raymmer

Was coming home today from a trip to Texas in rush hour traffic, when I heard a loud boom! My sunroof exploded! I haven't had the car for two months yet! I have done some searches and found that others have had their Mercedes roof explode, also. Oh well, I guess it's to the dealer tomorrow!

RJC

Did it shatter? Hope you're ok.

Diesel Benz

Was this the standard roof or the pano-roof?

Ctrl+alt+Elite

WOW

hyperion667

WT....????

more details! pix too if possible......good luck with this

myared

OK, is this a joke?

ImInPA

Probably kids dropping crap off of overpasses. Happens here every so often. Had it happen to one of my co-workers. Let us know what the dealer says.

RJC

That could really cause someone serious harm!

SolidGranite

I stand corrected.

Glad to hear you're ok. That sounds dangerous!

raymmer

Yes, it shattered, but being tempered glass it held together. I had the cover closed so we were not showered with glass. It was the standard sunroof. We were just driving down the interstate, no one was around us. It is at the dealers now. Haven't heard anything on it as of late. Just got back from a 2500 mi. trip and was exhausted. That's why I had not been back on since last night. Good thing was that I averaged 27+ MPG on the trip!
Thanks for your concern.

220S

It's actually not unusual. Unfortunately it's somewhat common.

I remember first hearing about this many years ago (from a BMW owner.) Do a search on E90Post.com. There is a rash of sunroofs exploding with BMWs (primarily 3 series.)

And then do a Google search under "my sunroof exploded" and you'll see that it can happen a lot and in all cars under the right circumstances. All brands.

Here's a good place to start. 8 pages worth of it happening beginning back in 2007 and affecting all brands of cars, including a E350 Mercedes: http://townhall-talk.edmunds.com/direct/view/.f1291fc/0

It's not the pano, but the standard sunroofs.

RJC

You're welcome and glad you had the cover closed. I could only imagine what could have happened if the cover was open as the shock from being showered with glass could have caused a serious accident.

RJC

Unreal

joensbca

Do you know why this happens only to standard and not pano sunroofs? I have a new E350 coupe with pano sunroof and this info has me a little concerned.

SolidGranite

Good question. My guess is there are way more regular sunroof cars out there versus pano.

RJC

The sliding portion of the pano roof is a larger size and different design, I'd imagine it's probably made to withstand extra force from flexing; if the glass is defective however then it's gonna probably break no matter. Fwiw, never had any trouble with the pano in the 55.

K-A

Wow! Scary, glad you're okay.

My guess as to why it won't happen with a Pano is that the Pano's seam-lines/gaps are a little bit wider than the moonroof. Maybe in the event of some major temperature chance or effect, or some chassis flex, the standard sunroof is so tightly squeezed in by the steel around it, it has a higher probability to "pop"? The Pano roof has a large opening, and considerably spaced out gaps (at least between the glasses), in comparison.

220S

This phenomenon is not rare and occurs in all brands of cars. Google search "exploding sunroof" and you'll get pages and pages of stories.

It appears that the most common answer has to do with Bernoulli's Principal (or Bernoulli Effect.) Here's a layman's explanation from a physicist.

"Exploding sunroofs are not a manufacturer's defect. They occur when the sunroof is closed and the windows are rolled up. Manufacturers are very good at making the cabins airtight so the inside of the car will remain at the same cabin pressure while moving as when the car is sitting still.

When you are driving down the freeway at 65 mph, the air rushing across the top of the car creates lift (Bernoulli Effect). If you are driving against the wind you can also add wind speed to your traveling speed, and soon have pressure differences similar to a tornado. In addition, the specific day's barometric may also be a factor.

The glass is sucked upward and breaks, thereby equalizing the pressure. This instantaneous change in pressure halts the upward suction, and the remaining glass falls. Sunroofs are positioned nearer the windshield where air traveling over the car is traveling in an upward direction. It is not technically a manufacturer's defect, but it is certainly a type of design flaw. All cars with sunroofs should be have a pressure equalizer as found in modern airliners."

I'm assuming the small area of glass in a sunroof (versus a full pano roof) makes them more susceptible to being pulled upwards. I suppose it could be argued that lesser glass would be more susceptible to being sucked upwards and breakage, too. Although I'm also assuming that there are DOT regs on the type of glass (and strength) allowed.

hyperion667

damn science is cool

RNBRAD

A Chemist would of got it right. Tell the Physicist it's called a nickel sulfide inclusion. It may not be the most common answer but it is the "right" answer.

220S

NiS has been brought up but it's a contaminate in all tempered glass. Therefore any float glass could break, but instead it's the sunroof. So why only the sunroof if NiS inclusion is the main culprit. There has to be something else instigating the breakage, hence the physicist's comments. NiS alone isn't the problem with sunroofs.

RNBRAD

It's probably more likely the heat in a sunroof causing the cristaline structure of the NiS inclusion to expand in the glass. This is something it does over time anyway. The heat would more than likely speed up this process where in other situations it may never manifest the inclusion. That is if this is more common in a sunroof than other places where tempered glass is used. There would be no other reasonable explanation unless the glass gets in a bind somehow or has a slight imperfection from the manufacturing process.

220S

Since tempered glass is under such high stress, it's clearly possible that even sitting tightly in a sunroof frame (with even a small contact with a flying piece of debris, i.e., a small stone, etc.,) could cause the glass to "explode." One commonality with the majority of sunroofs breaking is: while on the freeway at high(er) speeds. Hence the premise that pressure changes can be a catalyst for the breaking.

Side windows rarely explode like that even in heat. And yeah, then there's always heat stress and/or rapid cooling and the NiS inclusion can grow and rupture the molecular structure of the glass. But it seems ubiquitous with sunroofs in respect to other glass in the car.

But in the end it is kind of impossible to determine absolute cause of breakage (aside from the known NiS issue) since it happens quickly on the freeway and isn't quantitatively documented (it could easily be a tiny stone that the driver was unaware of in all of the exploding sunroof instances.) I think one would be correct in saying that the NiS issue is the only known variable, so you're certainly correct in bringing it up.

RNBRAD

I guess knowing 2 variables would help. #1. Does this happen only when the car is moving? #2. Is there more pressure (- or +) exerted on a sunroof than say a side window/windshield? Anyone possibly know either? It's just that tempered glass is made for strength and flexibility. Based on the angle of the windshield to the top of the car it should create more lift than compared to the angle of the windshiled to the side windows. I don't know how the front of the car would play in this though.

220S

That's pretty much the gist of the hypothesis. The breakage occurs while in motion and at relatively high speeds. There's more pressure exerted on the sunroof and more lift, as the physicist implied.