New to me W140 and some questions

[Kestas]

The engine wiring loom may or may not fall into the problem area. This was built at the cusp of the problem. An inspection under some of the wrap should give you an idea of whether you have the problem or not.

The head gaskets do go bad. I replaced mine prophylactically 100K ago.

You have a number of options to fix the odometer.

1. You could remove it and send it to a speedometer shop. I sent mine to Bob's Speedometer, a nationally known shop. Mine cost $400 to fix.

2. You could remove it and repair it yourself. There is information on the internet to guide you through the process.

3. You could buy the gauge or dash cluster set from eBay. I wish I did. I would have saved over $300.

 

[19jacobob93]

Just a wee update.

I retorqued the head bolts (55Nm +90+90) which almost completely stopped the oil leak. These M104 engines seem to famously leak through the head gasket externally at the back of the block where all the oil pressure goes through a single gallery. I read that a retorque will normally fix it, and if caught before it gets too bad it may remedy it indefinitely and prevent a future head gasket job. I hope this is the case because it definitely worked on this application and I am comfortable continuing running this Valvoline 15W40 that meets the MB229.1 Spec.
Swapped out 4L of the ATF with Maxlife synthetic.
Managed to source a couple of air filters online, a challenge since this is an early model with the giant round filters before they switched to panels.
Replaced a fuse and now all the soft close doors are working properly!
Pulled the cluster apart and removed the odometer, and I now have new gears on the way.
Tinkered with the throttle cable and it feels much more responsive now.
Changed the diff oil with straight 90.

I think the lower control arm bushings need replacing because it has the common 55mph wobble. When worn even slightly they are very sensitive to the slightest imperfection in the tyres, which mine will have flat spots from being sat for so long before the purchase.

 

[CincyDavid]

That's a lot of car for an M104...is it geared really short like the W126 300SE and SEL that had a different inline six? W140s are elaborate and can be tricky to work on, but it just might be the last true, old school MB design.

 

[19jacobob93]

That's a lot of car for an M104...is it geared really short like the W126 300SE and SEL that had a different inline six? W140s are elaborate and can be tricky to work on, but it just might be the last true, old school MB design.

I hear that a lot but it handles itself just fine. The gearing is short as it sits at around 3,000rpm on the highway, but these are programmed to set off in second gear and it accelerates fine. They only set off in first if you apply more than half-3/4 throttle from standstill and it takes off quite well with a 0-62 time of 8.4 secs.
The drivetrain is extremely simple luckily, but I can see some of the interior appliances being a pain, but luckily everything is 100% functional.
I am half way through replacing the head gasket on my old E36, and once that's completed I'll keep the W140 in the garage and use the E36 as a daily driver. The Merc is simply too clean to beat on every day!

 

[Benzadmiral]

Congratulations on one of the great road cars of all time. I had its immediate predecessor, the W126, with the smaller (4.2L) V8. Still miss the big gray beast.

Are those sheepskins on the front seats? My W126 had those from its previous owner. I keep telling people in this heat-stunned region that sheepskins really have no temperature, they are neither hot nor cold. Your back would sweat just as much on the leather seats alone as with the sheepskins, maybe less.

 

[19jacobob93]

Congratulations on one of the great road cars of all time. I had its immediate predecessor, the W126, with the smaller (4.2L) V8. Still miss the big gray beast.

Are those sheepskins on the front seats? My W126 had those from its previous owner. I keep telling people in this heat-stunned region that sheepskins really have no temperature, they are neither hot nor cold. Your back would sweat just as much on the leather seats alone as with the sheepskins, maybe less.

Cheers! And yes they are sheepskin covers. Cost the previous owners around $2k to have them custom made! I let her keep one for her ML500 so now I just have the driver's seat, arm rest, and have since found a matching steering wheel cover.
They are great for keeping the temperature stable and your back sweat free! As you mentioned they just have no temperature haha makes me understand how sheep can survive both harsh summers and harsh winters with that coat.

 

[atikovi]

That's a lot of car for an M104...is it geared really short like the W126 300SE and SEL that had a different inline six? W140s are elaborate and can be tricky to work on, but it just might be the last true, old school MB design.

Acceleration is "adequate" as they say and I have a gray market S280 which has even less power, but the manual trans supposedly makes up for it.

 

[19jacobob93]

Acceleration is "adequate" as they say and I have a gray market S280 which has even less power, but the manual trans supposedly makes up for it.

I knew it existed and never tried it until the other day, but the autos are designed to set off in second gear to avoid creeping and also to provide a gentler experience for the passengers. If you shift the lever down to '2' it sets off in 1st.
I tried this out when I was at the front of the lights at an intersection the other day and I thought I'd see how it goes so I put my foot down. It actually shredded the tyres in the dry and when it caught grip I was actually surprised how well it pulled!
The gears are very short so that obviously helps with the acceleration, but the M104 does a more than adequate job, especially compared to some older luxury cars I've driven with much bigger engines.
I've always told people how it's a big slow barge but that wouldn't be the case if I did the transmission mod to have it set off in first gear permanently.