infrequent, but that's another story). My friend and I changed all fluids and filters, including automatic transmission oil, coolant, and differential oil. Everything seemed absolutely fine, with no debris or any alarming signs. The first 5-10,000 km were fantastic in normal winter conditions.
The first issue: On the first really hot day (30-35°C in Europe), I found the expansion tank overfilled and noticed a small amount of coolant on the engine. The car was driven normally without any signs of overheating. Since there is no temperature gauge, I can't provide the exact temperature, but there were no indications of overheating, no loss of power, and the fans worked normally. We checked everything and found no signs of a head gasket problem. We bled the system and set the coolant level to medium. The following weeks were normal, and the car covered 1-2K km. A very important note: the weather was cold during this period.
Some numbers: To better understand the car's conditions, especially the DPF regeneration intervals, I started monitoring various parameters with an OBD II sensor. Fortunately, I've gathered some good statistics about temperatures:
For comparison, I have experience with petrol 6-cylinder BMW engines from the early 2000s, which are known to operate at higher temperatures with a cooling system under 2 bar of pressure and have a bad reputation for overheating. The thermostat opens at 93°C, and the fans turn on at 100°C. The maximum temperature I've seen with a worn-out viscous fan is 114°C on very hot summer days, with the fans at maximum speed while driving uphill. The temperature gauge remained in the middle, and there were no warning signs on the dashboard, so this should be considered a normal condition in the summer without overheating risk. My opinion is that the BMW's cooling system performs better compared to my Mazda 6 when it is in good technical condition (functioning thermostat heating, no leaks, new viscous fan, proper radiator cap), maintaining a stable 93-97°C under high load in very hot conditions. Take note - BMW has a viscous fan.
Why am I writing this? Because there are reports of a design issue with the 2.2 D engine, and I want to find a solution and help others. There are known issues reported in Thailand, Taiwan, and Australia—countries with hot summer climates.
In my case, ongoing investigations haven't shown gases in the cooling system during the sniff test, and the engine, which hasn't been disassembled yet, continues to function normally. I only experience issues on hot days when engine temperatures exceed 100°C.
Here's my theory: The head gasket may be damaged due to numerous heat cycles and insufficient cooling, especially during DPF regeneration in hot summer conditions under high load. After 100,000 km, this could lead to gasket failure. Other potential factors such as high surface roughness and flatness of the engine block and/or head, low-quality head gasket materials, or engine cooling design flaws may also contribute to the problem. However, I don't have sufficient statistical data to confirm these factors.
Furthermore, many cases involve engine replacements where the problem recurs. This supports my theory that there is a fundamental design issue related to cooling.
So I've developed some DIY actions and ideas for prevention before issues occur or for preservation after repair. These ideas are inspired by modifications seen in street-tuned cars with increased power, although our goal here is to maintain the engine's factory power levels. These suggestions are meant for discussion purposes only, and I want to emphasize that I cannot be held responsible if anyone damages their vehicle.
Starting from the easiest, with fewer interventions and the lowest risk of downsides:
1. Cooling system in perfect condition - Regular checks of the coolant level and replacement of components like the water pump, thermostat, and coolant based on mileage, not when they fail. Downsides - None, except that you might become overly cautious.
2. Increase airflow in the engine bay
2.1. Remove the plastic engine cover.
2.2 Remove the plastic skid plate and insulation under the engine.
Downsides - Increased engine or road noise, and some components in the engine bay may be exposed to heat or water. However, the severity of the gasket issue suggests that these concerns are of lower priority. Moreover, older cars didn't have such insulation, so it shouldn't pose a significant problem (you can reinstall it in winter if needed).
3. Reducing back pressure in the engine bay:
3.1. Partially removing the sealant for the bonnet next to the windshield.
3.2. Upgrading vent holes in the fender liners/inner fenders to help hot air escape.
Downsides - The sealant can only be removed on the sides due to HVAC inlets in the middle sections, I haven't tested what could happen if I remove the whole seal. Water can get into the engine bay, but that's common in many cars.
4. Coolant boost - improves heat transfer and reduces engine temperatures. I'm considering trying Amsoil Dominator or Red Line WaterWetter. Downsides - Some reviews mention potential water pump issues, though generally, it's considered relatively safe (like any automotive additive). Also, the effectiveness of a 4-5°C temperature reduction is debatable.
5. Performance low-temperature thermostat - it opens at 76°C and helps maintain lower engine temperatures while ensuring good efficiency and longevity. There's a story from a guy in Texas with positive experience using this thermostat. On a hot day under load, the engine temperature doesn't exceed 93-94°C.
Downside - I couldn't find one specifically made for this engine; they are sold out. That's why I manually adjusted the spring coefficient of my thermostat, but I don't recommend this without an OBD sensor as it can be risky.
6. Changing the start-up temperature of the electric fans to ideally start at 90°C and gradually increase speed up to 100°C could prevent internal overheating during aggressive maneuvers in high heat conditions, such as overtaking on a steep climb.
