New to me W140 and some questions

Joined
Feb 12, 2014
Messages
734
Location
Gold Coast, QL, Australia
Hi all,

Just picked up a pristine 1993 S320 and I can't wait to get to work on it, not that there's really anything to do...
It was originally up for $12k, dropped to $10k, then I managed to get it down to $9.6k. There was hard bargaining and I was aiming for $9k but I wasn't missing out on this beauty for such a negligible amount.
It is literally like new apart from one minor scrape to the front left corner, the interior is flawless.
It has the M104 3.2 I6 mated to a 5G-Tronic 5sp auto.
It drives like nothing else I've driven, even new high end vehicles, and I was sold immediately. The double glazed windows are excellent at insulating the outside and the suspension feels excellent, the engine smooth as silk (if not slow, but great sounding) and the transmission feels slightly harsh into 3rd which may be the valve body problem. I will first off try some Lucas transmission conditioner as I've had excellent results with it in the past on high mileage transmissions.

The odometer is stuck at 105,000km and the old lady I bought it from estimates it couldn't possibly be more than 50-60k over that mark given when it went. It seems to be a common problem with the trip reset button pin sticking in and then grinding the gears off - thus grinding the oddo to a halt forever. So if anyone has experience with fixing this problem please speak up!

I hear the engine wiring loom is a problem on these with its biodegradable insulation, and the only one I can find for sale is a new one for around $1,200! Hopefully this one holds up for a while longer...

Other things I've read are the head gasket oil leaks (timing cover leak looks to have previously been fixed) and the transmissions can be fairly temperamental, but the valve bodies are easy enough to replace.

For oil I am thinking about Castrol GTX High Mileage 15w50 and LM MoS2 additive. I feel these two will work together to make for a very smooth running and hopefully leak free M104 that will hold up nicely during our hot summers.

Anyone with experience on these beasts and the drivetrain mentioned I would love to hear any tips and advice as I would like to keep this in top shape for as long as I'm alive (or someone drives into me again!)
Anyone know of any significantly high mileage examples and how they run to keep my faith?

Cheers all!
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Do not mix that Castrol 15W50 and that Liqui Moly garbage. You really do not know what you actually getting with that. I would go high mileage synthetic oil in this case. It will have more than enough additives to address potential leaks where oil can mitigate such occurrence.
 
Do not mix that Castrol 15W50 and that Liqui Moly garbage. You really do not know what you actually getting with that. I would go high mileage synthetic oil in this case. It will have more than enough additives to address potential leaks where oil can mitigate such occurrence.
Unfortunately there's no such thing as a high mileage synthetic in Australia. ALL high mileage oils here are heavier weight blends.
I've had great results with MoS2 in the past in very high mileage and older engines for reducing leaks somehow but also for increasing compression slightly, fuel economy and overall smoothness of the engine.
What is your bias against MoS2 out of interest?
 
Unfortunately there's no such thing as a high mileage synthetic in Australia. ALL high mileage oils here are heavier weight blends.
I've had great results with MoS2 in the past in very high mileage and older engines for reducing leaks somehow but also for increasing compression slightly, fuel economy and overall smoothness of the engine.
What is your bias against MoS2 out of interest?
Do you actually know what you getting with MoS2? Like any LM product it is a lot of snake marketing. I used LM products, and even those loaded with MoS2, burned more than some pretty unknown brands. I think how "successful" your MoS2 usage is depends on application.
But, if it works for you, great. My concern would be catalytic converter and that thing might be pretty hard to find and expensive for SL320.
 
Do you actually know what you getting with MoS2? Like any LM product it is a lot of snake marketing. I used LM products, and even those loaded with MoS2, burned more than some pretty unknown brands. I think how "successful" your MoS2 usage is depends on application.
But, if it works for you, great. My concern would be catalytic converter and that thing might be pretty hard to find and expensive for SL320.
Yes, or at least according to the MSDS and VOAs on here it's just SAE30 with a bit of molybdenum disulfide and a splash of boron...
It really does say what they say it does but for it to be noticeable after adding it there does have to be some wear on the engine for it to make up the slack. It's also interesting to note that none of their oils actually contain MoS2 either.
It definitely depends on application, which is why I only apply it to certain engines - like I wouldn't add it to my new Hyundai yet.
I'm not concerned about the cat since as far as I can tell it burns next to zero oil, just has a minor seep at the rear of the head which is typical of all M104s.
I will add it to the current unknown fill (just been serviced before purchase) and see if I notice anything drastic... if I do I'll continue to use it at a half dose with the next oil change, if not I'll consider no longer using it.
 
what a wonderful car. This is one of the best - if not the best Mercedes ever made.

