Editing Saturn I4 engine (section)

==SOHC LK0/L24==
The SOHC (LK0/L24) cylinder head had 8 valves and was made of lost foam cast aluminum. The camshaft was located in the center of the cylinder head and driven by a chain off the front crankshaft sprocket. Motion from the camshaft was transmitted to the eight valves by the [[hydraulic lifters]] and [[rocker arm]]s.

The SOHC engine was used in the base model S-series vehicles (SC1, SL, SL1, SW1)

The LK0 engine first used TBI (Throttle Body Injection) for fuel delivery and was rated at {{convert|85|hp|kW|0|abbr=on}} at 5000&nbsp;rpm and {{convert|107|lbft|Nm|0|abbr=on}} at 2400&nbsp;rpm from 1991 to 1994.<ref name="Edmunds">{{Cite web|url=http://www.edmunds.com/saturn/s-series/1991/features-specs.html?sub=sedan&style=5884|title=1991 Saturn S-Series Features & Specs|year=1991 |accessdate=2012-10-30|work=edmunds.com}}</ref>

The L24 engine received MPFI (Multi-Port Fuel Injection) in 1995 which increased power output to {{convert|100|hp|kW|0|abbr=on}} at 5000&nbsp;rpm and {{convert|115|lbft|Nm|0|abbr=on}} at 2400&nbsp;rpm. In 1999, these engines switched from the recessed top pistons of the previous models to all new flat top pistons that were also used in the twin cam models. The cylinder head was also redesigned to keep the compression ratio at 8.8:1 even with the flat top pistons and now featured provisions for an air injection reaction system. This engine was used from 1995 to 2002.<ref name="Edmunds2">{{Cite web|url=http://www.edmunds.com/saturn/s-series/1995/features-specs.html?sub=sedan&style=981|title=1995 Saturn S-Series Features & Specs|year=1995 |accessdate=2012-10-30|work=edmunds.com}}</ref>

Some 1992 through 1998 L24 cylinder heads developed cracks in the fifth camshaft journal, located closest to #4 cylinder. The hairline crack would form between the oil feed port of that journal and the coolant passages in the cylinder head. Symptoms would range from overheating to low coolant, however, most cars affected by this issue exhibited oil migration into the cooling system. The resulting mixture of the two fluids would result in a thick brown "milkshake"-like mixture, visible in the coolant overflow tank.

Saturn released unadvertised policy which would cover this issue, extending the warranty on the cylinder head to 6 years or {{convert|100000|mi|km}}. Repair required the replacement of the cylinder head. and flushing of the coolant system. Badly affected cars would see coolant in the oil, as well as oil in the coolant, and would require the replacement of the complete engine assembly. Until the cylinder head casting was redesigned some time in 1998, some vehicles would require this repair more than once, and replacement cylinder heads could develop the same crack.

It was estimated that between 2% and 5% of SOHC Saturn S-Series vehicles were affected by this defect. DOHC engines had a different cylinder head, and did not suffer the same issue.