Preventing rust in the Z's lower front fenders

[inline6]

I've been thinking about how best to address one of the most common rust out areas on our cars, the bottom corner of the front fender.  There is a reinforcement panel which is crimped into the back edge of the fender, and where it twists at the bottom of the fender, it creates a trap for dirt and debris, which over time, collects in the bottom rear corner.  The debris which gets trapped here allows no air circulation so it holds moisture for extended periods of time, over and over again.  Eventually, bare metal gets exposed and rust starts.  

On my first 240Z, I bought brand new OEM fenders, and I sprayed epoxy primer inside this area along with paint.  That was in 1993.  Even though that car has seen relatively little weather (it has been stored in a garage for most of the years since), the lower corner of the passenger side fender started showing some raised bumps (indicating rust through from behind around 2011.  I also, unbolted the bottom of that cars fenders and blew out the debris and dirt a few times over the years with compressed air.  Still, these preventative efforts did not work.  With the 240Z I am restoring now, I want a better solution.

Initially, I thought I would address this problem area by cutting some oval vents to allow additional drainage from this corner, and additional air circulation for drying.  However, I think that would only be a slight improvement.  Instead, I now have in mind fabricating a small metal panel which will seal off this area completely, and therefore, not allowing any dirt or debris or moisture to collect in the corner at all.  Here is a cardboard mock up:  

    

 

I will extend the actual metal piece I fabricate a little further down than this cardboard template, so that the gap is closed.  I may pop rivet this piece on using the little tabs.  Once secured, I will use seam sealer to seal all the gaps.  Of course, I now need to do something to seal up the oval holes that I cut into the reinforcement panel, or water and debris will enter there and I will still have the same problem for the bottom inch or so of the fender corner.
 

[dutchzcarguy]

Interesting.. (Also for  @Yarb)  Mine are a bit rusty in that area..  but as i learned to make some for my 280zx i think i can make also some for my 240z..  The problem there is that it's 2 layers of steel .. and thats aways going to be a rust problem..  maybe take some of the orignal inside layer out clean it completly and close it with some sealer?

Edited November 7, 2021 by dutchzcarguy

[texasz]

I've read where some have sprayed that area with POR15 to seal it up and keep it from rusting.

[ETI4K]

I'd be very careful in trying to seal such an area.  If it is not 100% effective - to include preventing air in/exfiltration as it will carry water vapor which WILL condense inside that space at some point - then you'll be certain to seal IN water that makes its way inside. 

Perhaps cutting out that reinforcing panel altogether and applying modified design - one that is open and self-draining.  Sorry I can't be more specific about such a design.  I've given no thought to it as yet, but that same problem is headed right at me.  I have two new factory fenders to go on my car, and I am determined to prevent them from rusting.  I am also extremely reluctant to start cutting them up or modifying them in any way.  Right now it's an opportunity waiting for me  somewhere deep inside that tunnel, the light of which I am unable to see.

[inline6]

Deep!

That said, I think the worst option is spray coatings into this deep crevasse and hope for the best.  My fabricated parts will direct water away from this area and therefore, keep them dryer than they would be otherwise.  Additionally, I have coated these areas on more than one occasion with epoxy primer.  

Feeling good about it.  😎

[rturbo 930]

1 hour ago, ETI4K said:

I'd be very careful in trying to seal such an area.  If it is not 100% effective - to include preventing air in/exfiltration as it will carry water vapor which WILL condense inside that space at some point - then you'll be certain to seal IN water that makes its way inside. 

That was my thought too. I would think leaving a drain hole in the bottom would be enough to take care of that. The only concern then is stuff getting in through the drain hole in the bottom, which I don't think would be very easy, but I'm sure might still happen to a small degree. 

[ETI4K]

8 hours ago, rturbo 930 said:

The only concern then is stuff getting in through the drain hole in the bottom, which I don't think would be very easy, but I'm sure might still happen to a small degree. 

Someone on this forum did an interesting modification to prevent water infiltration at the drain holes in the rocker panels.  A similar approach might work for a drain hole in the fender.

 

[Captain Obvious]

Where do the cowl drains dump out? Do they terminate in the area the you're trying to keep dry?

[Captain Obvious]

Dug up a pic courtesy of @jfa.series1

[dutchzcarguy]

36 minutes ago, Captain Obvious said:

Where do the cowl drains dump out?

Ehmm.. arn't those rubber pipes the extra airinlet's from those cold air inlets you can open from those pull-knobs... under the dash? (both sides.)

It was only last week i asked myself why are those openings even there in the cowl finisher?  (Air for inside is pulled through the inner fenders not the cowl.. (hope i say this right?) ) 

Edited November 9, 2021 by dutchzcarguy

[inline6]

3 hours ago, ETI4K said:

Someone on this forum did an interesting modification to prevent water infiltration at the drain holes in the rocker panels.  A similar approach might work for a drain hole in the fender.

 

Yep, that was me also. 🙂

[inline6]

10 hours ago, Captain Obvious said:

Dug up a pic courtesy of @jfa.series1

Actually, when looking at this picture, you see the black line going vertically just in front of the hinges?  The area that will be kept dry is to the left of that line, but entirely on the fender itself, not the car body.  When the fenders are re-attached to the car, I will use a new, closed cell foam weatherstrip in the location of that black line.  This will keep much of the water coming from the cowl drain from entering the bottom of the fender where the rear reinforcement panel is spot welded to the outer fender panel, but with that said, my modification will keep the lower backmost corner of the fender (area between the outer panel and the inside of the reinforcement panel) dry.  Cowl drain functionality will not be hampered.

You can follow the rest of the progression of this work done to the fenders in my restoration thread if you are interested.  The link is in my signature.

Edited November 10, 2021 by inline6