Downsides - I've attempted to modify the software settings with a local tuning specialist, but they were unable to do so. Another option involves using an aftermarket relay and heat probe for manually setting the fans, but this setup must be isolated from the main computer to avoid triggering error codes. A third option is installing a complete aftermarket set of fans and control unit.
7. Performance aluminum radiator - This is the most complicated and expensive modification compared to points 4, 5, and 6. It may require additional components like hoses and possibly a water pump.
8. Heat insulation of exhaust manifold and turbo - These are the most heat-emitting components in the engine bay. Under normal conditions, temperatures in "Bank 1, Sensor 3" range between 150-300°C and can exceed 600°C during DPF regeneration. This heat remains in the engine bay when stopped at a traffic light, for example.
Downsides - Some materials and products, such as turbo blankets, can be expensive, and care must be taken not to overheat the turbo.
9. Software upgrade for power cut when the engine is too hot - I saw a YouTube video from Africa where they developed software to cut power when the engine is in danger of overheating. Maybe it is combined with lower fan activation temperatures too, but I'm not sure.
Downsides - It's unclear how reliable and bug-free this software upgrade is.
10. DPF and EGR removal - I am convinced that each DPF regeneration is gradually harming the engine, and they occur so frequently. The EGR system has its benefits, but I've seen potential root causes linked to the EGR valve.
Downside - Violation of environmental regulations and potential penalties for emissions. Why I include it on the list - because it is related to the issue.
You've grasped the essence of my point. If I come up with anything else, I'll add it in future posts. Why I am doing all of this - because Mazda has made a significant mess with this engine, and we need to resolve it; we have no other option. This is a major mistake that has persisted for many years, affecting not just one model or one batch from a specific year. My confidence in Mazda has been shattered, and I'm uncertain if I will remain their customer. It's disappointing because their dynamics, handling, comfort, interior, and exterior are unique, and they have the potential to be a leading brand.
How it started: The vehicle mentioned above has 160,000 km mileage with an excellent service history and no major issues. Oil changes were done every 20,000 km (which is too infrequent, but that's another story). My friend and I changed all fluids and filters, including automatic transmission oil, coolant, and differential oil. Everything seemed absolutely fine, with no debris or any alarming signs. The first 5-10,000 km were fantastic in normal winter conditions.
The first issue: On the first really hot day (30-35°C in Europe), I found the expansion tank overfilled and noticed a small amount of coolant on the engine. The car was driven normally without any signs of overheating. Since there is no temperature gauge, I can't provide the exact temperature, but there were no indications of overheating, no loss of power, and the fans worked normally. We checked everything and found no signs of a head gasket problem. We bled the system and set the coolant level to medium. The following weeks were normal, and the car covered 1-2K km. A very important note: the weather was cold during this period.
Some numbers: To better understand the car's conditions, especially the DPF regeneration intervals, I started monitoring various parameters with an OBD II sensor. Fortunately, I've gathered some good statistics about temperatures:
- DPF PM Generated %: Regeneration starts between 59% and 63%.
- DPF Regeneration Distance: With this car and driving conditions, regeneration occurs every 200-210 km, which many professionals I've talked to consider normal.
- Coolant Temperature: The thermostat opens at 82-84°C, which is visually noticeable as the temperature rise stops at 83-84°C and even drops to 81-82°C.
- Case 1: Ambient Temperature Below 20°C - Under normal driving conditions, the coolant temperature stabilizes around 84°C.
- Case 2: Ambient Temperature Above 20°C - The engine temperature starts rising up to 100°C, at which point the fans turn on. I've seen a maximum value of 106°C while driving uphill, which I assume is normal due to the higher operating temperatures of SkyActiv engines at 100°C and the fact that the fans activate at 100°C. When the engine bay is hot, the radiator struggles to stop the temperature from rising. On long descents, the temperature drops significantly to 85°C, and then when you gently start using the gas pedal, it starts rising above 95°C."
For comparison, I have experience with petrol 6-cylinder BMW engines from the early 2000s, which are known to operate at higher temperatures with a cooling system under 2 bar of pressure and have a bad reputation for overheating. The thermostat opens at 93°C, and the fans turn on at 100°C. The maximum temperature I've seen with a worn-out viscous fan is 114°C on very hot summer days, with the fans at maximum speed while driving uphill. The temperature gauge remained in the middle, and there were no warning signs on the dashboard, so this should be considered a normal condition in the summer without overheating risk. My opinion is that the BMW's cooling system performs better compared to my Mazda 6 when it is in good technical condition (functioning thermostat heating, no leaks, new viscous fan, proper radiator cap), maintaining a stable 93-97°C under high load in very hot conditions. Take note - BMW has a viscous fan.
Why am I writing this? Because there are reports of a design issue with the 2.2 D engine, and I want to find a solution and help others. There are known issues reported in Thailand, Taiwan, and Australia—countries with hot summer climates.
