Preventing rust in the Z's lower front fenders

[CanTechZ]

1 hour ago, dutchzcarguy said:

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?) ) 

Cold air for the vents comes from the front ahead of the rad support. Those rubber tubes are for the cowl drains, here is a good discussion on the subject. See post #6 by @Terrapin Z.

 

Edited November 9, 2021 by CanTechZ

[ETI4K]

7 hours ago, inline6 said:

Yep, that was me also. 🙂

I love the idea so I had snagged a pic with the intention of doing similarly on mine.

Sorry I couldn't properly attribute it to you.

[inline6]

32 minutes ago, ETI4K said:

I love the idea so I had snagged a pic with the intention of doing similarly on mine.

Sorry I couldn't properly attribute it to you.

Not a thing I care about - just decided to point out that it was me. 🙂

[Seppi72]

Perhaps, instead of fighting Mother Nature, you let her work for you?  Attach hoses to those cowl drains and terminate them in the area of your concern.  Then, when it rains, that water will work to flush out whatever crud that may have accumulated in the lower fender.  You could also periodically pull your cowl and then flood the drains with a garden hose to flush out gunk and follow up with a blast of compressed air.

[inline6]

Not a bad idea in concept, but the I think the problem is that the rear fender reinforcement panel, specifically because of how the shape of it twists at the bottom where it is then spot welded to the outer fender panel - it makes a "wedge" area which literally traps debris.  Sure, the water (gravity fed) will flush the area if you route the drain to this location, but I don't think it is accurate that it will flush out all of the debris.  Depending on the shape of the debris, it can get stuck in a way such that it will not get flushed out.  Also, focusing the drain from the cowl area, in addition to flushing with water, will add a new source of debris.  Anything that finds its way past the cowl panel vents in the top of the car will work its way to the cowl drain holes.  Think propeller seeds... or pine straw, for example.  Debris that doesn't flush out holds onto water every time it rains... thunderstorms... or possibly even sprinkles... or the car is washed, etc.  Thinking about it, I am now of the opinion that the main contributor of that debris in the first place is the cowl drain.

Edited November 10, 2021 by inline6

[Seppi72]

Maybe I did this too many years ago to actually remember doing it, but my cowl has black fiberglass glued to its underside that prevents any large items (and skeeters) from entry.  I guess that I roughed up the surface and used epoxy to hold the screening pieces in place.

[inline6]

Ah.  Yes, a modification of some sort to keep debris of a certain size from ever entering the cowl would be very helpful to the overall situation.

[davewormald]

Anything functional that comes out of this discussion will be of interest to me next year (or maybe the year after to be realistic)! The driver's side is identical. It really seems like a monumentally bad design to me! Hey, how about we funnel water and cowl debris into an enclosed, invisible area between two tight-fitting pieces of lightly rust-proofed metal?!

 

 

[inline6]

I know!  And, all the time and money that has gone into repairing and then painting 💰💰💰💰💰 on everyone's Z before us... and possibly will go into every one after us!  I mean, I REALLY don't want to have this area rust out again on my restored Z after I spend 2000-3000 hours and tens of thousands of dollars on it.  Just not an option.

For what it is worth, I considered removing the lowest 4-6 inches of the reinforcement panel, in order to remove this "trap", but there is one of two bolts which secures the lower fender here, and without it, the shape of the outer panel will be altered, and unsupported.

Edited November 10, 2021 by inline6

[cgsheen1]

Personally I would clean that area as thoroughly as possible and make sure the weep area was clear. Then I would pour rust modifier in-between the panels, letting it soak all surfaces and seep into the pinched seam and drain out the weep hole. Once that was complete, I would do the same thing with POR-15 making sure it coated all surfaces and sealed the pinch seams - again draining out the weep hole but making sure it stays open.

 Weep holes and drains are an incredibly important part of managing moisture and I would never eliminate or purposefully block them. 

(My son thinks you should separate the two pieces at the rear of the fender, then do the above, then put them back together using seam sealer. Probably involves a little cutting and welding... Important part of that is sealing both surfaces in there and keeping the weep hole open. POR-15 is stupidly effective.)

[ETI4K]

Since that area would likely flex on a regular basis, would you be confident the POR-15 would flex with it and remain adhered to the surfaces?  I've used similar products and they are extremely hard - which always raises a flag because with hardness, often comes brittleness.  I've never evaluated any of them on that basis so I am curious what you think.

[Seppi72]

Following up on ETI4K's observation, if I were going to go that route, I'd consider using a vinyl plastisol to seal the area.  That's the stuff you dip you tool handles into in order to give you a non-slip surface.

The vinyl formulation is heavily plasticized and exceedingly flexible.  However, it's thermal expansion values are a lot larger than those for steel so it is possible that it might pull away from the metal surface were they both to get very cold.

A flexible polyurethane coating (NOT POR-15 as it is crosslinked to provide chemical resistance) material might work as well; but I'd make sure it was based upon MDI isocyanate and not TDI so you get the greatest flexibility.