MCI 8 Alternator

[Sam 4106]

I need to replace the bearings in my MCI 8 air cooled, belt drive alternator. They were howling on our recent trip but I greased them and we made it home. I have the alternator out and the nut off that holds the pulley on. What is the best method of removing the pulley and fan? Will a puller be needed?

According to the manual the bearings have to be pressed off and the new ones pressed on, how large will the press need to be, so I can take the parts to the right place to have that work done?

Also, the belt tightener is a turnbuckle, so how tight do the belts have to be? The new belts are Gates XL 7417. I looked them up on the Gates belts web site but didn't find a tension recommendation.

Thanks for any help, Sam

[lostagain]

Pulling the pulley off: don't hammer on it. It is likely made of cast iron and would break easily. Are there 2 threaded holes near the centre? I would use a puller. If you don't have one, you can buy one, or you can make one out of a piece of flat bar stock, drill and tap holes in it for the bolts.

Belt tension: I don't know about a figure for the proper tension, but they don't need to be very tight. Too loose and it will slip. Too tight and it would be hard on the bearings and the belts. They might need tightened up after the first run.

Hope this helps. I do a lot of things by feel and eyeball method.

JC

[luvrbus]

It's a spline shaft the pulley comes off fairly easy after you remove the nut a small press does the job you just need a floor crane to lift the heavy sucker.

Stop by any O'Rellys and they will give you a belt tension gauge

good luck

[saddleup]

Sam, sure good to meet you, we moved to Patterson lake the day you left, going to set here the full 14 days. we are getting use to the trains, sort of.
Other than the alternator hope you had a good trip home, you guys that have not seen Sam's MC8 its a nice one he has done a lot of good work on it, Sam is definitely a Bus guy i was real glad to meet him and his wife.
Matt

[Sam 4106]

I got the alternator apart and was going to order parts from MCI but the only parts they had in stock were the drive end seal and gasket for the bearing retainer. The rest of the parts were special order and would take 2 weeks for them to get the parts. So, I ordered the bearings and seal locally to arrive Friday. The pivot bolt is badly worn because it wasn't tightened properly so a local machine shop is making me a new one.

Will it hurt the internal parts to clean them with a pressure washer or mineral spirits? Otherwise I will have to get some electrical parts cleaner, or, should I just blow them out with compressed air? The internal parts badly need cleaning so they will cool better.
The alternator was working fine except for the bearing issue and I don't want screw something else up.

JC and luvrbus thanks for your advise, Sam

[Sam 4106]

The new bearings are sealed on both sides but the manual says they should be sealed on one side so they can be greased from the zerk on the reservoir between the bearings. Anyone care to advise whether I should install them as sealed bearings or remove the seal on one side of each bearing so they can be greased? I lean toward just leaving them sealed but if I can get longer life from them by greasing them I will remove the seal from the sides toward the grease reservoir.

Any advise is welcome, Sam

[James77MCI8]

Hi Sam,

I would consult the bearing mfg. On the other hand consider how long the bearings have lasted with the inner seal removed. I would believe that a serviceable set up(greasing) will provide longer life if a regular service schedule is adhered too.

Best regards,
Rusty

[Sam 4106]

Hi Rusty,

I have no idea how long the bearings have lasted since we have had the bus only 3 years and 16,000 miles. I installed the bearings  sealed and they probably will last as long as we own the bus. These are some pretty hefty bearings. Thanks for your thoughts, Sam

[luvrbus]

Sealed bearing is the way to go Sam they last longer I haven't seen the greased type used in years rebuilding a 50D those were installed so you could run it as a oil cooled a way of saving a few bucks for Delco

good luck

[TomC]

Best way to rebuild the alternator yourself is to drive the alternator to a certified alternator/starter rebuild shop.  Then you'll have an alternator that works.  Good Luck, TomC

[Sam 4106]

Hi luvrbus & Tom,

I did install the new sealed bearings as they came. I see no reason to not repair my alternator myself since the only thing wrong with it was the single row ball bearing had started to sing. The manual says that will happen before failure. The alternator was charging when I removed it and I expect it will charge when I install it. There was nothing wrong other than the bearings. It was only $104.44 for the bearings, seal, O-ring, and bushings for the pivot. I have read where it costs hundreds of dollars to have a shop rebuild an alternator. Aside from the cost, which I can easily afford, I enjoy repairing things myself.

When I had a problem with one of my A/Cs I figured I had nothing to loose by trying to repair it myself so I took the electronic control board and thermostat off and discovered that all that was wrong with it was the transformer that makes 24 VAC from 120 VAC was bad. $100 fixed it. A new A/C from camping world would have been $699 plus shipping and a lot more work to R&R the A/C. Tom, I suspect you would have just taken your bus to camping world and had a new one put on. I am not always successful in repairing things but I enjoy the challenge and learn new things along the way. Nothing wrong with your method either. We all do things our own way.

Good Luck, Sam

[gus]

I always suspected that alternator rebuild shops don't do much more than replace brushes and bearings and paint them anyway, most other stuff doesn't wear out unless some coils short out.

It all depends on the $$ involved, sometimes rebuilt is not much more than parts - in that case I buy rebuilt.