Hey guys

my car has a grinding noise... under half acceleration. No noise when I cruise along lightly on the throttle, and no noise when I am WOT. It only seems to occur when I am 1/4 to 3/4 of the way on the throttle. It sounds like the motor is rubbing against something, or ... I dunno... does sound like it is coming from the passenger side of the front.

Any idea?

thanks

 

motor mounts

 

if the motor mounts were worn... it would cause a grinding only at half throttle? but not at full throttle?

 

the motor floats on the motormounts according to the amount of torque applied to it, at half throttle it's seesawing or resting completely, at full throttle it is fully torqued

you might test my theory by getting full boost and letting off the gas really hard, if you hear a clunk, it's your motor mounts

 

Interesting, I have the same symptom (very rarely though) and have just had my new engine put in...my mechanic told me the mounts were fine though

 

Hmm, 93BlackFD, your theory makes sense, but when I get on it, and let it off, I get a nice whoosh from my BOV, but no grinding... if I let off half way, I can get the grinding sound to appear.

Riccardo, give me a hollar if you learn anything new about it. Sooner or later, I'm thinking i'm going to head down to KD, when he has time, to get my bushing done and ask him about him about sound...

 

when you hear the grinding do you also hear the 2nd turbo venting?

 

Will do nycrx7
I think so potatochobit...

 

Get under the car and check your power plant frame (PPF) for cracks.

 

PPF? what is that? Is that the same as frame or related to the engine mounts?

 

yes.. powerplant frame.. it's wrapin around the driveshaft and trans

 

Also check your airpump for that noise.I had that happend to me.Under wot no noise.Under light throttle it squeeled like a banshee.While cruising it squeeled but not as loud.Your air pump may be fried.Or at least the pulley part.

 

i had a somewhat similar problem over the summer of 2003. the problem i had was my differential, that could be the grinding sound, but it was there throughout the ride, WOT, 1/4 / 1/3 acceleration etc.

 

speeddemon - its not a squeeling sound - it sounds like mental to mental grinding/rubbing. Not a belt sqeeling sound.

 

still check your air pump.cause the squeling sound it made was metalic.Not like a belt squeeling.It sounded like metal on metal.Does anyone know if the air pump pulley has bearings in it?

 

i was thinking it could be your 2nd turbo shaft with too much play, but maybe thats not it. the turbos are not leaking bad are they?

also have you replaced anything recently? check to see if the battery tray is not loose and pressing on the fans.

it could also be chipped gears in your transmission

 

Turbos are in good shape. No leakage at all.

The only recent re-installation was an airpump. I will double check to make sure its on tight, but I don't see how that would cause a grinding sound... and only sometimes. I also heard when airpumps go bad, they seize up. So then the belt would squeal.

I guess the thing is... no sound at idle or full throttle. Not even under soft acceleartion. Just when I go 1/4 - 3/4 acceleration. Or even when I let off slowly... I can make the sound reappear. . I mean I can punch it from a stand still to 100, and no sound. But do it slowly, and the grinding sound comes up.

THanks to those that have replied already.

 

i have the same problem..... please pm me when you find something that works!!!!

 

I've got a grinding sound...

Mine does seem to occur at low throttle, but only at low speeds as well.

Could this be the same problem?

 

Okay has anyone actually popped the hood and listened for the sound yet? Sounds like the airpump to me - it has an electromagnetic clutch that disengages the pump core from the pulley when under heavy acceleration and above a certain rpm.

 

Is the airpump a common problem, should I hear it during idle?

-C

 

Just unplug the airpump and see if the noise goes away or not. At least that will help narrow down the search since we can't hear it.