frustrated new '75 240d owner
 

I just bought a 1975 240d (115 chassis with 2.4L N/A) and was/am super excited about it. My alternator belt crapped out on me which in turn disabled my waterpump and the engine overheated. I don't believe anything major was damaged. Changing a belt seemed to me like a pretty minor deal, I've done it on countless other cars with nary a real headache. But after fidgeting with this Mercedes pulley system, I started wondering if MB intentionally made things difficult so you would have to take it to the dealer. To get to the alternator belt, you have to take off the other belt (is that other side running a vacuum pump or power steering?) I found three bolts on the front of that other side and one on the back. I loosened all of these and the pulley got looser but not loose enough to get the belt up and over. The alternator flanges have two bolts on the front and then another hex head that is also a cog. I assume this cog is how you put tension on the belt. On the backside of this cogbolt is a nut that I loosened (I assume that once loosened this cog can be rotated out or in by turning the hex). After loosening the back nut that cog still won't turn. This is all complicated by the AC unit that is attached directly above the alternator in my way.

So could anyone explain this system to me? Am I missing a basic notion of how this works? The old slide plate design sounds like brilliance right about now.

I also went to Napa today to inquire about a Chilton or a Haynes manual for this car. They looked it up and couldn't even order one for me. Plenty for the W123 but the venerable W115's seemed to have reached obsolescence in the Chilton/Haynes world. I have read about the cd you can buy on this forum, but $115 seems a bit steep to me. Are there other manuals out there anyone can recommend?

Thanks

well
 

welcome to benz ownership.

unfortunately you have encountered several of the most frustrating problems that exist in benz ownership world. the lack of basic access to the alternator belt and the frankenstein bracket holding the ac on that car. also mix in the alternator adjustment method which will strip if you put enough stress on it to get the belt really tight.

there is no easy solution to any of it. but with patience and persistance you can do it. be sure to buy benz original equipment belts so that they will last and not stretch. the adjustment on the power steering pump is counterintuitive but once you know how it works is not too bad.

these cars were designed to opeerate wo power steering or ac originally and that is the best way to have them. unfortunatelly not many want them that way anymore.

the 123 repair manual will be helpful. i also have an old chiltons from about 1970 that has a lot of useful things in it and another chiltons from about 1980. those two will prob be available from the internet.

beyond the problems we are talking about the 115 cars are very high quality, drive nicely ride nicely and last a long time with good care.

good luck

tom w

thanks for the words of encouragement...I really need them.

Is my reasoning right about that tensioning bolt on the alternator--if I loosen the nut on the back, the bolt should be able to turn on the front? And yes, that hex is stripped out from previous owners. Is this bolt available or is it strictly junkyard material by now?

Seems the bolt is not available at fast lane for a '75 240D? But you can look on fastlane to order it. It is available for a '77 240d, I assume it would fit, but I dont know for sure. http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1N21BPJIL1NF1AQVU3&year=1975&make=MB&model=240-D-001&category=F&part=Alternator+Adj.+Boltan
I just did this myself and it is not difficult, if I can do it anyone can. Loosen the nut on the back, get a bite on the stripped cam bolt from the front, I used small vice grips. The trick is turn the bolt clockwise to loosen the belt. I mention this because it seemed backwards when I was doing it. Heads up do not remove the bolt as it is a booger to get the spacer and the bolt lined up and back in. Hope my silverware drawer mechanical tip helped.

You can find the CD on e-Bay for $20 or less. I personally do not endorse these versions. There are also lots of paper copies of the engine and chassis manuals on ebay and at places like books4cars.com and tmcpubl.com. The Haynes manual for the 123 would work as the cars are really very similar mechanically.

The alternator bolt is common to many models and engines and should be easy to find.

Good luck.