Reinstalling fender - caulk, foam?

[SteveInOakland]

Please see 3 attached photos.

Getting ready to put one of my fenders back on, after cleaning and removing some minor surface rust.

Enrique offers the following advice:

You'll note that the drain tube for the cowling is right behind the fender support bracket, and the hose ends just a couple inches into the cavity. This is the source of the majority of sand and gunk behind the fender. The "drain" hole is actually the space between the fender and the inner brace on the fender. NOT a good idea and a prime rust spot for the 240 /260 / 280 series vehicles.

I'm doing that mod right now, and although NOT concours it is something that will eliminate that problem. I'm running a small section of hose from the drain to the space between the inner support and the body. In this manner the water that seeps into the cowling area will in turn drain directly to ground rather than into the space behind the fender.

As far as the inner fender support, make sure that the inner edge has the non hardening caulking still in good shape and that the outer edge also has the closed cell foam rubber also in good shape. The back of the fender (closest to the door) also takes closed cell foam rubber. You might have a hard time finding this as a loose item, but Pickup Truck Camper Tape is the same thing. You might have to double tape it to achieve the same thickness.

The top seam should also get a strip of caulking to keep it sealed.

--As far as the drain goes -- I'm not quite clear on where a newly installed hose would end up. Maybe somebody could mark on my tight photo of the drain area or further describe?

Otherwise, having trouble knowing where to put caulk and where to put foam. I've got the StripCaulk stuff and for foam, Ace "Wide Gap Foam Tape, Closed Cell, PVC."

The old stuff is so crudded up and brittle, who knows what it used to be.

Inner fender -- in Enrique's instructions I can't distinguish between the outer edge and inner edge of the "inner fender support."

For the fender itself, looking at my photo it seems clear there are two long runs that should get -- foam? The four spots on the inside top of the fender will be addressed by putting foam onto various steel supports on the body, seen above the strut in photo.

The "top seam" Enrique mentions -- what is that?

Finally, there's a place in top right of my fender photo that needs something, caulk it looks like? This stuff would probably be applied onto the body, not the fender.

TIA for any help!

Steve.

[beandip]

OK , first the top seam E is talking about is the line all along the top where the finder contacts the inner finder and it seals the spray from entering the engine bay. Now for the drain. First of all you need a plumbing part . A 1'' 45 degree elbow out of PVC . this will just fit into the stub of tubing showing in the picture and the angle down will be just right. Then to this you connect a length of vinyl tubing ,or hose . All these are available at Lows or Home Depot. The large hose is routed to the drain hole provided by Nissan , behind the rubber flapper so it will dump on the ground. I secured all this with silicone to keep it all in place . I have been running this for a few years and it works great. The cavity that is exposed as well as the inner fender , this I coated with POR . Contents of the cowl dumping into the cavity without the hose in place , is what causes the rust-out of the bottom of the front fender and will also start the rocker to rust when it is perforated there . I found dust , dirt and particles of leaves and fir needles at the bottom of this area on both sides of the car. fortunately I found it in time . I live in Oregon , but even if you live in the desert . When you wash your car this area gets wet and if there is a deposit of dust and dirt it takes a long time to dry and it will rust out over time . thanks to escanlon . He is the one that came up with this . Gary

[EScanlon]

Steve:

I added some text to your pictures to hopefully clarify what I wrote before.

The top seam that I refer to is actually the pinch weld seam of the Fresh Air Vent Tube. It is also the edge that the Inner Fender Weatherstrip Seal is mounted to. If you remove that piece of rubber, be careful not to bend the clips too much as they may be brittle. Also, when you replace the weatherstrip, make sure that the flat side of the "bulb" is to the "seam" and that it bends or leans TOWARD the tire. This is so that when the water gets splashed by the tire, the flow won't force it's way past it, but rather will make the seal tighter.

That top seam may or may not be completely pinched closed and caulking it's top edge prevents water from creeping into there as well as backing up the Inner Fender Weatherstrip.

The inner fender support is the one closest to the wheel/tire, and on my car was removeable. It was held onto the body by 4 or 5 screws. The inner edge of the support that is in contact with the body is what I recommended you caulk, and the outer edge is what takes the closed cell foam to come into contact with your fender and can therefore compress. By caulking the inner edge you are stopping water from the wheel well from seeping into the area behind the support. It is this area between the front and rear inner fender supports that houses the cowl drain tube, and tends to trap water and debris between the fender and the rocker panel metal. Since you're doing the work of carrying the drain water out of the vehicle, you might as well as seal the rest of the area well enough that it doesn't have moisture creeping in.

Those two "long runs" are supposed to be closed cell foam. This is to ensure that it can compress and seal, but also so that they won't impart undue pressure on the outer sheet metal of the fender and distort it.

The "rule of thumb" to differentiate between foam and caulk might be difficult to state and opinions may differ.

