Most reliable w108/w109/w111/w112

[TroutMD]

What would you consider the most reliable engine/model within these chassis lines?

TIA

[Sugar Bear]

Due to the age of these condition is a major factor in reliability so if you are looking to purchase condition really matters. Condition aside I'd look for carbureted inline 6 cylinder models. The injected models are getting hard to find parts for repairs and the mechanical injection models tend to use/burn oil/smoke IMO due to the mechanical injection putting in too much fuel at higher RPM washing oil off the cylinder walls; but, they ran really well!

[cth350]

there is a fellow near Ashville NC that likes to put M103 motors in the W108 & W111 cars. They look spectacular when he's done with them.

Those would be reliable cars.
-CTH

[Frank Reiner]

Originally Posted by TroutMD

What would you consider the most reliable engine/model within these chassis lines? TIA

The 108/109 chassis is the successor to the 111/112 chassis, and offers some refinements.

The M116/117 engines, as delivered in those chassis, are constrained by the D-Jetronic injection system. If it is replaced by an aftermarket, programmable fuel management system, those engines would be the better choice for reliability.

[aluminum]

[QUOTE=cth350;4297640]there is a fellow near Ashville NC that likes to put M103 motors in the W108 & W111 cars. They look spectacular when he's done with them.

Those would be reliable cars.




Ya that's Most likely JZ an Old time Mechanic fully qualified

I think he actually Lives in Burnsville NC > I call him sometimes when I get stumped on some parts swap

I used to Live in Black Mountain as a Kid for a Bit was totally weird Black People would step out in the street to let you pass by on the sidewalk was Racist back then > From the lower east side of NYC it was an adjustment .
Pot grew wild all over the place but it was Hemp for rope LOL


I think He bought those Cars with M103 Motor in them all ready Most of his iron is very hi priced but looks to be in great condition.


I find the 250 S Models to be reliable and they hold tune Quite well and Gas millage is Fair like 18 to 24 depending on elevation and driving habits , they certainly Have Plenty of power for normal driving however if your mechanical Inclined the 280 SE Models are certainly Engineering Marvels like 67 / to 72 >>

They ( the 280SE ) did Have Heating Issues with several Motor Changes ending with a different Block 1971 & 1972 with different water jackets and at least 2 or 3 different heads so you need to keep them cool with a good Radiator > The SL Heads swap if you learn your way around them along with the Camshafts .


However that said the 4.5 V8 is certainly the most reliable a bullet proof motor that with standard maintenance run over 200 K Miles all the time and to see them with an additional 75K to 100K Miles is certainly realistic
this I know first hand as I have had several & I agree with Frank that the M116/117 engines are the most reliable 100 % For sure and longevity
end of story and they get better gas millage then you would guess, you can cruise all day at Hi speed year after Year like its totally Normal



This 1975 SEL 4.5 SAME MOTOR as the W108 Etc I drove at hi speed for years and sold finally with 300 K Miles and I never had the head off EVER
and it ran great when I sold it still

[fonzi]

D-jet motors are what I would consider the simplest and most reliable. I played with carbed straight 6 w114 for a while before getting my hands on a v8 w108. It’s an older generation platform and a larger car, but I believe that it probably does better on MPG than any of the carbed cars. D-jets run a little rich typically but I think they are very easy to maintain and with all the r107 cars getting scrapped and even 4.5 w108s getting their rear ends taken for pagodas, there seem to be plent of them getting parted. The 4.5 is a nearly indestructible lower end. They are relatively cheap to get your hands on too. The 3.5 v8 cars don’t seem to be as common and might not be as reliable with higher compression. I don’t think I’ve ever found a d-jet I wasn’t able to get running. I’ve torn a lot of those apart too.

Now, MFI? I failed

Dual zenith carbs? I failed


I can only speak from my own experience.

My friend Jason Birch @rwd4evr seems to have plenty of success with single carb motors. I think they are simpler and easier.

[TZ_280SEL]

I have a W108 with M117 which is running modern EFI (Megasquirt). I use it as a daily driver. My weekly commute is about 400 miles and I drive this car about half the time. The modern EFI really makes these engines come alive in my opinion.

