windshield adventure

[busguy01]

Eagle 01. Stiff wind (30-40) from curb side. All windows closed. Load whistle then a "pohoff" and drivers side windshield blew out! Has happened twice under the same conditions. Firast time about 5 years ago just after haveing new winshiels installed. Only 15 miles from home. managed to hold onto windshield and stop. Glass guy came out and reinstalled. this time ( after 50,000 miles) was a bit further from home in stiff wind and rain. managed to reinstall and tape enough to get to campground. Reinstalled and got home. Just wondering if any one else has had this issue and what they did to fix. There is a small air lead around the entrance door and the rest of the bus is very air tight. Hate to have to drive it with the window open all the time to keep air pressure inside down.
Ideas??
Thanks JimH

[Busted Knuckle]

busguy01, wow I can't really say I'd ever heard of anyone having these problems, but it's possible! I do know that the early models of the MCI Rennisance were known for having the windsheilds "BLOW OUT" while sitting still in a parking lot on hot days, which was said to have been from being "too air tight"! But other than that I'd not heard of it happening. So if your coach is "too tight" how about opening the bathroom (or other) vent while driving to eliminate this problem? Sounds as if it could be very dangerous, and quite expensive, if your not so lucky as to be able to "catch & save" the windsheild next time, or it could cause you to have an accident. BK 

[Burgermeister]

If the problem is caused by positive pressure and  the bay doors aren't sealed, constructing something like a flapper door in the floor to relieve pressure,


I don't think this is the cause, however, IMHO.   

I'm thinking the "hole" in the windshield frame is oversized and the rubber is  insufficient to retain the windshield when the interior isn't that "tight"   What were the wind conditions?  A decent breeze from the back side, pressurizing the inside, even though slight may cause the problem.  There's lots of square inches of windshield and a marginal seal won't hold it in.

I base this "suspicion" on the descriptioin that the windshield was re-installed 5 yrs later with no mention of a new windshield rubber.  Knowing guys who do this for a living, they'd never try re-installing an aged rubber because of fears of breaking the windshield on re-install.  If your guy could do it without a new rubber,  I'd speculating that the hole's too big.

YMMV,

Marc Bourget

[Busted Knuckle]

Marc brings up a very good point! Also I'd check to see what they are using to "lubricate" it while installing it (especially on the one that fell out right after being installed!). I don't do windshields, as I have a guy who does it cheap enough that I can buy and have him install them cheaper than I can purchase them!(he buys in quanity!) And if he breaks it, it's on him ! But once he told me he used one thing for windshields & another for side windows, but I can't remeber what either was! I can call and check with him this week! BK 

[Len Silva]

If you are working with a fiberglass cap, I'd suspect the cutout wasn't done properly.

Len

[TomC]

Since having the Peninsula Glass windows installed, if I have everything closed, your ears will pop when closing the front door.  What I did was to put a small piece of wood (two popsicle sticks on top of each other) between the Fantastic fan knob and side to keep the vent cracked open all the time.  Now can come and go without the pressure differences.  Sounds like the pressure differential could be aggrevating the circumstance.  Good Luck, TomC

[Jeremy]

It's more likely that the windscreen was 'sucked out' rather than 'blown out'. If all the windows were closed, a wind on the outside of the vehicle couldn't 'blow' the window out from the inside, but it's very possible that a venturi effect around the front of the bus could create a sufficient vacuum to suck the glass out of undersized or worn out windscreen rubbers.

I remember driving down a road one day when I passed three identical trucks driving nose-to-tail in the opposite direction. They were tractors only (ie no trailers), and were obviously being delivered somewhere, and were moving pretty fast. As they went past I felt three very strong 'pressure waves' hit my vehicle, the third of which was so powerful that it blew (sucked) open the tailgate on my Range Rover. Obviously some combination of the size, shape and speed of the trucks had created some remarkable and very strong turbulance in the air; something similar no doubt happens when a crosswind of a particular strength and direction hits the front of your bus.

Jeremy

[boogiethecat]

Had the same thing happen on my Crown, twice too.  Turned out the newer windshields Crown made were 1/4" less in size than the old ones, and nobody seemed to care... except me when it popped.  I ended up (1) injecting a lot of sikaflex 1A (construction urethane adhesive) into the gap inside the gasket, and (2) adding two pieces of steel on the inside of the gasket that won't allow it to slip again.  Since then ne'er a problem.

[Burgermeister]

TomC's comment on pressurizing his bus surprised me.

There's more than enough paths for air to get in/out of  a MCI-9, that I can't see it happening (with a MCI-9, that is.

Jeremy,  I submit (just speculating, but with some basis) that you were experiencing serial high and low pressure events associated with each of the three trucks. The last "sucked" (no such thing in physics, always a pressure gradient)  "more" because there wasn't a "positive pressure wave from a "4th" truck, filling in the negative from the first two!

Finally, a venturi effect requires application of the Bernoulli effect (Isnt' that properly pronounced "Bern-new-yeah", Clarke?).

Good thinking, considering the point, but for various reasons, I think not.

The airflow around a bus wouldn't attach to the outer surfaces  sufficient to drop the pressure over a windshield enough to "pull" it out of the rubber.  It would still be caused by a pressure differential but It was most likely done by positive pressure from another source besides airflow past the front of the bus.

Onward and Upward

[Moof]

Bernoulli (bur - new - lee) or (just a loud sucking sound)

It's been a long time since I've heard of him.

[Dallas]

Bernoulli (bur - new - lee) or (just a loud sucking sound)

It's been a long time since I've heard of him.

Bernoolee,   Isn't he related to Bo and Luke Duke and the Gen'ral Lee?

[Moof]

Oh yea, they are related.  The Gen'ral had a carburetor.

[busguy01]

Windshield was installed using new rubber 5 years ago. Both times it blew out the rubber was still attached to the windshield. The rubber and windshield came out together. I was on the interstae when it happened this time. Last time was on a 4 lane. NO passing traffic in either case.

[tekebird]

Have not answerd if it is a standard eagle windshield.....or one being used in conjunnnnction with an updated front end.

If original windshield, I suspect the rubber, even if new has shrunk and will not hold the windshield properly.

If a Cap or updated front end.....same sypmtom with cause in inproper hole size or bad rubber.

[niles500]

T'is a puzzlement - might I suggest that you take it to the nearest HVAC company and have them perform a "blower door" test in which they pressurize or de-pressurize the bus and introduce 'smoke' to locate any leaks - the location and size of the leaks can rule in or out the possibilty of a blow out due to cabin pressure - If it is due to  that it would have to be some type of ram air effect IMHO to create enough internal pressure to blow out a windshield - If the test rules it out might I suggest a ribbon test to check for the previously mentioned 'venturi' effect - HTH