Roof Rust - Mythbuster

[bobenns]

Some members of this group seem to be spreading paranoia and misinformation about rust spots on the roof. I have read a number of posts on this topic today and find it amazing how misinformed some people seem to be on this topic, yet how willing they are to propagate myths such as the rust is coming from inside the roof, or it can't be fixed and thus spreading fear and alarm among other members of the forum. This is just an ugly unfounded rumor. Nothing is farther from the truth.

I had noticed a couple of bubbles about the size of a dime on the roof of my van when I first was looking it over after it arrived from Japan. I hadn't thought about it much after that as it is something you don't notice unless you climb up there. I was going to have my auto body friend look at it when he fixed a small dent in the rear quarter but by then I'd forgotten all about it.

So today I climbed up there and scraped the two bubbles off to see what was going on. They definitely are not coming from the inside. There are also several much smaller spots up there in the very early stages. The metal around these spots is rock solid. On the largest spot the metal is dished out with two pin holes completely through, but it is rusted from the outside, not the inside. This is most obvious.

Cause: When I first looked at them back in March I though "Air Pollution" in Japan. Anyone who is familiar with BC's once booming pulp mill towns will know about that. Acidic soot fallout from the pulp mills causes pitting of paint and if left long enough develops into the same kind of rust bubbles we see on these Delicas. Ever notice the car showers at the gates of some pulp mills so that employees can rinse their car off at the end of the shift?

Because the high roof models are so tall, the top of the roof has probably never seen a good wash or a coat of wax, and more so on the Crystalite Roof models. It is just too difficult to get up there and do the center of the roof. Besides you can't see up there unless you climb up on something. Even bird droppings will eat the paint in time, add to that acid rain and any dirty spot that stays wet longer will have more paint damage. Given 15 or more years of neglect and you have little perforations in the paint that allow moisture to contact the metal. Exposed metal, plus moisture, plus oxygen equals rust. So the little rust spots that start from tiny perforations of the paint will start to grow and expand under the paint, but we see the colour of the rust because the paint is perforated.

The idea that this rust is coming from inside is ridiculous. This is just a foolish rumor started by someone with no idea of what they are talking about and now being perpetuated by others who don't know any better. Rust that comes from behind the metal bubbles the paint alright, but there is no rust colour on the surface as there is no perforation in the paint. The bubble will contain water trapped behind the paint. We see these bubbles on vehicles that have had shoddy or hasty repairs done. The original rust or damage was not repaired properly and they just put filler over it. Water gets in from behind and rust eats the metal away from behind the paint. Again, there is no rust showing on the surface unless you puncture the bubble.

These vehicles have all been treated in some kind of bath that coats the metal in and out for protection from moisture, condensation etc. In only extreme cases where large holes allow water to flow inside could the roof can be rusting on the inside. But you would surely see water stains in the interior.

Some of the comments on this topic are simply absurd. It's as if your Delica will suddenly turn into rusty dust one day as you drive along, leaving you to skid down the road on your butt!!! Or the vehicle will suddenly break out all over in ugly blisters spreading like measles, the doors will fall off, your feet will go through the floor. The rust gremlins are insidiously eating away your vehicle from the inside and suddenly it's too late and it just falls apart. Fear of the unknown....

Body cancer like we see on vehicles from Alberta, Ontario etc is very prolific all over the vehicle. These rust buckets have been soaked in salt water. Look at the door bottoms, under the floor, at the frame, nuts and bolts are rusted solid, often the floor is gone, door hinges pull out etc. Now look around your Delica, unless it came from the North Island of Japan it is virtually rust free.

Can it be repaired? Absolutely! This can be done at home or by a shop.
First the rust must be removed completely, sand off the small spots, grind the bigger ones, get all the rust completely off the roof.
Use etching primer to etch the bare metal.
Repair the damaged surface with long strand fiberglass filler, sand and smooth with fine filler, be sure to etch any areas you expose to bare metal while sanding.
Now you can prime and paint, or use a Rhino Guard type product then paint.

