Hello and welcome to JA, if you dont want to get ripped off then you should be going to the dealership. The only time people with that mentality go to the dealership is after they've been to their own personal mechanic, who usually winds up just throwing parts at the problem, all the while bad mouthing the dealership, and then when they can't fix it, the car needs to go to the dealership, and we have to fix everything Big Jim couldn't, and also fix it the right way, yes we will charge you. Then the customer takes all the money they've spent, including Big Jims inferior parts that didn't work, and complain that we charged them that whole amount to fix their car. When in fact if they had gone to the dealer in the first place, it would have been fixed right the first time, and if it wasn't the dealer will make good on the repair. If you have had a bad experience at the dealer in the past, try a different dealership, but dont assume all dealers are only there to rip you off, we are the ones with factory trained techs, and the special service tools designed to be used on your car, not the places that advertise ASE mechanics, whose training is mostly GM based to begin with. Now, there was no recall on the Navigator for piston rings, so what exactly did you have repaired, and is this noise after the engine has started, or while the engine is cranking? Here is a copy of the TSB for engine noise on your truck, maybe this is what you had done?
This article supersedes TSB 06-4-7 to update the Service Procedure.
Some vehicles equipped with a 4.6L 3-valve or 5.4L 3-valve engine may exhibit a ticking and / or knocking noise after reaching normal operating temperature, or a rattle upon starting. The noise may be described as ticks, taps, knocks, or thumps. In some cases the noise may be a normal characteristic of these engines. In other cases the noise may require further investigation. Sorting out and defining the noise as reported by the customer is important to successfully diagnose and / or repair the condition.
Before starting diagnosis, it is critical to determine the specific engine noise the customer is concerned with. The customer should be interviewed to get their detailed perception and description of the noise, and to determine if the noise occurs at idle or above idle speed, and if the engine is cold, hot, or both. Attempt to duplicate the noise, and determine the source of the symptom. Refer to the following Service Procedure to help determine the source of the noise and if a repair is needed.
Once the above pre-checks are complete, check for sound level from the following components, in the order listed. Compare the sound from these components to the noise the customer is concerned with, to determine the source of the noise.
Injector noise (ticking) is considered normal. Noise increases with RPM hot or cold and is recognized at the top of the engine.
Lash adjusters can make a ticking / tapping noise noticeable at any engine RPM / temperature and is audible through the wheel well or an open hood. However, with the hood down, lash adjuster noise can be heard as a light tapping noise through the wheel well and is considered normal.
Tracing this noise must be isolated to a cylinder bank. If one bank is louder than the other bank, focus the diagnostic to the loud bank. If both banks seem loud with the hood down, compare wheel well sound level to another comparable vehicle.
Use a stethoscope on the top of the cam cover bolt heads to confirm which bank is affected. Move the probe from front to rear if necessary.
If isolated, only replace the intake and exhaust lifters on the affected cylinder bank.
The 4.6L 3V and 5.4L 3V variable cam timing (VCT) feature may emit a light knock in normal operation and is audible only at idle speed, with a hot engine (gear selector in park / neutral). However, it may be masked by or mistaken for other noises generated from either injector firing or a malfunctioning valve train as described above. The noise does not affect performance or durability of the part.
VCT phasers may knock at hot idle. It may be heard inside the passenger compartment, or the wheel well area. Some light noise is normal. The engine may require a cold soak overnight for a full diagnosis to effectively be made at hot idle, particularly when a VCT phaser is suspected. The knock is not prevalent at cold temperature.
If the noise intensity is more than a lightly audible knock at hot idle under 1200 RPM at engine operating temperature, replace the cam phaser using the "In-Vehicle Repair" Camshaft Phaser and Sprocket procedure found in the Workshop Manual, Section 303-01
Some 2004 F-150 and 2005 F-150, Expedition, Navigator, F-Super Duty, and Mustang vehicles may have a rattle on startup that lasts 1 to 3 seconds. If initial pre-checks have been completed and the noise sounds like it is coming from the front of the engine, replace the VCT Phaser Kit. If the engine continues to make the rattle noise after the initial startup do not exchange VCT.