[fonzi]

Originally Posted by TZ_280SEL

I have a W108 with M117 which is running modern EFI (Megasquirt). I use it as a daily driver. My weekly commute is about 400 miles and I drive this car about half the time. The modern EFI really makes these engines come alive in my opinion.

What transmission tires and average MPG are you getting? I’d love to use my 4.5 as a daily driver with regular fuel. I consider the concept of installing a manual transmission maybe even one with OD and possibly a 3.5 m116, but figure the premium fuel cost would defeat the benefit of the 3.5 (other than the higher revs with a manual trans). I assume the standard 3.27 rear end is what you are running. If a mega squirt is what I need to do to be able to help justify driving the car, I’d do it. I might want to add a catalytic converter too, but I’m not sure I’d be able to get it close enough to the engine to be hot enough.

[Frank Reiner]

A fuel-only control can be done with a MicroSquirt.
The D-jet trigger points cavity in the distributor can house a VR or a Hall sensor with a multi-tooth wheel for pulses.

[TZ_280SEL]

I am running the standard 3.27 rear end and the 3 speed. I’m controlling spark and fuel using a 36-1 crank wheel and Hall effect. No more distributor. I’m running GM LS-2 coil-near-plug and modern Bosch injectors. I use a stepper motor and a jeep 4.0 idle air valve for idle. Since I don’t have cam sensors, I run wasted spark and semi-sequential. I also have a euro 4.5 so I started out with 8.8:1.

I can run regular unleaded without detonation. I’ve been getting about 17mpg lately.

I did my conversion about 7 years ago and no issues. I’m running aDIY kit MS3

[Screwdriva]

I've been looking at a late model year W108 280SE 4Speed manual.

A concern remains the lack of parts availability to keep these cars running weekly (I've seen an alarming decline in spares availability with the W115 and W123 chassis). Is this something rooted in reality or am I just being alarmist?

[alabbasi]

None. 50 year old Mercedes arent reliable. Get a modern car if you want reliability, 73 GMC pickup if you want to be able to depend on a classic everyday. Parts availability and parts quality for anything older than a W210 Mercedes is becoming questionable these days which makes these cars near impossible as anything other than a hobby car.

[aluminum]

Along with just about all other 50 Year old Cars LOL


All in All I find them reliable if your mechanically inclined and can fool with them for mostly minor stuff but agree that as a Hobby like any old Car
is a good way to approach them



Worst thing about the W 108's along with the whole line of that era mostly
is / was the lack of Galvanized Metal in the rockers so it seems they are first to go along with the Drain Holes in the doors that should also have been Galvanized Metal


The at least 3 different 280 Type of 6 Cylinder heads heads tells a story for such a short Period of time that they have a lot of issues > overheating > aluminum porosity is a common problem on all of these heads


The V6 ML Motor like the common 320 type is a more reliable Motor but the list of better of course is long however to get 100,000 miles + on an original 250 250S 280 280S 280SE 6 Cylinder is very common
200,000 + on the 4.5 V8 Very common

[Idle]

Some random info....

I had a 6.3 with the V-8. This was not cared for at all as the original owner was an oil millionaire and looked at it as a disposable item. But even with 120,000 miles it ran perfect. So looking for a V-8 is a good place to start.

A 116 450se or sel is more like a modern car is is a joy to drive but look out for rust. And if you are on the west coast avoid any Mercedes with the west coast green emissions plate (this started in 1975 or 74). The thermal converter is something like a billion dollars to replace if you can even find one.

If you get a 116 consider changing the A/C controls to Euro because the US version with it's weird temp controller servo is a nightmare to service. Or plan on spend several hundred dollars to replace the servo because if it's not cracked now it will be eventually.

[Scrappy]

Wouldn't an M104 be a good choice for engine swap?

Mated to a 733.369 would make a decent drivetrain with 2:65 rear

differential

(substantial modification required to retrofit)

would it not?

What transmission and differential is being used in the M103 into W108

modification?

Scope creep here but just to say, I drive my 1970 W115 220D locally daily,

and between San Antonio and Austin frequently to run errands, on IH35 at

highway speeds.

It's a year older than me but probably in better shape...