Another method is to clean off all the loose rust and then use a rust converting product to treat the remaining rust with rust converter (tanic acid), then repair with fiberglass etc.

Using a Rhino guard type product after proper repair will guarantee you never get rust on the roof again, at least not for another 15 years or so. Dura Guard or any good Urethane based product is way better protection than a thin coat of paint and well worth it.

I'm posting some pictures of rust bubbles following this post.

Hope no one is offended by this, but Delica roofs rusting out from the inside is definitely a myth that needs to be busted.

Bob in Kelowna

[bobenns]

bubble1.jpg (31.26 KiB) Viewed 7357 times

bubble2.jpg (33.28 KiB) Viewed 7357 times

early1.jpg (28.6 KiB) Viewed 7357 times

rust from behind.jpg (27.97 KiB) Viewed 7357 times

[Jonny5ive]

It's as if your Delica will suddenly turn into rusty dust one day as you drive along, leaving you to skid down the road on your butt!!!

That's a funny image

Interesting point, although I have never thought much of this issue; rust is rust. Better to know where it came from, for treatment purposes, but I suppose rust is somewhat inevitable over time. And 15 years is a respectable age for any vehicle.

Thanks for the LD, Cheers.

[The Pinkfingers]

So what if you simply rhino line over the roof, without getting rid of the rust? Will it get worse, or just stay the same?

[bobenns]

So what if you simply rhino line over the roof, without getting rid of the rust? Will it get worse, or just stay the same?

You need to get rid of the rust in most cases. It may well be arrested if it gets really well sealed in, however if any moisture can get at it in any way it will continue to expand and you will see bubbles under the Rhino Liner. Suppose there are pinholes through the sheet steel. Moisture, condensation etc. will get at it. If you live on the coast there is plenty of humidity. In the interior you have extreme temperature ranges from inside to outside in winter and summer. In winter you have ice on the roof and heat on inside. Any moisture inside will condense on the cold metal if it can get to it. With A/C running through the roof vents in summer on a hot day, that roof gets damn hot, you can fry eggs on it. There will be some condensation happening.

All vehicles get a little rust no matter how well they are made. In places like California they develop rust in certain spots where condensation collects. Old vehicles down there that have no rust on the body and underside will have rusted out around the windshield, never having seen snow or salt. That's why people who collect expensive rare cars keep them in climate controlled buildings, same temp 24 hr a day, 365 days a year, least impact.

For a DIY person just scraping off the loose rust and treating the rest with rust converter before putting on the Rhino will probably be good enough for a very long time. Smoothing it out and sealing it behind fiberglass would be better.

My friend across the street is a certified class 1 auto body tech with years of experience. He paints cars for a living and is damn good at it. Works at one of the better shops in town where they take pride in doing the job right. So I take my advice from him. I showed him the roof yesterday and told him the theory about rusting out from the inside. He had a good laugh but has heard stranger stories at work.

His shop wouldn't just coat it with Urethane, they would insist on repairing the damage first. It would be rather annoying to see the bubbles coming back from under the urethane coating after spending $300 or so to get it coated. Even if the customer insisted that they just put the coating on they wouldn't do it. They wouldn't want their name associated with half/ass work.

If someone has already put the stuff over rust I'd say keep an eye on it and if it starts to bubble up then repair that spot properly.

I suppose the main point I was really trying to make about these spots is that they are common, they are there because the high roof wasn't cared for as well as the side panels, they are easy to repair, and they are not a sign that your vehicle has some insidious hidden cancer that is going to show up some place else and eat the whole car. Common sense has to prevail.

