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Discussion Starter · #1 ·
Referring to the ends of the U shaped tube under the engine.
Bought a used 2016 Smart Fortwo Prime (gasoline engine) recently and would like to take good care of my new toy.
In the winter, road salt are used all the time around here and I wonder if I should do something about those 2 big openings.
Are those 2 openings connected to each other (pass through)?
Should I plug it up with a pair of rubber caps (saw them on ebay)?

Do I (should I) hose it down through the holes with water to flush out any salts or debris?
I can blow dry it with a electric leaf blower afterward to keep it dry inside.

Thanks in advance
 

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Not recommended to seal those holes in the De Dion tubes because that would allow condensation to remain without a way to evaporate. Much better off leaving them open and hitting the car wash as needed during the winter months. YMMV. :)
 

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Discussion Starter · #3 ·
Not recommended to seal those holes in the De Dion tubes because that would allow condensation to remain without a way to evaporate. Much better off leaving them open and hitting the car wash as needed during the winter months. YMMV. :)
So the correct term for that thing is "de Dion tube". Nice to know.
I just probed it with a long wooden stick at one of the openings this morning and feels like hitting something "soft" at the end (about 18in down). I will have to wait for some warmer weather to investigate further. I hope it is not home to some hobo critters already :)
Anyway, thanks for the advice.
 

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My 450 had aluminium ones fitted by a previous owner. It took a slide hammer and some serious muscle before they would come off. That being my experience, I wouldn't recommend fitting anything to the ends.
 

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Discussion Starter · #8 ·
Aluminum with holes...... View attachment 62431
Looks very nice, but still appears to have holes. May not be suitable for the weather over here.
I will go for plastic caps in the winter and open it up for the summer. My thinking is that "water is okay", but "salty water is not".
 

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I have a set of plastic caps on the wife’s 451 , been on all summer . I plan on popping them off soon to inspect . I’ll report back on them .
 

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I knew of a couple club members, who made plugs. Out of PVC caps. I really don’t see any purpose of capping them off. If smart wanted them block off. They would have welded them shut. I’d just leave them open.
 

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I like the looks of the tubes being capped. I made up a set of caps from polished stainless and Brabus decals. I check them regularly and have found no corrosion issues. It helps that my car is garaged and only been in the rain twice in over 10 years.
62439
031.JPG
 

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Discussion Starter · #13 ·
Just to complete the thread:

I have decided to put on a plastic cap to the tube for the winter (as you can see, we do snow here...). I can remove it for the summer. It is not too hard to do.
Before:
62502


After:
62503
 

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Discussion Starter · #17 ·
So, apparently, there's a old thread about this long time ago here: Save Our Tubes (De Dion that is).
I just discovered it.
However, I will leave my plastic caps in place and check it again in the Spring.
By the way, there is no critter living in there, I checked with a leaf blower before installing the plastic caps :)
 

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Discussion Starter · #20 ·
Update:
After 2 winter seasons with the plastic caps installed, I finally open it up to take a peek inside the tube.
The plastic caps did a good job of preventing salty water from going in.
I can still see some rusts forming around the edge of the opening (inside and outside) but they seems to be "normal" when comparing with the pictures I took before installing the caps.
What I will do next, is to spray some rust inhibitors (e.g. Fluid Film) in the area. Let it dry out for several hours before putting the caps back on.
Will also spray from the holes in the front of the de Dion tube next time when I crawl under the car (e.g. when changing motor oil)
In conclusion: I will keep the caps but will spray with rust inhibitors for more protection against salty slush in the winter around here.
May be I will update this post again after anther 2 winters?
 
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