I used caulk on the metal edge of the body right above where the captive nuts for the bolts that hold the fender from all the way below the sugar scoops (mine were off), up and around the "nose" of the metal, to just in front of the access panel.

I also used caulk at the upper end of the "seam" just in front of the windshield in order to "dam" up the water flow that might creep down into the upper part of the door and direct it to the drain hole between the metal edge mentioned previously and the "seam". Make sure that that drain hole, which should be right by the plastic bellows that direct air into the fresh air vent, is open and free of obstructions. You do NOT want to plug it.

Foam got used wherever the metal supports touched body/fender. Those 4 rectangular pieces and the two long runs. Those all need to be able to compress and give. You want to use just enough foam that it's compressed slightly - not crushed - and not so much that it distorts the sheet metal due to it's bulk.

I outlined the "drain" tube and where it would exit. Hopefully that will explain it better than trying to describe the opening behind the little flapper rubber. Speaking of that flapper rubber, if yours are rock hard or missing you can make your own out of semi-truck splash guards. It's basically 3/8" cracked cord rubber. If on the other hand, they've just acquired a bend to them that renders them ineffective, you can swap them side to side and the bend will be reversed.

Hope this helps.

Enrique

[SteveInOakland]

Thanks to you both! Great, thorough answers.

Ought to be helpful for a lot of other people too.

An interesting thing is that my outlet tubing, for the cowl-area drain, has an OD of about 1.5”, which is bigger than what you guys are talking about. Finding tubing/hose to accommodate is slightly more difficult. I’m going to try to do this without the elbow piece, due to space considerations at that size. If I end up with anything presentable, will post photo.

--Steve.

[EScanlon]

Steve:

I figure you have looked at these pictures often enough, but they're included here for clarity.

Look closely and you'll notice that I'm using a 45° PVC Elbow of 1-1/2" OD, which is then inserted into the cowl drain tube. The cowl drain tube is then clamped over the pvc elbow.

The clear pvc hose then fits into the 45° elbow and you cut the flexible pvc tubing at an angle. This angle cut gives you a long tongue of clear pvc which you insert into the elbow to follow the outside line of the inner tube curve. The intent is to NOT have a ledge inside the 45.

Remember you're essentially necking down the tubing twice within the bend of the 45.

Where it exits the cowl drain plenum, you'll again cut it at an angle, but this time facing towards the back of the car. Don't cut towards the front or you'll catch the edge into the air and you'll have crud blowing UP through the tube and then in front of your windshield. By facing BACK, the air is forced to venturi around and help suck dust and debris OUT of the tube, especially when it's dry.

When the material is wet the venturi is still enough to PULL water through as well as help disloge debris that may fall into the cowl. When you wash the car, pour enough water through the cowl to disloge any debris as well as dissolve any dried salts. If you note any change in the manner in which it pours out of the drain you'll know that you need to poke a length of weed-eater cable to dislodge it.

In the Pac-NW there are a lot of pine trees and I have a neighbor with a large Maple in her front yard. This is the system I came up with to avoid having the same problem that other's have had...rusted front fender doglegs that eventually causes the rocker panel to perforate and rust from within...and then emerge at the REAR of the rocker. If this happens, it is not at all uncommon to have a completely rotted rocker panel. That sometimes spells death for many cars.

The links to the pictures are from my gallery, the clear pvc hose hasn't been final trimmed since the fender is still off the car. I link it so that you can see that it will not interfere with the fender bottom once mounted and how it is behind the flapper valve.

HTH

E

http://www.classiczcars.com/photopost/showphoto.php?photo=2601&cat=500&ppuser=1490

http://www.classiczcars.com/photopost/showphoto.php?photo=2602&cat=500&ppuser=1490

[SteveInOakland]

Thanks, Enrique. No, I hadn't found those photos in your gallery. --Also, it hadn't occurred to me to put the new drain tubing *inside* the elbow.

So are you talking about the new drain tubing extending down below the bottom of the fender?

One more question -- there's a kind of 3/4" wad of, maybe foam, or something harder, at one upper inside, front corner of the fender. In other words right up above the headlight, but over at the corner. Does that ring a bell? One of mine fell out, the other is still in there. I'm not sure quite what it's meant to do.

Thx,

Steve.

[EScanlon]

Steve;

Actually the exit end of the clear pvc tube ends up being just above the bottom edge of the fender. It just barely protrudes out of the plenum hole (that triangle hole I outlined in your picture). There you can see that there is plenty of space for the tubing to exit and still remain above the fender line.

Then when you cut the end at an angle you should just barely notice it when you lie on the ground looking right behind the tire. It's a bit wet in Vancouver right now, otherwise I'd step outside and take a picture for you.

As far as that "bit of foam" in the front corner, it doesn't ring a bell. Could it be a cocoon, or some other insect's nest? That's just a wild thought, but you'd be surprised at what you can find.

