# Chugging sound when rear windows of vehicle are open **URL:** \ **Category:** Factual Questions\ **Created:** [August 30, 2021, 8:23pm UTC](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795 "2021-08-30T20:23:18Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![PozhanPop](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pozhanpop/32/8022_2.png) [@PozhanPop](https://boards.straightdope.com/u/PozhanPop)\ **Post date:** [September 1, 2021, 9:26pm UTC](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795/21 "2021-09-01T21:26:28Z")
That is a bit of information about the bug that I have never come across. Thank you ! ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [September 1, 2021, 10:14pm UTC](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795/22 "2021-09-01T22:14:59Z")
> [@jjakucyk](#): > > When closing a car door you need to give it some oomph to get it to latch, and the large area of the door when closing against an airtight cabin would cause it to bounce off the bubble of air in the cabin. Yes air is compressible, but the act of closing the door causes a spike in pressure that tries to get out around the same door, pushing it out. The harder you slam the door the harder the air bubble pushes back. If you could slowly creep the door closed then it would be fine, but in most cars then it’s not fully latched. That makes zero sense. Closing the door makes a rather insignificant increase in air pressure. Air can escape around the edge of the door right up until the gaskets close the final gaps and the volume of the car is very large compared to any air pushed by the slamming door or displaced once the gasket closes the gap. This sounds like a misconception someone got about a tricky latch and then compounded through confirmation bias. ---
**Author:** ![Limmin](https://avatars.discourse-cdn.com/v4/letter/l/f04885/32.png) [@Limmin](https://boards.straightdope.com/u/Limmin)\ **Post date:** [September 1, 2021, 10:42pm UTC](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795/23 "2021-09-01T22:42:13Z")
Oh, the effect is really noticeable to me! All windows closed, I must slam the door to get it to close (current vehicle, an Impreza). One door’s window open? Doors shut with the lightest touch. In fact I’m constantly telling my teenager to not slam the door, to watch if a window is open first. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 2, 2021, 1:37pm UTC](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795/24 "2021-09-02T13:37:09Z")
> [@naita](#): > > That makes zero sense. Closing the door makes a rather insignificant increase in air pressure. Air can escape around the edge of the door right up until the gaskets close the final gaps and the volume of the car is very large compared to any air pushed by the slamming door or displaced once the gasket closes the gap. The closer the door is to fully closed, the smaller the gap through which air can escape to relieve cabin overpressure. A car door is very large, with an area of maybe 1200 square inches; a tiny cabin overpressure of .05 psi won’t generate much outflow through the very narrow gap that is formed as the door is _almost_ closed, but it will produce 60 pounds of force resisting that final closure. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [September 2, 2021, 2:22pm UTC](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795/25 "2021-09-02T14:22:30Z")
> [@Machine\_Elf](#): > > The closer the door is to fully closed, the smaller the gap through which air can escape to relieve cabin overpressure. A car door is very large, with an area of maybe 1200 square inches; a tiny cabin overpressure of .05 psi won’t generate much outflow through the very narrow gap that is formed as the door is _almost_ closed, but it will produce 60 pounds of force resisting that final closure. Perhaps I let faulty intuition about what physical factors would matter run away with me. It still seems strange to me that such a phenomenon would be car specific to such an extent that I’d never experienced or heard about it. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [September 2, 2021, 2:58pm UTC](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795/26 "2021-09-02T14:58:06Z")
Many cars are/were never made well enough for it to be a factor. There needs to be good seals around the steering column, pedals, parking brake, wire harnesses, shift levers, release cables, window glass, seats, trunk, and the doors themselves. Newer cars that are generally well put together may provide a relief through the climate control system, which in my experience tends to open the outside air damper when the car is turned off (or when the system itself is turned off) rather than leaving it closed/recirculating as it would usually be in the summer. Since recirculating generally isn’t an option in cars without air conditioning, I think most of those dampers are electronically controlled even if the rest of the system is manual. I suppose the heating system in older cars were too small to allow the air out fast enough for a closing door, or there were too many restrictions in the heater core, ducts, and grilles. Some convertibles will automatically roll down the window about an inch when the door is opened, which seems like another way to handle this, but it looks like the reasoning there is to get a better seal between the window glass and the gasket. Since convertibles have windows without frames, if the window was all the way up it could only press against a flat gasket when the door is closed. However, rolling the window back up after the door is closed lets the top edge of the window insert into a slotted gasket which is much better at keeping rain and wind out. ---
**Author:** ![Limmin](https://avatars.discourse-cdn.com/v4/letter/l/f04885/32.png) [@Limmin](https://boards.straightdope.com/u/Limmin)\ **Post date:** [November 19, 2021, 7:05pm UTC](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795/27 "2021-11-19T19:05:53Z")
> [@naita](#): > > That makes zero sense. Closing the door makes a rather insignificant increase in air pressure. Air can escape around the edge of the door right up until the gaskets close the final gaps and the volume of the car is very large compared to any air pushed by the slamming door or displaced once the gasket closes the gap. I’m only adding some additional info here because it just popped up in my YouTube feed: In explaining why rear windows sometimes break, a possible reason is the burst of pressure caused by slamming doors, if the rear vents are stuck shut. What rear vents, you might ask? Please see this video, about the first 3 minutes of it, in which the host tears apart the trunk liner and shows us these little air vents that relieve pressure caused by shutting your car door! [https://www.youtube.com/watch?v=V01OuuGlbbo](https://www.youtube.com/watch?v=V01OuuGlbbo) ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [November 22, 2021, 3:00pm UTC](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795/28 "2021-11-22T15:00:46Z")
> [@Limmin](#): > > I’m only adding some additional info here because it just popped up in my YouTube feed: In explaining why rear windows sometimes break, a possible reason is the burst of pressure caused by slamming doors, if the rear vents are stuck shut. > > What rear vents, you might ask? Please see this video, about the first 3 minutes of it, in which the host tears apart the trunk liner and shows us these little air vents that relieve pressure caused by shutting your car door! > > [https://www.youtube.com/watch?v=V01OuuGlbbo](https://www.youtube.com/watch?v=V01OuuGlbbo) I think those trunk vents exist so that you can close the trunk lid without a fight. For those vents to be effective at limiting the pressure rise in the cabin, you’d need a good flow path for air to get from the cabin to the trunk, and there generally isn’t one, unless you happen to have the rear seats lowered. If these vents were intended to limit pressure rise in the cabin, we should expect to see them in pickup trucks, even though they don’t have trunks. Anyone here own a pickup truck? Can you confirm whether these vents exist somewhere in your truck’s cabin? ---
**Author:** ![california\_jobcase](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@california\_jobcase](https://boards.straightdope.com/u/california_jobcase)\ **Post date:** [December 2, 2021, 1:27am UTC](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795/29 "2021-12-02T01:27:56Z")
I have a 2009 Ford Ranger pickup. The vents are there, located in the doors, and there is no buffeting. ---
**Author:** ![california\_jobcase](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@california\_jobcase](https://boards.straightdope.com/u/california_jobcase)\ **Post date:** [December 2, 2021, 2:31am UTC](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795/30 "2021-12-02T02:31:38Z")
As for the flow path in sedans that you mention, they’re usually in the package shelf behind the rear seat. They can be mistaken for speaker grilles sometimes. [Previous page](https://boards.straightdope.com/t/chugging-sound-when-rear-windows-of-vehicle-are-open/949795.md?page=1)