FORD KNOWLEDGEBASE OASIS 4.6 DOHC:
TSB'S MISC
Known Problems:
1.Coolant Flow (cylinder head) - 2003-2004 DOHC heads have a flawed casting and coolant flow design on the first revision of the head that causes coolant to dead end in the back of the driver side head and causes the 7 & 8 cylinders to run hotter than the others. This results in a ticking sound that occurs when the valve guides and/or seats warp due to running too hot and the ticking itself is the sound of the valves not seating correctly and tapping because of it. The problem is more prominent on the Cobra and Mach 1 due to their high performance nature and tendency to be driven hard.
This problem was also found on the 1999-2001 4.6L DOHC Mustang Cobras.
2.Dieseling Noise - Many times a dieseling noise is found to be from a loose timing gear retaining bolt. Easy fix just remove the cam cover and retighten the bolts to in/lb specs. Make sure the bolt is coated with a mild amount of teflon, but not threadlocker.
3.Oil Filter Suggestion - It is recommended that you use Motorcraft oil filters. They have a drain back valve that keeps oil from draining back to the pan when the engine is off. Most aftermarket filters do not. This prevents knocking on start up and eventual damage from it.
4.Oil Suggestion - Use only 5w20 weight oil if that's what it call's for. The tolerances are very tight in the valvetrain and any heavier of an oil can eventually cause valvetrain problems because the hydraulic components stay pumped up and never bleed down like they should when the engine is running
5.Timing Chain Tensioner - Ford Motor Company has told its dealers that 2000 through 2003 model year Ford Crown Victoria and Mercury Grand Marquis vehicles may exhibit a grinding noise from the engine timing chain area. This noise, according to Ford, may be caused by excessive wear of the timing chain tensioner arms. The tensioner arm has an aluminum base with a nylon surface. The condition can also be detected by fine nylon and or aluminum particles present in the engine oil.
Bad timing chain tensioners have been reported on other 4.6L vehicles as well.
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