Years ago when ever one bought a new car a high percentage would always pay the dealership extra to have it undercoated with some kind of black stuff that cover the entire bottom of the car including the exhaust system ;it would drip for days . if they were honest they would take a wand and spray inside the doors,rockers etc.It seemed by undercoating it actually promoted rust,a moisture barrier maybe. I did this years ago on a new ElCamino and it was a joke.It flaked off ,they never used a wand , the car rusted out in no time and even the frame finally rusted through behind the rear tires. I have put on a bunch of patch panels,have already done a lot of welding on my present model A project.Do you undercoat your old cars that you have redone,is there a product that is any good or is best left alone and not undercoated at all? Gene in Minnesota
It's always been my opinion the proper management of water and corrosives are more important to the life of the metal. It has to be treated, sure, but it also has to drain. In some cases there's clean out holes that are capped and meant to be opened and washed out now n then. The issue with undercoating failures is the clogging up of the engineered management designed into the body. Foreign car builders have little to no concept of road salt, hence they rusted beyond our worst nightmares in many examples.
You are confusing 'undercoating' with 'rustproofing'. Undercoating was a high profit item that mostly served as soundproofing and did little, if anything, to deter rust on a long term basis. I NEVER saw undercoating applied anywhere but to the underside of the vehicle, not in rockers or inside quarters. It was usually an asphalt based product that got brittle as it aged, cracked, separated from the surface and DID hold water promoting rust. Rustproofing, on the other hand, IF properly applied underneath AND inside the quarters, rockers, etc. was usually a paraffin based product that did not dry out, remained tacky and flexible and did indeed offer improved resistance to rust out. Ray
The DYI stuff in a rattle can is usually "rubberized". The stuff will shrink and crack soon enough leaving a space for water and salt to stay between the body and the undercoating. I'd use bed liner if I ever had to do it again.
I have used the rattle can rubberized undercoating. nothin' to brag about. i now spray on the green phosphate bearing primer and then the bedliner. sad truth is, it is nearly imposible to get anything in the seams where the rust seems to always start. Just keep a lookout for any rust starting and fix it asap. Or keep it out of the weather(inside), no fun either.
I will go along with the old rubberized undercoating holding in moisture. When I bought my Olds it had all that dealer installed stuff on the bottom of the car, even the underside of the hood. I used a heat gun and scrapped all that shit off. It was also sprayed inside the trunk. It was in some spots that was hard to remove, so I fugered it wouldn't hurt so left it. About 4 years ago I had some spots of rust on the panel inder the trunk lid. I never thought anything of it, cut out a small piece, welded in a new piece, ground the paint off the other sports thinking it was just something right under the paint caueing the problem, and repainted the panel. The next year, the rust reappeared. This time I removed a strip about 2 inches high the whole length of the panel. There was that nast ass undercoating there, I scraped all the rest out and repainted it again. Two years later and no rust this time. I am sure it had moisture trapped between the panel and the undercoating causing the problem.
It seems that bedliner is the most popular with most of the responses.I never thought of that ,but will give it a try . It will sit out of the elements most of the time,but in order to enjoy the car one has to drive once in awhile in the rain Right ?
I also changed from the spray on rubberized stuff to bedliner. I am sure whatever you use that you will do a far better job of application than the old dealers did.
That's funny, cause everywhere I've removed the old original stuff from the front & rear wheelwells, bottom of the floor or inside the doors or quarters the metal is like new.
Here is one more vote for bed liner. We epoxy primed and then bed lined the underside of my Son's rpu body. We used two part bed liner and had to buy a special ($100) gun to shoot it, but it really went on nice and there is no question it will be protecting the body for a very long time. It was messy to spray, over spray got everywhere, but it was worth it. Also, about 20 years ago I bought a Capri from my Son and I painted the bottom with Petit Rust Lok Primer. It is a urethane and is made for the steel underwater components of a boat, so it is VERY tough and will not let rust start. We sold the car and it went to Ohio and went through 4 winters with salt on the road, then we bought the car back. When we climbed under it the undersides look like the day I did them 20 years ago. I think I will do the underside of my 46 with it and then maybe bed liner it. But DO NOT GET THIS STUFF ON YOUR SKIN ! It does not come off and no chemical or thinner will touch it. I wore it all over my body for 3 weeks before it finally started to fade. Don
What $100 gun did you have to buy to shoot bedliner? I have never seen a do it yourself kit that is not just sprayed through a a regular $12.00 Shutz gun.
