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Vacuum Leak in Dash - 2002 ETC


coolnesss

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There's a soft vacuum leak sound coming from the dashboard area.  My guess is that's it's the A/C system.  Is this typical - how much of the dash do I have to take out to get to it, or should I let a tech do it?

THANKS

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If you are talking about the 2002 ETC, I can't think of anything vacuum actuated under the dash. I'm pretty sure even the P-brake release was electric actuated in 2002. 

The only thing I can think of that might make that sound is some of the inside air temperature sensors had a small electric motor that would draw air across the sensor. I'm not sure 2002 had that even.

Wait for @Cadillac Jim to chime in he has access to the FSM....

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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The Eldorado never changed platforms after 1992, and the 1998 and later models mixed design details with the Seville/Deville of the same year and the Eldorado, depending on the item.  As OldCadTech says, you need the FSM for the given model year to make sure.

According to the 2002 FSM, the temperature doors are controlled by stepping motors that are run by electrical signals.  No vaccum on the controller or the temperature doors.

The doors that control the inside air/outside air are vacuum operated.  The doors that control circulation from the defrosters, dash vents, or floor vents are vacuum operated.

Poking around in the HTML available to me as the 2002 FSM, I find a vaccum actuator schematic.  The vacuum operated under-dash items are:

  • Air/Defrost door
  • Air up and Air down actuators (two actuators in one housing)
  • Recirc vacuum actuator (has a hose obstruction that implements a time delay)
  • Parking brake release

You could start by checking the parking brake release to see if the vacuum is making it all the way across the car.  Start the car and leave it idling in Park for a few seconds, press the parking brake and wait a few more seconds, then take the transmission out of Park.  If the parking brake releases, you have vacuum all the way across under the days.  This does not mean that you don't have a vacuum leak, it just means that you don't have a hose pulled off somewhere.

There is a vacuum tank under the hood.  The vacuum hose from it goes to the firewall with a tee, the other hose goes to the throttle body.  You can place where the vacuum goes through the firewall by spotting the hose off the vacuum tank.

The vacuum control assembly is behind the glove compartment.  It's mounted against the firewall.  The FSM R&R procedure is to remove the glove compartment, but you can probably detect whether the main hose is off, or otherwise find the leak, by just removing the insulator panel (the leather panel under the glove compartment) and using your ears.  If it's back there but you need to be more specific, you can use

  • A 3/4" heater hose about 3 feet long, one end to an ear and poke the other back there to find the leak
  • Do the same thing with a mechanic's ear
  • Use your imagination

The vacuum hoses run from the vacuum control assembly to each of the actuators except the emergency brake release, which is all the way across the car, so you can follow the vacuum hoses from there to the actuators.

CTS-V_LateralGs_6-2018_tiny.jpg
-- 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.

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does the leak change tone as you change the air flow settings?

also does it leak in park? If it does not then you will want to check the green vacuum line that runs to the parking brake lever.

More than likely one of your lines is disconnected. In my experience with this setup it is not common.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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I think that the biggest tip is to use a hose as a mechanic's ear for finding vacuum leak hiss under the dash.

CTS-V_LateralGs_6-2018_tiny.jpg
-- 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.

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22 hours ago, Cadillac Jim said:

I think that the biggest tip is to use a hose as a mechanic's ear for finding vacuum leak hiss under the dash.

If you are hard of hearing like me, 5/8" heater hose.... :bluesbrothers:

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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  • 4 weeks later...
On 10/23/2017 at 6:39 PM, rockfangd said:

I also ask Are you sure it is a vacuum leak? and if so how are you sure?

Not doubting you. Just curious

It is audible at idle in the cabin.  It's unmistakable.

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Have you located it yet?

CTS-V_LateralGs_6-2018_tiny.jpg
-- 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.

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