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How to Repair the Damaged Suction Port Bolt Threads on a Loncin Water Pump

Laura Published on Jul 03, 2020 View Comments

In this video, we show you how to Repair the Damaged Suction Port Bolt Threads on a Loncin Water Pump.

Health & Safety Warning - Please ensure that you have safely prepared the machine and workspace. If you are unsure about any aspect of the task please seek professional advice.


Today we're going to show you an easy way to re-thread the bolt located on the suction port on a Loncin 25zb21-1.2Q Water Pump using a M6 x 0.1 Helicoil Kit. Firstly remove the pump case using a 10 mm socket spanner, keeping the bolts safe. Then disconnect all the parts on the suction hose, to reveal the screw hole or holes that need re-threading. Before starting you will need to determine the size of the helicoil needed to re-thread. As a top tip, a simple and cost effective way to know how far to drill out a damaged thread is to measure the depth of the hole and mark this on the drill. You can use tape so you know where you need to drill to. You may want to use a vice to hold the part in place. Next, get the 6mm drill bit provided in the Helicoil 6mm Kit, then drill out the hole using a power drill. Now, using the tap (knowing the size and the pitch), place this in a ratchet to easily re-thread the hole. Place the ratchet in straight, start off slowly to make sure you have aligned the tap correctly. Turn until you have re-threaded the hole and then release by unscrewing the ratchet. Now, get the installation tool and adjust so you know the measurement of the hole depth for the new insert. When you know the size, attach the spring on the end of the tool, making sure the tang is in the slot. Now place this in the hole twisting the new helicoil until it is secure, this should be half a turn below the surface. Do not twist against the direction of the thread, as this could damage the spring. Then remove the tang at the end of the spring. Gently tap this with the break tool provided, the tang should snap off. You can now reattach the parts back, including the check valve and suction flange. Aline the bolts and washers back and then tighten with a 10mm socket spanner. As you can see you have now repaired the damage thread/s, so the bolt/s can now securely be screwed back. That's how you re-thread the bolt/s located in the suction port on a Loncin 25zb21-1.2Q Water Pump using a Helicoil Kit.


Parts and tools included in the Repairing the Damaged Suction Port Bolt Threads how-to video.

  • 6mm Helicoil Thread Repair Kit - 902 1538

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