Daft W123 300D nut and bolts sizes
 

It is often said “they don't make 'em like they used to” - in the case of the W123 that's true. Working on these cars certainly gives me the feeling that I'm working on an old fashioned vehicle.


Take a look at this list of the daft sized nuts and bolts I've found on my 1981 300D – keep in mind that these are just standard hex head fasteners – I'm not talking about special tools...


Here are the favourites


Prop shaft 46mm and 41mm (Open end spanners)
Flex disc bolts one side 17mm but the other 15mm??? (Why?)
Fuel tank sender 46mm (You can just about get away with a spanner)
Fuel tank drain / strainer 46mm (need a socket when tank is in situ unless you are lucky)
Front crankshaft bolt OM616 / OM617 (27mm socket)
Diesel injectors (Deep 27mm socket if you are lucky with the overflow pipes)
Glow plugs – 20.8mm (this almost falls into the special tool category but seriously use a good quality adjustable spanner)
Differential fill and drain plugs 14mm Allen key
Pitman arm retaining nut 36mm
Idler arm bolt and nut 24mm (Not really daft – but good to know)
Oil cooler line union nuts 27mm


Notable 12 points


Big end nuts 14mm 12 point socket
OM617 later type head bolts M12 12 point key
Front shock absorber lower bolts 12mm 12 point socket
Flywheel to crankshaft bolts 12mm 12 point socket


My top 3 surprises:-

1. 7mm Allen key that holds the parking brake shoes locating block on the trailing arms in position
2. 16mm headed bolts that hold the steering box onto the chassis
3. 24mm flat ring spanner needed to access the trailing arm mount bolts

Having had to get all of this I can conclude not only is no such thing as a cheap Mercedes – there is also no such thing as a cheap tool kit to maintain your Mercedes!

I notice you do not mention any SAE threads... a MB AC system will have some of those... ( at least here in the US ) ...

The worst case I have seen was my 1957 XK140 Jaguar... it had Whitworth ( English ) thrown in randomly with the metric and US threads with no way to spot them.. working on an old car with rusted and stuck nuts and bolts anyway... and then having some weird ones included... a great way to round off heads and have to go to ' a bigger hammer' often.

huh
old Brit bikes like my BSA M20 used -

BSWhit,
BSFine,
BSCy,
BSPipe,
and BAs threads, plus various 'bastard' left hand threads for odd bits like the petrol cap.....

all on the same bike:D!

Since when are the glowplugs 20.8mm? I've always removed them with a 14mm and a 7mm.....

Flex disc bolts one side 17mm but the other 15mm??? (Why?)

Not the first time I've seen a nut bigger than the head of the bolt on the other side.


Glow plugs – 20.8mm (this almost falls into the special tool category but seriously use a good quality adjustable spanner)

20.8mm ~13/16 = spark plug wrench.

Here it is:-


http://www.startekinfo.de/etools/content/tool.jsp?toolno=617%20589%2000%2003%2000

So are old bikes more expensive to maintain than an old Mercedes?

AC. AC? Never had it - never even owned a car with electric windows!

yup, as noted, the old big glow plugs use 13/16" socket.
and the newer head bolts are not 12 point keys... they are xzn TRIPPLE square keys... NOT the same as torx or 12point standard!

What kind of glow plugs do you have? The Bosch in my 83 is 12 mm

Quote: "Fuel tank drain / strainer 46mm (need a socket when tank is in situ unless you are lucky)"

The barb fitting that screws into the strainer is 19 mm. If you're lucky a 19 mm open end will get the 46 mm strainer off and not the 19 mm barb.

So you only have to own one 17 mm and one 15 mm, and with the savings you can go get some of the other sizes you need!

Look at it this way -- it means you don't need to own a second 15mm wrench to use as a counter-hold. A 15 and a 17 will do the job. I actually think that's pretty clever.

I used to own a Honda...the thing I liked best about that car was every bolt head had the size socket it needed stamped on top. If it said "10", you reached for a 10mm wrench, and so on.

Really? I never noticed that on my old 1980s Civic - but then it rarely went wrong...

...now that's not to say that my W123 is a pain in the backside - I'm the pain in the backside this time: I just can't stop taking it to bits and putting it back together again.

Good point - I should have tried that. However, when I did the job I was determined not to join the "how do you get diesel out of your clothes / hair / eyes?" club. I'm happy to report I was successful due to a nice little siphon pump and a Jerry can.