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Farm Machinery Digest: Testing your diagnostic skills

Ray Bohacz for Progressive Forage Published on 01 April 2021

Situation No. 1

You are thinking about investing in another self-propelled sprayer for the farm. You do not want to buy a new one since this unit will only be used for foliar feeding and fungicide application.

You had a bad experience a few years back when you seriously dinged up and killed some crop due to herbicide residue. You vowed to yourself to eventually get a dedicated sprayer for in-season crop care and nutrition.

You found an excellent unit a few towns away. The seller said it worked well until recently when the pressure would not stay steady. He felt it needed a new pump and priced the sprayer accordingly. You agreed with his diagnosis and took the unit home.

Upon removal and disassembly of the centrifugal-style pump, you noticed the housing was pitted internally, the tip of some of the impeller fins broken off.

Confident you’d found the issue, you bolted on the new pump and hit the field … only to find the same pressure problem existed. Perplexed and frustrated, you ask around for some advice, and this is what you receive.

A: Farmer A says the new pump is defective and has the same problem as the one you replaced.

B: Farmer B believes the gauge is wrong, and the old pump was fine.

C: Farmer C says the old pump ate some dirt from the tank, and it must still be in the system – that’s why the impeller is damaged and the volute pitted internally.

D: Farmer D is adamant the original pump was damaged by cavitation, and that is why the pressure is jumping around.

Situation No. 2

You finally have the chance to go into town and get new tires for your wife’s SUV. When the tire shop pulls off the front wheels, they notice the outside brake pad on the left caliper is almost metal-to-metal.

The shop owner suggests installing only new pads since the rotors look good. He says it is straightforward since the pads slide in from the top without removing the caliper. You give the go-ahead, and the work is done. Is the problem solved, or will the one pad wear prematurely again?

A: Farmer A says all disc brake pads wear unevenly, and there is nothing you can do about it.

B: Farmer B says the brake rotor is uneven and wearing out the one pad faster.

C: Farmer C says the caliper is not returning, and the one pad is always rubbing slightly.

D: Farmer D tells you the piston in the caliper is leaking, and only the one pad stops the SUV.


Situation No. 1: Farmer D is correct. There is an issue with the plumbing either to the pump or from it to the boom that is causing cavitation erosion. The clue is the pitted volute (housing) on the pump and the broken tips on the impeller. Due to the restriction, air bubbles are forming that destroyed the pump. If you do not find the problem, the new pump will be damaged in short order.

Situation No. 2: Farmer C knows the reasons why the outside pad is worn. A brake caliper with only one piston is a floating design and needs to return when the brake pedal is released. The hydraulic piston (inner pad) is returning. Still, the pins/bracket the caliper floats on is dirty, rusty or lacks lubrication. The outside pad is dragging slightly.

Since the shop only slid in new pads, the problem will still be present. The outside pad will drag since the proper procedure was not followed. end mark

Email “The Hotrod Farmer” Ray Bohacz with your machinery-related questions. Visit his site – Farm Machinery Digest  – for technical articles and to listen to his Idle Chatter podcast, which has listeners in 67 countries. Also tune into Farm Machinery Digest Radio on Sirius/XM Channel 147.

Ray Bohacz
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