Wednesday, March 18, 2020

Water Pump Rebuild

PROJECT 51: Water pump rebuild. Typically, when rebuilding an engine with lots of miles on it, the water pump is replaced without a second thought. For a Chevy 350, the prices I found range from around $30 to $80. For the MG, a professionally-rebuilt unit (the new ones they make are NOT recommended) is $250, and that is using a cleaned-up original sixty-something-year-old cast iron body.
When I took my pump off the car and cleaned it up, I discovered that it had a bronze body, and after some research, I found out that it was an aftermarket unit made in the 70's, and is highly desirable because the bronze won't corrode the way cast iron does. It also has a six-blade impeller, where the stock unit has only four, and therefore moves more water.
I held onto the improbable hope that I might be able to reuse it, but although the impeller turned freely, there was obvious "cogging" in the bearings, probably caused by corrosion. When I dismantled it, I could see that water had leaked past the seal and collected between the two open-sided bearings, causing rust in one spot in the rear bearing, resulting in that cogging.
The bearings are a common metric size, and I could find several sources for those, but the seal was a different matter. Even if one of the MG part-supply houses had sold a rebuild kit (which they don't) it would be unlikely to fit my aftermarket pump.
I took the old seal assembly out of the pump, but without a manufacturer and part number on it, it took a good deal of online searching and several phone calls to finally locate a company that could supply this type of seal, and then some e-mailed photos to narrow the search to a part number.
Many thanks to Kara Gardner of "Champion Hi-Tech of Oklahoma, Inc." for her diligent help in finding a manufacturer for my seal!
A slight modification to the hub of the impeller was required to use the ceramic mating surface of the new seal, but that will produce a better and longer-lasting seal against coolant leakage.
After polishing the bronze body for show (the original would have been painted MG-red) the new bearings and seal components were assembled, and the unit is ready to be attached to the engine.
Total cost to rebuild: $52.

Water pump still attached to engine.

Old and new bearing.

Old and new seal,

Seal seen near seal-mating surface of bronze impeller.

Turning the impeller to fit the new ceramic mating surface part.

New ceramic mating surface part in place.

New seal in place.

Rebuilt water pump ready for installation.

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