Some teething issues with a new 300D
 

Hi all,

I've recently acquired a 1984 300D Turbodiesel, and it's been driving rather well for the most part. I've been poking around the engine bay and--as a complete mechanical novice--have a few questions. I've been obsessively reading up on these cars and this forum has been an invaluable resource!

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Checking the dipstick, it seems like I have a little too much oil. How much of an excess (volume-wise) does this represent? Is it something that should be rectified immediately?

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Checking the coolant. Is a clear green color correct for the coolant?

https://farm4.staticflickr.com/3917/...15313077_c.jpg
What is this, and is it OK for it to be detached? At first I thought that it looked like the primary fuel filter (!), but then checked near the fuel pump:

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Primary filter is there. Needs to be replaced, along with the hand-primer and some of the fuel lines.

I've been noticing a bit of white smoke at idle (dissipates once the car starts driving). Planning on doing a valve adjustment soon, as well as changing the fuel filters and flexible hoses. Hopefully that should get things running better!

Yeah, if you can remove some oil, good.

These cars like orange coolant, aluminum friendly.

Appears to be electrical, not sure. One of the vacuum orifices have been plugged, I bet your door locks don't work.

Yeah, new filters and a new primer are in order. I wouldn't worry too much about the oil smoke, but when you adjust the valves, install a new gasket there too.

That's maybe 1/2 a quart of oil. Did you change it when you bought the car?

Green coolant is not ideal. Not instant death, but not ideal. The best bet for coolant is Zerex G-05. You may have to ask for it at the local auto store. Some keep it "in the back".

That cable doesn't look like a factory piece I've ever seen.

As mentioned your vacuum system will need some help. Do your automatic door locks work? How about the climate control system?

I wouldn't worry too much about too much oil. I did that a few times by checking the oil cold and then putting too much in. The trick is to check while the car is up to operating temperature.

Green color coolant is fine although the system should be regularly flushed.

On pic #3, is that coming from your instrument panel? It looks like your speedometer cable. Are you getting an accurate speed rating and is your odometer/trip timer working?

Dkr.

The oil level may be fine, depending on when you checked it.


Proper oil level check is around 5 minutes after shutdown for MB.

The shop that changed the rear trailing arm, axles and bushings did an oil change as well, so that may be the source of additional motor oil. I'm not sure about the type of oil they put in, so I'm thinking of changing the oil filter as well as switching to Mobil 5W40 Turbodiesel Truck oil when I do the valve adjustment.

Alright. We'll get that changed out ASAP, then.

Great! I'll assume it's not critical, then.

None of the above, though the car is getting a new set of ceramic-copper fuses today. It's been displaying a certain amount of endearing (but ultimately annoying) electrical quirks, and a quick check of the fusebox revealed several fuses that had reached the end of their useful lifespan.

The transmission has also been displaying some occasional hard shifting, which leads me to believe that it isn't receiving enough vacuum. I'd like to ultimately reduce the vacuum system to a bare minimum--enough to ensure proper operation of critical functions, and plugging off the rest.

Regarding the light smoke at idle and the poor(ish) fuel economy, I'm hesitant to come to any conclusions (and/or get unnecessarily concerned) before I do a valve adjustment and replace the leaking injector fuel lines.

Ah, good to know. Oil was checked cold.

Odometer and trip timer are working. Speedometer is a bit shaky from 0-15 MPH, but stabilizes once I reach high speeds.

Fuel gauge is a little wonky, though. Seems to have a margin of error of about 1/5 tank at any given time, as flutters between 1/3 and 1/2 tank while driving. Obviously I'm unsure which reading is correct, and it's not the most optimal situation for assessing my fuel situation :mad:

can you take closer pictures and some from different angles of that thing thats been disconnected? i'm intrigued.

The shop that changed the rear trailing arm, axles and bushings did an oil change as well, so that may be the source of additional motor oil. I'm not sure about the type of oil they put in, so I'm thinking of changing the oil filter as well as switching to Mobil 5W40 Turbodiesel Truck oil when I do the valve adjustment.

