i looked under my max and the whole bottom of my max is rusted, the heat shield around the rear o2 sensor fell off from the rust, dont know if it will make a difference,

should i buy some underbody coating and spray it over the rusted parts, how does it work, should i be concerned or just leave it

 

damn well I'm assuming if you leave it, the rust will start eating away at the metal still... how's ure exhaust pipe and muffler lookin underneath there? I had an old car that was left out in the elements for 3 years... wasn't driven. The first thing went was the muffler... it fell apart literally inside because it was rusted. The entire pipe underneath there is still rusted, but thank god nothign bad so far.

 

wd-40....lots of wd-40......that'll do the trick

 

well, is it just minimal surface rust? are you talking exhaust or frame?

 

I've got frame rust
Is is too late to start rustproofing now? And is it fixable, or should I expect it to eventually eat away until the max deteriorates

 

All cars driven daily in the NE United States or anywhere they salt the roads as much as they do here will rust.

You can undercoat till your hearts content and it probably won't make a bit of difference.

Yes the frame and every iron-based metal on the car will eventually all turn into a big pile of reddish powder.

My advice? Don't worry about it. Wash it as soon as the roads are clear. Hose the salt off underneath with a pressure washer. The drive-through car washes don't do anything to the "undercarriage" except dampen it which makes it worse.

It's all you can do. Heavy undercoatings can actually make things worse. Any coating subjected to gravel at 90mph getting ripped up from the road will develop tears and holes. Then you could actually end up with salt nicely sandwiched between the torn undercoating and the steel....

Purging the air and flooding a sealed garage with Argon gas is the only thing that will slow it down...

-RMB

 

if using a pressure washer , is there any places under the car that i should avoid spraying that may cause damage, or is it ok to spray the whole area, i seen in a auto parts store that they were selling a flexible silicone under body coating in a spray can , so this will not do any help to stop it, so i should just prepeare to save some extra money for a new max once this one detoriates apart

 

RMB: I would have to agree and respectfully disgree with you . Certainly the laws of Physics dictate that moisture + salt + metal = rust, and over the long run complete deterioration. However, an oil based underbody coating can significantly slow down the rust process. The key is to dispell moisture, and a heavy coat of oil based spray will certinaly do that.

I am curious however what you mean by "undercoating"? Are you referring to some sort of a rubberized coating applied to the underbody? Or a thick oil based spray which is designed to dispell moisture. I agree that a rubberized coating will just hold in moisture, dirt and salt (especially once cracekd by road debris) --> very very bad