Fan motor re-oiling?

[Rich Feldman]

This is about porous bronze bushings surrounded by felt oil wick, such as one might find in a diffusion pump cooling fan.
Mine are in a kitchen exhaust fan motor, too neglected & gummed up to start.
Here it is after being cleaned inside and out.

The tail-end bearing cover is completely closed on the outside, and looks sort of like this stock picture on the inside:

After the bearing areas were soaked in WD-40, the shaft spins freely. But compressed air applied around the bushing produced not a single bubble at the flared ends of oiler tubes. And WD-40 is not a motor lubricant.

Any hints on how to clear the tubes and/or remove the WD-40 from felt, before re-oiling?
I'm about to learn how much a replacement motor (probably with inferior bearings) costs over the counter.
A whole new exhaust fan (with inferior, open-frame shaded pole motor) would cost only $80.

[prestonbarrows]

Getting gunk out of small plugged orifices is usually a job for a can of carburetor cleaner.

[John Futter]

Rich
sintered bronze bushes need to cleaned with dichloromethane (methylene chloride) or diethyl ether. These are the best degreasers made.

After cleaning I assume you can get the shaft out of the bearing a very good grade of light oil mobil 1 0-50 is good is used by you blocking the bearing lower with one finger and filling the bearing to the top with oil and then using another finger press your two fingers very firmly to force the oil into the sinter.
All old school motor mechanics were taught this for flywheel spigot, starter motor, alternator, generator etc bush bearings

[Jerry Biehler]

Or after you clean it out the bearing put it under light oil and put it in a vacuum chamber and pull it down till the bubbles stop coming out. Release the vacuum and the oil will push into the pores. That's how they do it at the factory.

The only problem if if the bearing ran without lube for too long the internal pores on the shaft will be clogged and it will never get oil and the shaft will get worn out.

Grainger and Johnstone Supply both sell a wide variety of these replacement motors. Grainger usually does cash sales but Johnstone will want a company name, so make one up.

[richnormand]

I had good success over the past few decades (ie: most motors still working) with this.

First : total clean with brake cleaner (carb cleaner too). remove all gunk and let soak overnight to attack the outer layer of the sintered bearing.

Two: remove marks on shaft with fine emery paper. Then, using a small rounded file slightly smaller than the shaft (as used to sharpen a chainsaw, 1 to 2 mm diag) I do a gentle file of the contact surface. Do not overdo it however.
This will open the oiling surface.

Three: apply penetrating oil such as "Liquid Wrench" and let soak for a week and renew when dry.

Four: if possible prepare a container of light oil, immerse the "bearing" and heat on a hot plate until you see lots of bubbles coming out of it.

Five: let cool for a day. The idea is to get the oil sucked back in the sintered bearing matrix. repeat as long as your patience allows.

Six: reassemble and oil with motor oil (non detergent). The detergent (as used in car oil) damages the motor coil wire varnish.

I have several small motors (and friends) that have been going for more than 15 years now in all sort of applications.

Oil with a drop of motor oil every 6 months if possible (like my aircon and exhaust fan on the furnace, more difficult on the 2001 Subaru cabin A/C fan)
but they still all work!!!

[Jerry Biehler]

Use a real oil like #10 spindle oil, it will last longer.