I have a 1985 300SD with a starter that won't crank while hot after long drive, only solenoid click. If I wait 5 to 10 minutes it will start without issue as it does when cold. Is this a common issue with this starter or is this a sign of more issues to come? I read that wrapping the starter with high-temperature insulation could help keep it seizing from the heat. Does anyone have experience with this that they could share? Thanks..

I don't have an answer as to why. However, I would be curious to know what happens if you put a Volt Meter a crossed the Battery Terminals when you attempt to start when it is Hot.

If it clicks when and the Voltage remains on the High side that would be an indication that the Solenoid goes back the plate inside is not making contact with the 2 Contacts that send the Voltage to the Starter Brushes.

Do the same test when everything is cold and see what the difference is.

Also Your Starter designed similar to a Delco Starter from the 1960s and 1970s so if you found a troubleshooting Guide for that it might apply to Your Starter

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84 300D, 82 Volvo 244Gl Diesel

The Wire Junction/Terminal block is supposed to be under the Battery Tray somewhere.
Try using a Remote Starter Switch or a Jumper Wire on the Terminal Block and see if the Engine Cranks OK there.
If it works there OK every time you have some issue with the Electrical Circuit somewhere.

Another check that could be made is to see if the Voltage to the small terminal on the Starter Solenoid is the same cold and Hot.

Also could the wires be loose down there at the Starter?

There is sort of some info at the below site but you need to go down about 8 posts or so; part of it is sort of funny as the OP is not getting what the guy who is trying to answer is saying.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

Battery and the Battery Ground
"Your first goal is to determine the state of charge of your battery. Turn your headlights on and see how bright they are. If they are of normal brightness then you are probably OK. If you have a voltmeter, put it across the terminals of the battery. A fully charged battery will read around 12.5 volts, a dead battery will be less than say 11.8 volts. If your battery is dead, charge it and then proceed to the next step.
The battery earth=Ground could also be bad or marginal. This will mean it tests correctly if it is not engaged, but experiences a steep drop (often only when the engine is hot) as soon as you engage the starter. That will make the starter turn slowly or not at all or reduce the voltage remaning to the point where the coil cannot prodcue a spark. A braided earth strap could look great on one side, but have many broken stands on the other. Here is an example in the image."
The above from the below site
Starter Troubleshooting

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84 300D, 82 Volvo 244Gl Diesel

Jump terminals 1 and 3 in the junction box on the passenger inner fender well directly across from the alternator the next time it happens and then report back.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

You can replace starter,or fashion a starter shield to protect from heat.Or do like me,I wrapped the exhaust with heat proofing

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

Not to steal the thread but; if the Starter had been working previously and now is not working when it is hot now what would have happened to it to cause that?

I have never read any specifics on that.

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84 300D, 82 Volvo 244Gl Diesel

On the turbo models,isn't there a heat shield between the turbo and the starter or is the heat shield for the battery?

I had a starter on my 83 that would not start when hot and would just click and would have to let it cool overnight before it would start again. Battery and ground strap was good. This problem confounded me for a few months and it turned out to be partially shorted winding on the rotor that became more severe from heat. The short was due to a worn bushing causing the rotor iron core plates to pinch the winding causing a partial short to the core. I took the starter apart and rebuilt it with a good used rotor, new bushings and it's been fine since.

Other things you can try is check starter RPM (should be 140 RPM or above), starter current (should be around 300 amps). Mine was drawing 500 to 600 amps due to the partial short.

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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

Thank you all for your replies. If the issue is heat related I believe I will have a limited window to troubleshoot this since the 10 minutes or so of it not able to crank only existed after 60 minutes of 60mph driving (arriving at 1st yard sale.) Thinking it may be battery issue I hooked battery jumper to car and it started but I think it was more to do with it cooling down because I left car running for the next hour or two while visiting other yard sales and stopped by auto store for free alternator/battery check and everything seemed good. I turned car off for the battery check and only got click without crank again. Applied battery jumper and no change. After battery jumper was removed it started and this was only a minute or two while off and not able to crank. This was also after driving slow speeds in neighborhoods and much idling. Also on hour drive home same issue as previous hour drive, waiting about 10 or so minutes and starts instantly. This is what caused me to assume that high speed/temps (90-100c) caused it to take longer to cool while the same amount of time but at lower speeds/temps (80c) only took a tenth of the time to cool. I don't know if this is a new issue or its because outside temps are in 80s & 90s.
What made me first think it could be overheating of starter was reading this even though not Benz related..

"It's not unusual for a starter to "seize" at high temperatures if the internal clearances are excessive. You may ameliorate the problem (temporarily, usually) by surrounding the starter with high-temperature insulation. It that doesn't help, replace the starter."

I don't believe I will be driving again till next Saturday so updates will be delayed. I may just let the car idle till I get to a yard sale where it has cooled enough to expect only a minute or two cool down. Also I'm thinking a heat shield/exhaust wrap couldn't hurt. I will try to report back on voltages in the various states described when issues repeats and report back, as well as what jumping at junction box yields, and how much current it draws. Thanks everybody!

Since the starter is on the bottom of the engine, it is unlikely to get heat soaked, especially not from a high speed drive where there's lot's of air movement.

I'd suggest the simple things first:

1. disconnect the battery then clean , tighten the starter terminals

2. clean and tighten the ground strap

3. clean and tighten the battery terminals

4. Get the battery load tested and the alternator tested for proper charging at Autozone.

See if this fixes your problem before doing anything else.

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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

My 85 300D had a heat shield on the starter and alternator. I think this is specific to CA models since the exhaust, intake, and turbo are unique. Indeed, the starter looks different than my 83, with the solenoid in a different place, but maybe they you can rotate it with the started housing unbolted.

I think we are making this a lot more complicated then what it really is.....wrapping it with this or that, is like putting a bandaid on a gun shot wound...

Here's the quick n dirty answer.....replace the starter......

Starters aren't meant to last hundreds of thousands of miles, eventually you will need a new one. What happens if you don't replace it when it gives failing warnings, is that it will eventually take out bigger and more expensive things....eventually your battery, the alternator.....and then if your really really luck the starter will ground its self and fry your entire electrical system...

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^^ X2 Just replace the starter and be done with it.

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2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold

Don't know about a 300SD, on a 300D turbo, the starter is a PITA job to replace and a good rebuilt is not cheap. Starters last a long long time if not abused (such as extended cranking, or cranking with a low battery- both will overheat the starter). I would recommend diagnose and replace only if the starter is bad. It would suck to replace it and have the same problem.

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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

On one of the Russian Parts sites all of the little Bushings, Bearings show up in the Parts Catalog.

That does not mean Mercedes sells all of them but there is a good chance as there is no major electrical damage someone can fix their own Starter.

Getting the Starter off of the Car seems substantially harder than taking the Starter apart.

It could be the OP's Starter simply needs a good cleaning.

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84 300D, 82 Volvo 244Gl Diesel