consciousmechanic Posted December 1, 2010 Report Share Posted December 1, 2010 I have a 1998 Eldo Sport Classic Edition W/4.6L Northstar. The intake makes a very annoying high pitched whistle at high vacuum (it stops during the opening of throttle body) Is this a common occurence and what is required to fix it? No engine codes, but occasional rough running and stumbling. I can't find anything obvious, but I suspect an intake leak, and I would like some insight before tearing into it. Any info would be much appreciated. John Link to comment Share on other sites More sharing options...
Cadillac Jim Posted December 1, 2010 Report Share Posted December 1, 2010 This is clearly a vacuum leak, and the possibilities are numerous. You could start with the hoses connected to the throttle body and look for disconnected, cracked, or deteriorated hoses. The PCV valve, located on the rear cam cover on the passenger side, may be stuck open. Also, make sure that the dip stick is there and is all the way down, and that the oil filler cap is tight. Leaks in the manifold gasket do happen too. Once you have eliminated leaks related to the vacuum hoses on the throttle body and the crankcase, you can look at that. One simple way to do that is to take off the beauty cover and listen. I would use a tube, holding one end to your ear and passing the other around the perimeter of the manifold. Also, listen near the FPR, which is at the rear of the manifold on the driver's side, where the fuel lines come up from under the car and bend over toward the manifold. Also, check the seal of the MAP sensor, which is in front of the FPR. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
Texas Jim Posted December 1, 2010 Report Share Posted December 1, 2010 It sounds like you are in the right track,,,suspecting a vacuum leak. Check all vacuum hoses, of course and also check the intake bolts. Link to comment Share on other sites More sharing options...
Ranger Posted December 1, 2010 Report Share Posted December 1, 2010 It IS a vacuum leak. It's the manifold over pressurization (flapper) valve in the tunnel behind the P/S pump. It may need a new seal or maybe you can just reseat it, but in either case you will most likely have to remove the manifold. Link to comment Share on other sites More sharing options...
consciousmechanic Posted December 1, 2010 Author Report Share Posted December 1, 2010 Ok,Ranger! Thanks to All for the info. The gasket set is easily available for the manifold, but how about the flapper valve seal? Cadillac dealer only? I don't want to take it apart without having the parts to fix it on hand. Link to comment Share on other sites More sharing options...
consciousmechanic Posted December 1, 2010 Author Report Share Posted December 1, 2010 Update: FYI The high pitched whistle was coming from the manifold over-pressurization valve. By sticking a long screwdriver past the power steering pump and under the intake, I could manipulate the valve a little and make it stop. However, as soon as I rev the en, it's back until I push on the valve again. I guess I'll have to see about replacing it. Thanks to everyone who helped solve the mystery! Link to comment Share on other sites More sharing options...
adallak Posted December 1, 2010 Report Share Posted December 1, 2010 Update: FYI The high pitched whistle was coming from the manifold over-pressurization valve. By sticking a long screwdriver past the power steering pump and under the intake, I could manipulate the valve a little and make it stop. However, as soon as I rev the en, it's back until I push on the valve again. I guess I'll have to see about replacing it. Thanks to everyone who helped solve the mystery! Ranger is da man! The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
rockfangd Posted December 1, 2010 Report Share Posted December 1, 2010 pics possible? the valve can be seen without intake removal? I have heard this before (not on my deville) but in other cases GM FAN FOREVER Nice, clean, luxury= fine automobile Link to comment Share on other sites More sharing options...
Ranger Posted December 2, 2010 Report Share Posted December 2, 2010 If you get down on just the right angle, twist your head and hold your tongue just right between your teeth you might get a look at the valve. Not sure if the seal is replaceable or if you will have to replace the valve aka flapper door. Link to comment Share on other sites More sharing options...
Cadillac Jim Posted December 2, 2010 Report Share Posted December 2, 2010 Wouldn't it be easier to use a mirror? Thank you, Ranger. We all need to remember this one. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
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