When I was in school in Ontario I couldn't afford an expensive car. I drove old cars that I got cheap and I repaired them myself. They put a lot of salt on the roads there and cars get very rusty. You would see lots of vehicles with big rust holes in them. Engines outlasted bodies as a rule. I preferred white vehicles, I had an old white Astro van, a used delivery truck. Every spring I'd go around it with sandpaper and a few spray bombs of white tremclad and touch up the rust for another year. It would look real good till about Christmas. By spring it looked like hell again. When my vehicles got holes in them I'd patch them with galvanized sheet metal patches, attached with sheet metal screws. Once the patch was fastened in place I'd grind the screw heads down till they were almost flush with the metal. Then I'd smooth over the edges with bondo and hit it with a spray bomb. It would last for years that way, the galvanized metal would never rust. It looked rough but I never got pulled off the road because of rust holes. Eventually the vehicle would need some expensive repair and at that point I'd send it to the crusher. $500 cars can last up to 5 years sometimes.

These Japanese Delicas are absolutely mint by comparison with a 15 year old van in Ontario or Alberta. Those little spots on the roof are nothing. If you haven't got spots on the roof, you will have soon. This is Canada, Eh!

Bob in Kelowna

[vixentd]

In my opinion, and several other car restorers, the roofs do not rust out because they are not waxed or washed. Many cars have the paint completely pealed off and worn off by the sun and weather and still do not rust. I just finished a 1937 chev that had been left outside for the last 30 years and had no rust in the roof! No paint left on the roof either.

Sandblast the bubbles you claim to be surface rust from the outside and you will find microscopic holes. How will you know? Simply paint over the rust bubble you sandblasted and a bubble will soon appear. That is the moisture coming through from the back side. Landcruisers suffer the same problems as the Delica's. The inside surface of the roof was never painted properly on either vehicle and moisture is evaporated and rises and collects on the highest spot. Without proper protection the rust starts on the underside and works it way to the top. Look carefully at Canadian Landcruisers and you will almost always see bubbles on the edges of the roof. I have restored over 15 of these over the years and everyone has rust bubbles in the roof. One had been maintained by the original owner who even had it coated with a life time wax, and still waxed it several times a year. The paint 15 years later still had its lustre but rust bubbles in the roof it also had.

What makes the difference is the ability of moisture to raise to the top of the roof. On landcruisers the moisture comes from the wheel wells and migrates up the side pillars and collects on the roof as condensation when the vehicle cools. I have removed many headliners to show people the condensation on the roof. Often the wheels rust out first and allow the area behind the wheel wells to collect moisture. Delicas have not been exposed to our climate for the last 15 years and have limited moisture buildup, as typically there are very few around with rust perforation in the quarter panels.

On the Delica you will not have generally holes in the wheels wells but you will have large areas of metal that warm and cool and produce the same effect as a cold glass of water on a hot day. Water droplets.

The method of treatment outlined is excellent, as long or short strand fiberglass works perfectly as it is waterproof and does not allow the moisture to get underneath the paint once the hole is patched with it.

Rust is cancer and the cheapest and easiest way to deal with it, is to purchase a spot sandblaster for around $45. They will recycle the sand and not make a mess in the interior. Blast our all of the rust then follow the above guide.

The quality of the metal and the coatings or lack of it used on the unpainted areas of the JDM vehicles is causing the problem. Wax and wash your roof as much as you want and you will still find the rust bubbles appearing as they are starting from the underside. In cars in Canada, areas that moisture is concentrated due to mud build up etc. will also rust from the back side.

You might want to seek a second opinion on your myth re rust not coming from the back side. I showed the pics to several other body men who focus on car restorations, and they concur it is coming from the underside.

By the way Rhino lining was used on the Grizzly truck produced in BC, and many of the 40 or so produced suffered serious rust underneath the Rhino lining. You might want to spend a few dollars on this product.
http://www.canada-por15.com/

[jrman]

There is a lot of great information on this post - and I'm not going to get into a debate here one way or the other, but I know that the paint quality on my delica's roof was very bad from the factory. Many delica's have a whitish cloudy roof - the autobody guys call is "delamination" of the paint - thought doesn't necessarily mean rust - just poor factory paint job and/or extreme climate conditions or both. Anyway - I didn't have any rust on mine (noticeable anyway) but still chose Rhino for a variety of reasons - the main 2 were cost ($300 including some patching and filling of a big dent) from Steve at North Shore Rhino, and the second reason is that I'm able to put my canoe on top without a roof rack. I sliced those cheap foamy floaty things down the middle and put them on the gunnel's of my canoe...tada...no rack required. I wished to avoid putting a rack on since I would have to remove it to fit into my parkade at work.....Rhino's been on just over a year and I'm still happy with it.

