Hi all, I have a question with regard to my W123 300TDT (1984).



Recently, on two occasions I tried to start the engine, but the starter motor just spun fast without turning the engine over at all. Both times, I turned the ignition off, let the glow plugs fire again, and then started the car as normal.


I gather this is a faulty solenoid(?)



I have a spare starter motor, but I'm curious if it's possible to just replace the solenoid rather than the entire starter. (I have read that the starter motor is a bit of a bear to remove, so if a partial replacement is an option than I will consider it.)


Thanks in advance for any info you can provide. I couldn't own a Benz without this forum!

Is this a station wagon?

Usually this indicates the sprag clutch in the Bendix is failing, not very expensive to replace .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Agree with clutch/Bendix drive is failing. When weak they usually act up in cold weather. Unfortunately it requires removal and disassembly of the starter and yes not an easy starter to change due to limited access to the top bolt.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Thanks VWNate1 and Sugar Bear. It has indeed been cold lately.
I have a used starter motor in the parts bin, but I think I'll try to get the local mechanic to install it.
I appreciate the help!

Be smart and replace the brushes and solenoid too, using only BOSCH or ECHLIN brand solenoid .

That top bolt is a PIA, I used abut 3' (maybe longer) of 1/2" drive extensions and the longest flex handle (misnomer : breaker bar) to break it loose first, then the rest of them came out without too much difficulty .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Sure is! 5 cylinder turbo wagon, federal version.

I rebuilt my Starter about 3 months ago and the screws that holed the Solenoid in are Phillips head and all 3 stripped out when I tried to remove them. Even with me using a hand impact wrench.
I had to drill out the heads to get the solenoid off.

So not being able to get the solenoid retaining screws to turn would be a major reason someone could not change the Solenoid on the vehicle.

I am not sure where people come up with the names for stuff that the do but the cutch mentioned on the Starter is commonly called an over running clutch.

That pinion/overrunning clutch on mine had a what looked like a Bosch part number on it.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

Many are simply poorly educated and don't bother to learn the proper names of things .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Why I posted the picture that shows at least some of the names used in the USA to describe parts on a Starter so it was not just my opinion.

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84 300D, 82 Volvo 244Gl Diesel

You are right.... Bosch starters has what is called an overrunning clutch, not a Bendix. A Bendix is coaxial to the starter motor shaft, where an overrunning clutch is not.

To not strip the 3 solenoid Phillips head screws, use a propane torch to heat the body of the solenoid to soften the copious Loctite before using an impact driver, otherwise they will strip. This was a tip from a local starter rebuild shop. You have know the length of the screws beforehand in order to place the heat at the right spot.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I replace the screws with stainless steel allen head ones.

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84 300D, 82 Volvo 244Gl Diesel

FYI that “pinion gear” is a good $50 if you can even find one. And, by time you replace the solenoid, brushes and whatever else people tell you to replace, you’ve essentially purchased a new starter. This may not have always been the case, but in my experience (couple months ago) unless it’s in need of a cleaning and or perhaps a single easily sourced part, it’s simply not worth rebuilding.

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1981 240D 4sp manual. Ivory White.

Although I have a used starter motor here, I'm going the extra mile. I ordered a remanufactured starter and it'll be here in a few days. I'll have it installed next Monday.

Thanks for all the help!!!

Unless it was rebuilt by a BOSCH rebuilder, expect mediocre results and short life .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better