Ram Turbocharge Noise Diagnosis

12 Valve Cummins Diesel Engines

From the Star Center News

Some owners of 1994-97 Dodge Ram trucks equipped with the Cummins diesel engine may complain of various types of turbocharger noise. The following noises may be among those :

Remember, what is heard as turbocharger noise may not be caused by a noisy turbocharger. Before replacing a turbocharger perform the following diagnosis.

A.    A loud whine or whistle is heard during acceleration and increases or decreases with rpm and load.

This condition is most often the result of a loose clamp/hose at the turbocharger compressor outlet, charge air cooler (CAC) inlet, CAC outlet or at the intake manifold.

1.    With the engine running at idle and the transmission in Park or Neutral with the parking brake set, feel for boost air escaping at each connection between the turbocharger compressor outlet and intake manifold. For limited access areas, spray soapy water on those connectors and look for bubbles.

2.    Check the exhaust manifold and exhaust system for leaks.

B.    Exhaust howling (Spooky-hoot) during turbo boost conditions.

This condition usually occurs over a narrow speed range and may be caused by a muffler tuning issue. This condition can be diagnosed by wedging a 2x4 wooden block between the frame rail and the flat area in the middle of the muffler. Repeat the conditions at which the noise occurs.

This condition cannot be corrected at this time; however a new muffler is being evaluated and is expected to be available in early 1997. NOTE: The muffler is now available, see TSB 11-01-97 for an update.

C.    Loud popping, whooshing, flushing, fluttering, noise emitted during closed throttle deceleration.

This condition is caused by inability of the engine to intake higher boost levels that are present at the beginning of closed throttle deceleration. Pressure generated by the turbocharger has nowhere to go, thus causing it to "stall" or "surge". The noise will sound as though it is coming through the air cleaner, however this is a normal condition. No damage will be sustained and the turbocharger should not be changed for this condition.

D.    Low boost pressure.

Low boost pressure is usually a symptom of low fuel injection pump fuel delivery and is associated low power complaints. Refer to TSB 18-29-95 for proper diagnosis.

Turbocharger wastegate adjustment should be checked for proper operation. Refer to the applicable model year Dodge Ram Service Manual for proper adjustment procedures.

Generally turbocharger replacement will be related to turbine shaft failures or turbocharger housing seal leaks. To check for turbine shaft bearing damage, perform the following steps:

1.    With the engine off, remove the air cleaner to turbocharger intake tube.

2.    Visually inspect the turbocharger compressor fan. The fan blades should not contact the fan housing and the fan blades should not be chipped, bent or damaged in any way.

3.    Check the end play of the compressor to fan. A small amount of fore/aft play is normal. Excessive play that would cause fan distortion or fan to housing contact is not acceptable. In this case, replace-the turbocharger.

4.    While pushing the turbine shaft left, right, up and down, gently rotate the compressor wheel. The compressor fan should turn freely by hand, if it doesn't replace the turbocharger. Other causes of turbocharger failure.


Last Update: October 15, 1999