[bobenns]

I just finished a 1937 chev that had been left outside for the last 30 years and had no rust in the roof! No paint left on the roof either.

I think the quality of the steel and coatings is definitely a factor, carbon content, alloys, anodizing etc. Remember the early days of Japanese imports and people were often claiming they were made out of recycled cans. A friend of mine swore there was a Pepsi label embedded on the inside of his dad's Toyota car door. Then there was the Hyundai Pony, definitely a poorer quality steel, talk about blisters, the whole car turned into a blister. Up until somewhere in the 70's Chevrolet had a practice of overbuilding everything 15% above spec. I was told this by a man who used to audit the books at GM Oshawa. One of the reasons why the early 70's Chevs usually finished and won the demolition derby's, heavier frames and heavier sheet metal. After they changed the specs the later Chevs just folded up like cheap suitcases. I think 77 was the last year for the heavy guage Chevs, as 77 and earlier are the ones most sought for demolition cars.

Sandblast the bubbles you claim to be surface rust from the outside and you will find microscopic holes. How will you know?

Tomorrow I am going to tackle the spots on my roof. The largest spot has two pin holes going through, the second largest appears not to be through yet, but the other small spots should tell the tale. If I put a suction cup over the small rust spots the cup should gradually come unstuck if there is any microscopic holes through to the other side. I'll take one off the kitchen window that I know stays put on a solid surface and try it. I'll take some pics of what I find and post them.

The inside surface of the roof was never painted properly on either vehicle and moisture is evaporated and rises and collects on the highest spot. Without proper protection the rust starts on the underside and works it way to the top. Look carefully at Canadian Landcruisers and you will almost always see bubbles on the edges of the roof.

Very Interesting! But the Delica bubbles right in the middle of the panel. Bubbling at the edge may have something to do with seams.

My friend was telling me today that the manufacturers often cheap out on the coatings on the roof. Very thin layers applied. JDM vehicles also are taken off the road by 15 years or so, no one can afford to license them after that no matter how good the condition appears to be. So they are manufactured with the knowledge that they only have to last 15 years at most.

I would really like to see the underside of a high roof on a Delica, I'm not interested in tearing mine apart to see it though, but someone may have some pics from working on the power shades.

Well now I'm thinking I could take down the center light and see what's visible behind it. Damn! I really don't want to mess with the roof interior as my shades all work well. Wonder what's involved in removing the big light?

Good discussion. I guess I have to shit or get off the pot. As I have small rust spots on the roof directly above that center light I guess I have to take that light down and have a look see. That should tell the tale. If it's coming from the inside then the underside of that panel should be pretty much covered in heavy scaling rust by now as it is showing through on top at spots all along the center panel. If it's clean then it's coming from the outside.

Bob

[Green1]

just to clarify, regardless of wether the rust started inside or out, if there's any pinhole through you'll probably need access to both sides do to a "proper" repair, correct?

[docsavage]

I have all the stuff removed from my roof, so here is what it looks like from the inside:



This is what it looks like outside. There are a couple small bubbles and scratches from when I tried to get it out of the garage after lifting:



A close up of the front cross brace inside. You can sort of seen that the spot welds holding it are seperated and rust is showing in the holes. This is how it looked immediately after removing the roof liner:



Hope this helps clarify some of the issues with roof rust. Pardon my poor photography, but that was never a strength.

James

[mararmeisto]

If I remember correctly from one of the importers' discussion on this topic, those 'broken' spot welds are exactly where the rust-through problem happens.

