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Starting a long neglected 6.9.....

8K views 39 replies 6 participants last post by  Dikdaan 
#1 ·
Ok here's a sort of off the wall question:

I'm looking at a 6.9 that has been laid up (for unknown reasons) for the better part of 25 years.....or since 1992....

It hasn't be started, run or otherwise touched in that time and has been stored, covered, outside.

Christ....where do I even begin with it?

Obviously before I crank it over I would do the requisite mystery oil in the cylinders, draining and replacing all fluids, dropping the fuel tank, fuel filter, pumps, all of that.

But not knowing why or how it was parked is the difficult part. My plan is to tow the car to my home shop to do the tear down, but is there anything specific that I should be looking for??

My experience with 6.9s is just about ZERO, but I have been a Benz wrench turner for most of my adult life and I'm fairly capable. Fairly.....but I know when to call in the pros!
 
#3 ·
Good luck, first off! As a 6.9 owner I call tell you you have your work cut out for you.
Suspension is where a lot of your $$$ will go. Assume it is cactus, as this is the main reason these glorious cars get kicked to the curb. The owner gets handed a 5 figure bill to correct/replace the system and that is that, as they say.
The K jet system is very robust, as long as you have pristine fuel supply and no vacuum leaks. I would replace the entire fuel package at the back for starters, these are common across the board for 450's so relatively cheap and available. Also replace all vacuum lines.
Transmission, drop pan and replace filter and all new fluid. This too may be a reason why it got laid up. The transmission is unique to the 6.9 and a possible failure point. If you see a lot of metal flake in the pan it's bad news for sure.
 
#4 ·
Thank you so much! This is the kind of information I am after. The car is sitting on jack stands, and appears to have been for quite some time so I'm assuming that the failure that lead to it's demise was somewhere in the suspension. Beyond that, strangely it looks as though the car was parked with the shift lever in the Low gear position.

The seller, who is the grandson of the original owner has little to no information about the reasons why the car was originally sat idle.....so it's a bit of a mystery, but my offer to buy the car (if such an offer is to be made) will reflect not only it's current condition but also the lack of history on it's pre-parked state.

I appreciate the feedback, I bought a W123 280CE in similar state about 3 years ago and completed the restoration of that car in the Spring. I enjoyed the process of bringing it back to life, it's been a joy to own, and now I'm kicking around the idea to take this restoration on......guess we'll see!!!
 
#5 ·
Welcome to the insane asylum! I've been working on my 6.9 for 2 years now, mostly getting the mechanicals in order. You pretty much have to go thru every system on the car to get running correctly after sitting that long. Then you can move on the rust.

Your fuel system will probably need complete rebuild, including all new hoses and filters. your FD and WUR are probably going to need rebuilt.
Suspension just plan on new pressure tanks and hose rebuilds, maybe leveling valves. Brakes need a good look at. ALL rubber parts will have no doubt perished.

I've replaced about 900 parts so far and am very close to having a car that I can actually drive more than 5 miles at a go.

hope to see you on w116.org, a great group there! A great source for fixing all your problems and finding parts.
 
#10 ·
Spent some time with the car the other day, I don't believe that the seller is correct on the amount of time the car has sat to be honest. The seller is guessing, as it belonged to a now deceased family member, that it hasn't been run since the early 90's but in going through stuff I have a feeling the car has sat for less than 10 years.

Obviously I'm guessing too, but when I looked at the oil, it was wet, viscous, and generally in pretty decent shape. It was also spot on in terms of level. Same is true for the anti-freeze, and brake fluid. Couldn't get eyes on the trans fluid. The piece that threw me was that the windshield washer fluid, although kind of mouldy looking and overall gross.....was just about full too. It was completely obvious to me that no one had touched this car in ages, prior to me opening the hood the other day and someone had prepared for the cars long slumber as the engine was wrapped in a blanket, batter removed cowling plugged accordingly, etc.

The question now is of course what caused it's parking. My guess is going to be the suspension based on the fact that the car is sitting on jack stands, but at this point it's anyone's guess.

I've also agreed to purchase the car. Asking price $500.

I'm sure it's going to be an incredibly expensive adventure, but there was a piece of me that had to throw the dice on this car.
 
#11 ·
@ $500 you are in good shape for sure. If the trans went kaboom or another catastrophic failure you can make your money back and then some in parting it out.
FYI though, with the 6.9 you read the oil with the motor "full hot" and running, in the same fashion as you would read the transmission fluid. You cannot accurately read the oil with motor cold. These M100 engines are very robust and very rarely do they go tits up. The bottom end is built like a tank. Top end they do suffer from the very common valve guide wear which was a common issue of Benzes of this era. But normally you can drive the car with no major gripes because of this. Pulling the heads on this motor is $$$$ so do not even go there unless you are highly skilled as the parts alone is extremely expensive. If the chain feels loose over the sprockets then wind in a new chain as a preventative measure but again this is not a common failure point, as the tensioner is of the ratcheting type, so the chain remains tight, not like the M116/7 motors which have the non - ratcheting tensioner, and the common "death rattle" on high mileage ones on start up, with high miles on original chain - a recipe for top end to eat itself along with brittle guides.
If you need hydro suspension parts refurbed I can do that for you at a fee. Send me a PM if interested.
 
#12 ·
Thanks Dikdann!! I have a feeling I'll be reaching out to you about those suspension parts.

My plan is as follows: get the car home to my shop, get everything drained and ready to try to start it, then go from there.

