I Bought A Gallon Of Rust-Proofing

pcb

The Diagram Dude
:
2002 MP5
I've decided to make my own undercoating,... 2 parts tar, 2 parts grease, 1 part varsol. Cook on medium low for 20 minutes. Brush on underside of car.

Its my own messipe,... I think it might work.
We'll see.

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I'm gonna miss the asbestos though,... they always ban the good stuff.
 
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pcb

The Diagram Dude
:
2002 MP5
I got a new camera (cell phone). I think this is better:

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This is part of what I'm up against: (that spot had little holes in it,... so didn't last)

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This is an example of my painting skills from last year (lots to be desired but the rust didn't come back !!)

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This is a spot I forgot to do last year: (tailgate)

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nicqcrenaud

Member
:
protege5 2002
looking forward for the outcome! do you think it will have a very thick of rather thin consistency? I'm also thinking this will probably create a seal similar to rubber undercoating but it might not be a bad thing after all. I just discovered my driver side carpet is pretty wet all the way down to the rear seat, it's probably(hopefully) a firewall leak but if it's coming for below then a sealing coat would help.
 

pcb

The Diagram Dude
:
2002 MP5
Well,... I took some pictures of my underside and it still looks pretty wet with oil.

I may be putting off my undercoating for a few months to let it dry up a bit.

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Check out this link for leaky spots. I've gotta do this myself.

http://www.mazdas247.com/forum/showthread.php?123827490-firewall-cabin-water-leaks

I think what I'll do is whip up a couple of small "test" batches of goo and test it on an open area. I might even wash off the oil on a small area to see how things stick and penetrate.

What I'm really after is something as durable as asphalt undercoating that doesn't dry up and make things worse.

I'll try the different solvents to see how they compare. I'm leaning toward acetone because it should evaporate out of the grease and tar but be very thin initially.

I know some spray grease works using solvents,... it sprays on and runs but then the solvent dries out of it and the remaining grease is then very thick. Something like that would be perfect.
 
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Installshield 2

Gothenburg Superiority
doesn't look like you're in too bad of shape, rust wise...let us know how it turns out...i'm about 50% done with my spring rust prevention s***...so far so good.

All i'd suggest, although i don't know exactly what your homemade stuff is chemically, is to do it in very thin layers...I used that 3M professional undercoating stuff on two spots so far...the 2nd turned out WAY better, because i spent all day letting it dry between coats...i ended up having to reapply it on the 1st section i did, because i didn't leave enough time between coats...

a month later, the 'thick' coated area never dried properly...the exposed coat dried fully, but i could tell it was extremely tacky underneath...and the whole job was easily picked away with a small screw-driver...I did it again, allowing hours between coats, and its far better than before...and that time i also used half of what i did before...you can still dig it off if you go nuts at it, but it created a much better protective barrier...How it dries isn't all that important; if its petroleum based...water isn't getting through it...period...just make sure the areas you coat have no way of water getting in 'beside' it, if that makes sense...
 

pcb

The Diagram Dude
:
2002 MP5
OK,... The main thing I'm wondering, is if over time, the coating will dry out to the point of being like a coat of paint kinda like the original undercoating on the car. If that happens, water will certainly find it's way in 'beside' it and can creep under the coating never drying and held right there at the metal surface.

I have more scraping to do before I apply anything and it has all shown up since last year even though I go to Krown yearly,... but I don't know how it would have been without the Krown or the original factory undercoating.

I want the whole thing to stay sticky,.. like grease so it would hopefully 'seal' up any pebble nicks that may happen.

You've got pretty much the same weather as I do (although I don't know how salt use compares) so this may be a good comparison.

I remember on many cans of different undercoating, they mention how their product can 'self seal'

So I'm going for the oily and semi-tacky approach although I'm sure I'll have all kinds of crap stuck to it,... dust, dirt and pebbles. I just hope I don't have to scrape it all off and do it the normal way.
 

nicqcrenaud

Member
:
protege5 2002
Well,... I took some pictures of my underside (my car's underside,... not my own) and it still looks pretty wet with oil.

