Sill car jack pick-up plugs

[UTn_boy]

Wouldn't these plugs just end up trapping moisture expediting rust formation?

Indeed.  That's why Mercedes didn't install plugs in them.  the earlier models that had them had constant problems with rust and moisture retention using the plugs. 

[ptashek]

Wouldn't these plugs just end up trapping moisture expediting rust formation?

There shouldn't be any moisture in the first place, and the jack tubes are the main ingress point...

If all you have in the sills is factory rust-proofing, then I guess any trace moisture would be an issue. If my car was anything to go by, after all these years the OEM stuff has degraded to tiny, thin blobs of wax here and there, and the rubber plugs are hard as rock and don't seal anymore.

With the tubes plugged, fresh rubber plugs in the sills, and good rust proofing material in all box profiles it's a non-issue.
The recommendation I got from my restorer was a check every two years, and a top-up as necessary.

[rumb]

meh   

[UTn_boy]

Lucas, if one drives their car on a cold day and parks it in a warm garage, everything will condensate.  If the car is stored in a garage that is cooler than outside, the same will happen.  This is why so many garage kept cars end up being extremely rusty.  It doesn't matter if wax preservative in present or not, moisture will adhere to any surface.  This is why Mercedes quit using jack hole plugs.  It's far more effective to allow the moisture to dry on its own than it is to trap it. 

[ptashek]

Lucas, if one drives their car on a cold day and parks it in a warm garage, everything will condensate.  If the car is stored in a garage that is cooler than outside, the same will happen.  This is why so many garage kept cars end up being extremely rusty.  It doesn't matter if wax preservative in present or not, moisture will adhere to any surface.  This is why Mercedes quit using jack hole plugs.  It's far more effective to allow the moisture to dry on its own than it is to trap it.

It is, however if you look at the construction of those tubes and how they're attached to the inner sill, you will notice that they're not sealed against the chassis providing a perfect ingress point. They act a bit like a vacuum cleaner, where the front tube generates the vacuum and the rear tube sucks up road dirt, water spray and whatever small particles are flying around. This is why the rear usually rots first (at least on cars I have seen).

I'll be checking all box profiles next year (part of my warranty deal), with a bore scope camera - I'll post pics if I can get them.
I'm not saying I'm right, but it's worth a shot as on a basic science level it makes sense to me

[UTn_boy]

Don't you think that any vacuum created while driving would suck debris out?  After all, the air is going over the openings which would create a vacuum within the rockers disallowing too much debris from entering.  Though, yours may be ok since it's been coated.  I hope the repairs you had done are long lived! 

[marku]

Wouldn't the drop in pressure in the sill caused by the airflow over the two openings draw moisture in? Or even the way a central heating radiator works drawing water in the front end and out the back? The tubes are at quite angle but open at the inner end and the sill  and the adjacent front footwell does rot though not the rear.

[UTn_boy]

If there are other openings in the sills, then yes.  If non rusty and rubber plugs are tight, then there shouldn't be any other openings in the sills.

[ptashek]

Don't you think that any vacuum created while driving would suck debris out? 

Out the front, yes. Not out the back, as the drop in pressure is likely to be smaller there.

[UTn_boy]

So how do we control the volume of air going over the openings front and rear?  Or do we know there to be a difference?

[oversize]

Surely condensation cannot be a reason to leave them open?  If that were true you'd have to leave large breather holes in all box sections....

[UTn_boy]

Oversize, that was my point earlier.  If you park your car in a warm garage on a cold day, everything will condensate.  The opposite is true, too.  If you drive a car on a hot day that's been in a cool garage, condensation will occur.  Granted, the moisture content in the air is a crucial variable, here.  Arid days and climates don't have to worry about this issue. 

[floyd111]

Solution:
Put the plugs in before you go for a drive, and take them out when you park it indoors.