r129 starter issue
 

I guess there's a first time for even the unexpected. I've replaced starters in the past, mostly for brushes or solenoids. It had been working fine without any problems, a rebuild about ten years old. It starts up like it always does but this time it's making a hell of a racket. Sounded a lot like a real bad pulley. saw some smoke coming up from starter area. stopped it and tried to start again and all I could hear was the starter reviving up. I had it towed home, put it into my shop/garage, pulled the starter and found the gear on the pinion gear had sheared off or somehow came apart, maybe the gear is pressed in. It could not retract nor could it engage anything, except make a heck of a noise running on the flywheel. I didn't think it was possible for it to break like that. luckily I still had my old starter, it's old, but I can still drive my baby until my rebuild comes in. will take a look inside of the starter sometime to see just what happened.

Hello, You were smart to shut it down and pull it out. A friend of mine purchased a 5 yr old American built diesel 4x4 with quote " a seized engine" on KIJIJI. Bought it real cheap. Tow bill from the logging site to my private shop was $200. Wiring from battery was melted as was the post on the battery. 1 battery was dead from unrelated issue. Starter was seized , engaged in ring gear. At some point a piece of the gear broke off and had wedged itself solidly, jamming the ring gear. We pulled the starter, turned the diesel backwards with a wrench and fished some broken bits with a magnet. Put a new unit in,plus 2 batteries and a few feet of wiring. He is still driving it. Hang on to your "OLD" starter I hope it gives you peace of mind and many years of trouble free service after you rebuild it. PS I rebuild all my own alternaters and starters. Usually but not always its brush , then solenoid , followed by bearings. Allan

I got the new aftermarket starter installed and does good. The defective starter's bendix gear came unpressed from the drive ring. I took the original bosch bendix assembly off my spare's tired motor and put it on the defective starter's good motor. It bench tested good. so now I have a good back-up that I hope to never use. the aftermarket stuff may not always marry to oem.

Broken off teeth on ring gear
 

Good evening @brookings ,

I have a R129 SL500, where I experienced the following too and was wandering if there were some other underlying problems you detected after a few kilometres with your starter/ring gear.

my SL was standing for a good 10-15 years and I have brought it back to life after cleaning, replacing the petrol tank and a few minor things. I drove it for a short while +-20 minutes, 10km switched the engine off and wanted to re-park it after 5 minutes. I just heard a snap/crash sound after which the starter would only click and draw down the voltage in the system and not make any other sound or movement. After push starting and driving it back to the mechanic, we saw two teeth missing. Now my question is to make sure there is no underlying problem that will cause the new ringear to snap teeth too? What is your thought on this?
the starter spins freely if connected to 12 volts directly.

Appreciate any comments, answers regarding the breaking of teeth on ring gear.
Best regards
Tim

https://cimg6.ibsrv.net/gimg/mercede...30a901913f.jpg
https://cimg9.ibsrv.net/gimg/mercede...958a9ca8a7.jpg

I'd replace both the ring gear and starter. I'm not sure this would be an issue on a merc, but you may ask some one at a repair shop about torque converter balance after replacing gear.