The car is getting a new set of ceramic-copper fuses today. It's been displaying a certain amount of endearing (but ultimately annoying) electrical quirks, and a quick check of the fusebox revealed several fuses that had reached the end of their useful lifespan.

The transmission has also been exhibiting some occasional hard shifting, which leads me to believe that it isn't receiving enough vacuum. I'd like to ultimately reduce the vacuum system to a bare minimum--enough to ensure proper operation of critical functions, and plugging off the rest. Door locks don't work, and neither does the climate control. But that could be due to the fuses, as well.

Regarding the light smoke at idle and the poor(ish) fuel economy, I'm hesitant to come to any conclusions (and/or get unnecessarily concerned) before I do a valve adjustment and replace the leaking injector fuel lines.

Coolant will be changed ASAP.

Will do!

I'm interested in the cable too. The outside looks like the speedometer cable as well as the location, but the connector makes it look like something electrical.

When I bought my current W123, it had the remnants of an alarm system which had been partially dismantled. There was a smaller connector like this that was disappearing behind the firewall. Is it possible it was for an alarm?

Dkr.

Here we go!

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Took the opportunity to replace my instrument cluster with one that actually has the clear plastic window :) Thanks uberwasser for the guide on ifixit!

Before
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During
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After!
https://farm3.staticflickr.com/2925/...b2e5f4ec_c.jpg

Off to a good start!

ooohh... its puurrday now.


That cable looks like it was for a sound system... its just in a really weird spot.

Check the trunk for signs of screwholes or manipulation for speakers or boxes.

Then, one day when you're really bored, open up the panel underneath the steering wheel.

Agree. I bet it would reach over to the positive side of the battery if you tried to reach it that way.

New fuses!

Before:
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After! (much better)
https://farm4.staticflickr.com/3925/...7292922b_c.jpg

I left #5 empty simply because the guide on the back of the fuse cover seemed to indicate that it served no purpose... is it standard to leave the socket vacant? Dear P.O. stuck a 25Amp fuse in there as a precaution, I suppose.
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Yes, #5 is vacant on your car.

The red jumper between #13 and #14 isn't typical, however.

Thanks! I tried (two or three times) to post a lengthy answer to your first response further up the thread... but it got stuck in moderation-purgatory for some reason.

Long story short: the shop that did the trailing arm and the axles threw in an oil change and inspection for free. Not sure what oil they used, so may replace the whole thing soon and migrate to 5W10 Mobil 1 Turbodiesel truck synthetic.

Car hasn't had a valve adjustment done in at least 4 years, so I'm essentially thinking that all of my light smoke/mileage problems will improve (if not be entirely solved) by an adjustment, as well as replacing the leaking fuel lines, fuel filters, and a good injector cleaning.

After that, I'm planning on troubleshooting the vacuum system (suspected source of slight transmission gremlins), replacing the belts and replacing the front shocks (completely shot from years of potholes, I imagine).

Will probably eventually get to the timing chain, but apart from that, I don't plan on making any further steps towards restoration: it's a slippery slope, and the car lives in such harsh conditions that I feel like it would be more worthwhile to just enjoy it while it lasts.

Zerex G-05 is available on Amazon for $14.35/gallon :) Eligible for Prime shipping

Unless you're in a really cold climate, there's really not much benefit from using synthetic in this engine.

Conventional oil will do just fine.... fantastic, even.

And if you have smoke and blowby issues, thats even more reason to use conventional. Shorter oil change intervals.

The large wire is probably a ground for the now removed sound system.
You need a new main vac line, for sure. Those nipples get brittle and like to break. Vacuum will affect a lot of things; trans, brakes, door locks, engine shut off.
Valve adjustments make a world of difference.
Green coolant should definitely be flushed and replaced with Zerex G-05.
We're here to help.

X2 and by your photo in post 12 (street is at elevated level over building foundations), and pothole comments it seems that you are from Chicago IL. I go to synthetic from Nov to March.

That odd cable is definitely aftermarket audio. The clear bulge is a fuse holder.