Looking at it from another angle, this would make perfect sense because the metal is thinnest there, and a rust-through would happen where the metal is thinnest. Also, condensation inside the vehicle is going to rust the metal where there is a lack of protection (a broken weld) vice a painted-over section.

[vixentd]

There is probably no preventative measure that can be taken to avoid this. All the waxing in the world will not prevent the metal weld once broken from suffering from this. It will be interesting to see if all Delica's rust out on the same spot. Many cars will do that where ever moisture can be trapped. The weld is made at the factory and the vehicle is then painted. Once the spot weld is broken moisture can get at the untreated metal or weld. The body acts as strength and I would imagine any off road use would put strain on the top spot welds. Patches often welded in on rusty vehicles will usually rust out the same way, as often it is impossible to seal the inside surface of a patch.

This may be the reason that most manufactures do not spot weld bodies any more. All structural adhesive. They say it is stronger and will flex instead of breaking and also will not cause rust.

The pictures are a good reminder of what the structure looks like. You may want to insert some structural adhesive with some weight on the roof and then apply your fix, after the weld area can be cleaned up. These spot sandblaster are cheap and really work well.

http://www.performancemetalshaping.net/ ... 616294.htm
There are several brands of spray bombs that have a rust inhibitor that will act to convert the rust and also act as a primer.

My diesel doesn't suffer from this! lol But then again it doesn't have 4 wheel drive!

www.vixenrv.org

[bobenns]

Nice pictures James. That does help clarify it for me a lot. Out of curiosity, how long did it take to strip the inside of that roof James?
Also James, do the blisters we do see on your roof correspond directly to spot welds?

I started to disassemble the roof light today but soon found I would be taking down a heck of a lot more to get the roof exposed. I took down enough of it to where I could see parts of the roof panel above, just parts though, using a flashlight through holes and spaces around the light. What I could see was clean painted sheet metal, but I could only see a few very small areas of the roof. I saw no rust anywhere.

I am relieved to see in your pictures that large areas of the inside surface are not covered in rust as that is the image that was conjured up for me by some of the posts and led me to start my mythbusting. So maybe it's Bob that's been busted instead eh! Although I'm still not totally convinced that the rust actually starts on the inside and rusts through to the outside. I will elaborate shortly.

I was looking at the spots on the roof again today, looking for a pattern to them, most are pretty random but there are 3 little spots in a row that correspond well to that support that is popped in your pictures. They are very small but the arrangement is exactly the same with two a little closer together on the drivers side. I would imagine that the same spot welds eventually pop on all the high roof vans as the body twists and works. High roof owners are probably all in the same boat with this one. So I do have to concede that some of these roof spots are caused by broken spot welds on the inside, but not from a general rusting out of the roof from inside, which is good. The rust on the outside though is spreading out under the paint. And some of the spots are certainly just from damage on the painted surface.

It would be interesting to see if any one else has inside and outside pictures of this problem in different stages, especially later stages than James' roof. I'm curious if the rust spreads on the inside like it does under the paint on the outside.

Someone posted pictures of very large rust spots on a roof. I was trying to find them tonight but could not. I would really like to look at those again.

So here is my theory on the rust spots above the spot welds.

Years ago I worked at an auto parts factory in Windsor. The place was called "Hull Thompson". Frank Hull, one of the owners, was Bobby Hull's uncle, at the time Bobby was playing in Winnipeg and was a legend. I was very flattered to know his uncle, I was 19 at the time.