We didn't buy a do it yourself kit, we went to a Dupont paint dealer (where Dan had been buying all his primers and paints) and bought the two part (catalyzed) bed liner. It has been about 4 years since we sprayed it, so I forget exactly how the gun worked, but I think we loaded the bedliner mix cartridges into the bottom of it somehow. It is in the shop and I can take a look at it next time I am there. Don
You don't need no Stinkin Undercoating. Its a waste of time, money and causes rust. Paint is all I use. The 63 BelAir in my avatar has no undercoating, no rust anywhere, has original floor and trunk pans. Car was built in Atlanta and still has small traces of red Georgia clay in a couple of spots.
Yeah, me too but I think the stuff the factory applied is different and way better than the aftermarket undershield they are talking about. The factory stuff seems more oily or tar-based to me.
I have been using this stuff for years. I really like it. I get it at West Marine. I like to fog on color when it begins to tack-up, and re-coat with a full coat of color when it dries.
I don't know about rust protection, in California it's not an issue. But the fenders on my RPU have been coated with Rhino Liner. It is a great cushion that protects the fenders from those cute little stars rocks cause when the tire throws them up.
I sprayed the underside of my Willys coupe with UPOL raptor liner. Can be tinted to the color of your choice looks great and very tough stuff.
[QUOTE="41GASSER, post; I sprayed the underside of my Willys coupe with UPOL raptor liner. Can be tinted to the color of your choice looks great and very tough stuff.[/QUOTE] X2; I've used a couple times and really like.
Mine is a driver not restored just a vintage vehicle . Once a year I take used trans fluid and spray the entire under side , door jams , under the hood , and anywhere else I can . Drive it down some wonderful dusty Michigan back roads and thats it . This maybe is the original undercoating not invented just done by many back in the day along with me in present .
I recall my dad saying back in 57 about 5 guys at the Ford dealer they worked at all bought new 57 Fords. My dad's was undercoated but he probably picked a cheap process. 4 of the 5 cars (including my dad's) rusted out in a few years. One guy sent his out to a Texaco station that did undercoating using a Texaco product if I recall correctly. 10 years later it still looked good without ever having body work or a repaint.
There is the answer. YEARLY. Im surround by salt water (in the air), we use salt on the roads and it is above and below freezing all winter. I buy undercoating in 5 gallon pails. I used dripless undercoating, fluid film which is pricey but good, atf, hydralic fluid. I have heated up and melted wax toilet rings mixed with chainsaw bar oil and sprayed that with a shlultz gun. if it can creep into seams and is redone yearly it can not hurt. Also if you wash the road grime off frequently that also helps. If you are doing a frame off, seal and coat the metal with the best you can afford. That said you probably will not drive that in the wet weather or salt.
Haha, I knew a guy in the 60's who kept the old oil when he changed the oil in his 56 Ford. He would then put the car on a lift and shoot the hell out of the underside with the old oil.........he put it everywhere, even in the doors. Even with Pennsylvania salt in Winter that car was absolutely rust free.............but it always smelled like old oil ! Don
A friend of mine on Cape Cod did the same thing with his 4wd pick up. Another friend that lived in a log cabin up north would mix used engine oil with gasoline and spray the cabin exterior annually. He'd vacate the premises for about a week, and NO SMOKING within 100 feet.
Everywhere that I removed the undercoating (hard & black with a corragated look) from my 38 the parent metal looked like new!. I cleaned it and painted it with POR-15, it still looks perfect seven years later. What ever Henry used in 1938 was ugly but darn good.
I went through the pain (and it was painful, thankfully half the floor was rusted away) of removing all the original undercoating that was left on my '62 Merc, only to spray new undercoating back on right away again. I used the 3M Body Schutz undercoating with their "special" applicator gun (just a fancy air nozzle, really). We will see how it holds up over time.
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