Noise with motor off key on behind intake manifold.
 

99 ML320.
When the key is on and the engine not running I hear a noise coming from the rear of the intake manifold. Perhaps from the air breather tube. It whirrls or runs or hums constantly.(with key on engine not running).
I've been trying to figure out why I have occational no start problems.

Anyone know what this is ? Thanks.

So far replaced fuel filter to try &
fix starting problem.

The filter update and new fuel lines made no differance.
I ordered a new fuel pump today. 9/9/2004

The noise is probably from the auxiliary water pump. IT runs to help heep hot spots from damaging the all aluminum engine, esp when hot.

Would have no effect on hot re-starts. Most likely problem that causes hot re-starts is the crankshaft flywheel speed sensor.

ML320 no start at times.
 

The no start situation has been when the truck is not hot.

However, the reply is greatly appreciated.

ML320 no start at times.
 

The no start situation has been when the truck is not hot.

However, the reply is greatly appreciated.

The noise you're hearing is most likely the throttle actuator but I doubt it's the reason for the no-start problem. The crank position sensor is the most likely culprit.

throttle actuator
 

should that continously run ?

My '96 S500 (M119) also makes a "whirring" noise when the key is on, engine off. Removed the air cleaner assembly and the noise is clearly coming from the throttle body area... its done it for as long as I've had the car... always thought it was normal but don't have another to compare it to...
Anyone?
Thanks.

Noise
 

Thanks
I was hoping that I just never noticed it before.

:) :)