My Adaptive Speed Control has always worked perfectly and still does. But it has started making 3-4 squeaks, as if something mechanical needs some oil. It happens when the traffic in front slows a bit so I slow a bit. I think it only gets less throttle, I don't think the brake applies. With the ASC not in use, I never hear that sound.

Does anyone know about this system? When I look in the Service Manual I only find electronic parts. I see no mention of anything mechanical. But how does the throttle normally work, cable or wire? If wire, something mechanical must release the tension. And the brake? Maybe the sound is the system pumping a bit of brake pressure to be ready.

I'm just guessing, anybody that knows about this system?

Thanks

 

The system certainly uses the vehicle braking system but whether or not that is the sound you hear I don't know. My x150 Service manual has a description in Section 310-03 at page 2440.

 

Yeah, the ACC brakes about made me die once when I went to pass a slow car and another car pulled through the lane I went around. Brakes about put me into the dash while I was at Full Throttle.

 

Throttle is electronically controlled.

Would help if you could describe where the noise is coming from specifically...

 

I'm not sure, my guess in engine room

 

I think I've ruled out the throttle system, it's all electronic, and the normal Adaptive Speed Control trips where throttle opens and closes a bit based on speed of car ahead and incline/decline, there's not that noise. I'm pretty sure it's brake related. It comes on when the speed reduction is slightly more than just lifting the throttle. Either the brakes are applied or prepared (latter is my guess). And, the noise is higher if more brake is needed. but if a lot of brake is needed, no noise.
I think the noise comes from engine room, straight ahead.

So my guess is Hydraulic Control Unit (HCU). That's a complex mechanical thingy that has pistons and valves that both reduce pressure (ABS) and increase pressure (DSC & Adaptive Speed Control). Why it has started to make noise I don't know, and I'm pretty sure there's only one remedy, new unit. But since it's time for winter hibernation, I won't replace it, I'll wait till it gets worse. I don't expect brake failure, but maybe ABS/DSC/ASC failure. We'll see.

Any further ideas?