In matter of 5 days after buying a new '08 Sonata it developed an annoying squeak in the rear glass area but only during cool/cold mornings. After I isolated the source of the squeak to the rear glass area, I inspected it from the outside and discovered that the lower corner of the rear glass on the driver's side actually moves in and out! This flex was the source of the squeak. I took it to the dealer and the service manager said a similar squeak has been a continuing problem with windshields but not the rear glass. He said he just tested five new Sonata's and all the rear glass on the same corner flex when you push on the glass with your fingertips. He said that there is a Hyundai Technical Service Bulletin on this problem with the windshields and the recommended fix is to apply silicon lubricate, which the dealer did last Wednesday. Well this morning, the squeak is back! Lubricating is not the solution, but only a temporary fix in my opinion. Do any other Sonata owners have a sqeak in the rear glass on cool/cold mornings and/or discovered that the lower driver's side corner of their rear glass actually flexes when you push on it with your finger tips? This is not typical for glass in other cars and I think it's a design/installation flaw. Please provide some feedback.

This post has been edited by lwoosley: Apr 14 2008, 07:29 AM

I just checked mine. It doesn't move or flex, nor do I have any squeaking or rattling issues.

IF (and that's a big IF) your service guy actually checked other Sonata's in stock that had the same problem, then there may have been an installation issue or some other quality issue at the plant around the time those cars rolled off the line.

I'd try another dealer to see what they say.

just checked my '06 and there is zero flex...

Having accidentally overlooked this topic, I just posted my own grievance an hour ago regarding this issue on my 08 Sonata.
I don't think my rear glass flexes, but a faint yet moderately annoying rattle comes from the upper right half of the rear glass, where it meets the roof. I've also read about the DuPont Kryton lubricant "fix" per TSB.
I'll see maybe I'll try my dealer here in Toledo.
My car's manufacturing date is December 13, 2007 as far as I know, but I'll have to double check.

This post has been edited by gabebalazs: Apr 14 2008, 11:03 AM

I have a 2008 also and I have an incredibly annoying rattle coming from my rear decklid area. I'm almost positive that it's the deck itself, but the idiots in the service dept told me it was the gas tank and there's no fix for it! I'm sure that there's a clip missing or something, but I really don't want to try to find it myself and end up making it worse. ARGH!!!

I have an '08 Sonata, and there is absolutely NO flex or movement in the rear glass in any corner. Your rear glass must not have been sealed correctly. I did however have the windshield creak problem with mine, but the creak came from the far lower passenger side of the windshield, not the upper part as the TSB referred to. I fixed mine with a shot of WD40 under the passenger windshield pillar. It's been a month and the creak has not come back. The dealer should look into re-sealing your rear window.

doesn't WD40 deteriorate rubber? I'm thinking of using white lithium grease, that shouldn't hurt rubber.

This post has been edited by gabebalazs: Apr 14 2008, 07:57 PM

The WD40 website says it is safe for metal, rubber, plastic. It softens some adhesives, which I thought may have an effect on the adhesive for the glass, but no problems have appeared. Now, if it was known to dissolve adhesives, then I wouldn't have used it.

More information and clarification: Like the comment from "boehmb", it's a creaking sound rather than a squeak. Last week, the dealer in Fairfax added some DuPont Kryton lubricant (as the TSB calls for the similar windshield creak) to my original creak area on the driver's side, lower corner of the rear window. This morning, the driver's side of the rear window did not creak...it's now coming from the passenger's side of the rear glass. BTW: the corner of the rear glass did not flex this morning.