2000 LC 293,xxx miles, on cold start ups there is a squelch that sounds like it's coming from driver side behind the firewall, very distinct inside the cabin, hard to locate in the engine bay over the engine noise. Some times it'll last about 30 seconds. Other times it'll go for a bout a mile down the road before the sound stops. Sounds hydraulic, just replaced the serpentine belt about 5k miles ago, doesn't sound like a belt squeak, slight vibration in the brake pedal when the noise is present. No abs light, no engine light, no soft brakes or failure (brake pedal feels normal). Brake fluid is still clean, power steering was just flushed last week (thought that may have been the culprit). Replaced the A/C condenser 3 months ago and had to drain/recharge the system, working good and still cold. Sound is not RPM based.
My trusted mechanic could not duplicate the sound. Talked with one of the local dealerships techs and he said he wasn't sure what it could be.
I'm leaning towards a Brake issue, but not sure where to start, and wanted to rule out it possibly the transmission (doubt it is, but not 100%)
So I guess I should just ask, any ideas?