Loud hiss coming from behind dash!
 

Hello,

I am new to this forum and have a problem that I can't figure out.

I just replaced my fuel plate and now all of a sudden I have what sounds like a vaccum or boost leak comming from under my dash somewhere near the fuse box area. This did not happen before I chaned the plate, but as soon as I fired it up afterward and started to drive down the road there is was. It sooms to be tied to my boost gauge? I have inspected the line and there are no kinks, rubs, or anything else wrong with it. The boost gauge registered 25#'s of boost prior but now only will register 15#'s. The hiss starts at 6#'s and only gets loader as the boost goes up. I also checked the connections and all are tight and don't seem to be leaking.

Can anyone give me any advise? Please??

-Scott-

I have just totally unhooked the boost gauge at the engine and capped the lines and the problem is still there, so it is not the boost gauge or the lines for the guage. What else could it be?

-Scott-

If it were a truck at work I would install the air charge test tool and pressure up the system to see if the sound could be duplicated. Essential tool at the dealer if you have access.

Air horn/plenum gasket leak or one of the rubber joints in the turbo plumbing , if I were to take a guess

what about the boost tube running from the afc to right below the intake horn?

Well, I'm an IDIOT! I found the problem. I forgot to tighten the clamp on the hose that goes to the intake horn. I removed it to have more room to work and when I put it back on I tightened everything else but left it loose! The sound it made sounded like it was coming from the dash, but now it is fixed. Thank you all for your help in this matter! KD460's reply made me think of that and sure enough that was it.

Thanks Again!

-Scott-

RE: Hissing Sound, has anyone installed 2 boost gauges, one on the air horn and one between the turbo and first rubber boot? This would allow you to monitor for leaks in the plumbing and intercooler.

My brother-in-law (he is a heavy duty mechanic who works on Cat equipment) suggested I do this.

Any feedback would be welcomed.
Thanks.

Even if the leak was large the gauges would read the same. The only thing two gauges may tell you is if there are any bottlenecks to flow in the system.