Dust Ingress Prevention

[Pajshomoneroguntero]

I've turned my thoughts to the potential for dust ingress. I've come across a few threads where the two rear vents (behind the bumper) were responsible for allowing the dust in. Is this something I should address now? Given the NX is still relatively young can I reasonably rely on keeping the dust out by correct setting of the climate controls? Is the failure of the rear vents related to aged components?


I've driven a little bit of dirt and haven't had to report any dust getting in but the roads weren't real dusty either.


Where else is the dust likely to enter on the NX? I was going to get under the car again soon and start sealing up anything that looks likely.


Is there an issue with dust buildup into the rear door handle and what are the solutions? Actually what is the problem because I'm mentioning from comments I think I've seen to this issue?

[spot01]

On my NW & NX I have found dust tends to enter past the lower seals on the rear passenger side doors. The dust marks are easy to see on the car door frame/footplates after some distance on outback tracks. I place an old T shirt along the rear footplates up against the lower inside of the doors to reduce it. I run the vents on fresh with the fan up, but it still comes in.....

[MarkAW]

If you’re worried about dust wait till you get into some water (not try to be a smarta$$)

[stumagoo]

those vents behind the rear bumper are cabin vents, they are their to stop the pressure build up as you close the door if they are sealed off then you run the risk of popping other seals as the door closes and allowing dust in or generating wind noise/whistle as you drive

[Mundy55]

As I have previously noted, I have found that, contrary to all vehicles I have used in the past, it is best not to run on recycle in dusty conditions. If I do, I find dust comes in all the doors in varying amounts and especially in the rear door. This appears to be because travelling at speed on recycle causes a negative pressure inside the cabin which draws in the dust. However, if I run on flow through air, it pressurises the cabin which prevents the dust ingress. The cabin filter takes out the dust in the flow through air. Arguably an expensive solution given the need to replace cabin filters more frequently but, for me, better than dust throughout the cabin.

[Kingbrown]

Here's a picture of the rear vent from my PB Challenger. Pajero arrangement would be similar I'd expect.
Mine was removed on the day I received the vehicle. After 10's of thousands of k's of dusty desert tracks, the inside of the car is as clean as it was when new (6 years old).

I'll accept that it relieves pressure if the doors are slammed shut (I've learned to be gentle), but I have not had a problem with any other seals being affected by cabin pressure.

Mention has been made that the vent also relieves pressure if airbags deploy, but I think I'll have bigger issues to worry about than venting pressure if airbags go off.

Apart from flopping around on bumpy roads and thus allowing dust into the vehicle, the flaps also release any positive pressure that would be built up by the vent fan, thus allowing dust to enter via other gaps such as door seals.

Keep your vent control selected to outside air with the vent fan on and keep out of other people's dust and you shouldn't have a problem.

[Ian H]

This appears to be because travelling at speed on recycle causes a negative pressure inside the cabin which draws in the dust.

I may be wrong but I can't work out why that would be the case. When air is flowing over and around the vehicle it speeds up and therefore has less pressure, like the top of an aeroplane wing. So wouldn't the pressure inside the vehicle be more ?

[Pajshomoneroguntero]

On my NW & NX I have found dust tends to enter past the lower seals on the rear passenger side doors. The dust marks are easy to see on the car door frame/footplates after some distance on outback tracks. I place an old T shirt along the rear footplates up against the lower inside of the doors to reduce it. I run the vents on fresh with the fan up, but it still comes in.....

I'll keep it in mind and keep the pillows away from that area.

those vents behind the rear bumper are cabin vents, they are their to stop the pressure build up as you close the door if they are sealed off then you run the risk of popping other seals as the door closes and allowing dust in or generating wind noise/whistle as you drive

Here's a picture of the rear vent from my PB Challenger. Pajero arrangement would be similar I'd expect.
Mine was removed on the day I received the vehicle. After 10's of thousands of k's of dusty desert tracks, the inside of the car is as clean as it was when new (6 years old).

