OM617 Starter motor access, is it tighter on a coupe?
 

I'm trying to get to the top bolt of the starter motor. I even have the manifolds off for other reasons. You'd think that would make it easier to access the top bolt of the start. I was able to get the 10mm hex into to the bolt since I have access from the top. But, there is no way to turn it's so far back in there. If I do manage to snake a bunch of extensions backwards and including the high impact flex extension I bought from Mercedez source, there will no way to actually turn it. It seems like the engine would have to come out just to get the starter out. Does anyone know if these coupes have tighter clearances around the engine and starter?

Should be the same.

You just have to piece together extensions and u joints then make sure your business end is well seated in a cleaned out socket. Then put on a 18" breaker bar on it and give it heck!

To crack the top Allen head bolt loose:

I sprayed the head of the bolt with penetrant the day before.
Also I cleaned out the recess with brake cleaner and cotton swabs.
Then tapped the 3/8 drive Allen socket home to make sure it is well seated.
Then placed the 3/8 drive rachet in the bolt and tried to tighten the bolt a bit.
(Penetrant, tapping the bolt, and tightening the bolt all serve to break loose corrosion)
You don't want to strip out the recess in the Allen bolt!!

Next I positioned the trolley jack under the horizontally positioned rachet handle.
I placed a length of scrap 2x4 between the rachet handle and the jack and slowing began pumping up the jack.

I actually lifted the engine about an inch without cracking the bolt loose.
Adding my weight to the PS fender a couple of times (like trying to check shock recoil) was needed to finally crack that top bolt loose.

I haven't yet had to do this but ....

My plan is to cut a hole in the floorboard for access and fabricate a screw-down cover plate for future access.

Edit: Posted to wrong threead.

I found its much easier to just drop out the exhaust piece from the turbo too the union joint underneath the car ,no contorting,3ft of extensions , or swearing involved.

OK, I got the top bolt loose. I actually did it from the top since I had the manifolds off. Mine wasn't very tight so I used nothing but a hex socket with a 10mm tubing wrench on it.

But, to my surprise the BOTTOM bolt is proving difficult. I'm terrified of stripping out the inside of the socket in the bolt. It seems a bit loose in there. I put PB Blaster on it and now it is sitting to let it soak in. I'll use a blow torch to heat it up before trying today after work. Any other tips insure that I don't strip out the socket in the bolt?

Try to tighten it a bit before you go the other way.

Starter Bolts
 

Put the top bolt back in and tighten it .

CLEAN THE SOCKET PART OF THE SCREW !!!!! use a tiny screw driver , ice pick etc. until it's HOSPITAL CLEAN or you're going to regret it....

TAP THE ALLEN BIT INTO THE SCREW ! .

Then add your 1/2 drive extension or whatever .

Good luck ! it''s a nut buster to be sure .

Same on all W123's regardless of body style .

Cutting a hole in the floor is a fools errand you will live to regret .

Got one out that was starting to round the internal hex by epoxying the hex bit into the bolt head. Worked really well. If it feels like it is going to strip internally, stop.

Good luck!!!

Well I got both starter motor bolts out. Used PB Blaster and a torch to heat up the bottom one. The top one was not too tight.

What is the best and strongest replacement starter motor? I don't want to have to replace it for another 345,000 miles. Are there any that turn stronger and faster?

Also, where would one get a replacement bolt? One of them is a little stripped inside the hex hole.

Get a genuine Bosch starter (rebuilt by Bosch) with the heavy duty genuine Bosch solenoid.http://www.peachparts.com/shopforum/...h-solenoid.jpg





Most aftermarket rebuilders use a smaller, weaker solenoid which will fail prematurely.
http://www.peachparts.com/shopforum/...h-solenoid.jpg




http://http://www.peachparts.com/sho...h-solenoid.jpg

Starter to transmission case bolt. MB part number: N000912012161
Available new from dealer, Amazon, etc, or used from local junkyard.

The first time I changed a starter on a w123 I nearly went insane trying to get at the bolts. After I learned to use about two feet of extensions and a socket joint snaked up along side the transmission it became a thirty minute job

Mine is out now. So, no worries. I got to it from the top while my manifolds were out. But, I'm curious as to how you got it out using extensions. Mine has a heat shield around the transmission that is in the way. I thought that heat shield couldn't come out unless the transmission came out. But, with that heat shield, there is no way to get any extensions in there to get to the top bolt.

Rebuilt Electrical Units
 

BOSH brand and only BOSCH BRAND ! .

It'll say on the box .

Alternators too, yes it really does make a difference .

Try ********.com, they often have them .