2018 Nox HVAC Issue Emerging - TerrainForum.net: GMC Terrain Forum
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post #1 of 29 (permalink) Old 07-02-2017, 08:13 PM Thread Starter
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2018 Nox HVAC Issue Emerging

Hi!

So day 2 with the new Nox and I've detected a curious problem. Hwy speeds with recirculate on I am getting a thumping noise from the rear. When the recirculate is turned off to get fresh air, the thumping goes away. I've narrowed it down to the rear cabin vents they install in cars to relieve pressure inside the cabin. From what I understand though - it shouldn't be trying to 'vent' if recirculate is active as it's pulling in it's own cabin air into the HVAC system.

So before I go to the dealer I've been looking around and decided to check the mode door for inside/outside air. What's interesting is sitting idle and choosing between recirculate on/off - the mode door doesn't move... It did after awhile of poking around in there to see if it was stuck... So turned off the car, waited and started it again. The mode door started acting funky again. The only way I can reliable change the function is if I turn off the HVAC completely, select the mode back and forth and then the door moves.

I did check to make sure I turned off all "auto" functions I could see on the system.

And really I don't know if the two things are even related? I know the vents start venting if outside air is selected and the air needs to escape so the pressure doesn't build up.

Soooo I'll keep this post updated - I will have to call my dealer service contact in the morning to see if there is even a fix for this yet.

T

2018 'Nox 2LT // 2.0L TURBO V4 AWD // Nightfall Gray Metallic // 18" Wheels, Pwr Liftgate, Class II Tow Package, Blind Zone Alert, Heated Seats, Remote Start

2013 'Nox 2LT // 3.6L V6 AWD // Ashen Gray Metallic // 18" Wheels, Pwr Liftgate, Tow Pkg, Jet Black Leather (TRADED 2017)
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post #2 of 29 (permalink) Old 08-23-2017, 08:32 PM
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Thumbing noise in rear end

I too am getting a thumping noise in the rear end of my equinox. I've had the 2018 premier edition for two months now. At speeds over 45 miles an hour I get this thumping sound that it sounds like it's coming from the rear end and I am not sure what it is. I thought it was the gas banging around because it does it from when I have 3/4 of a tank of gas or less. Never thought it was part of the AC unit, I run it on fresh air no recirculation and it makes this sound. Not sure what it is but I guess I need to bring it to the dealer to find out why.
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post #3 of 29 (permalink) Old 08-24-2017, 10:55 AM
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Service Information




Document ID: 4849237
#17-NA-265: Flutter or Boom Noise from Rear of Vehicle - (Aug 21, 2017)
Subject: Flutter or Boom Noise from Rear of Vehicle
Brand:
Model:
Model Year:
Date Breakpoints:
Engine:
Transmission:
from
to
from
to
Chevrolet
Equinox (VIN X)
2018
2018
SOP
Ingersoll Assembly built prior to June 1, 2017
Ramos Assembly built prior to June 23, 2017
San Luis Potosi Assembly built prior to June 26, 2017
All
All
GMC
Terrain
2018
2018

Involved Region or Country
North America, N.A. Export Markets
Additional Options (RPOs)
Condition
Customer may comment on hearing a flutter or boom noise from the rear of the vehicle. The noise is most noticeable while driving above 25 mph, with the HVAC off, or in recirculation mode.
Cause
The cause of the condition may be the rear pressure relief valves (PRVs) opening and closing.
Correction


Note: The installation of an acoustic insulator panel (1) and block (2) will help to dampen the noise.

Verify the condition and install a rear acoustic insulator panel and block, following the repair steps in the Service Procedure below.
<a id="d1852e212">Service Procedure
  1. Remove the rear fascia and both rear pressure relief valves (PRVs). Refer to the appropriate Body Pressure Relief Valve Replacement procedure in SI.
  2. Install the acoustic insulator panel along the backside of the chamber between the rear body panel and the inner rear panel, following these steps:
    1. Slide the insulator panel (1) into one of the PRV openings.
      Important: Ensure that the insulator panel is centered and DOES NOT BLOCK any of the holes in the body.
    2. Center the insulator along the back side of the chamber.
    3. Tuck the outside edges of the panel into the corners.
  3. Install the acoustic insulator block (1) in the middle of the chamber, between both PRVs.
  4. Reinstall both PRVs and the rear fascia. Refer to the appropriate Body Pressure Relief Valve Replacement procedure in SI.
<a id="d1852e275">Parts InformationCausal Part
Description
Part Number
Qty
N/A *
INSULATOR ASM-BODY RR PNL
84313892
1
N/A *
INSULATOR-R/END LWR PNL REINF
84313893
1
* For warranty transactions, DO NOT mark this/these parts as the Causal Part. Enter the word “Bulletin” in the Causal Part Description free-flow text field.
<a id="d1852e359">Warranty InformationFor vehicles repaired under the Bumper-to-Bumper coverage, use the following labor operation. Reference the Applicable Warranties section of Investigate Vehicle History (IVH) for coverage information.
Labor Operation
Description
Labor Time
1480868*
Rear Acoustic Insulator Panel and Block Installation
1.6 hrs
*This is a unique Labor Operation for Bulletin use only.
Version
1
Modified



