Hi Guys, I just bought this 2007 Expedition Limited 4x4 60,000 miles and didn't notice a few issues when test driving it or they just popped up.
When I am going 60mph+ I hear a rythmic humm from what seems like either exhaust resonance, engine, or a bearing/drive shaft issue. I had the tires which are fairly new, rotated and balanced, which made no difference in the noise. I can not drive through the noise or dull vibration. One of the odd things I noticed, is that the rythmic humm will get less noticable after 5mins of driving or so with the cruise control on. It is both audible and I can ever so slightly feel it in the steering wheel and under my feet.
Had the shop check wheel bearings, they said those are good from what they can tell. The exhaust system is not loose.
I recently changed plugs with SP515's, but did not change COP's or boots. The humm was there before the plug change. Could this be a failing COP causing the engine to run a little wierd at that speed? If I rev the engine from idle it does not rev perfectly smooth to 2000-2500rpm, it seems kind of choppy or slightly bumpy. Does any of yours rev like that in park?
I am kind of at a loss, any suggestions are appreciated. Thanks
When driving at 60+, put truck in nuetral, sound change? When driving and you hear the hum, turn wheel right or left a bit, sound change? That will load the bearings. Put front tires on back and test. Still there? Still feel it in the wheel?