The PowerStroke engine was introduced in 1994 by the Ford Motor Company. International Truck and Engine Corp. developed the engine to make the Ford trucks more versatile. The manufacturer and automobile company wanted a powerful truck that would be able to work hard under loads and still be a daily driver. Over time, the PowerStroke developed some problems, which included an excessive knocking noise during idle.
A technical service bulletin (TSB) was published on the 2000 Ford Excursion truck in October 2003 about an idle knock occurring on the 7.3L PowerStroke engine. The diesel engine has a combustion knocking noise as a common part of its operation, but the TSB noted the occurrence of above-average knocking noises. After investigation by local maintenance departments, technicians discovered that the engine was being operated at low oil levels, causing the engine components to operate with less lubrication. The lack of lubrication caused the engine to make a knocking noise when idling that was louder than normal.
The PowerStroke engine has head bolts that secure the cylinder heads to the engine. These head bolts have been known to stretch under pressure. The stretching causes the PowerStroke head to loosen, which causes the engine to begin knocking at idle, as well as under normal operation. The type of head bolts installed on these engines is considered the weakest link on the PowerStroke engine, according to International Power Stroke. The information website states the head bolt issue is one of the most common problems found in the 6.0L PowerStroke engine.
Soot and Oil
Another cause of high idle knock on the PowerStroke engine is the buildup of soot and oil in the Exhaust Gas Recirculation (EGR) assembly. The buildup causes the valves to clog and fail over time. As the soot and oil build up in the EGR valve, the turbocharger over-boosts. The valves begin to build up soot quickly, making the engine knock during idling. Fuel efficiency is also reduced because of low combustion temperature when the PowerStroke idles. The combination of soot buildup, low combustion temperature and EGR valve clogging causes a knocking noise to develop during idle.
Cylinder Head Gasket
One TSB published by the manufacturer of the PowerStroke engine reports that the cylinder head gasket is developing a premature leak. Once oil begins to leak out of the cylinder head, the engine begins to lose oil rapidly. As noted earlier, running the PowerStroke engine with low oil causes a knocking noise to develop during idle and under normal driving conditions. A PowerStroke owner must take the vehicle into a qualified automotive technician and have the cylinder head gasket replaced with a new service-only gasket once the leak develops. No recall had been announced on this problem at the time of publication.