It's aftermarket something electrical and higher gauge (higher power). Perhaps a subwoofer? Do the speakers and stereo look upgraded?

Dkr.

My guess is for an amplifier. That cable probably goes all the way to the trunk.

Hi all,

Thanks for all of the advice and help so far

Some updates: car was driving better and better with time (have put about 400 miles on it since getting her) until this weekend, when she lost power on the highway. The first time, pulled over, re-started the motor and floored the gas in neutral, which seemed to solve the issue. The second time, she started sputtering with very little power. Crawled into a parking space and shut her off. Today, she wouldn't start (cranks, starts briefly, tries to run at low RPM, then dies out again).

Doing some research, it seems like the most likely culprit would be the fuel supply. The fuel filters looked like a good place to start.

So I changed out the primary and spin-on filters, unscrewed the hand-primer to get the fuel primed in and... nothing. No squeaks, no leaks, no pumping--my old-style primer pump seems to be *completely* ineffective. So, as of right now, I'm waiting on a new Bosch primer pump to come in. Hopefully that'll solve the issue, otherwise it's looking like it'll have to get towed to the shop (I don't have the space/resources to empty/clean the fuel tank in order to get to the strainer.)

Fingers crossed! Really hoping to get her back on the road within the next couple of days... otherwise I'll have to cancel my weekend plans and call a tow truck! D:

Old pre-filter--looks pretty grimy in there

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New spin-on:
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You shouldn't need the primer pump for a filter change. Try cranking it and that old gal should push through the bubbles. Also, do you use an additive in your fuel? I always run Diesel 911 (there are many brands and I'm sure someone here will ring in on their favorite to give you some other ideas). If the filters are a gunky issue, then the lines will have some build up, the tank will be cruddy, etc. A diesel additive will help clean the system and remove any moisture.

On the vacuum, you mention earlier in this post that you want to tackle that system and get it to the bare minimum to see if it changes the shifting. With that one nipple capped off, that is the bare minimum I'm afraid. The first place to start is to replace that line from the pump to the booster. That's about $30, and very well worth it. Also, the rubber connectors look cracked. Those little b**tards can drive you nuts of one of them is leaking. That's an annoying and surprisingly expensive job (I think that was about $30ish, too, but for dang little rubber bits, just felt like a lot!) but also a very good idea. I learned to do that with the first one of these I bought and have saved myself headaches by doing it on all of them right off the bat after.

Another thing to look at is the ALDA system. Here's a great walkthrough on cleaning a banjo bolt and line that gets gunked up over time. We did this on our rust...I mean...wagon and BOY what a difference that made on shifting and just general happiness of the vehicle.

Mercedes ALDA boost system service

Good luck!

are you in Galveston?

New York City :)

Is it really safe to crank the air out of the filter without priming beforehand? I don't want to end up with air further down my fuel system. As of right now, the filter is only about half full (see attached photo)

Did you replace both filters? Or just the small one? I know you posted a picture of the large spin on filter but I didn't quite catch if you had actually installed it yet.

Haven't installed it yet. Waiting on the o-rings and Diesel Purge to get in before swapping the spin-on out. The old one Should still be full of fuel.

Then it's fine to just crank to start. There's very little air in the pre-filter. Also, you will find that it is never really full of fuel, there is always a small pocket of air in there.

The large spin on filter is another story. You should fill that up with fuel, fresh motor oil, veggie oil, diesel purge etc (combustible fuel of some kind basically) right to the brim before installing it. And then pump it up with the primer as well.

Great. :) thanks for the tip. If she starts back up, the inline filter will have been the primary problem. If not, then onto bigger challenges.

She's back from the dead! Blew out a huge amount of smoke upon starting (scared the neighbors off their stoop), then idled rough for a little. Shut her off, started her back up and no smoke on the second round. Still not as smooth as before, but I've only let her idle for a couple of minutes.

