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Alternator casing spun bearing repair

Webley91

Cast Iron
Joined
Feb 13, 2009
Location
London, England
I have a failed alternator from a Mitsubishi 2.5l Diesel engine. It is believed that the internal electronic regulator has failed, which can easily be and cheaply replcaced.

On disassembling the alternator, I found that the rear bearing had spun in the aluminium casing. The bearing is the type with a groove in the outer race to hold a spring clip. I am unsure of the correct term for this type of bearing (see link below). The spring clip was found to be broken into two pieces when disassembled. This had presumably allowed it to spin in the bore.

I have considered boring out the bearing housing and fitting a steel sleeve. This would not be necessary if a bearing with a suitably oversized outer race could be found.

From what I have read, these bearings are not interference fitted to allow for expansion due to heat. Is this correct? If so, whay clearance would the bore need to be machined to?

There is also a groove in the bore in line with the position of the spring clip. Was this groove machined by design or worn into the bore by the loose bearing?

Link to the image of the specific bearing:
https://www.shop.bendiks.pl/eng_pl_140432-NS-Bearing-36739_1.jpg

Thanks for any information.
 
I would assume the aluminum housing bore would expand more than the steel bearing when all is up to temperature??? Likely if I had a reason to use that bearing I'd have a press fit with a counterbore to help squeeze that funky ring down on assembly.

Good luck,
Matt
 
Junkyard? Lookup the alternator Mitsubishi most likely put that alternator of other engines. Engines are built up sort of like a Lego bricks the starters, alternators, power steering pumps are made by other manufacturers and are bolted on them.
 
Green Loctite bearing fit is just made for this application.....a shim cut from a drink can is also a handy accessory............Ive spent 50 years in industrial maintenance ,and have used all the "cures" that the experts pooh pooh.......Incidentally ,for some reason engine belts are fitted crazy tight ,causing bearing fails like this.......when I buy a vehicle ,first thing I do is slack off the belts ,before bearings fail prematurely.
 
Green Loctite bearing fit is just made for this application.....a shim cut from a drink can is also a handy accessory............Ive spent 50 years in industrial maintenance ,and have used all the "cures" that the experts pooh pooh.......Incidentally ,for some reason engine belts are fitted crazy tight ,causing bearing fails like this.......when I buy a vehicle ,first thing I do is slack off the belts ,before bearings fail prematurely.

You don't want to use Loctite if the bearing is intended to float in the housing. I think this one appears to be designed to float. Is the other side bearing held/locked?
 
AFAIK all asian alternators are made by outside vendors. The back case should be a common size. The only difference is usually the pulley on european alternators. most made by bosch.
Bil lD
 
To me it looks like the spring is there to prevent the outer ring from spinning in the housing
Impossible to hold a bearing in a aluminium housing that gets hot
You could bore the hole to fit the bearing with a tolerance ring(google that if you do not know what it is) Best solution IMHO if you have meat enough

Peter
 
Thanks for the replies. I have attached photos showing the bearing and housing. This alternator has a vacuum pump mounted to the rear which is driven by the splined shaft.

As far as I know, this alternator was made by Hitachi.

I did think of using the rear casing from another alternator. They were used with many variations of the same engine in a range of vehicles. Apparently these bearings commonly spin and wear the bores, so another unit would likely have the same problem.

These engines are also not often found in UK junkyards. This engine is now over 30 years old. It is rare to see anything made before 2000 in a junkyard here. These used engines are also commonly exported as complete units when the vehicles are scrapped.

I believe the front bearing is locked in place. I have not disassembled the front end as the front bearing still turns smoothly.

A replacement regulator can be easily bought for around the equivalent of $20 USD. I thought it would be worth repairing as a spare unit as the windings are undamaged. I originally hade a quote of over 200 UK Pounds to have it rebuilt, but this was before I had disassembled it and found the spun bearing.

The vehicle currently has an unbranded new replacement alternator fitted, which was half the cost of a rebuild. While it is working now, I am sure it will not last as long as the original.

What would be the best way of removing the bearing from the shaft without damaging the pressed steel cup underneath?

alt_shaft.jpg

alt_housing.jpg
 
I'm curious why a vac pump would be needed? What does it do?

I also agree...most people way overtighten belts. I had a friend whose father was a make-ready mechanic at a Chevy dealer...he had 25 years on the job when I was a teenager. One day we watched him tension a water pump/alternator belt by using a 4 foot crowbar for leverage. He was telling us how he replaced a lot of alternators and water pumps at work and home because they were always breaking because they were made so cheap. I asked him why he was making the belt so tight, he said to make sure it didn't slip. Even as a teen, that seemed like BS to me and I told him I thought it would overload the bearings and cause them to fail. He mulled that over. About 5 years later he told me he had stopped overtensioning the belts at work and the failure rate sure seemed to go down!
 