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post #4 of 29 (permalink) Old 08-24-2017, 04:05 PM
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Wow - I can't believe GM's testing of the new vehicles did not reveal this problem before production. I wonder how many people will put up with the noise or their dealer will tell them that the noise is normal? Sounds like the vehicle was rushed into production and there many be other design flaws and defects.
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post #5 of 29 (permalink) Old 08-24-2017, 04:17 PM
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agreed
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post #6 of 29 (permalink) Old 09-21-2017, 12:47 AM
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any body had the repair done and did that stop the noise, I am getting the same issue on mine
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post #7 of 29 (permalink) Old 09-21-2017, 09:15 AM
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Quote:
Originally Posted by mike6681 View Post
any body had the repair done and did that stop the noise, I am getting the same issue on mine

It's under warranty, it's free. . . . get it done. ..
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2019 GMC Acadia SLT-1 3.6L LGX V6 - Build Date: 4-11-2019 - Bought 6-22-2019

SOLD - - 2015 Equinox LTZ 3.6L FWD Champagne Silver Metallic *Build Date 1-08-2015 *

SOLD with *38,865 miles 8-15-2019.

Last edited by JayTee2014; 09-21-2017 at 10:37 AM.
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post #8 of 29 (permalink) Old 09-22-2017, 01:11 PM
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I have had my 2018 Nox back twice for this noise and they claim they can't hear it all the time. When I brought it the second time I had everything out of the back including the spare tire. I had the assistant service manager sit all the way in the back in the spare tire well and he said he could hear it when I was doing about 30 mph and it got louder the faster I went. He called me after and said they couldn't fix it because the noise went away. I was really pissed because anybody who sat in the back was saying the noise was always there. After I brought it home me and my son started driving around trying to find the noise. Found out the HVAC has to in recirc mode to make the noise. Found the noise in the rear vent flapping open and closed or as GM calls them pressure relief valves. Found this bulletin in this thread and I called them and made another appointment and referred to this document number. They are saying they can't find the document. I emailed them a copy and they wanted to know where I got it. I am bringing the Nox in Tuesday and a copy of this document and I am going to stand there and make them do this. Wish me luck! I will let you know how it turns out.
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post #9 of 29 (permalink) Old 09-22-2017, 01:26 PM
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So what does it actually sound like. Is it a thumping? Its not really loud but loud enough to hear right?


I haven't had this problem myself but curious to see what I should listen for.

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post #10 of 29 (permalink) Old 09-24-2017, 03:27 PM Thread Starter
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Sorry everyone for not posting more recently! End of summer fun I guess heh.

Anyways, I've had a piece of paper from the dealer in my glovebox that has the doc ID 4837929. This was found when the service guy looked up my vehicle by vin - but the issue is as described on what BigB posted. "Interior Boom Noise While Driving Above 25 MPH" and "At cruising speeds with the HVAC system off or in recirculation mode a boom noise will eminate from the rear of the vehicle." Direct quote - interesting to see "eminate" spelled wrong lol.

As far as the other issue of not always going into recirc - I've chalked this off as it's part of the system being set on auto because it does eventually switch properly after driving a few miles and the cabin cools down.

T

2018 'Nox 2LT // 2.0L TURBO V4 AWD // Nightfall Gray Metallic // 18" Wheels, Pwr Liftgate, Class II Tow Package, Blind Zone Alert, Heated Seats, Remote Start

2013 'Nox 2LT // 3.6L V6 AWD // Ashen Gray Metallic // 18" Wheels, Pwr Liftgate, Tow Pkg, Jet Black Leather (TRADED 2017)
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