There is a number of things that could be causing the problem. The most likely thing is that a bearing on the motor is going out. The other possibility is that there's a foreign object stuck in the impeller. The best thing to do would be to DISCONNECT THE POWER and then remove one of the pipes connected to the pump. See if the impeller (the wheel with vanes on it) turns freely. If it doesn't turn freely and there's no foreign objects, then it's a bearing going bad. You should turn the pump off because it could damage itself further. Depending on your mechanical skill or availability of a local motor shop, it might be cheaper to get a new motor or whole new pump than it would be to repair it.
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There is a number of things that could be causing the problem. The most likely thing is that a bearing on the motor is going out. The other possibility is that there's a foreign object stuck in the impeller. The best thing to do would be to DISCONNECT THE POWER and then remove one of the pipes connected to the pump. See if the impeller (the wheel with vanes on it) turns freely. If it doesn't turn freely and there's no foreign objects, then it's a bearing going bad. You should turn the pump off because it could damage itself further. Depending on your mechanical skill or availability of a local motor shop, it might be cheaper to get a new motor or whole new pump than it would be to repair it.