We help people repair plastic
John Deere hoods frequently get cracks in them. When they do, we get phone calls. "How do I fix my John Deere lawn tractor hood?" they ask. "It's made of 'plastic'." they say. The "plastic" from which *most* John Deere lawn tractors are made is polycarbonate. This is a very rigid plastic and, when it gets cold, it gets brittle and breaks easily. With all of the vibrations from the mower, not to mention the bumps that the mower has to endure, it's no wonder they break. Not only that, but when you turn off the mower, all of that heat from the engine tends to "cook" the plastic making it even more brittle.
This polycarbonate plastic was used for years back in the 90's on Ford, Mercedes, and Hyundai bumper covers. The car manufacturers don't use polycarbonate anymore for several reasons. When a polycarbonate bumper gets in a collision (especially in freezing weather), the bumper would shatter and not absorb much of the impact. Of course, the main reason the manufacturers don't use polycarbonate for bumper covers anymore is because polycarbonate is more expensive and heavier than, say, polypropylene (which is what they use now).
Polycarbonate can be easily repaired. We did it, and body shops did it for years. We still do it occasionally.
We had someone local bring us a John Deere lawn tractor hood that was cracked in several places. He used packing tape to hold it together. Of course, it didn't hold very well or he wouldn't have brought it to us! He said he wasn't too concerned about the appearance. He just wanted it repaired. That made this job much easier.
Since we get so many calls about repairing John Deere lawn tractor hoods, we thought we would do the world a favor and show you, step-by-step, how to repair them.
As you can see, this John Deere lawn tractor hood was cracked all the way down the length of the hood. The plan is to remove the tape residue, align the crack, and tape it together temporarily, then weld the backside.
We need to get that tape residue off. It doesn't come off with soap and water, so you'll need to get some Super Prep Plastic Cleaner. It has some mild solvents and alcohol in it that will emulsify the tape residue without attacking the plastic. Wipe it off with a clean paper towel in one direction. If you need to clean it some more, be sure to expose a clean part of the paper towel. Otherwise, you are just spreading the goo around.
To hold the damage in alignment while repairing, we used some Aluminum Tape. This aluminum tape is really thick and more rigid than that stuff you get at home improvement stores. Not only that, but it is super sticky.
Polycarbonate tends to get crusty and oxidized over time. The heat radiating from the engine oxidizes it quicker. Your welding rod will not melt together with the crust, so you need to get rid of the crusty surface. To get the best weld, you need to weld to un-oxidized plastic. We used a rotary tool with with a carbide cutting wheel to remove this crusty, oxidized surface.
We used the polycarbonate strips to weld along the crack line. This will give a stronger repair than using the 1/8" inch (3 mm) rods.
To further strengthen the repair, and to help prevent it from re-breaking, we welded a "T" at the end. Cracked plastics normally re-break at the edge, so by "T'ing" off the repair at the edge, you will reduce the chance of a re-break.
After the weld cools off, it is safe to remove the aluminum tape from the other side. After peeling of the tape, we noticed that the repair was really strong. We had originally planned on welding along the crack line with the 1/8" inch (3 mm) rods, but that would have been ugly, and John Deere owners seem to be really proud of their green machines. Even though the owner *said* appearance wasn't important, we decided NOT to weld the visible side in the interest of appearance.
We "T'd" off the repair at the edge to strengthen that spot (since that is normally where re-breaks occur). Since we didn't weld the visible side, we decided to "T" it off in several locations on the backside to compensate for not welding the visible side.
Here is a picture of the completed repair, and it is VERY strong. Not pretty, but strong.
welding john deere tractor hoods