4104 fan dreaded fan hub failing

Nel · May 26, 2019, 06:52:18 AM

I took a short 120 mile trip yesterday and on my way back home heard a loud metallic clicking sound matching the rpm of the engine. pulled over and thought it was something internal to the engine. I shut down the engine and looked closer and noticed the fan blade was just touching a bolt head holding on the shroud. Well guess what the fan hub was slowly pulling away from the engine just as I always feared and btw I always checked for play on that hub everytime I had the hood open and there was very little so, I was able to turn the fan by hand with a lot of resistance and push it back towards the engine , I took a gamble and drove it home very slowly for 60 miles keeping the rpms at about 1000, 30 mph the whole way and got it home, I wasn't in the mood to go thru the whole towing fiasco so took a chance.
So now the question , I know there is a pto coupling listed somewhere for 1500 bucks as a last resort and original is unavailable but what other ways has this issue been repaired successfully ?
I've heard welding hub and balancing, electric fans, etc.

Thanks Nelson

luvrbus · May 26, 2019, 07:02:48 AM

Find a RTS scrap yard with the belt drive fan from a 6v92 not a hard job to convert over to a belt drive on the 4104 with the 6-71 engine then your problems are solved

Geoff · May 26, 2019, 09:17:33 AM

Wow!! I'd have to see that one.

TomC · May 26, 2019, 09:27:39 AM

When I bought my AMGeneral, it had a three V-belt setup that was a pain since you'd have to remove the fan to replace the belts. My mechanic suggested I change to a gear drive setup for the fan-which I did. Now the fan is a normal right hand rotation, but is not clutched so it runs all the time. It has been reliable with no problems. Sorry, I don't know who made it. Good Luck, TomC

chessie4905 · May 26, 2019, 10:01:35 AM

Take some time to give Luke a call. He may have an idea or help.

dtcerrato · May 26, 2019, 11:07:08 AM

Nelson we're hoping we don't live that nightmare on the way home from AK. We'd been watching ours as it has been showing some different characteristics lately. You really gambled on the slow run back to the house - as the radiator would have been next. Scott may have one in his arsenal but the risk is also there with used old stock. I'll try and dig out info I've saved on a new alternate setup that may incorporate a thermostatically controlled hub assembly. Until then I'd leave it shut down. You are a lucky one to have caught it prior to catastrophic failure. I posted recently that our hub has been showing signs of more flexibility but has not moved from it's index markings. Thinking about having a "top hat" retainer made that would bolt under the main center bolt to prevent the fan portion from moving toward the radiator. Great find & being proactive! Let's keep this discussion alive as it could benefit anyone of the many 4104 owner's on the board.

luvrbus · May 26, 2019, 02:09:54 PM

I have 2 front drive PTO coupling from the 8v92 ,they won't work on 6-71 or I would give you one.If I could only find it I have a new coupling for the 4104 Larry gave me when we changed his to a belt drive.Those are not that hard to change to a belt drive,I tried to post a photo but Photobucket is holding my photos hostage trying to squeeze me for money

chessie4905 · May 26, 2019, 03:48:00 PM

I wonder if those bare pieces could have polyurethane injected in the space after a proper alignment jig made?

luvrbus · May 26, 2019, 04:06:37 PM

Quote from: chessie4905 on May 26, 2019, 03:48:00 PM
I wonder if those bare pieces could have polyurethane injected in the space after a proper alignment jig made?

The ones I have use rubber pressed in ,I read in the PM guide from a long ago for Greyhound those coupling were a routine maintaince item every 100,000 miles so they must have been a problem way back

Nel · May 26, 2019, 04:43:49 PM

Thanks for the replies, I'm hopefully going to try to repair this problem another way other than using the oem part, I would think any nos parts or used parts, if available will result in the same problem and I'm pretty sure it was a routine maintenance item to replace when they were in service, not an option now. I will keep you posted on the repair. Nelson

luvrbus · May 26, 2019, 05:38:17 PM

A belt drive with a fan clutch is the way to go IMO,you can do wonders with a couple of pulleys,some pillar block bearing ,1 inch shafts and mig on those old buses

chessie4905 · May 26, 2019, 06:32:34 PM

https://dieselpro.com/detroit-diesel/vibration-damper/671-vibration-dampers.html

chessie4905 · May 26, 2019, 06:32:45 PM

https://dieselpro.com/detroit-diesel/vibration-damper/671-vibration-dampers.html

https://www.ebay.com/itm/Viscous-Damper-Detroit-Diesel-5177763-IN-LINE-3-4-6-71-Vibratech-Inc-A-16590-Bal-/222860982992?redirect=mobile

dtcerrato · May 27, 2019, 12:33:04 AM

Chessie that's not the part, the fan hub bolts up to the vibration damper. It's a lot smaller in diameter & about 5" long. It's sometimes called a PTO coupling.

chessie4905 · May 27, 2019, 04:55:11 AM

The rubber mounting was for the vibration and flexing of that heavy fan blade. How about a lightweight fiberglass fan of same capacity without the rubber setup.
The other option is to find an old look city bus and get the hydraulic fan setup off it. It will work on the 4104. We had one on ours.