I'm getting a squealing noise (tough to describe) from under my dash when the boost goes above 15 psi. Under normal driving and low boost...nothing. Above 15 psi and it squeals until I let off. I don't know what's more irritating, the noise or not being able to find it! Could it be a vacuum line that's seeing pressure for some reason; perhaps a bad check valve? I'm guessing here since I have nothing to show for my work so far.

Any ideas? Thanks!

 

Might sound silly but, have you checked the line controlling the boost guage? Could it have rubbed on something and have a leak? Split? Just be loose fitting on the boost guage?

 

Check to see if you have the updated coolant pipe coming out of the head for the heater core. I had the exact problem many years ago and found the TSB on dodgeram.org

 

My boost gauge is electric (Edge w attitude), but that's a good tip. I've not heard about the coolant pipe TSB, so I'll check into that now. Do you recall the TSB number?

 

TSB 09-04-99? It's worth a look, I'll report back.

 

If it is only when boost is over 15psi and does it every time it is a boost leak. If it sounds sort of like when you let the air out of a balloon but throttle the end, it is a loose boost hose.

 

I'm not ruling anything out at this point. It sure sounds like it's inside, but you all know just how quiet these trucks are.

 

check all the bolts on the intake plate at the head and where there air horn/grid heaters bolt to the intake. i had a really bad high pitch squeal and it turned out to be the bolt loose at the head and it was leaking boost.

 

the lower intercooler boots are notorious for rubbing on the bottom edge of the fenders. check both sides, i had to bend the pinch weld a bit to get them away from the boots for some piece of mind. remember, they grow and expand with boost!

 

make a boost tester and put some air through the system with an air compresser. I had a leak on my intake manifold. I had to replace my gasket. It sounded like it was in the cab. I even tore apart my boost gauge and air line.

 

Same here. Sounded like dash but was the gasket. We used "the right stuff" gasket maker and fixed it in minutes after the boost test to find it.

 

Do you have a good, test design that will let me pressurize the system? I've used these on turbo cars (gas) but not on a diesel. Seems like it would be easier...

 

Check your exhaust manifold bolts, front to back, top to bottom. Make sure they're there and tight. It will make that sound too because of the gasket/opening.

 

I just took a abs cap and drilled a hole for valve stem. Then I put it in my turbo tube.

 

Just being clear, the inlet to the turbo? Did you back off the valve springs to insure the pressure stayed in the inlet track?