I have a new 2006 Ford Explorer, 4.0L engine, with only 6500 miles on it. At around 4000 miles I started to hear a squealing noise coming from the engine when the car is accelerated above 2000 rpm and the noise continues to 3100 rpm. Below this rpm it is smooth and quiet. When the gear changes (at > 3000 rpm) from 4th to 5th or from 2nd to 3rd, the whistling goes away immediately.
When I press on the gas to raise the rpm back to around 3000 rpm, which shifts it down one gear, the noise returns until the rpm increases above 3000 rpm, the gear shifts to the next higher, rpm goes down and noise immediately fades out.
I must add that this whistling noise can be heard clearly when the car is cold. After traveling for a long distance (specially long highway distances) this noise is very faint and sometimes it disappears completely at the said rpm values when shifting gears. But then the next morning the noise is back at exaclty these rpm values (fading away when the gear shifts). It is driving me crazy. I changed the transmission oil with no effect.
I am suspecting a bad water pump bearing is causing this, but wanted to get some opinions before going for this (warranty covered) repair. BTW, is the water pump gear-driven on the Explorer? Is replacing the water pump unit a big job, will they need to lift the engine?
Thursday, January 11th, 2007 AT 5:59 PM