Can I paint over old paint?

Yet another question for my project tractor. I have a '70 4520 with most of the paint still on it. What i was planning on doing is wire wheeling the ligtly rusted spots (mainly the frame rails) and then shooting JD primer over the spots where the wire wheel went. The thought crossed my mind to just shoot the primer over the whole unit right over the old (still intact) paint. After the primer I would then start painting with JD paint. The sheet metal would be taken down to bare, primed, and painted. This is my first paint job so I am a bit lost. Has anyone else painted a tractor this way? Keep in mind that this tractor is still used as our main tractor.

It's not necessary to put primer over the old paint, just the bare metal. It would only be necessary to scuff sand the old paint so the new paint can adhere. The most important thing is to clean the oils and chemicals off the old paint. It doesn't make for a very good paint job to paint it over the old paint but it will work. The old paint has a duty life and when it fails and starts to peal off it will take the new paint off with it.

"The old paint has a duty life and when it fails and starts to peal off it will take the new paint off with it."

And that is what I was worried about. The problem is that the engine and transmission have been redone so I really dont want to sand blast. I am not sure how I would go about taking the old paint off the engine. I suppose I could wire wheel the trans ok. Have you even been in this spot Stephen?

on workers.. i take the tins down to bare then prime and paint.

ont he cast body I pressure wash and degrease a few times. wire wheel out any rust, then pressure wash again .. after drying.. I prime and paint. plenty fine for a worker. for a show machine I'd wire wheel or otherwise strip her as much as possible.. cast included.

Thanks soundguy! This is the route I will most likely take. In addition, I will try to strip all the easy to reach places (on the cast) with the wire wheel and prime and paint. Thanks for all the help. I love this forum!

keep in mind that as the others said. when the old paint lets go.. so will the new paint. that said. on a worker.. it is better than rust.

A lot of times I will shield the parts I don't want to sand blast but mostly I dismantle a tractor as much as feasable to repaint. If you go the route of the wire wheel I think you would have better luck with a polycarbide stripping wheel for an angle grinder. It's a lot more aggresive than a wire wheel. I use the harbor freight #94017. I stripped most of the paint off of a 16' utility trailer with two of these wheels.

Use epoxy primer over the bare spots. Hal

Yes it is! I just cant really get to some places on the tractor without splitting the tractor, or so it seems. For the most part, I will take it down to bare and prime. I will check out those discs Stephen, sounds like they hold up well too! Being more aggressive, do you have to watch for the metal (especially the cast) getting too hot? I have a general idea as to how I will do this project thanks to you, Soundguy, and EL Toro! It just seems like a huge undertaking, but y'all have made sound like it is something I can do. Thanks!

I painted the trans and engine of a case 970 built in 1974 several years ago and all I did is degrease it good, wire brush anything thing that was rusty and then painted it with CIH paint. Its still fine though faded a bit. I think that old paint if its not rusty is baked/stuck on there pretty good. But if this would have been say on truck or something that sees road salt and harsh condtions ... it probably wouldn't have stood up well. Tractors (at least mine) don't see that kind of abuse just dirt and ... grease!

Thanks Chase. I think I saw a picture of your tractor when I was digging through the forum. I couldn't really see any fades in the paint though? I thought it looked like new! Mine just has grease, oil, and dirt too (mainly by the hyd remotes). I guess I will play it by year and see where this goes. Just like you said, I think the original paint is on there pretty good and I dont know if I trust my ability to seal it like they can at the factory. As soon as I get the rattle can cab off of there and remove the floor plate, I will be better able to see if the paint that is covering the cast pieces now is the original or if it was a quick spray before sale type of deal. Reguardless of what happens to the cast, I will take the sheet metal and side rails down to bare as there are multiple dings and nicks in that. Anyway, thanks for the input!

If its your first tractor paint job then for sure use the paint from your local JD dealer. It will be the correct match and is easy to use. I've painted several things over the years on the farm. The first tractor tear down and paint I did was a 1966 MF super 90 and man was it in rough shape when I started!!! I pressure washed.... degreased... presure washed and washed with varsol and so forth till I got it clean. It was terrible but it came out pretty good. Sheet metal I just sanded by hand, no sandblasting. I used MF paint from the dealer for the engine, pannels and rims. That loader was called robin so at the time I went to my local auto store and bought a quart of automotive paint that was a close match. I don't even remember what kind of paint it was anymore it likely was an acrylic enamel paint with out hardner. It sprayed on real nice I recall and I had just a mickey mouse spray gun at the time. That tractor I sold right after I painted it. I did a Case 970 paint job and that was a lot of work too. Its a working tractor and gets used on the farm still. Looks ok but I see lots of flaws in my paint job up closer!

This was stripped with aircraft stripper and a pressure washer and the discs from harbor freight took Tin to
bare metal and fame down as good as I could.. Napa epoxy primer and Jd paint..

Well Chase.....I must not be too picky because those look nice!! If my 4520 turns out that nice.....I'll be happy!! Thanks again!!