A little rust underneath the car !

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Ominous11

New member
Hey there,

I'm new to the forums and want to say hi first of all :)

Alright my g/f just bought a 03 Mazda 3. It pretty rust free for the entire body of the car. However underneath the car just pass the rocker panels is starting to rust ( more like surface rust ). The worst part I would like to fix is just pass the driver side front wheel. It starting to form a hole. It not rusted threw yet but I think it would be if it went another winter. I've taken some photo's to help.

I don't need to make it look crazy pretty but I want to make sure it solid for 4-5 years
 
Well, you're going to want to clean that and use a good rust converter. Honestly I think Eastwood has the most comprehensive selection of products for this, but they are expensive.
 
I would clean well then rust converter then maybe some of that roll on bedliner to add some strength and added protection.
 
Like Setec, not sure what you've got there in the first pic until you are able to clean it up. For the 2nd pic, that looks like you could just brush off the surface with a wire brush, get it good and clean, (I'm not familiar with Eastwood products others mention here, but sounds like that would be the next step), then just some rubberized undercoating from an auto parts store should seal that off nice for you.

If you do have a hole in the first pic, you could either rivet in some sheet metal (from the inside under the carpet if you can get to it...looks like the footwell of the backseat but can't tell for sure), or fiberglass, again from the inside. On the outside fill it in with a little blackjack and spray undercoating.
 
Fist step of Mazda ownership:

Put car on a lift. Apply undercarriage spray liberally.

wurth-high-build-underbody-underseal-10.gif


As you aren't the original owner then you will need to clean all that rust up, then conduct a thorough cleaning of the wheel wells and frame rails, then seal/protect those areas with an undercarriage spray.

Notice how dark and black the wheel wells are on my old Speed3? Multiple coats of undercarriage spray the first week I owned the car.

alki4.jpg
 
Sandblast, rust converter, etch primer, paint, undercoat, paint, and heck even more undercoat.
 
I would rather spend the time to first find out what caused the rust - was water leaking into the car?

If you dont find what caused the rust and it was coming from, say, the opposite side of the rust, then all the fixing in the world is not going to last very long, since the water is still leaking probably into the car..

It looks like very thin sheet metal there.. if you lose all that metal in one spot because its rusting away, the panel is now very weak in that spot..

Dont you want to see about replacing the rusted out area with a new piece of metal?

Good luck!
Dan F
 
I appreciate all the feedback from everyone !

So I've taken the first step after reading everyone comments. I've grinded down the rust to nice bare metal. Now I'm off to Crappytire to get some rust converter.

It's a nice size hole even though it's not the best picture. I would rather fill it with something over just putting a piece of sheet metal over it.

Thanks for the advice ElLeon. I'll defiantly buy that and do the wheel wells !

Stockdgs- Everything is probably from salt over the years ! I live in Canada, Ontario and they layer the roads with salt in the winter... I don't think it's from water damage. It is pretty thin however I don't have the time or the experience to weld new metal in. I took must of the rust away so now I was wondering if I could pack it with something to fill it and even out the hole. Ss there something I can go over to keep it from rusting again ??
 
That's rust looks like it needs to see a body shop to me. You can slap some stuff on it - but its likely to do little good in the scheme of things.

The rust needs to be completely cut out, a new panel fabricated, and then welded in. Or, the rocker panel needs to be replaced.

I've just been through a body shop rust repair and found out the rust you see is usually the least of it.
 
The best paint/coating I've used is POR 15. Wire brush any loose rust and apply it. This stuff is fantastic. Started using POR 15 many years ago and never dissappoints, never found anything better.
 
Stokdgs said:
I would rather spend the time to first find out what caused the rust
Dan F
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Clearly you've never owned a Mazda. It could be the gentle breeze of a spring day, or the violent lick of the devil's tongue upon the paint which caused the rust. :lol2:

Doesn't matter. It has a chance to rust.

You have to protect the underside of a Mazda yourself. Their factory "lifetime" undercarriage spray is worthless, so you have to handle it yourself.
 
ElLeon said:
Clearly you've never owned a Mazda...
Click to expand...

Mazda's got nothing on Datsun's, Volkswagen's, Vega's, Renault's, Fiat's of yesteryear to name a few when it comes to chronic rust out vehicles. Dan hit the nail on the head, check first to see if there is something specific causing this area to rust. As someone who has undercoated hundreds of vehicles, sometimes undercoating is the best answer and sometimes all the undercoat does is seal the rust pocket in and not allow air to the affected area. Panel failure is inevitable if that is the case. Going price used to be $99 for most cars and $149 is where trucks started.

Sidebar that some might find humorous. Picture this, imagine what happens when someone leaves the pressure sprayer nozzle trigger engaged and simply unplugs the airline to the undercoating tank when finishing previous a job. A 20 gallon container of Chevron's best "black tar" undercoat sits there waiting for the next guy to plug the air line in not realizing the nozzle is ready to spray. Now the guy that's plugging the air line into the tank isn't holding the nozzle so it's kind of like a fire hose that no one is holding on to. I watched one of the mechanics in a shop I worked in literally undercoat a female customer who was walking through the adjacent bay.

I wasn't involved other than to herd the tire busters from the shop as they were all but rolling on the floor laughing at this poor woman and the mechanic that had just undercoated her. This petite lady was now striped black, hair, glasses, blouse, pants and all. It was ugly. The look on the mechanics face was priceless. The back shop customer service counter's location was moved shortly thereafter. :)
 
Don't forget to pull the interior wherever the hole is. You don't want to find out later that the rust spread inside the panel where you can't see it until it breaks through again.
 
Setec Astronomy said:
Well, you're going to want to clean that and use a good rust converter. Honestly I think Eastwood has the most comprehensive selection of products for this, but they are expensive.
Click to expand...

True, but not as expensive as the repair after it eats through. I have used the in frame coating and the rust encapsulator paint.

Dave
 
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