rattles in engine compartment

[Hocky]

I've got this 1994 C180 which has this rattle which is there one day and not the next. Its intermittent and sounds like something loose like hoses, wires or brackets or even washers or screws running around somewhere in there. Seems like it would be almost impossible to isolate where it is as the noise comes only when the car is moving not at idle. Is this a common problem with older Benz cars, anyone? What can I do without having to climb into the area while the car is moving and listening or putting a stethescope in a few places to find the loudest and closest spot. This would be almost impossible as the noise in the engine bay will drown out any of this. Please help if any of you can come up with possible culprits and most likely spots, thanks.

[psfred]

Yikes, a '94 is an "older" Benz? What does that make my two '72's?!

Rattles while moving are usually things like loose strut mounts or something else associated with the wheels, although you could get something that rattles only when the engine is rotated from torque.

I'd check the condition of the engine mounts -- they should be about an inch higher than the frame a the widest part. Also, look for something loose -- a broken serpentine belt tensioner comes to mind, along with a bad belt tensioner shock.

I believe there are some plastic covers in there, too, so one of them may have a clip or screw hole broken off, allowing them to rattle when the car is in gear when vibration is higher.

Eventually you are going to have to poke around and look. Most likely a broken clamp or holder, or something coming loose.

Peter

[Hocky]

Thanks Peter for your comments. I have found some potential trouble spots for the rattles and looks like some loose wiring/ tubing which could vibrate with the engine's frequency of vibration while it is running and during accelerations. There is a loose bunch of wiring right under the windscreen next to the brake vacuum whatever-youcallit. I have tried to tie this up with one of those nylon strips and some foam. There is one thick wire next to the right front fender near the headlamp's back which could also rattle and this has also been tied up to the chassis. The third one is the thick tubing on the left side next to the ABS which has a large rubber ring around it to absorb vibrations. This ring has gone hard and could also rattle against the chassis. Will try to tie this up soon. Other noises could be some loose screws or washers in the small area where the windscreen washers reside under the rear end of the hood because this was opened by the repair shop to replace broken spray jets when they repainted the hood. Other noises may be in the sunroof, but hope I am wrong as they will be hard to trace and remove.

[Hocky]

I opened up my bonnet/hood and saw 3 plastic hatches/covers. small ones under the wiper end of the hood where the windscreen jets are and these are loose and look like they would rattle loudly in sequence with the motor's vibrations. I will tape these up and maybe finally silence the noises for good. Any other ideas about where the noises are coming from??? Doesn't sound anything like the suspension although it is a bit stiff and does make the car go a bit hard over holes and road surface imperfections.

[Hocky]

Yeah! Today, I have taped up the loose plastic hatches under the wiperjets end of the hood. Hope that when I drive the car tomorrow night, the rattles will be gone for good! Hope so. I cannot find any other thing that may be loose in there except for the aircon hose from the compressor which I will tie up to the chassis in a few minutes. My safety belt still squeaks as I move my body in the driver's seat. This one I cannot solve. It is quieter now, but still there. When I jack up my seat, it stays. However, when I get out and back in again, it "bonks" back to the lower original position. Shouldn't it keep its position mechanically unless the gears are gone or the mechanism is loose???