Q: Noisier engine after service on 1996 Toyota 4Runner

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I just had my timing belt, water pump, thermostat, and all the small heater hoses in the back of the engine and under the intake manifold replaced by the dealer. So now the car runs fine but is noisier, I hear a sort of howling or lower pitched whining noise. The noise itself is annoying and so far they have not been able to tell me what it is. They say it is normal engine noise but it never sounded that way before the service. I hear it at idle and when cruising around 30mph or so.
(2) Answers
(1) Comments
did the check the wheel bearings? they can cause a howling noise at lower speeds when driving
It makes the same noise at idle. It does sound like a wheel bearing though, but that's not what it is. The noise appeared after they did the service. By the way it's a 3.4L with 4WD.