I opted for my VW Phaeton, since W140 in good condition are very rare in Europe nowadays ant the Phaeton's interior reminds me so much of the W140.
 
That really is a wonderful car. I love that vintage.

The W140 is built like a bank vault. A very solid car. The M104 is a very reliable and straightforward engine, but, if I recall correctly, a head gasket every 100,000 miles is to be expected, much like the M103 straight six before it.

I don’t see anything to be gained from the witches brew you suggest.

A good Xw40 synthetic, that meets MB 229.5, would be a great choice. You’ve got several down there and I would just pick one you like.
 
good luck!! an xxW40 should do well unless its an oil burner. let the oil blender do the additives as they are smarter than us!! of course parts will be $$$$ as its a Benz + DIY is best + learn as much as you can on-line especially on forums for your model. buying older can save $$$$$. like my 2001 TT225Q roadster which was about 45 thou new but a few years ago 18 thou got me a great fun car with under 40 thou on it, but in reality its a VW golf with AWD that was later used on the golf R with the VR6 but i prefer the 1.8T esentially the same but beefed up unit in my 2001 wolfsburg jetta.
 
Not trying to scare you but it's not uncommon for the a/c evaporator to develop pin holes and leak refrigerant. The evaporator is cheap but it's like a 24 hour job to replace.
 
I wouldn't use any additives in this engine or transmission, there are reports of not only settling of the MoS2 (I have seen this in my own engine) but also hydraulic lash/lifter clogging issues. If I bought this I would make a plan and get the parts ready to do the HG then pick a time at your convenience not letting it go till it lets go.

Go through it with a fine tooth comb, change all the fluids and check everything including wire connectors under the hood, people have a habit of breaking the tabs on them and don't bother to repair them, this very common with Euro cars and can cause real misery with intermittent connections.
 
Thanks for the replies everyone I appreciate it! I may give the MoS2 a miss and save myself a few bucks but I really did like the way it made my old inline 6 Falcon feel...
It does look like it has had a diet of synthetic given that it looks like new under the oil cap - not even a trace of varnish.
Given that these engines are famous for leaking I was actually thinking about avoiding synthetics, but it does look like it's lived off them... It is a real shame we don't have any HM synthetics here though and all are xxW50s... If synthetics have more/better seal conditioners I may be convinced though!
 
That really is a wonderful car. I love that vintage.

The W140 is built like a bank vault. A very solid car. The M104 is a very reliable and straightforward engine, but, if I recall correctly, a head gasket every 100,000 miles is to be expected, much like the M103 straight six before it.

I don’t see anything to be gained from the witches brew you suggest.

A good Xw40 synthetic, that meets MB 229.5, would be a great choice. You’ve got several down there and I would just pick one you like.
I have read a bit about the head gaskets online! Seems hit and miss... People are either getting 300k+ miles without needing it done or it happens two or three times in that mileage. Hopefully the newer Elring gaskets are better.
Would the head need shaving on such a long block or is it a case of checking and doing what's necessary?
 
I have read a bit about the head gaskets online! Seems hit and miss... People are either getting 300k+ miles without needing it done or it happens two or three times in that mileage. Hopefully the newer Elring gaskets are better.
Would the head need shaving on such a long block or is it a case of checking and doing what's necessary?
I would check with a good straightedge and put it back together. I don’t think it needs to be decked every time.

I just checked and reinstalled the head on the M103 (1992 300E) and it sealed up and ran for another 80,000+. It was totaled on an icy road (It was my step-son’s car) at that point, but the head was still solid and leak free...
 
I would check with a good straightedge and put it back together. I don’t think it needs to be decked every time.

I just checked and reinstalled the head on the M103 (1992 300E) and it sealed up and ran for another 80,000+. It was totaled on an icy road (It was my step-son’s car) at that point, but the head was still solid and leak free...
Ouch that's a shame! My last car that I really cared was totalled after someone pulled out in front of me. I'm quite paranoid about the same happening to this thing already!

That's good reassuring news about it hopefully not having to be redecked each time. I guess growing up in the UK we had a few small French cars and I'm used to once the head gasket went in those the head basically either had to be decked within a mm of its life and sold on, or it was scrapped. Of course the W140 is a whole different beast though.
 
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