Cadillac Repair: Whistling noise from engine, intake manifold gasket, inch pound torque wrench

Question
I have a 1994 Concours with the 4.6 Northstar (103,500 miles).  I have recently been noticing a whistling noise from the passenger side rear of the engine below the power packs.  I have removed the plenum cover and resealed it having no effect on the noise.  Could I have an intake gasket leaking as it does sound like a vaccuum type whistle (PCV has been changed and tube cleaned).  You can hear it very well when the hood is open and when the engine is turned off the whistling dies out slowly not stopping immediately when the engine is turned off.  If it might be the intake gaskets how much work is involved and can it be tackled at home without having to pay the high price of the dealer?  Also I have an oil leak that is only present when the engine is cold and once it warms up it stops.  I am having to add about a quart of oil every 2000 miles.  Considering the miles and what is going on this car is still getting 22-24 mpg on the highway at any speed.

Answer
Hi Don,

    Since the noise is obvious what I would do is use a mechanics stethoscope with the probe removed and use the open end of the hose to try and isolate where the noise is comming from. If you used a 3 foot section of 1/8-1/4" vacuum hose held to one ear that could also work.

    The intake or plenumn gaskets are suspect as is the brake booster check valve. They have been known to make some strainge noises.

    If it is the intake manifold gasket the only special tools you would need are an inch pound torque wrench and a fuel line separator tool. Those can sometimes be loaner tools at the Autozone, Oreilly or Pep Boys. Otherwise to buy the fuel line separator isn't too expensive. I would recommend a good shop manual or subscribe to alldata. com for your car. With that info available to you it shouldn't be too difficult a job.

    The Northstar is known for oil leaks from the rear main seal and the oil manifold where the block meets the bearing saddle. There are chemicals that will slow down or stop a leak but I would be cautious useing them. 1 qt in 2k miles isn't really alot so you might just monitor the oil level dulling fuel fill-ups and add as needed unless the leak gets worse like leaveing a puddle when the engine is running.

   Hope that answers your questions. Bill