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2008-2013 Cadillac CTS General Discussion Discussion, Hi, I'm an engineer, tell me about your sunroof in Cadillac CTS Second Generation Forum - 2008-2013; WillK, I understand you perfectly. I also work for a global corporation and know first had how things work…… As ...
  1. #31
    MoFex's Avatar
    MoFex is offline Cadillac Owners Connoisseur
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    Re: Hi, I'm an engineer, tell me about your sunroof

    WillK,

    I understand you perfectly. I also work for a global corporation and know first had how things work……

    As I said before, I have great respect for you for reaching out to the end customers. GM needs to do more in that area. This is how you design a product that customers actually want to buy, add to it reliability and quality and you win loyalty! I said many times I will buy GM cars if they are equal quality to competition and I actually like them. Even if I had to pay more! The CTS was the first one from GM and Malibu is the second. So you guys are doing something right, just keep going.

  2. #32
    Delta is offline Cadillac Owners Fanatic
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    Re: Hi, I'm an engineer, tell me about your sunroof

    Quote Originally Posted by WillK View Post
    The closest I can offer to advice with current production vehicles having sunroof issues is that the most practical solution available is adjustment of the glass panels. I am somewhat familiar with the adjustment procedure in production, but not at all familiar with the service adjustment procedure aside from the fact that I am aware that it is different than the production adjustment procedure. As far as how the glass would ideally be adjusted in production, it wouldn't be practical for dealers because it would involve a fixture that would take up too much space and cost too much for any dealership. And it wouldn't take anything complicate like lasers or a vision system, it could probably be simulated...

    I haven't searched for the dealer adjustment procedure, but if I read it I could probably offer my general assessment as to whether it could be improved.
    the service procedure is as follows:

    1) road test until you can find a long enough stretch of road without traffic to duplicate concern.
    2) go back to the shop and find another tech that isnt busy/ doesnt mind not making any money for the next hour or 2
    3) road test again with said tech
    4) pull over, one tech gets out and holds the glass, the other loosens the torx bolts.
    5) adjust front and rear glass by look and feel (expierence desperately needed here)
    6) road test again (noise is probably worse)
    7) repeat until a) you get frustrated enough that you give up or b) said tech needs to go make some money and cant waste any more time dicking around with you.............

    a screw adjustment means that one tech could drive (hell a porter could drive you around) while the other turns an adjustment screw until it sounds better, then go back to the shop, ship vehicle, please customer (with their vehicle being fixed, not... nevermind).

  3. #33
    Delta is offline Cadillac Owners Fanatic
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    Re: Hi, I'm an engineer, tell me about your sunroof

    Quote Originally Posted by WillK View Post
    Well, to my mind, the suggestion begs the question as to whether there are any concerns originating from the rear glass...

    The degree to which the system would function better with a given configuration, given the choice between the rear glass attaching to the sunroof module or attaching to the roof openning reinforcement panel in the body, depends very much on the production process. But even if it was done that way it wouldn't be practical as a service procedure because of the complexity of the change, it would involve changes to the sunroof frame and weld-on body components. Basicly, the rear panel shouldn't be moving anyway and as long as all the relevant components are within print specifications and adjustmets it's a design that should be pretty hard to mess up. If I'm wrong about that I'd be interested to look at it further.
    There are concerns coming from the rear glass. We were playing around with one in the shop one day and decided to actually see where it was coming from (slow day). We road tested a car with a wind noise and applied masking tape all around the front windows and front glass of the sunroof and it still had a noise, but improved. So we applied the tape across the middle of the 2 glasses, still there but greatly improved. Applied tape around the rear glass seals and it was completely gone (now it was just heard from the mirrors, dont even get started there).

    Replaced seals and gutter and it was 100x better. But, at the same time, I can almost gaurantee it will be back at some point.

