How to Rebuild a Gear Pump

Gear pumps are positive displacement pumps capable of pumping virtually any fluid at high pressure. Used in a variety of applications, gear pumps have the ability to pump fluids with high viscosities, such as motor oil. Gear pumps contain gears that rotate and mesh to provide the pumping action and are always used as an engine component. The engine operates the pump mechanically, under its own power, so the pump and engine work in sync. Gear pumps are rebuildable, provided they are not overly worn down. One of the most common gear pumps is the automobile oil pump.

Instructions

1

Pour any excess fluid out of the pump and dismantle the pump housing. At the bottom of the gear pump is a series of bolts. Remove all bolts with a wrench, and take the bottom cover off. Scrape the old gasket off using a gasket scraper. Wipe off the gears and inspect them; look for excessive rounding of the gear teeth. If the gear teeth are worn way down, the pump is not serviceable.

2

Keep the pump upside down and place a metal straightedge, edges up and down, across the bottom of the pump, making sure the gears fall in their normal operating position. Place feeler gauges between the gears and the straightedge until the distance between the two is found.

3

Determine the minimum gear-end clearance either by locating it in the pump manual or contacting a pump supply store featuring your pump's brand. Remove the gears from the pump housing by holding the pump right-side-up.

4

Place emery sanding paper on a flat, level surface, and sand the bottom metal surface of the main pump housing until the recommended minimum gear end clearance is achieved. Find the feeler gauge matching this clearance and gradually sand the pump housing until the correct feeler gauge fits between the gears and the straightedge. To replace the gears, put the gearshafts into the housing and let them fall into place. Take great care not to oversand the housing, exceeding the minimum gear end clearance

5

Break the pump down again, taking out the gears. Clean everything thoroughly with an automotive parts cleaner. When finished, blow each part dry using an air compressor.

6

Grease the gears and inside of the pump housing completely with petroleum jelly. This lubricates the pump for priming and is washed away when the pump fills with motor oil. Put the pump back together; the gears normally have indicator arrows showing their proper placement in the pump. Replace the gasket, and bolt the bottom plate back on the pump. The pump is now ready to be installed and primed.