Fan Bearings

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    Hi, I noticed Her (’27) fan bearings seem loose: being afraid of destroying the beautiful original cellular radiator in a failure, I think I need to go in. What will I find when I dismantle the fan hub?


    LOOSE is ok, as long as we are talking just a bit of play or clearance. What is important is are they smooth, silent when the fan is spun, with the fan mount in your hand, or in a vise? If they are noisy, then there are most likely pits in the ball bearing races and balls.

    The hub holds ‘Special Compound’ from Duplex, made for Pierce. It’s pretty close to the ‘600W’ gear oil that the Model A guys use and sell for transmissions.

    Greg Long


    By loose, I mean I can move the blade tip about 1/4 inch. My fan has an Alemite fitting on the hub, so I hit it a stroke with my grease gun.

    I will remove the fan and see what’s inside.


    As long as your are dismantling the fan hub, I suggest replacing the bearings with sealed bearings. No further lubrication required.


    Randy: the bearing clearance is adjustable on the ’27 fan hubs. if when you take it apart, you find it to be in good condition, just reassemble it and adjust the bearing to have just a .001″ clearance.

    These hub-type fan bearings are supposed to be lubed with a thick LIQUID lubricant. Not chassis grease. Grease does not flow, a liquid will.

    The proceedure to lube the hub is to turn the hub so the alemite fitting is pointing up from the horizontal. Something like a 10O’clock or 2Oclock position. fill the hub with liquid lubricant, 600W works well. Once full, then turn the bearing hub so that the Alemite fitting hole is horizontal, and let the excess lubricant drip out of the hub. Reinstall the Allemite fitting.

    The result will be to have plenty of lubricant in the hub, but not too much so that it will leak past the gap between the shaft and the moving hub. Most of these do not have a seal to keep excess lubricant in the hub. The proper level of lube will not leak out of the hub.

    I know there are modern bearing equiped fan hubs for the ’29 and later engines. but I”m not aware of any modern bearing replacement setups for the mid 20’s cars.

    Maybe Paul knows of a machinist who has done the fan hub like you have?

    Greg Long


    Thanks everyone for the valuable information! I have some 600W.


    Got the fan apart after I returned from Kerrville. The bearings looked fine, but there was no oil, only grease. I cleaned everything up, put it back together, adjusted for minimal play, and put some 600W in. The fan seems fine now. The leather seal was not good but it did not throw any oil out. No doubt it would if I put enough in.

    I would like to convert to sealed bearings; the housing ID and shaft OD do not seem to be standard for a bearing I could find in a catalog, so perhaps some machine work is needed? If anyone has done this and would like to describe how they accomplished this, feel free to comment.


    Is the ’27 fan hub the same design as my later ’35 845? I ask because I just went through mine and the owners manual says it should be filled with 30 weight oil. I was amazed at the elegant (actually gilding the lily elegant) design of this thing which amounts to a centrifugal pump where the oil is forced out to the wall of the hub and then gets interrupted by a single paddle as it flows to the front to force a little bit of oil to flow into the inside diameter tube with the bearings. Ball bearings generally only need minimal lubrication usually of light oil and I think P-A jumped through hoops with this design to try and give the ball bearings the right level of oil. If the ’27 is the same system 600W oil seems a lot thicker than necessary and I don’t see a benefit.



    The fan hub on the Series 80 is different from the later straight eight. Read Greg Long’s earlier post this topic: he is expert on the Series 80.

    Thanks everyone for the information!


    The benefit of the 600w is that it is less likely to find it’s way past the primitive oil seat in the fan hub.

    The bearing design is very different for the S80, compared to the later cars’ fan hubs.

    Greg Long


    Apropos to the rear slinger seal discussion, the later hub has no seal but simply relies on the fill level to stay just below the shaft when stopped and centrifugal force keeps it away from the shaft when turning. No seal to wear out. I was lucky in that my bearings were in such good shape that without the drag of a positive seal I could determine a significant out of balance on the fan blades and counterweight it to adjust.


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