Durring a recent QOT pass It out of the blue made a loud howling noise and boost fell off. After that pull the boost hasn't dropped but it still makes a loud howling noise as it builds boost. So what could it be? There is some side to side shaft play but zero in and out. There are no signs of contact with the housing or damage to the impellers. I checked for any possible boost leaks but have not seen any but im going to pull all the piping, carb hat ect apart and make sure its all good.

 

more vibration?
how much side to side play is there
checked if the blades are damaged?

 

See if a coupler has a small rip in it.

 

Nut loose on the compressor?

 

No the blades are not damaged at all, the nuts are tight also. When i get a chance ill inspect all the couplers and seals though.

 

yea it is

 

loud siren noise is usually metal to metal contact, are you looking at the turbo while its still on the car ?? if so thats not inspecting it, id take it off and really inspect it, it might be out of balance

 

It was pulled from the car and inspected there is no signs of damage or touching. The side to side play is quite a bit but still not enough to hit the housing. Maybe a quick rebuild is in order.