Hi Folks,

I have a 98 C70 HPT with 96,000 miles on it. I'm regular with all maintenance, etc. However, just recently within the last two days I started noticing a bizarre growling sound coming from what appears to be the engine compartment. I'm having difficulty diagnoising exactly what it is. Any help on this matter would be greatly appreciated.
Here's what I'm hearing and experiencing:

1.) Under hard acceleration from 30 to 40 mph, starting at about 2500 RPM I begin to hear a deep growling noise with a slight vibration coming from the engine and interior floor. This is unlike the normal turbo spooling that I am acustom to. It is much more of a metalitic grinding sound, unlike the air boost sound that usually comes with hard acceleration of the high pressure turbo.

2.) There appears to be no noticable turbo power loss.

3.) The sound increases in volume should I slow to a light and the transmission down shifts to 2nd gear, then I begin to accelerate again.

4.) The growling sound lasts about 1 to 2 seconds and can easily be duplicated.

5.) There is no difference with the engine under load of the a/c or additional people in the vehicle.

6.) This only occured at low speeds in 1st and 2nd gear.


Possible Diagnosis?

Is it possible that the turbo is clogged or the wastegate need to be cleaned?
Or is is possible that a vaccum line is cracked or broken and that is creating this problem. Or is this a transmission problem and has nothing to do with the turbo at all.

I'm completely puzzled....
So any one experiencing this problems or something similar please share your solution and comments.

Thanks in advance for your help.