Turbo Whistle sound gone
 

Hello, I have a 2002 volvo s40 1.9t, a couple of days ago, I used CRC valve & turbo cleaner to clean my turbo. I sprayed it into the air intake, after everything was done, I got one error code, I hooked up my scan tool, it says turbo charge overboost condition. And I just cleared the code and the car ran fine, but I think I don't hear the whistle sound which is from the turbo that I used to hear when I try to accelerate hard anymore. And I think my acceleration is not as good as it used to be. I was guessing I might damaged the turbo or the turbo got disabled. I don't know how to test the turbo, any thoughts? Thanks,

the turbo itself is just a housing with turbine blades that pump air. Usually when they fail its due to a leaking seal or a bearing so its not likely you damaged the turbo. What makes the turbo system is its control system - pressure sensors that feed the ECU to allow it to actuate the waste gate to relieve excess pressure based on driving conditions. So what can mess things up are bad vacuum lines, a sticky or bad waste gate, a bad boost sensor etc. About the only way to test the turbo that I can think of is to pull off the top hose reach in and see if it can spin freely. My first step would be to look for torn hoses/boots/vacuum lines. It could be possible you are losing boost in the big tubes going to/from the intercooler.