Check out this link for leaky spots. I've gotta do this myself.

http://www.mazdas247.com/forum/showthread.php?123827490-firewall-cabin-water-leaks

I think what I'll do is whip up a couple of small "test" batches of goo and test it on an open area. I might even wash off the oil on a small area to see how things stick and penetrate.

What I'm really after is something as durable as asphalt undercoating that doesn't dry up and make things worse.

I'll try the different solvents to see how they compare. I'm leaning toward acetone because it should evaporate out of the grease and tar but be very thin initially.

I know some spray grease works using solvents,... it sprays on and runs but then the solvent dries out of it and the remaining grease is then very thick. Something like that would be perfect.

yep thanks for the post, I actually read it before but my leaks are mainly coming from very bad weatherstrip on the driver side doors so i'm gonna start with that and take a look at the firewall area later.
 

pcb

The Diagram Dude
:
2002 MP5
My most recent oil undercoating was Krown (the stuff in the pictures,.. two days after spraying). Last fall, I used a few cans of Rust Cure, but by last month, before going to Krown, it was looking pretty dry.
I think I'll be giving my homemade grease/tar idea a try soon. I think the Krown has dried or absorbed enough to get the grease/tar to stick without dropping off.
My in tank fuel filter is on the top of my list though and I intend to be on it in the next few days.

I still highly recommend going to Krown,... they can get to spots that we just can't reach ourselves and it's thin enough to seep into all the cracks and crevices. I think it's well worth the $135.

I saw three different P5's in the past two days and they were all completely rusted out around the wheel wells. I've seen well over a hundred different P5's in my area over the past three years and only two or three of them were in as good a shape as mine, with no visible rust.
 

pcb

The Diagram Dude
:
2002 MP5
I finally got around to making a test batch of undercoating using four big tablespoons of both the high pressure grease and roofing tar (roll roofing glue actually which I only bought because it was the cheapest,... I think it's a bit thinner than regular tar) then I put it in a steel bowl and cooked it on the stove till it blended nicely.

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Then I went out to look for a spot on the car to try it,... I found the backside of the rear bumper was really nasty with big flat chunks of metal flaking off so I spread some around there. The Krown spray had soaked in pretty good because it was so porous. It went on great and because it was still almost hot , it was quite thin and spreadable. It was kinda like a gel.

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Then just for the heck of it I tried some on the spare tire molding under the car that is in pretty good shape and still dripping with Krown spray and I was quite happy to find that it all blended together awesome. No oil and water kinda thing,... I guess oil, grease and tar blend easily. The mixture thinned out a bit more because of all the Krown spray, but overall I'm really excited about how it's working.

Starting with a surface that is soaked with oil is fine and that's good because you can spray it down with probably anything like Krown, Rust Cure or Fluid Film,.. let it soak into the cracks and crevices for a couple of days then put on this top coat without worrying about dry spots or sealing in moisture. It's super cheap too,.. the roofing glue was $12 for a gallon and the tube of grease (which I have cut down to about half size so I can scoop it out) was less than $3. So I don't mind whipping up piles of this stuff and caking my car with it.

I do have to save some tar for my actual roof which is in the process of being replaced (I'm doing it myself cause I'm a cheap ass,.. $750 instead of the $2,800 quote I was given.)

I just went out to check the condition of the remaining mixture in the bowl in the garage and it has stiffened up quite a bit and isn't as sticky,... I'm thinking that is good too because it won't be as messy if I rub up against it and won't rub off as easily.

I supposed the only real test is time itself. I wonder what this coating will be like in a few years,... I really don't think it's gonna dry up, crack and let in moisture like the factory undercoating did.

I'm thinking my spray at Krown next year might soak in to the mixture and soften it up if it's hardening ??

Fingers crossed.
 
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pcb

The Diagram Dude
:
2002 MP5
So I finally crawled under my car to attack the rust before winter kicks in.

What a fricken mess...

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That's a hole through the frame rail.

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That's a hole right through to the carpet in the rear right passenger footwell.

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These are some gas vent lines rusting all to hell. They're hidden up under the gas tank.
This is after I hosed them down with undercoating spray.

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That's the hole through the floorboard. (the gravel driveway is showing through the hole).

