Trouble finding exhaust leak 99 Deville Y motor
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Northstar Engines and System Technical Discussion Discussion, Trouble finding exhaust leak 99 Deville Y motor in Cadillac Engine Technical Discussion; I have a leak that sounds like its right behind the speedometer. A muffler shop said it was the stainless ...
  1. #1
    DanDeville99 is offline Cadillac Owners Member
    Automobile(s): 1999, 1993 Deville
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    Trouble finding exhaust leak 99 Deville Y motor

    I have a leak that sounds like its right behind the speedometer. A muffler shop said it was the stainless steel flex joint in front of the Cat. I was not totally convinced but bolted on a whole assembly with an aftermarket Cat from a 1998 Eldo parts car. (high mileage, severe head gasket symptoms)

    Unfortunately, the same noise up front was still there and I know I have a good seal at the manifold donuts. I CANT FEEL a leak around the EGR snorkel tube. I did not have a known good used one available and when I found out it was 120 at Cadillac, I decided to hold off until I asked at this forum.

    Is it normal for an aftermarket Cat to turn on code p0131? I changed the rear 02 sensor thinking the eldo one may of been different. The code is 02 related. I did note the front o2 was in a different location so I left it alone on the deville and plugged the port on the Eldo pipe. Since the factory cat was not plugged I think I will have to change it back but hoped to have some ideas on the exhaust leak before I got into another exhaust project. Even the smoke test at the tail pipe did not reveal anything. I HOPE these cars do not crack manifolds, LOL

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  3. #2
    ewill3rd is offline Cadillac Technician
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    Re: Trouble finding exhaust leak 99 Deville Y motor

    First, you don't have an exhaust leak at all.
    Your shift cable is broken.
    Look behind the accelerator pedal, there is an oval shaped rubber grommet, the retainer has broken off and it is open to the engine compartment allowing normal engine noise into your car.
    Replace the cable.. not really an easy job but....

    Second, Converters don't set O2 sensor codes, O2 sensors do. Converters set converter codes. (P0420 in your case).
    Probably a bad sensor.

  4. #3
    DanDeville99 is offline Cadillac Owners Member
    Automobile(s): 1999, 1993 Deville
    Join Date
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    Location
    Upstate NY
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    41
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    23

    Re: Trouble finding exhaust leak 99 Deville Y motor

    Quote Originally Posted by ewill3rd View Post
    First, you don't have an exhaust leak at all.
    Your shift cable is broken.
    Look behind the accelerator pedal, there is an oval shaped rubber grommet, the retainer has broken off and it is open to the engine compartment allowing normal engine noise into your car.
    Replace the cable.. not really an easy job but....

    Second, Converters don't set O2 sensor codes, O2 sensors do. Converters set converter codes. (P0420 in your case).
    Probably a bad sensor.
    Thanks Ewil, I checked and the yellow plastic where it meets the black firewall as well as the rubber grommet are all tight and intact. I thought for sure that this must be it since the leak does make the engine sound like its in the car with me. While it was cold I started it and ran my hand along that EGR tube. I did feel a slight leak near the bottom. Not sure if its in the large nut connection or if there is a crack in the manifold between the EGR and the flange where the intermediate pipe to the cat bolts on. Very frustrating and I only had a few minutes to check things before it got too hot.

  5. #4
    ewill3rd is offline Cadillac Technician
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    Re: Trouble finding exhaust leak 99 Deville Y motor

    Well if that grommet is good then you gotta keep looking I guess.
    Seems odd, I rarely see leaks on those.... if ever.
    Good luck!

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