driving with rear window open

[jmccorm]

it will suck exhaust fumes into the interior of your vehicle. What are you trying to do poison your family. Good grief use some common sense..

I can't tell if this is comedy, gross misunderstanding of the basic fundamentals of airflow, or the result of advanced aerodynamic computation based upon a detailed model of the Wrangler JL which shows significant cabinet ingress.

Either way... well done, sir!

PS: I don't see how the physics of this would possibly work, but since someone else actually confirmed this, color me surprised!

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[pjtait]

it will suck exhaust fumes into the interior of your vehicle. What are you trying to do poison your family. Good grief use some common sense..

IIRC, the YJ and TJ owners manuals specifically said not to do it for just this reason.

 

[Naylia]

Had a convertible, and you get buffeted in the back of the head by wind, not wind in your face. The air flows over the top of the windshield and then back down. But the cabin footwells and behind the windshield basically becomes a low pressure zone that air then rushes to fill making air flow from the back towards the front cabin. A wind screen is a really common convertible add-on that disrupts this creating a still bubble of air in your front cockpit. I could see how the air could flow all the way over the top of the jeep, over the raised window glass, while then air actually rushes back in through the rear windows. However, this should be easy to test. Have someone sit in the back seat with long hair and look at which direction their hair blows.....If the hair blows forward...problem. if their hair sits still to blows backward, probably ok in my wildly unscientific analysis.

 

[Joe98]

I have a 2 door and had to carry something long. I had the window open but i tied it down so that it wouldn't bounce.


The auto correct changed "2 door" to "3 food"

 

[Retired Dave]

As far as I know, fast moving air has lower pressure than slow moving air. If you have ever seen an old jeep driving down the road with a soft top, or even a bikini top, it looks like it is puffed up. This is because the fast moving air outside the vehicle or over the top of the vehicle has higher relative velocity and lower pressure than the air inside the vehicle. Since the air inside the vehicle has higher pressure, it is trying to get out to the lower pressure area creating a "bubble effect". If you open just the back window, you no longer have a high pressure bubble inside the vehicle, but instead create a bunch of turbulence. This turbulence is what I think has the potential to bring exhaust in from the back. If there is no other inflow of fresh air, Jeep's engineers and lawyers probably thought there was enough potential for exhaust fume build-up in the cabin to cause harm, so they had to warn against it. If you open the windows or take the doors off, the mixing in of fresh air is probably much greater and does not have very much potential for build up of exhaust fumes.
All that garbage does not really answer the OP's question, but it that is where this thread seemed to end up. My opinion on the back glass: I rode around in my CJ for years with the back glass open or the rear window out in the soft top, but I also invariably had the windows open in these situations. Not much chance of breaking the glass in the CJ because it had a fiberglass frame, but I am certain it was not very good for it (spring struts, connection points, etc.). I doubt it is very good for the JL either, from a structural/mechanical standpoint. That said, I have to believe that anyone riding around with their back window open would also have their other windows open or the doors off, so exhaust build-up in the cabin is probably a non-issue.

 

[Clint Eastwood]

Used to do it all the time with my 2 door S10 blazer back in the day. Would help to equalize the air so with the windows down the side of my head wouldn't get blasted.

Haven't ever really tried it with the Jeep since it's a 4 door. But I surely wouldn't be worried about it.

 

[Clint Eastwood]

A very intelligent observation. Carbon deoxide is known as the silent killer. You are a very intelligent person.

Someone should tell Coke & Pepsi.

 

[Terminex]

I just have the regular hard top, but the other day my dog asked if we could ride with the back window open, and I told him. "there is just no way."

Talking to your dog - OK

Hearing your dog respond in English - you are crazy and need help


At least that is what the voices in my head tell me when i have conversations with my dogs. (they also get angry because i don’t always listen to them.

 

[Retired Dave]

A very intelligent observation. Carbon deoxide is known as the silent killer. You are a very intelligent person.

I am sure you probably meant carbon dioxide, but even if you spelled it correctly you would still be wrong. Carbon monoxide is known as the silent killer, not to be confused with methane, which is sometimes known as the silent but deadly. Be careful out there.

 

[swampflyer]

Someone should tell Coke & Pepsi.

they know

 

[swampflyer]

Had a Porsche that drove me crazy with exhaust fumes in the cabin. Looked and looked trying to find where it was coming from. I thought the rear hatch was leaking and sucking in the exhaust but no. Got a tip from an old timer use a smoke generator inside the passenger area and turn on the air and fans full blast close the doors. Bingo success. You could see the smoke coming out around both rear tail lights. Replaced the seals and no more problem.

 

[Jeepsmashin]

I did drive with the rear widow open while transporting a bench press bench and as others said, the dampers and widow would move on bumps. I wouldn't do it again.

 

[Naylia]

As far as I know, fast moving air has lower pressure than slow moving air. If you have ever seen an old jeep driving down the road with a soft top, or even a bikini top, it looks like it is puffed up. This is because the fast moving air outside the vehicle or over the top of the vehicle has higher relative velocity and lower pressure than the air inside the vehicle. Since the air inside the vehicle has higher pressure, it is trying to get out to the lower pressure area creating a "bubble effect". If you open just the back window, you no longer have a high pressure bubble inside the vehicle, but instead create a bunch of turbulence. This turbulence is what I think has the potential to bring exhaust in from the back. If there is no other inflow of fresh air, Jeep's engineers and lawyers probably thought there was enough potential for exhaust fume build-up in the cabin to cause harm, so they had to warn against it. If you open the windows or take the doors off, the mixing in of fresh air is probably much greater and does not have very much potential for build up of exhaust fumes.
All that garbage does not really answer the OP's question, but it that is where this thread seemed to end up. My opinion on the back glass: I rode around in my CJ for years with the back glass open or the rear window out in the soft top, but I also invariably had the windows open in these situations. Not much chance of breaking the glass in the CJ because it had a fiberglass frame, but I am certain it was not very good for it (spring struts, connection points, etc.). I doubt it is very good for the JL either, from a structural/mechanical standpoint. That said, I have to believe that anyone riding around with their back window open would also have their other windows open or the doors off, so exhaust build-up in the cabin is probably a non-issue.

I could see how glass up could make it worse since hot exhaust rises, gets trapped by glass and then could flow in. Glass removed seems less problematic.

 

[Traktor31]

I have the soft top but, from everything I have ever read is that if you do put a rear hatch window up, always also roll down the backseat windows too because of the exhaust. The rear window being up could catch the exhaust and push it back into the car. Like I said, that's just stuff I have read over the years so.

As far as the shattering stuff, it seems like other people have answered that too.

 

[Clint Eastwood]

I have the soft top but, from everything I have ever read is that if you do put a rear hatch window up, always also roll down the backseat windows too because of the exhaust. The rear window being up could catch the exhaust and push it back into the car. Like I said, that's just stuff I have read over the years so.

As far as the shattering stuff, it seems like other people have answered that too.

Yes, you definitely would want other windows open when driving with the rear hatch up.

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