Good to know that it was such a simple problem. I think I'll continue to go ahead with the replacement of the spin-on filter, diesel purge and certain leaking fuel return lines, just for the peace of mind. :)

The picture looks like one of those giant in-line fuses used for monster stereo amplifiers. That would likely have been connected directly to the battery or the output of the alternator.

Wow, that pic really shows how bad off the main vac line is.. I didn't know both nipples were jacked up.

My advice, considering all the good information posted already, would be to grab some StarTron tank cleaner. It breaks down a lot of the gunge that builds up in the fuel tank. A benefit of that is that the guide wires for the fuel sender will be cleaned somewhat and give your fuel needle a considerably more accurate reading.

http://www.peachparts.com/shopforum/diesel-discussion/189366-fuel-sender-85-300d-cleaned-pics.html

http://www.peachparts.com/shopforum/diesel-discussion/312129-star-tron.html

Looks like it might be a power cable for a stereo amp or maybe some :cool:kind of old two way radio

Yep your main vac line is in really bad shape, make that the number one thing to replace.

Pelican Parts - European Automotive Parts and Accessories - Porsche • BMW • Mercedes • Volkswagen • Audi • Saab • Volvo • MINI

The red wire in the fuse block is not a jumper, it's a power feed for something under your dash...

I would check that wire out. Fuse c is the aux fan power feed. One side of that fuse goes directly to the battery without any protection. I don't know which side of this fuse is the protected side on a 123 but if you are on the unprotected side with that tap, it could cause you a major problem. It looks like the insulation is pinched in one of your photos.

I suspect it might be part of your aftermarket audio setup to get unswitched power for the head unit.

However in later 123s there is a 2 pin connector under the radio location that was meant for the electronic Becker 612 to provide illumination and memory backup power. The analog 599 just used switched power and ground.

Speedometer cable is going bad or just might need a little lube (a few drops of ATF from the head end works good).

Fuel tank sender can be cleaned, I posted on this thread with how to do it:
http://www.peachparts.com/shopforum/diesel-discussion/327569-w123-out-diesel-1-8-tank.html

Some updates: took her on a ~700 mile round-trip to Burlington and back (which, in hindsight, was pretty ballsy [edit: dumb is more like it], considering my overall uncertainty regarding the condition of the vehicle).

The good news:

• No major fluid leaks
• Proper (~30) MPG for highway driving
• Handled pretty well on the highway. Needs new tires as well as an alignment, but good other than that
• Made it there and back

The bad news

• LEAKS. SOMEWHERE. I'd had some experience driving her in rainy conditions, and things seemed perfectly fine. However, the rain this past weekend was TORRENTIAL, and I discovered a small lake forming in the rear passenger side footwell. The wheel wells and floors are rust-free, so I'm suspecting a rear window seal leak, or a sunroof-related leak.
• Confirmed the presence of gunk in my fuel tank. Made the mistake of parking her nose-down on a sharp incline, and the same rough/no start and power-loss returned. Parked her on the same incline nose-up the next day, and she started and ran like a top.
• Transmission is still a little wonky. Essentially completely unpredictable. Seems to be happiest on long highway stretches, and seems to run smoother cold (??). In city driving, will sometimes behave just fine, but occasionally flares, clunks and shifts hard on a seemingly random basis (generally only once the transmission has warmed up, however). I don't suspect that the transmission is completely gone, since I know that it's capable of shifting perfectly when it feels like it.
• Fuel cap seal seems to work well. When filling up, the car starts to leak diesel fuel out of the tank lines and from another unidentified point under the rear passenger fender. Once the cap goes back on, the leak stops. I'm guessing the pressure created by the seal might be holding the fuel in?
• Rough start after sitting for the evening. For the first start of the day, the engine starts a little rough (as if it was a little short on fuel). Give her some gas, however, and she's fine for the rest of the day.

I f you have a leak of fuel under the rear passenger side of the engine, there is a very good chance the rubber portion of the fuel line is rotted and is leaking, it will also cause air to get sucked in and cause your other issues you are having...

The drain for the door area, also runs under there...so another possibility is the seal is leaking and running down the drain, causing a leak...

Some photos:
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