Ring Gear

[diesel don]

I just took my starter off for a replacement. When the rebuild shop looked at it they encouraged me to inspect the ring gear before reassembly.

Problem: Probably 5-8 times during the last couple of months my starter found a spot that sounded horrible when attempting to crank. It almost sounded like you were trying to start the car with it running. I suspect this is because the starter was spinning before it was engaging.

Question: Is it a common thing for the ring gear to get chipped teeth or wear out? I'm worried because this sounds major? I'm not even sure if there is room enough to inspect it?

Any advice would be greatly appreciated....

Don

[JimSmith]

diesel don,

I believe this is a "normal" wear event after several hundred thousand miles, or some very high number of starting cycles. The engine stops when you shut it off with the crank in one of four positions, which correspond to one of the four pistons approaching top dead center on the compression stroke that stopped the engine. In reality the number of positions may be less as wear causes one or two positions to be favored (a little higher compression increases the chances that piston will be the one that stops the crank than another piston in a cylinder where there is slightly less compression). So, as the car gets older the ring gear teeth that are used in the initial engagement and application of torque get fatigued faster than the rest of the ring's teeth and consequently get worn off or break off. So, what you have is not normal for a car with low miles, but for something with high mileage, it is probably more common than not. If the starter motor bendix or the pinion gear has some worn features that prevent the easy, full engagement of the pinion on the ring gear, the problem is likely to happen sooner.

On my car I did the clutch at the same time, even though at about 185,000 miles it showed about 60% of its original thickness remained on the disc, and the throwout bearing. Getting to the ring gear or clutch mechanicals is the same task and is much more than half the trouble.

Hope this helps, Jim

[diesel don]

Thanks Jim:

I appreciate the reply as I'm going out to the garage now. I hope I can get a glimpse at the teeth in the thing.

Don

[diesel don]

I could visually see about 15 teeth or so and they looked ok. Nothing chipped off or anything. I reinstalled the starter and she fired well. But as my problem was intermittent, I'll have to wait for a month or so to see if it is truly fixed.

Don

[JimSmith]

diesel don,

I noticed you have a five cylinger Diesel model, and so you will have five favored positions where the starter engages the ring gear. The intermittent nature of the problem is an indication that only one or two of these positions is damaged. When the starter engages the other spots it works fine.

The starter can also make the noises if it is having a problem getting the pinion gear fully engaged before the starter motor cranks. This is usually an indication the bendix/solenoid assembly failing, and this usually leaves marks on the face of the ring gear teeth.

By now you must be getting good at taking the starter out and putting it back in. I got pretty good at it on my 240D as, until the ring gear problem was fixed, I took the starter out a couple of times thinking it was the problem.

Good Luck, Jim

[diesel don]

Jim:

Thanks for the thoughts. I was banking on the idea that the starter itself was responsible for the intermittant problem because it was spinning before engaging. When the shop examined the starter they noticed that problem along with the brushes getting tired. They also noticed the shavings.
If my ring gear has some damage I'm going to be bummed because swapping that starter once was enough for a lifetime for me. My little finger on my right hand isn't typing so well right now. Heavy bugger!
Put it back together last night and started it some 6x today. So far so good but if I hear that sound again.....

Don