  4. #34
    WillK is offline Cadillac Owners Fanatic
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    Re: Hi, I'm an engineer, tell me about your sunroof

    Quote Originally Posted by Delta View Post
    the service procedure is as follows:

    1) road test until you can find a long enough stretch of road without traffic to duplicate concern.
    2) go back to the shop and find another tech that isnt busy/ doesnt mind not making any money for the next hour or 2
    3) road test again with said tech
    4) pull over, one tech gets out and holds the glass, the other loosens the torx bolts.
    5) adjust front and rear glass by look and feel (expierence desperately needed here)
    6) road test again (noise is probably worse)
    7) repeat until a) you get frustrated enough that you give up or b) said tech needs to go make some money and cant waste any more time dicking around with you.............

    a screw adjustment means that one tech could drive (hell a porter could drive you around) while the other turns an adjustment screw until it sounds better, then go back to the shop, ship vehicle, please customer (with their vehicle being fixed, not... nevermind).
    The procedure *should* involve setting the gap between the roof and the glass panel to some target value, and my opinion in general is that the best way to achieve this would be through the use of appropriately sized spacers placed as 2 spacers on each side of each glass panel, and then flushness is achieved by straight edge. The procedure should take 1 person at the top to make sure the panels are positioned and one at the bottom to tighten or loosen the screws. The procedure should tell an order in which the screws are to be adjusted and tightenned.

    That's just my opinion and I don't have the numbers it should be set to clear enough in my head to quote them at this time.

    I know your procedure was tongue-in-cheek, and I recognize your frustration at the fact the service procedure as executed hasn't been effective.

  5. #35
    Delta is offline Cadillac Owners Fanatic
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    Re: Hi, I'm an engineer, tell me about your sunroof

    Quote Originally Posted by WillK View Post
    The procedure *should* involve setting the gap between the roof and the glass panel to some target value, and my opinion in general is that the best way to achieve this would be through the use of appropriately sized spacers placed as 2 spacers on each side of each glass panel, and then flushness is achieved by straight edge. The procedure should take 1 person at the top to make sure the panels are positioned and one at the bottom to tighten or loosen the screws. The procedure should tell an order in which the screws are to be adjusted and tightenned.

    That's just my opinion and I don't have the numbers it should be set to clear enough in my head to quote them at this time.

    I know your procedure was tongue-in-cheek, and I recognize your frustration at the fact the service procedure as executed hasn't been effective.
    None of those procedures or specs are in SI for a technician to access.

  6. #36
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    Re: Hi, I'm an engineer, tell me about your sunroof

    Since I'm no engineer here is the problem:
    I get in the car and drive it I hear... creeeak creak... squeek squeek!!!
    Go over a little stone I hear... creeeak creak... squeek squekl!!!
    Make a left turn I hear... creeeak creak... squeek squeek!!!
    Make a right urn I hear... creeeak creak... squeek squeek!!!
    You get the picture...


    Amen to that! I don't have a wind noise...I have creaks and squeeks. This dual panel sunroof is the dumbest idea that's ever caught on in my opinion. I don't want to be baked under glass, I don't want a cheap sun screen that also makes noise, and I don't want to hear these noises. Put a regular single pane sunroof back in the car and all problems are solved!! I like sunroofs, but would not buy another car with one of the dual panel ones...so just stop putting them in GM vehicles or at the very least make them a stand alone option. Next problem?

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    Re: Hi, I'm an engineer, tell me about your sunroof

    Quote Originally Posted by Delta View Post
    None of those procedures or specs are in SI for a technician to access.
    Okay, well I'm sure that the service procedure doesn't make reference to working on the adjustment until you need to go work on something more profitable... I've read a reference to a TSB for adjusting glass and I've got to imagine that there is some target value, whether it's quantitative or it's qualitative (such as the gap being equal on both sides or something about achieving slight compression of the seal but not overcompressing it)

  8. #38
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    Re: Hi, I'm an engineer, tell me about your sunroof

    Quote Originally Posted by Merge View Post
    Since I'm no engineer here is the problem:
    I get in the car and drive it I hear... creeeak creak... squeek squeek!!!
    Go over a little stone I hear... creeeak creak... squeek squekl!!!
    Make a left turn I hear... creeeak creak... squeek squeek!!!
    Make a right urn I hear... creeeak creak... squeek squeek!!!
    You get the picture...