Could you take a picture of the remaining one? Then one of us on the site is bound to identify it.

E

[SteveInOakland]

One more question -- there's a kind of 3/4" wad of, maybe foam, or something harder, at one upper inside, front corner of the fender. In other words right up above the headlight, but over at the corner. Does that ring a bell? One of mine fell out, the other is still in there. I'm not sure quite what it's meant to do.

As far as that "bit of foam" in the front corner, it doesn't ring a bell. Could it be a cocoon, or some other insect's nest? That's just a wild thought, but you'd be surprised at what you can find.

Could you take a picture of the remaining one? Then one of us on the site is bound to identify it.

OK, attaching two shots. The second one has now fallen out as well, so you'll see me holding it. I think it was a hunk of putty the factory put in to stabilize that corner, which otherwise is pretty wobbly, at least when off the car.

Thx,

Steve

[EScanlon]

OK, attaching two shots. The second one has now fallen out as well, so you'll see me holding it. I think it was a hunk of putty the factory put in to stabilize that corner, which otherwise is pretty wobbly, at least when off the car.

Thx,

Steve

EXCELLENT OBSERVATION!

This is one of those little tiny details that so many people might glib over and never notice. In fact, I don't know that it would even show up in the FSM or any other technical literature, but I believe others will also note that they have discovered the same little item.

Once you pointed out where and what it was, I remembered that I also had it on mine. Other cars that I've worked on have either not had it, it wasn't noticed/noticeable or I fail to recall it being there. On my car, and on Gary's we POR'ed the underside of the fender, and on the other cars I worked on, we undercoated, or the undercoating was still intact. As a result it can easily be overlooked.

But your post clarifies exactly what it is for.

The stamped fender has a very distinct and sharp corner along two axis. It is very difficult to bend metal along 2 axis without having excess material bunch up and cause a problem in the stamping. For this reason, often times in manufacturing production, they'll cut, grind, or "fold" the excess away when the design calls for this type of bend. Then again, they can just notch the sheet of metal before they do the second bend.

Unfortunately, when they notch the sheet of metal, it introduces an edge very close to where the bend is made AND with the subsequent vibration stress over the years, the bent corner now becomes slightly annealed. Annealed metal can begin to crack due to the hardness it has acquired over the non-annealed metal around it. These are referred to as "stress" cracks.

In addition to the possibility of the stress crack, there is also the fact that with a hole so close to the finish edge of the piece, that it could literally, LEAK from the water being splashed up in to the wheel well.

This is the "fix" that you are seeing. The caulk not only seals the cut metal close to the bend, but also helps support the piece to minimize the stress right at the bend.

When I did my fenders I used POR all over the inside, and it was in those corners that it would seep through to the "finish" side. Once it hardened, I didn't have that problem any more, but it alerted me to the possibility of water leaking there in vehicles without that "plug".

If someone else knows differently, please post.

As far as your vehicle, if you are planning on doing some further undercoating / rust-proofing, keep it in mind to ensure you coat the corner. Otherwise, at least push a bit of the caulking into that corner to ensure that you don't have a leak to the outside.

E

[geezer]

I had the same wad in the same location. I believe it is a thumbable putty used in certain places to isolate against possible vibration of the adjoining metal pieces. It is also used to seal gaps where needed. We used a similar substance here that was painted over. After going through the ovens it expanded and adhered very well. With age it does not fare so well, hardens, becomes brittle and falls out easily.

[SteveInOakland]

This is the "fix" that you are seeing. The caulk not only seals the cut metal close to the bend, but also helps support the piece to minimize the stress right at the bend.

When I did my fenders I used POR all over the inside, and it was in those corners that it would seep through to the "finish" side. Once it hardened, I didn't have that problem any more, but it alerted me to the possibility of water leaking there in vehicles without that "plug".

If someone else knows differently, please post.

As far as your vehicle, if you are planning on doing some further undercoating / rust-proofing, keep it in mind to ensure you coat the corner. Otherwise, at least push a bit of the caulking into that corner to ensure that you don't have a leak to the outside.

Thanks, and to you also Geezer. Yeah, I'm using Por on the funkier parts of the fender's inside. Once the Por sets up, I may scuff it up in that corner and mash a small hunk of Bondo in there.

Another question arises. There's a rubber nipple-like piece that sits in a hole in the fender sheet-metal, near the area where the headlight-holder bolts on from behind.

I uploaded a photo of this to my gallery because for some reason it doesn't want to attach to this post. You'll see the piece marked here--

http://www.classiczcars.com/photopost/showphoto.php?photo=23714&cat=503

Do you figure this is just to seal the hole that happens to be there? When you check out how the fender and the headlight scoop line up, there doesn't seem to be any other purpose for it?

TIA,

Steve.

[EScanlon]

Picture is held for approval.

I'll confirm when it does get posted.

E