In my case, ongoing investigations haven't shown gases in the cooling system during the sniff test, and the engine, which hasn't been disassembled yet, continues to function normally. I only experience issues on hot days when engine temperatures exceed 100°C.
Here's my theory: The head gasket may be damaged due to numerous heat cycles and insufficient cooling, especially during DPF regeneration in hot summer conditions under high load. After 100,000 km, this could lead to gasket failure. Other potential factors such as high surface roughness and flatness of the engine block and/or head, low-quality head gasket materials, or engine cooling design flaws may also contribute to the problem. However, I don't have sufficient statistical data to confirm these factors.
Furthermore, many cases involve engine replacements where the problem recurs. This supports my theory that there is a fundamental design issue related to cooling.
So I've developed some DIY actions and ideas for prevention before issues occur or for preservation after repair. These ideas are inspired by modifications seen in street-tuned cars with increased power, although our goal here is to maintain the engine's factory power levels. These suggestions are meant for discussion purposes only, and I want to emphasize that I cannot be held responsible if anyone damages their vehicle.
Starting from the easiest, with fewer interventions and the lowest risk of downsides:
1. Cooling system in perfect condition - Regular checks of the coolant level and replacement of components like the water pump, thermostat, and coolant based on mileage, not when they fail. Downsides - None, except that you might become overly cautious.
2. Increase airflow in the engine bay
2.1. Remove the plastic engine cover.
2.2 Remove the plastic skid plate and insulation under the engine.
Downsides - Increased engine or road noise, and some components in the engine bay may be exposed to heat or water. However, the severity of the gasket issue suggests that these concerns are of lower priority. Moreover, older cars didn't have such insulation, so it shouldn't pose a significant problem (you can reinstall it in winter if needed).
3. Reducing back pressure in the engine bay:
3.1. Partially removing the sealant for the bonnet next to the windshield.
3.2. Upgrading vent holes in the fender liners/inner fenders to help hot air escape.
Downsides - The sealant can only be removed on the sides due to HVAC inlets in the middle sections, I haven't tested what could happen if I remove the whole seal. Water can get into the engine bay, but that's common in many cars.
4. Coolant boost - improves heat transfer and reduces engine temperatures. I'm considering trying Amsoil Dominator or Red Line WaterWetter. Downsides - Some reviews mention potential water pump issues, though generally, it's considered relatively safe (like any automotive additive). Also, the effectiveness of a 4-5°C temperature reduction is debatable.
5. Performance low-temperature thermostat - it opens at 76°C and helps maintain lower engine temperatures while ensuring good efficiency and longevity. There's a story from a guy in Texas with positive experience using this thermostat. On a hot day under load, the engine temperature doesn't exceed 93-94°C.
Downside - I couldn't find one specifically made for this engine; they are sold out. That's why I manually adjusted the spring coefficient of my thermostat, but I don't recommend this without an OBD sensor as it can be risky.
6. Changing the start-up temperature of the electric fans to ideally start at 90°C and gradually increase speed up to 100°C could prevent internal overheating during aggressive maneuvers in high heat conditions, such as overtaking on a steep climb.
Downsides - I've attempted to modify the software settings with a local tuning specialist, but they were unable to do so. Another option involves using an aftermarket relay and heat probe for manually setting the fans, but this setup must be isolated from the main computer to avoid triggering error codes. A third option is installing a complete aftermarket set of fans and control unit.
7. Performance aluminum radiator - This is the most complicated and expensive modification compared to points 4, 5, and 6. It may require additional components like hoses and possibly a water pump.
8. Heat insulation of exhaust manifold and turbo - These are the most heat-emitting components in the engine bay. Under normal conditions, temperatures in "Bank 1, Sensor 3" range between 150-300°C and can exceed 600°C during DPF regeneration. This heat remains in the engine bay when stopped at a traffic light, for example.
Downsides - Some materials and products, such as turbo blankets, can be expensive, and care must be taken not to overheat the turbo.
9. Software upgrade for power cut when the engine is too hot - I saw a YouTube video from Africa where they developed software to cut power when the engine is in danger of overheating. Maybe it is combined with lower fan activation temperatures too, but I'm not sure.
Downsides - It's unclear how reliable and bug-free this software upgrade is.
10. DPF and EGR removal - I am convinced that each DPF regeneration is gradually harming the engine, and they occur so frequently. The EGR system has its benefits, but I've seen potential root causes linked to the EGR valve.
Downside - Violation of environmental regulations and potential penalties for emissions. Why I include it on the list - because it is related to the issue.
You've grasped the essence of my point. If I come up with anything else, I'll add it in future posts. Why I am doing all of this - because Mazda has made a significant mess with this engine, and we need to resolve it; we have no other option. This is a major mistake that has persisted for many years, affecting not just one model or one batch from a specific year. My confidence in Mazda has been shattered, and I'm uncertain if I will remain their customer. It's disappointing because their dynamics, handling, comfort, interior, and exterior are unique, and they have the potential to be a leading brand.