    FIX IT NOOBS!!! How do they miss something like that?????????
    From the information in your description, the events causing the noises you describe sound like events where there would be suspension movement. I don't know if you've had this issue since the car was new. It does not sound like what I would expect. There are other engineers more directly involved with whatever components would be causing your noises, and the best way to bring these issues to their attention is by having the problem fixed by a dealer under waranty. The waranty process creates data about issues that gets reviewed during the development process. Parts replaced under waranty come back to GM Tech Center and get reviewed by engineers. Your waranty isn't just about fixing your car, it also improves future product and/or repair procedures.

  9. #39
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    Re: Hi, I'm an engineer, tell me about your sunroof

    Quote Originally Posted by GrayGhost View Post


    Amen to that! I don't have a wind noise...I have creaks and squeeks. This dual panel sunroof is the dumbest idea that's ever caught on in my opinion. I don't want to be baked under glass, I don't want a cheap sun screen that also makes noise, and I don't want to hear these noises. Put a regular single pane sunroof back in the car and all problems are solved!! I like sunroofs, but would not buy another car with one of the dual panel ones...so just stop putting them in GM vehicles or at the very least make them a stand alone option. Next problem?
    If the noises are coming from the sunroof, and it's not during openning or closing, I'll make a mental note and see what I can look at the next chance I have. What I can suggest is this:

    Pay as much attention as possible to the specific conditions and location where it occurs so you can have the dealer able to do the same thing at the same place. The most severe conditions should be something that causes twisting forces on the body, which is most commonly seen going into or out of a sloped driveway while turning.

    And I can say that vehicles absolutely go through testing that twists the body. That is a regular part of durability courses for vehicle testing during development, and in most cases it's even part of the test course that vehicles go through during production. This applies pretty much in general across the automotive industry.

  10. #40
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    Re: Hi, I'm an engineer, tell me about your sunroof

    From the information in your description, the events causing the noises you describe sound like events where there would be suspension movement.
    No, the noises come from the sunroof...he's simply pointing out that if the car is moving, it makes noise. I am aware that the trim around the sunroof is a major contributor to the noise, but I also don't believe there is enough stuctural integrity in the roof with this type of sunroof, which causes flex, contraction and/or expansion...causing noises. I'm not an engineer, but I did stay at a Holiday Inn Express recently.

  11. #41
    louiefl99 is offline Cadillac Owners Enthusiast
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    Re: Hi, I'm an engineer, tell me about your sunroof

    Quote Originally Posted by Delta View Post
    There are concerns coming from the rear glass. We were playing around with one in the shop one day and decided to actually see where it was coming from (slow day). We road tested a car with a wind noise and applied masking tape all around the front windows and front glass of the sunroof and it still had a noise, but improved. So we applied the tape across the middle of the 2 glasses, still there but greatly improved. Applied tape around the rear glass seals and it was completely gone (now it was just heard from the mirrors, dont even get started there).Replaced seals and gutter and it was 100x better. But, at the same time, I can almost gaurantee it will be back at some point.
    My personal experience was that at some point adjusting the front panel only would not stop the noise and I needed to start adjusting the rear panel. My suggestion to make the rear panel fixed would be so that you would eliminate one set of adjustments. I realize this is impossible for current production, but for the next generation it would be a different story. I would be fine with a narrow trim piece between the two glass panels if it helped to rigidly secure the rear panel. I'm sure someone could design a simple screw driven cam / wedge to raise and lower the front panel on the fly. I don't think the adjustment is quantitative, so don't give the technicians a numerical range - the consumer doesn't care either, they just want it quiet.

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    WillK is offline Cadillac Owners Fanatic
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    Re: Hi, I'm an engineer, tell me about your sunroof

    I'd be interested in whether anything like pushing up or pulling down the headliner makes a difference.

    Bear with me, this is a seperate issue from the wind noise but I think this does sound like something I can investigate as well.