I'm curious why a vac pump would be needed? What does it do?

Provides a vacuum for the brake servo and vacuum operated engine controls.

This type of alternator is fitted with a double vee pulley driven by twin belts. It is common for one belt to stretch more than the other and squeal. Over tightening is a common problem as the quick solution for this is to tighten the belts.
 
Looks like you could get a thin plate made to fit the slot diameter and cut it in half then put it on and press it off. Ie using the slot as the point of contact.
I have not got my head around how it fits together as it looks arse about in the picture...sure the fan would be on the outside, but the seal position looks wrong in regard to the spine.
It appears you don't have much meat to play with in regard to sleeving the bore so will be out of luck.
I would put new bearings in it and loctite the loose bearing in place...if it heats up the alloy housing should expand faster than the shaft.
As long as the bearing is not too loose in the bore...if its really loose you may be out of luck also.
those small bearings sure spin at a hight rpm if you do pulley ratio calcs and refer it to the engine rpm.
 
What would be the best way of removing the bearing from the shaft without damaging the pressed steel cup underneath?


View attachment 296776
Careful application of angle grinder works even if it doesn't sound kosher. Heated split copper ring(name??) if you have lots of bearings to remove.
If you have TIG welder it also works miracles with bearing puller. (apply some preload to bearing puller and heat the bearing race with TIG.
 
Very common repair not a common alternator. Some after market suppliers offer tolerance rings for the repair. Press fit should be very light or if possible dimensions the same size. The tolerance ring is a stamped steel wavy thing that lightly grips the bearing. You still have to bore the housing. I would do this a lot to save the time of waiting for a replacement part or if part unavailable. (by the way, I am an auto electric shop or 40 yrs standing) There maybe a bearing that is same inner dimension, same thickness, bigger OD but you wont be able to get it past the brushes. Tim
 
What kind of car is it? Maybe there are some on Ebay...

Two belts....a sore spot. In the olden days, you would go into a store and ask for two 8984FH belts IN A MATCHED PAIR.

These belts were cut right next to each other off the master roll, and kept together. That way, their length was the same within a very tight tolerance.


About 20 years went by since I needed a matched pair of belts...I went into the auto store and the 20 year old there looked at me with the usual 'auto parts counter stare' when I asked for a matched pair.

I ended up calling Gates with a WTF? question when I couldn't even find any in their catalog...they told with a wavering degree of confidence that 'we probably don't need to do that anymore because they're all so close anyway." That's modern English for 'we found a way to cut costs and raise the price at the same time'.
 
Here is a parts diagram and a photo of a new unit to better show how it fits together.

The spline in my photo drives the black vacuum pump on the rear of the unit. The windings have an internal fan at both ends.

The bearing shown in the diagram is part number 14205Q. The rear casing is shown in the diagram but is not available as in individual part.

alt_diag.jpg

alt_new_2.jpg

I assume that the tolerance ring would not be suitable if the bearing is intended to be floating in the bore?
 
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Here is a parts diagram and a photo of a new unit to better show how it fits together.

The spline in my photo drive the black vacuum pump on the rear of the unit. The windings have an internal fan at both ends.

The bearing shown in the diagram is part number 14205Q. The rear casing is pitured beneath but is not available as in individual part.

View attachment 296806

View attachment 296805

I assume that the tolerance ring would not be suitable if the bearing is intended to be floating in the bore?


For a floating bearing a tolerance ring is fine You just have to have enough meat to bore it out that much

Peter
 
From your post, you are looking for a 150,000 mile repair.

Using patches such as tolerance rings works very well, way over 150,000 miles, for other people besides me. In addition to failing soon, they also cause me to lose untold hours of sleep knowing I have a BandAid on my car.
 
For a floating bearing a tolerance ring is fine You just have to have enough meat to bore it out that much

Peter


Thanks for the reply.

The outer diameter of the bearing is 35mm, with an 11mm depth. Internal diameter is 15mm.

According to a tolerance ring supplier's web page, the bore required for a 35mm bearing tolerance ring is 35.60 to 35.65mm

There would likely be enough material there to bore out to that diameter.

The site also says "Used as a bearing mount where the bearings are required to float axially."

This may be the solution.

I would also think that if the tolerance ring was used, the spring clip on the bearing would not be required.

Bearings without this clip seem more widely available than those with the clip.
 








 
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