The factory made auto parts for all the American motor companies at the time. They specialized in long, narrow parts, like chrome trim, long braces etc. anything long and narrow. The steel they used came in large rolls and they used rolling machines to shape the lengths which were then stamped, punched etc. in punch presses to the required specifications. It was pretty dull and tedious work. One of the parts we made was the channels that hold the glass in wind up windows. On those parts a bracket was spot welded in the bottom center to fit the window winder mechanism. I worked that job a number of times on the night shift when large orders needed to be filled. The spot welding was probably pretty crude compared to todays automated systems, it was pretty much done by hand. There were two welds done simultaneously with two pairs of copper electrodes. You had to put the parts in the holder and use a handle to push the electrodes against them from both sides while it welded them together with electricity. You had to judge by the colour when it was welded right, too red, or not red enough and it was a bad weld. Every 100 pieces you would take the part and break the weld to see how well it was holding. If it just popped apart it was no good, it had to tear apart. You would hold the longer piece in a clamp and use a bar to wiggle the smaller piece back and forth till it separated. if one weld was stronger and one weaker you had to dress the electrodes and test until you were getting both the same. It was tedious but not as tedious as a punch press.

So applying that experience to these spot welds that let go on our roofs I come up with this idea. If the weld is decent it takes some work, wiggling, to get it to separate. It gradually tears apart, pulling metal out of one piece or the other of the two parts that are bonded. The wiggling stresses the areas that finally let go. You typically have a little bit of a dimple left on the other side of the sheet metal before it finally lets go. I doubt that they just go pop the first time the van body is twisted. It probably takes some years before those spot welds actually let go. So in the process of this working the spot weld the paint on the outside becomes damaged, weakened, cracked from the movement below it, the paint separates from the metal at that point. So based on James' pictures, while a little rust may start on the inside at the damaged point, rust starts on the outside surface as well where the paint is damaged. That rust on the outside then spreads outwards under the paint eventually producing the bubbles we find.

I don't think that the rust starts on the inside and eats it's way through, I think there is very little rust on the inside. The outside is exposed to much more moisture (electrolyte).

We need more pictures and input from people who have taken the interior off the roof. Perhaps some parts vans sitting around even.

I tried the suction cup idea on one of the very small spots. Put it up there this morning and drove around all day with it. It was still on good and solid when I parked for the night. Doesn't seem to be drawing any air through the roof yet, we'll see in the morning. I figure if the rust spot has come through from inside then the suction cup will eventually release as it can draw air through from inside.

The obvious complete solution to this problem would be to remove the roof interior entirely and repair the inside and outside. That looks like a very big job to fix some very small spots. I am betting that the rust on the inside is very little compared to what is outside and I am inclined to go for a good repair from the outside with fiberglass as it is bound to last a good 10 years, probably the remainder of the vehicles life.

As far as re-bonding the cross member goes, it can be done when and if it becomes necessary to remove the whole interior of the roof for a better reason.

In any case I will do the prep work on the roof tomorrow and see how much rust has gone right through the metal.

Bob

[mararmeisto]

Nice pictures James. That does help clarify it for me a lot. Out of curiosity, how long did it take to strip the inside of that roof James?
...Bob

I once overhead someone comment that Mitsubishi built the Crystal Lite window blinds, and then built the L300 AROUND them! Point is, taking apart the roof inside the van has usually been reported on this forum as a "weekend project" - as in it will take you most of the weekend.

Unless you're like Mystery Machine who gutted the rear of his van and put none of it back in (he turned one into a work van). Look at the thread for "the new Mud Monkey" - he's posted lots of pictures showing how much 'stuff' in bolted/snapped/glued/held-in-place in the back of these vans.

[docsavage]

Oddly enough, the rust spots do not correspond to any bubble on the roof but appear to be further back on one of the rear cross braces. I will spend some more time out there tonight as those pictures were hastily taken at lunch. It must also be noted that my vans life in Canada had been mostly in Williams Lake where the relative humidity is around 30% or less on average, and a few months up here in the Bulkley Valley where RH is usually 45% or less. In moister climates, the rusting may be worse.

In terms of stripping the roof, I spent about 4 hours. I was not keeping any of the panels, only the Crystalite shades and the flourescent light, so I broke a lot of clips and just tossed all the screws. If one were to disassemble with the intent of reassembly, a lot more time keeping track of things would be required.

James