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Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
Satisfied Customers: 25632
Experience:  Technican turned service manager with multiple lines of equipment and rental units.
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I'm working on a c9 engine thats in a Transit bus. Makes a

Customer Question

I'm working on a c9 engine thats in a Transit bus. Makes a humming noise like a siren only when its under load. Changed all hoses on intake side changed intake manifold and still has a noise like a siren on the intake side of engine. Performed fuel and air verification tests all passed. No loss of performance and turbo boost psi all fine
Submitted: 6 months ago.
Category: Construction and Road Equipment
Expert:  Curtis B. replied 6 months ago.
The noise can be leaking exhaust gases on the turbo outlet side. It whistles like a person blowing across a piece of cellophane. As turbo boost increases, the pressure in the manifold builds, and the gasket/seal or cracked pipe leaks and makes the noise. Look for evidence of a minor exhaust leak. Can be anywhere between the turbo and the exhaust manifold, to the manifold gaskets. And can be on the intake manifold side. which will not show as a leak, but can be found by spraying with soap and water mixture and looking for air leak. Noise will be related to the pressures generated by the turbo!
Expert:  Curtis B. replied 6 months ago.
Did you find the whistle?

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