3M rubberized undercoating

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are you using it to prevent rust on the underside?...or trying to use it as a 'bedliner'?
 
it will last for a while, but nothing will hold up to the sheet on the roads in the winter. You'll have to touch it up, I would suggest a touch job once a year, before it gets out of hand.
 
Honestly, I've never had any luck with it, it dries up and cracks then just holds the salt water..

I gave up on commercial undercoatings and now just spray all my cars/trucks with a mix of SAE30 and bar and chain oil, a little messy to apply with an undercoating gun, but works great.

Steve
 
It's a good preservative! Leaky rear main seals, tranny pans, axles.. its all good for automatic rust proofing lol
 
moshiersr said:
Honestly, I've never had any luck with it, it dries up and cracks then just holds the salt water..

I gave up on commercial undercoatings and now just spray all my cars/trucks with a mix of SAE30 and bar and chain oil, a little messy to apply with an undercoating gun, but works great.

Steve

What kind of gun do you use?
 
My buddy uses roofing tar instead of the 3M stuff for the fender wells on his 4x4 because it holds up and applies easily.
 
I use a cheap harbor freight gun that looks like this and just use an old oil quart container for the bottle, but I can't seem to find anyone that sells them anymore.. it cost me ~$5-6 a few years ago.. It just sort of spits out the oil.

I've actually used roofing tar as well when patching holes in the floor of my old K5 blazer... I miss that old tank.. The tar works well to seal up patch panels just really really messy
 

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Since roofing tar (cement, really) was mentioned, I'll point out that I've used it also. But, one thing I do for more spotty undercoat is Tree Wound Paint. I suspect this is just asphalt paint, but in the brush style can it is so convenient. Holds up pretty well for me, but I'm not in the rusty north. My Canadienne cousins, however, have been spraying the bottom with SAE 30w for at least 25 years.
Oh, and after someone mentioned bedliner, I was reminded of a friend (in Ohio) who rebuilt a truck and used Rhino liner for the undercoat. I don't know how well that lasted, but he thought it was the best possible U-coat. (Expensive, as you know.)
 
I have a 94 nissan pickup I use for hunting, hauling wood, and plowing the driveway. I had it undercoated at Ziebarts when I first bought it but it is starting to rust.
Someone told me to use a product called por 15 they say it will not rust again once applied. Kind of pricey not sure if I will do it or not.
 
POR15 is ok, you have to follow the application instructions to the T or it will flake and peal, and you have to top coat it or it will degrade over time.. Rust bullet seems to work better and is cheaper!

I used to use WD40, but it seemed to wash of easy and didn't last too long. I still use it to make the frame on the Jeep look nice and shiney and new once in a while.. It's like tirewet for your frame LOL (I know I know its a jeep..)
 
Keep up that undercoating, otherwise it can cause more trouble than its worth. When it cracks, it provides
infiltration points for salt and moisture.
 
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