  13. #43
    WillK is offline Cadillac Owners Fanatic
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    Re: Hi, I'm an engineer, tell me about your sunroof

    Quote Originally Posted by louiefl99 View Post
    My personal experience was that at some point adjusting the front panel only would not stop the noise and I needed to start adjusting the rear panel. My suggestion to make the rear panel fixed would be so that you would eliminate one set of adjustments. I realize this is impossible for current production, but for the next generation it would be a different story. I would be fine with a narrow trim piece between the two glass panels if it helped to rigidly secure the rear panel. I'm sure someone could design a simple screw driven cam / wedge to raise and lower the front panel on the fly. I don't think the adjustment is quantitative, so don't give the technicians a numerical range - the consumer doesn't care either, they just want it quiet.
    The adjustability of the panels is that they can be adjusted in the up and down direction and the forward/rearward direction.

    Really, it's not unlike any movable panel adjustment. Body shops have to adjust doors, hoods, trunks, etc to specified gaps and it's done by loosening screws, setting the panel to position and tightenning the screws.

    If timing and resources weren't an issue, the most likely design change for improving this sort of issue would probably be an improvement to the seal cross section that would make the overall design less sensitive to adjustment and variation. But there could be a number of other fixes, or even issues of something that wasn't built as specified. I can't say at this point what the solution is, I'm just saying what kind of solutions could be under consideration on a generic seal issue.

  14. #44
    wesiii is offline Cadillac Owners Member
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    Re: Hi, I'm an engineer, tell me about your sunroof

    This dual glass panel sunroof is a flawed design:

    1) This design has about 40% more area for leakage than a standard single glass panel, steel roof design. Both glass panels rely on rubber perimeter seals which eventually will shrink allowing leaking of air and water. More perimeter = more leakage.

    2) With greater perimeter and potential for leakage, the drain lines are inadequate and unable to keep up with the leak off. This has caused every CTS sunroof owner consternation upon finding water leaks in the cabin. I replaced all 4 of mine with 1/2" id, vice 1/4" id stock hose and no longer have water leak issues.

    3) Fabric "Sun" screen lacks opacity, does nothing for noise cancellation, and has black lines from the rolling mechanism. Compare that to a "standard" sunroof shade that completely blocks the Sunlight and due to it's thickness, also reduces noise.

    I don't understand the thought behind an all glass roof. I want a sunroof so I can open it to let in air and sunlight. When I'm not in the mood or the weather does not permit, I want air and water "tightness" and don't want sunlight in. I can't see any reason to have the sunroof closed with the shade withdrawn. I wanted a CTS with a sunroof, however, this design is so bad that I will not buy another vehicle with this type of sunroof, from any manufacturer. Cadillac should ditch this design and go back to a conventional type ala STS. In comparison, I also have a 2002 F150 Supercrew(Harley Davidson) with a factory sunroof and even after 10 years, when I'm on the Turnpike doing 90, it's still as quiet inside as a.....Cadillac (should be).

  15. #45
    WillK is offline Cadillac Owners Fanatic
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    Re: Hi, I'm an engineer, tell me about your sunroof

    As far as sunshades, what you're referring to is a matter of whether the sunshade is fabric which rolls up like a roller window blind or a hard sunshade panel. Now, I can say this: A hard sunshade panel is not necessarily immune to noise issues. I might be able to acknowledge it if asked, but there is an example I am aware of where such a panel has seen a revision due to a resonance issue.

    Fabric sunshades do not necessarily mean translucency. For the time being, I must leave it at that. There might be (and probably are) roller sunshades that are translucent and are in production, but I don't at this point know all sunroofs in production across all OEM's.

    As for the choice to configure the sunroof option as having the larger glass area, engineering's role is making that configuration practical. It's marketting that makes the decision to choose a particular configuration.

    Once that decision is made, the choice of roller fabric sunshade becomes necessary when the open glass area of the roof is more than half of the overall roof area. With a hard sunshade panel it is necessary to have at least as much area available for the panel to slide into it - like a pocket door (one which slides into your wall rather than swings open).

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