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Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you. Also keep in mind I don't know if you are a pro or a novice, so feel free to add any additional info at any time.
White smoke from that tube is a BIG BIG red flag. The smoke is a sign the the engine has serious internal problems. Also the story about a fuel pump that is too powerful is just bull. There is no way a pump can cause these symptoms. CAT engines are great quality, but the down side is they are expensive to repair. With white smoke out the blow by tube, it will take some serious repairs, where the engine has to come almost completely apart. You might find once you open it up that it is far more than a ring as suggested. If it needs a complete rebuild, and you have it done, expect $12,000 to $14,000. I have dealt with Buses a lot, you try to find a southern bus, from areas where road salt isn't hardly ever used. Most buses from northern states have serious rust issues, it's often hidden. States like Texas, Arizona, New Mexico, Southern CA, and so on normally don’t have the serious rust the northern state buses have. Rust is probably the #1 issue when buying a used school bus. Go over all of this and if you have any more questions at all, I am here to help. Good luck with it, have a great day, and Thanks for using Just Answer.
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