Engine/Transmission (1998.5 - 2002) loud hissing sound on hard pull

[BGoodale]

Guys,I need your help. About a year ago I started to hear a hissing sound on a long pull. I had put a psm fresh air intake on and thought that maybe that was the problem. But I have taken that off and it is getting worse. I back off a little and the noise goes away. I've got gauges and the boost is about 22 psi and if I let off a little the noise goes away. Do I have a turbo going bad or what? My truck is mostly stock . Any ideas.

 

[mweiman]

Have you checked for a boost leak? Check all of your hoses, piping, clamps, intercooler and intake manifold for signs of a leak. What year is your truck and what have you done to it? 22 Psi sounds a little low but I would doubt that it is your turbo, more likely a leak. If you don't see something obvious you can also make a leak tester out of some pvc caps and a regulator.

Matt

 

[RustyJC]

I had a boost leak in the tubing that went to my boost gauge in my 2002. It only showed up when boost was over 20 PSIG, so it was tough to track.



Rusty

 

[BGoodale]

Thanks guys for your help. My truck is an 01 auto with 187,000 miles on it. I do have an edge ez box that I keep on the #2 level most of the time. Because of the box I was limited to 20 psi on boost so was advized to use a j hook which I have done. The boost is now about 25 psi at it's highest. But this hissing sound started before all this was done. Would'nt I show a lower boost if I had a leak? I agree that it soulds like a leak but I've checked connections and can find no leaks, but will re check. When I'm not pulling the sound goes away or is highly diminished. . I do have a pac brake and wondering if there is a leak in the those lines? Also have a muffler elim kit with the 3" exhaust . So any more ideas would be greatly appreciated. I guess I'll keep driving the truck, just hope I'm not doing any damage. Thanks, Brett

 

[GCroyle]

Brett,



I think there has been several write ups about isolating and pressurizing the intercooler, tubes, clamps and hoses with a controlled shop air source and pluging the end and I even sprayed soapy water on my '97 to find a loose boot clamp.



Don't forget possible intercooler leaks, spray it also or pressurize and see how well it holds as a closed pressurized system.

 

[DIESELWRKS]

I would try and pressurize your system first before anything. I have also had the top plate going into the head where your manifold air horn connects leak. usually people will get cuts on the lower intercooler boots on both sides due to how the trucks fenders will rub into them. there is a couple wright ups on people using pieces from home depot, etc to make a pressure cap. if you have access to a air compressor. usually loose boots are pretty loud at any boost level.

 

[Midnite]

Pressurizing the intake system is always good because most people have at least small boost leaks that they never know about.

However, I'd be amazed if you could hear a boost leak under the hood at a near-full throttle pull. I think I'd be looking at the tubing for the boost gauge inside the cab, and especially make sure your connection to the gauge itself isn't leaking.

 

[RustyJC]

I looked for weeks under the hood for my boost gauge tubing leak. It sounded like it was coming from under the hood, and you wouldn't believe how loud it was. It turned out to be where the hose slipped over a barb fitting on the back of the gauge.



Rusty