Is there anything I can check/clean/drain from the suspension prior to trying to start it??
 
#14 ·
I assumed there would be a lag in terms of the suspension rising, but do you know, since the car has sat so long on jack stands, will the suspension immediately bottom out when I lower it down? What I'm asking specifically is will I have a hard time rolling it and loading it onto a trailer?

Thanks guys!!

Sean
 
#15 ·
yes, it will lower all the way down. I put a small block under the front cross bar so that I could still get my short jack under the car. With the car that low, sometimes the leveling valves are too far turned to activate. Pulling up and down on the fender tends to activate them. Maybe you will need to jack up and the let down until the valve take over. If you drain all the fluid from the system it can get harder to rise the first time. Search the forum for others that have gone thru the same thing.

When you take the accumulators off they will leak huge amounts of foamy fluid. the foam is the nitrogen mixed into the fluid. It will leak like a stuck pig. The fitting tend to get very stuck tight, use a torch to heat up a bit and that helps a lot.
 
#16 · (Edited)
Rumb made all good points. For me I would just add to drain and clean the tank first. Normally the fluid is extremely dirty unless you had a fastidious owner. The fluid should be clear, at least golden in colour. What you will most likely find is a colour that looks like Coca-Cola! To drain the tank you need to remove it from the mounts (you can access the bottom mounts from the driver LHS fender well, much easier). You would also need to remove the pressure regulator from the top of the tank to do this. As Robert has stated these fittings can be hella tight after all these years. Localized heat with propane torch for sure, and you need to get some good flare/line wrenches otherwise you will round off the fittings for sure. They might even be too tight and you will have to wrench them off with vice grips, then replace with metric bubble flare brake lines. Wash the tank out with solvent or similar (kerosene etc), then mount the tank and drop in some fresh "ZH-M" fluid, about 2.5 - 3 litres from memory. You also need to replace the filter under the pressure regulator, they are super cheap and very good to replace on a regular basis. The system needs clean fluid to run well. Thus I would advocate to make sure you run as clean as you can for the first start up.
Indeed these cars sink extremely low to the ground and then you cannot move them without huge effort. Wooden blocks to start with just to give you some clearance is a good tip.
On a well sorted system, it should rise with no revving of the engine, in about 30 sec to 1 minute tops. At first the rise is slow but towards the end it rises quickly. Not rising or very slow rising usually points to a weak pump, or faulty pressure regulator or both. Pumps are a known weak spot but they can be rebuilt. Do not run ATF in the system, it will eat your seals! Once you have cracked the lines, you need to also bleed your pump. with the system down, open the connection from the pump at the pressure regulator, then point the open end of the hose into the filler hole of the tank, and start up the engine. This will cycle fluid through and purge air from the pump. Then reconnect after about minute of purge and start up.
Also a word on safety. The system runs at extreme pressure of about 2500 psi, so keep that in mind. Safety goggles and gloves are a must. Hydro oil under such pressure can pierce your skin and this can end up being fatal so be very careful!
Another very good site for 6.9 owners is www.w116.org
 
#23 · (Edited)
While we're at it:

410 = Electric Sun Roof
494 = "California Version" (emissions related)
518 = Becker Mexico Radio
531 = Automatic Antenna
581 = Automatic Climate Control
592 = Heat Insulating Glass
639 = Elimination of Warning Triangle

I think that's it for the codes on rad support. Your Data card will have all the codes complete.
 
#26 ·
It's not a pretty situation. I really can't buy the car without the paperwork being at least somewhat in order. In NJ at least, you can't even scrap a car without a title so it would be dicey to take this one.

The seller is trying to resolve it on his end and at the same time I'm going to take a shot at using the Vermont "loophole" which allows you to register a car in Vermont, even as a non-resident, without a title and then you take that registration to the DMV here in NJ and they *might* give you a title.

It's a nightmare scenario
 
#31 ·
Sorry for the absence guys!!!

So I'll give a sort of brief update:

The title issue was resolved, I have a title, in my name here in NJ and we're good to go in that department.

The other piece of good news is that the engine/trans combination is serviceable in that it starts and has the power to move the wheels........no idea on the shifting or anything as we haven't gotten that far.....

Because I can now confirm that there has been a catastrophic failure in the suspension, although I don't know what, where, or how.

The other complication at this point is that car is more or less stuck in the mud and completely and utterly pancaked. The suspension goes full flat.

So I'm going to have to flatbed it home to figure out the next steps, but the project lives on and we'll see what's next!!

Thanks so much for keeping an eye on this project!!!
 
#33 ·
" the Vermont "loophole" which allows you to register a car in Vermont, even as a non-resident, without a title and then you take that registration to the DMV here in NJ and they *might* give you a title. "



Can you elaborate on this? I have a Hercules Wankel motorcycle which could definitely benefit from this situation.

Thank you!

Mike/Florida
 
#35 ·
Hey guys, just touching base here. Some minor news, the car has been moved and is now safely in my shop. I'll update some pictures later, but the word "pancake" just about adequately states the current situation........I would be a HIT in the lowrider circuit.

So we're getting started here! Step one will be getting some sort of blocks into the suspension so that I can easily move the car around. The owner lost the key in the process of cleaning out the house.....so that's a fun little side project. But at least it keeps me from being tempted to try and start it!!!

I am going to need a hell of a lot of support and help when it comes to this suspension, so anyone out there that has offered......BRACE YOURSELF! hahahahah

Thanks for checking in guys, I'm going to upload some pics later this week
 
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