I just acquired a 1985 Mercedes 300TD... It's been sitting around a while, neglected.

I noticed the air intake hose (the ribbed hose that's about 3 inches in diameter) is missing and am having a tough time finding the part that mounts onto the chassis between the headlight and the grille (it's simply not there on the car for the intake hose to connect to). I'm going to improvise for now and grab some flexible tubing from the hardware store for now.

I wasn't sure if this lack of fresh air (it only draws air from inside the hood) would cause power issues, since it's really sluggish, especially after slowing down from a high speed. It just feels like it's not even downshifting. I have to come to a halt before it will re-accelerate better. I read somewhere that the ALDA could cause this if the banjo bolt is clogged. Is this true, and if so, how does that operate?

I also am just now putting on new fuel filters and think this will help a bit, but doubt that the car will feel like my powerful 300SD. I think there are bigger issues.

I replaced the main vacuum line from the pump to the brake booster since a nipple to one of the vacuum lines cracked, but I took it off of a 300SD which is slightly longer and has a different check valve (which I have blocked off). Would anything in the vacuum system affect acceleration and/or odd shifting (ie way too late)? I noticed last night that the ignition cut-off wasn't working (which is an obvious vaccuum issue). I have a MityVac kit and will start diagnosing pressure leaks based on other forum posts.

I also changed the fuel hand primer pump (also off of my 300SD) since the screw-on style one wouldn't draw any suction. The new hand pump draws the fuel fine, and the car starts easily, but the power is non-existent - it takes flooring the pedal to notice the car budge AT ALL (starts fine ok). I am replacing the secondary fuel filter (since it seems to have been there for years), but would air leaking into the fuel line (from some connector I messed with or from the wrong sized fuel filter) cause this weak power?

I changed the glow plugs from a known working vehicle.

Another odd thing I noticed is the steering seemed a bit loose. I could rock the steering wheel back and forth about 1.5 inches without any movement from the tires. At 60mph+ it just seems a bit scary. I tried adjusting the hex bolt on the steering box but I think I did it the wrong way (clockwise is wrong I think) because now the car wanders even when I keep the steering wheel still and takes a few seconds before it connects together to be responsive.

I also noticed before any of these changes that you could precisely time that at 40mph the engine would suddenly rev up significantly, as if the turbo kicked in or if it downshifted. I would have to let off the gas pedal for it to shift smoothly without revving/spiking.

I noticed separately that it would almost not give reasonable/full power (not talking major power, just something reasonable for a car) unless I floored it and even then only sometimes. It almost seemed like the throttle wasn't being pulled all the way. Is it worth adjusting the gas pedal linkage? I notice between my 300TD and 300SD that the wagon's pedal needs to be pressed down quite a bit before any movement is noticed at all (it seems to be loose/linkage related), and if so, could I make the pedal press on the throttle more easily?

Another thing that I did was change the motor mounts (since one was pulverized) and notice now that the engine rocks/bounces back and forth significantly more than before, when at idle.... But once I press on the pedal it smooths out. Before it just made a loud clunking noise like an elephant (probably since one side was knocking against the chassis with the broken mount). I was going to do a valve adjustment and change the injector tips, put in a fuel cleaner additive that I was recommended (for diesels, to clean out the soot/etc), and was wondering if there's anything else obvious (besides the idle adjustment bolts on the fuel injector) to check?

Also, on top of the valve cover is a 3-wire plug that creates contact when at full throttle. On the 300SD's I notice that what's there is a vacuum system of some sort. What is this electrical item on my wagon? Is it exhaust/emissions related? One of the wires is stripped and it's not staying on all the time. Is it important, or can I ignore it?

Welcome to the forum!

Everything you mentioned has been discussed in great detail many times here. You have got your work cut out for you from the sounds of it. Tackle one thing at a time. The 85's vacuum system is a little more complicated than the others. But, not too bad (I figured it out).

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AJ

1985 300D (SOLD)

Welcome to the Forum.

Wow, that is quite a list of things to do, looks like you go ahold of one very neglected TD. where are you located? put that in your Signature, might be one of us close by to give you a hand.

Adjust the valves, that really will make a difference if it hasn`t been done in a long time.
Change the fuel filters. the spin on, loosen the 22mm bolt and spin off the filter. the bolt shaft has 2 "O" rings that do the sealing. there is no gasket under the bolt head.
I use ATF, Diesel purge etc... to fill the filter. that way it will be clean coming out of an unopened bottle, vs Diesel in a fuel can. don`t want to dump dirt/water etc... into the filter.

remove the banjo bolt at the rear of the intake manifold. you will see a whitish plastic line attached to it that runs behind the valve cover to a switch over valve next to the brake booster. then the line runs to the ALDA.
pull out the banjo bolt and clean it, usually plugged up with gunk. and clean the line out to the SOV and ALDA. If that is plugged it will kill the performance. use some spray brake cleaner and blow it out with an air hose.

