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AERA Technical Bulletins – October 27, 2021

Cylinder Head Coolant Leak On 2016-2020 Mazda SKYACTIV-G 2.5L Engines

The AERA Technical Committee offers the following information on cylinder head coolant leaks for 2016-2020 Mazda SKYACTIV-G 2.5L engines. Customers may complain of coolant leakage under the vehicle or on the engine itself.
These engines have reported coolant leaks at the cylinder head around the exhaust manifold. There may be cracks present at the stud hole (1) or on the outside of the exhaust manifold (2).

Measuring Valve Seat Runout

The AERA Technical Committee offers the following information regarding the basic understanding and importance when measuring valve seat runout. 
Valve seat runout is sometimes referred to as TIR (Total Indicated Reading). Runout is defined as the radial separation of two concentric circles centered on the datum point and drawn such that one coincides with the nearest and the other coincides with the farthest point on the profile. Although this is accurate, it is only part of the equation in regard to valve seat machining that can result in valve and/or guide failure.



The Duramax engine was a turning point for General Motors in the light-duty diesel market and the engine’s legacy for innovation continues today. A strategic partnership with Isuzu created a direct injected 90-degree V8 turbocharged diesel that redefined the market. The 6.6L LB7 was initially rated at 300 bhp and 520 lb-ft of torque which was greater than both its North American competitors (7.3L Power Stroke and 5.9L Cummins) at its release in 2001. The four overhead valve engine design was the only over square diesel in the light duty market with a 103mm (4.055″) bore and a 99mm (3.8976″) stroke. The LB7 was topped with high swirl aluminum cylinder heads paired with an electrically controlled common rail fuel system to produce an efficient, quiet and well-mannered engine comparable to its gasoline counterparts.

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Podcast Episode 12 – Torque Plates

Steve and Chuck take a deep dive into the why you should use a torque plate when honing the cylinder block and its importance. Also, do you know which car manufacture and model just hit the 50 million mark in sales? They will inform you as well as which engine hit the 2 million production mark in 1955. Take a listen and subscribe to the Engine Professional podcast!

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