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This is after I patched the hole with some 5 minute epoxy and some pieces of fiberglass weave,... took 20 minutes,... real easy.

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Bringing this thread from the dead :)

Well done on the repairs, after seeing something like that I would probably go home and cry. What you have is in better shape than mine though :\

Anyways, has the rust come back? You did a good job of cleaning it, but didn't see you rust proof it.
 

JetSkiGuy

Member
:
Mazda Protege5
He has sealed the rust with his tar mixture. If no o2 or h2o can get to the metal it can not oxidize.
 

pcb

The Diagram Dude
:
2002 MP5
He has sealed the rust with his tar mixture. If no o2 or h2o can get to the metal it can not oxidize.

That's why I use "oily" type undercoating instead of "rubberized" types (like most asphalt undercoating). The rubberized stuff "dries" then cracks then lets water in, then it creeps underneath and can end up making things worse than if you had just left it.

BUT oily undercoating can attract dust and dirt,.. can seep for months,.. then end up all over you and your passengers clothes.

The tar grease mixture I made has worked quite well,.. It dried out enough to not be so messy but didn't "harden up" like straight roofing tar would have. There is enough grease in the mixture to keep seeping to the metal so that the water/air seal is maintained.

I did go under at one point and the test area underneath and behind the rear bumper was doing well. Some of the mixture came off in big flakes,.. BUT,.. the metal underneath was 'wet",... so I just caked more on.

I also went back to Krown for my yearly spray last April again and that worked out good as well,... the oily spray kinda "re-hydrated" the tar mixture and soaked in.

The 3M stuff mentioned earlier in this thread is kinda a whole different thing. That stuff needs a perfectly clean surface then tries to "bond" to it chemically. If I had to remove all the rust down to bare metal on my car I would be left with just a few plastic moldings and not much else.

On a related topic,... I remember reading that at the time our cars were built (I don't know about now), the metal used to build them was almost 100% recycled metal. All P5's were built entirely in Japan and it was part of their politics to recycle.
Apparently, it is very difficult to remove all the impurities in the reused metal and the remaining impurities (however small) is enough to make our cars "eager" to rust.

I would suggest to anyone,.. especially in the "salt belt",.. to get your car undercoated. I go to Krown (here in Canada) where they drill holes (1 or 2 dozen) then use wands up to 4 feet long to reach inside the hollow spots of the body and frame. The stuff they use is a thin synthetic oil under high pressure and it comes out as a "fog". It covers Everything then seeps and creeps into the cracks and crevices. It takes them 45 minutes to do my car. It was interesting to see that they don't spray behind the side mirrors anymore. Apparently there were a few cars where the mirror glass fell off after the spray soaked in. I got them to spray behind my mirrors again. It keeps the motors working.

I went to a different place years ago where they just sprayed the bottom and were done in less than 10 minutes.

I don't know what kind of choices you Americans have but I would advise to find a place that drills holes.

The holes aren't too bad,.. the have little plugs they pop in and even coat the hole with white grease to help reduce rust.
 

pcb

The Diagram Dude
:
2002 MP5
Yes, but if he didn't clean the rust completely (difficult to do), then the rust will come back and spread to other metal...

You don't need to clean the rust when you use "oily" type spray,... just remove the loose rust and spray it on.

BUT I wouldn't feel comfortable putting my tar mixture straight on the rust,... I think that would seal some moisture and air in,... I hose it down with thinner spray, let it soak then apply the Goo.


By the way,.. Scrapping the rust then applying the Goo under my car was probably the worst car related work I've ever done. What a disgusting mess,.. crap falling in your eyes and hair,.. your grease covered tools are slipping out of your slimy hands,... Aaaa.
 
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:
2002, Protege5
Man I can't even imagine doing all of that work. But i guess it is a must up North. Really I think my car was bad from really poor maint. Evident by the rest of the cars condition.

I bet that was nasty work scrapping and then applying that tar stuff. I bet if you get that stuff on clothes it is never coming out...

I was under my 06 F150 just touching up some small spots of surface rust and applying some sound deadening coating under the cab, and that was messy. I can't imaging doing what you did. Luckily my truck with 121,000 miles looks brand new. Plus I just got some new leather Katzkin installed.
 

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