The linkage ends are a ball and socket. they just pop off, and I bet they are dry and rusty from not being lubed. FSM says to use ATF. I just grease them up with a little brush. If they are dry, that will make the linkage stick both ways. make sure the rod behind the injection pump has full travel. have some one push the peddle down and see if it runs up against the stop. also with the engine running, push the stop lever and see it it will kill the engine.

use your Mity vac on the eng shut off valve behind the IP to see it is working.

The brown vac line is the engine shut off.
The green line is to the climate control
The yellow lines is for the vacuum supply tank, and the other one goes to the drivers door. the supply tank is only for the locking the doors,fuel cap, and trunk.

so you can plug off these various systems to isolate the vac leak.
as I remember, there should be 22hg vac from the pump.

The air intake hose shouldn`t really cut down on your power issues, at idle you would be pulling in more warm engine air, but at speed there is enough cool air blowing in. check the junk yards for the part.
the only thing in the vacuum system that could have an effect, is if there is some vac on the fuel shut off valve. If the crank case has too much pressure, it also could affect that valve also. make sure your line from the valve cover to air cleaner is open.

There is a fuel screen in the fuel tank, that being plugged could also cause some of your sluggishness.

Check the Resourced tap at the top of the page. some good DIY pictures and diagrams.

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Today I changed the oil, filter, and oil pan gasket (some dummy didn't put one on there, or it disintegrated), and put new fuel filters on. I also replaced a cracked fuel return line and cleaned the ALDA banjo bolt.

The engine runs smoother and accelerates/decelerates 'ok', but doesnt compare to the oomph of my 1983 300SD (I suspect the previous 300SD owner was the original and had the fluids changed regularly and a valve adjustment, etc... it's just in impeccable condition).

I measured the vacuum (blocking off everything but the brake booster), and it's only pulling 14 Hg. The main vacuum line is on really tight. I suspect maybe the vacuum pump is faulty? I was driving it a few times at high speeds last week and noticed that the brakes (ie the booster) cut out ENTIRELY and so I had to pump the brakes to stop. Scary stuff. It was random and the next minute might have worked. But tonight it was rock hard and responded much more quickly.

I also noticed tonight that the transmission was suddenly shifting very hard (but luckily was downshifting ok). I read that the transmission depends upon a modulator to shift smoothly? And that there's also something on top of the IP next to the ALDA that is vacuum/transmission related?

I have a 300SD parts car that may (or may not) have a functioning vacuum pump - could I tell if it works before installing it? The parts car (while it ran) may have had vacuum issues, but I suspect it was because someone threw out most of the tubes except for the essential parts.

The engine runs much smoother and actually accelerated at a tolerable level, but definitely felt MUCH different than my 83 300SD. The sedan gives me a real strong boost as I gradually press down, but with the wagon I have to push hard in order for it to kick any acceleration in. It's like comparing a jet engine to a train, or a purring kitten to a roaring lion. I'll try lubing the linkage and also the valve adjustment.

One significant thing I noticed is that when cold, the engine literally wobbled back and forth quite a bit (it almost looked like the engine was going to jump out or tear out of the new engine mounts), but after the engine warmed up, it was much smoother and quieter and didn't shake so much. What could be the cause of that?


I also noticed a hard metal tube going to the lower end of the passenger side of the radiator (with an end that fits a wrench, not a hose/clamp), and it's leaking pink fluid. Is that transmission fluid? And does that mean the transmission fluid routes through the radiator?

Minus the obvious vacuum issues (esp. potential brake cut-out and annoying ignition not cutting out) and the (still) scary loose steering, it's almost tolerable, despite feeling really different than my 300SD.

What's your elevation? 14 inches of vacuum may not be bad depending upon how high you are. Yes, the transmission cooler is in the bottom of the radiator.
Have someone step on the accelerator to the floor and check the linkage under the hood to see how it is behaving. Does it move the rack to full open?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The wagon was SUPPOSED to be a project car, but my new 300SD has serious rust under the middle of the driver's side trailing arm, right next to the shock absorber. And either the shocks or the springs are worn out because there's a LOUD creaking noise pretty much over any slight bump or turbulence in the road. Any work will require the trailing arm to be replaced, which is definitely a 2-3 day project. Hence it would be nice to have the wagon functional.

I live in NJ, so that's basically sea level. If 20-25 Hg are supposed to be normal/average, I suspect something isn't right. I'll poke around some of the other posts.

Not an unusual failure even outside the NE.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13