If you are referring to undercoating your exhaust... DO NOT do it. The exhaust is much hotter than the temperatures at which the rust proofing is intended to be used at. Not to mention the use of heat sheilds on the undersides of most newer vehicles, which should not be undercoated either. I have seen many vehicles that have been undercoated and they just go nuts with the stuff, coating everything from fuel filter and fuel/brake lines themselves. Good luck if you ever have to replace something.

Typically, exhaust will rust from the inside out which is why you really don't know you have a bad exhaust system until it literally falls off.

There are two schools of thought with undercoating. The ones that think its the best thing since sliced bread and have done it on all of their vehicles for ever and a day, and then there are people like me that look at it objectively. I see way too many cons to very little pros. Take it for what you will.

 

well, like I said earlier, my truck's a rusty bitch anyway, so I will probably not do it, since there's not much hope for her at this point

 

If you have rust already, then your best bet would be a rust inhibitor/encapsulator like POR15. POR15 is a GREAT product. I've got a small spot on a seam in the engine bay of my Bonneville that I will be treating with POR15 as soon as we have some crappy enough days that I can pull the b'ville apart while driving the Bravada. POR15 typically comes with a rust dissolver that is used to clean the surfaces, then a rust encapsulator that will keep any rust that isn't cleaned off from doing much of anything, then the final coating is a rust inhibitor that will keep new rust from forming.

 

At Krown Rustproofing you can watch them spray your vehicle. They don't spray the exhaust but some of the stuff does drip then burns off in the first few miles of driving. Beware that the vehicle will "drip" for a few days and can make a bit of a mess on your driveway. Its does wash off but I park over at the mall for a few days to spare the mess. There are some places that use a non-drip formula but I heard it doesn't protect as well. Anyway Swartlkk has made a few good points about the do's and don'ts...

 

for some reason i noticed the blazers i have owned , the body has held up amazingly the 95 i drive now has an almost perfect body

 

Viciouss, glad to hear you say that... I've got a 2000 and I was taking a peek under the truck yesterday and I see a little bit of rust but I was thinking that when I bring it into the body shop for a few other minor things I might have them look at that too.

 

My blazer has a lot of rust underneath. Matter of fact, I was going to have it rustproofed, or treated, but as soon as i saw this, im not going to anymore. I'd rather have some rust, than have 2 junk the car.

 

i know were talking about underbody here but i still think the biggest problem with ppl is that they dont wash there car enough. i live in minnesota and we get loads of salt and i hate it. all you have to do is wash your car often and it does wonders i wash my car on avg twice a week sometimes more i cant stand seeing dust dirt and especially salt on any car. my feeling on the subject is washing and waxing regularly on the body is best. as for what kyle said i agree, i wouldnt underbody coat it unless it was brand brand new, also alot of ppl think mud flaps look stupid or tacky who cares it saves the car in my opinion.

 

I actually think mud flaps look nice and that they do help. I have a GM set of four brand new in their packages. I have never installed them because i want to have my rear bumper painted at the body shop, and the mudflaps go on the inside of the rear side bumper. I can't wait to paint it so i can put them on. And i really wanted to get rid of the rust because since it's a truck, it's high and you can see the rust underneath. My solution to this cosmetic problem is that im going to get running boards which will give the truck a better look, will allow me to get into it easier, and most importantly, cover up and hide the rusted area underneath the truck.