300SDL alternator bearing sizes?
 

I'd rather not have the car down for a day and take 4 hour round trip via city bus across town to pick up the bearings after disassembling the alternator.

In short I'd rather pick them up ahead of time, anyone know the sizes off hand by chance?

Why not just source another alternator? By the time you shell out for quality bearings, you're probably 50-75% the cost of a 2nd hand alternator. If you don't have access to a press and pay a shop to do the bearing pressing, you will have paid more than a 2nd hand alternator.

2X

Don't know what the problem is with your alternator, but, if you spend the time and money to throw in the bearings, and you still have a problem then what???

Well, the alternator is very loud and the pulley has coarse feel when spun.

In your situation, I would get a good used alternator w/ brackets for $15 at the junkyard or ebay (have a spare in the shed). That way you can swap out and deal with the rebuild at your leisure, shopping for quality bearings cheap on ebay. You can judge the bearings in a used one by a spin-test. If Vreg/brushes are bad, you can easily swap that later from your old one with alternator on the car.

Removing the alternator is a bit$h on these engines, and if you start down the "fix mine" path, you might run into problems. If your only car, a trip to the JY might be tough then, though you could still drive it if you charge the battery full and tie a nylon rope to keep the water pump & fan turning. I have squeaked by on worse red-neck fixes for a time when young and foolish.

I would go to the junkyard, problem is I don't know which Mercedes alternators fit nor do I have any clue how to rewire them if the connectors are different.

If your car is still operational, I am sure that somebody at the junkyard would be able to identify the one you presently have in the car, and match it with the ones he has available. Most junkyards today are all interconnected by computers regarding parts, and if one doesn't have it, they can usually find one at another yard that can fit your needs.

LOL! :D

Once you have the bearings removed, you can measure them to determine the size. Measure the inside diameter of the hole, outside diameter of the bearing, and the width of the bearing. Measure in mm not inches. You can then look up online which bearings you have. There is only a handful of different ones used by MB in recent decades, so it should be easy to identify them. If you have some solvent and can clean them up, you should find the part number or bearing model number stamped into the edges of the bearing race. I have found that the rear alternator bearing goes bad a lot more often than the front one, probably due to the front one getting the cool intake air, and the rear one getting the hot "exhaust" air. The rear bearing is a lot easier to change than the front one too.

Your new bearings model numbers should end in -2RS. The "RS" indicates a sealed bearing, which is the same type as your originals, and the "2" means <strike>double-row bearing</strike> rubber seal on both sides, same as your original.

You will also want a new plastic tolerance ring, as these are usually brittle from heat cycling and age and tend to break during alternator disassembly or reassembly.

The bearings should only cost a couple of dollars, same for the tolerance ring, these parts are very inexpensive.

For my om606's Bosch alternator, the rear alternator bearing measures 17x40x12, the MB part number is A0079817325 and it's a standard 6203-2RS bearing. The cooresponding 17x40x12 tolerance ring is Bosch part number 1120591103.

I would not be surprised if these om606 alternator parts were all correct for your car as well, but please measure first. Also be aware that if you have a Valeo alternator, the replacement parts are completely different between Bosch and Valeo and they are not interchangeable.

The 2 in the bearing number indicates a rubber seal on both sides.

Oops yes you're right, I was thinking of something else, good catch. Either way, he definitely wants the "2" in his replacement parts.

chart

Any Mercedes alternator up to the w210 will fit. If you're willing to swap in a sprinter voltage regulator you can fit some of the post 2000 150a alternators. I installed 150a alternators on my om603 and om606 both from R230s. They were going dirt cheap on eBay for a while nearly brand new.
https://i.imgur.com/s5K4KqI.jpg
https://imgur.com/a/w7Oyk

Yup, good alternator interchangeability with MB's. I have a 150a CLK430 alternator in my w210. It's not plug-n-play, but the mods required are simple.

What mods are necessary? How do I do them?




Sounds like a route I'll take.