I'll accept that it relieves pressure if the doors are slammed shut (I've learned to be gentle), but I have not had a problem with any other seals being affected by cabin pressure.

Mention has been made that the vent also relieves pressure if airbags deploy, but I think I'll have bigger issues to worry about than venting pressure if airbags go off.

Apart from flopping around on bumpy roads and thus allowing dust into the vehicle, the flaps also release any positive pressure that would be built up by the vent fan, thus allowing dust to enter via other gaps such as door seals.

Keep your vent control selected to outside air with the vent fan on and keep out of other people's dust and you shouldn't have a problem.

[ATTACH]40006[/ATTACH]

Interesting. 1 for 1 against. I presume mine are still working as they should, ie sealing on negative pressure. Just wasn't sure if these cabin vents were something that were poor design from the outset. Maybe I'll leave them be for now.

I may be wrong but I can't work out why that would be the case. When air is flowing over and around the vehicle it speeds up and therefore has less pressure, like the top of an aeroplane wing. So wouldn't the pressure inside the vehicle be more ?

You've mentioned it. The flow around/over the vehicle creates the low pressure. The higher cabin air will vent to the lower over the top. Basic venturi principle. However the pressure under the car will be higher again. I guess the pressure is relative which can get lost when using terms like "high" and "low". So the inside is lower than the underside but higher than the flow over the top. Hence there is a pressure gradient. Not sure if I've made that any clearer though

[Ian H]

That's confirmed my thoughts, thanks.

The Paj is hardly an aerodynamic shape so there'll be air separation all over the place causing vortices and disrupting the flow.
Now we are getting really technical

[Kingbrown]

The flow around/over the vehicle creates the low pressure. The higher cabin air will vent to the lower over the top. Basic venturi principle. However the pressure under the car will be higher again. I guess the pressure is relative which can get lost when using terms like "high" and "low". So the inside is lower than the underside but higher than the flow over the top. Hence there is a pressure gradient.

I've seen very messy examples of that problem in the toilets of railway passenger coaches when travelling at speed (in the days when waste was dropped on the tracks).
A #1 would splash back up at you due to air that was being forced up the chute from higher air pressure beneath the carriage. Thankfully the density of a #2 allowed it to continue its proper descent (unless you'd had a heavy night on the turps).

[Mundy55]

I may be wrong but I can't work out why that would be the case. When air is flowing over and around the vehicle it speeds up and therefore has less pressure, like the top of an aeroplane wing. So wouldn't the pressure inside the vehicle be more ?

On reflection, I can't argue with your logic. All I know is the system works: run on flow through in dusty conditions and in non dusty, run on recycle (at the risk of hijacking this thread, the hopeless climate control system seems to manage better on recycle than flow through on my vehicle).

[dbart1961]

ok, so I drive with my drivers window down and the back of the car is full of dust. I have tried a few methods but always end up with the rear of the car filled with dust. So, what is best? windows shut and re circulate or windows shut and vent open?

[erad]

Mundy55 wrote "On reflection, I can't argue with your logic. All I know is the system works: run on flow through in dusty conditions and in non dusty, run on recycle (at the risk of hijacking this thread, the hopeless climate control system seems to manage better on recycle than flow through on my vehicle)."

If the vents at the rear of the car are sucking in dust, they can also be sucking in exhaust fumes as well. Not good at all... This is precisely the reason I always use fresh air on the ventilation system. Also, in cold, wintry conditions, you get a lot more fogging up inside the car on recycle. Fresh is best, although in extreme heat, the A/C will struggle to keep conditions inside the car to a comfortable level.

Last week, I was in Sydney, and the smells of the city... I was very tempted to use recycle and accept the risk of gassing myself with exhaust fumes rather than inhale all the fumes of the city (I didn't, but it was tempting). I've obviously been in the country too long.