Just this past week I replaced the fuel tank on my 48 yo MF 135. The inside looked like the OP’s. Rust scale and black muck. The new tank from Cross Creek Tractors cost about $200. Don’t wait too long to address the issue or it can destroy the primary fuel pump AND injector pump. Please don’t ask me how I know. $$$
Going through this right now with my MF 1240. I drained the tank and pressure washed the inside as best I could through the fill cap. Got a gallon of 30% white vinegar, diluted with 1 gallon of water and poured it in. Almost immediately I had pin hole leaks in 3 spots.
I had to jack the back up and remove both wheels and rops to remove the tank. Once the tank was off the tractor I was able to get the fuel gauge sender off and that opened up a new avenue for the pressure washer. Between the vinegar and pressure washing it did a decent job cleaning it up.
I ordered the KBS kit which is supposed to arrive Wed. A new tank is almost $700. Spent $50 on the sealant kit. Found a coupon for 12%off. Hopefully by the end of next weekend I'll have it put back together. Fingers crossed the sealer works and holds up for many years.
I finally got the kit yesterday. I am going to start the process of cleaning the tank and prepping it. What I have learned is the kit is a reasonable value. While you can source the cleaner and rustblast as generic chemicals the cost of small quantity wont net any real savings.
The KBS Klean is essentially:
3% potassium hydroxide - caustic potash aka lye
1% 2-Butoethanol - a degreaser
I think you would do just fine using a quart to gallon of 3% lye solution depending on size of tank with some lose nuts or coins to shake and roll around.
The KBS Rust blast is just 10% phosphoric acid that should be diluted to 5% with warm water. You can buy 15% food grade phosphoric acid on amazon. There are tile/grout cleaners that are phosphoric acid but they also add hydrochloric acid which is bad for metal. 10-15% acetic acid (white vinegar) will clean just as well in my opinion but it will not leave the phosphated surface which inhibits rust growth.
So if you are going to seal the tank might as well use the kit. They also sell a putty mix for larger holes. Just buy the jbweld epoxy putty steelstik instead. Or you can use the fuel tank jbweld kit that includes sandpaper and mesh.
I will try and take pictures of the tank after each step and post them.
If your going to put something in the tank to physically get the rust off use a piece of chain. It acts like gravel/nuts and bolts but if you get one piece out you get them all out.
I have used those gas tank sealers before with good results. You should also try to use electrolysis to clean it after the big junk is gone.
If your going to put something in the tank to physically get the rust off use a piece of chain. It acts like gravel/nuts and bolts but if you get one piece out you get them all out.
I have used those gas tank sealers before with good results. You should also try to use electrolysis to clean it after the big junk is gone.
I’ve seen or heard of then attaching the tank to a drum concrete mixer or rear tractor tire to aggitate. Nearby neighbors may not be to happy with the noise.
