I bought a good condition 84 300SD a few days ago. It's gold color and dark brown inside. The exterior is free from rust (except for a few little spots) and the interior is in good condition. It's a two owner vehicle with only 200K miles. I paid $3000.

I checked over it well before purchase and did notice a few things. On the positive side, the tranny fluid looked clean, the primary fuel filter was changed, and many of the rubber hoses have been changed. The cruise, windows, and sunroof work.

I also noticed an oil leak on the driver side of the engine. I'm thinking that the oil filter gasket is leaking or the oil cooler lines.

Lastly, the engine runs smooth at idle and starts up immediately in the 55 degree weather. However, when I put the car in drive, I get a vibrating feel and slight rattle until giving the car gas. It seems to even out after being warmed up. Could this be the transmission mount?

Here's a picture of the oil leak. I'll also post a link to the sound the car makes when in drive. Any thoughts on the sound?

300SD issue - YouTube

If the Oil Cooler Hoses are in fact leaking do not drive the Car until they are replaced. People have ruined Engines due to Oil Starvation when an Oil Cooler Hose comes apart.

If the Lid on the Oil Filter is leaking do not over tighten and strip it. Remove the Lid (Engine off) and take a look at it. You will see that the Lid is sealed by an O-ring and tightening it will not increase the seal.

Also note that loosening the Oil Cooler Hose at the Oil Cooler often results in stripping the threads on the Aluminum Oil Cooler Nipples. There is repair Nipples for that but it requires cutting the Old Nipple off, drilling and tapping for replacement Fittings.

For details to try to avoid stripping the Oil Cooler Nipples. For details on that and other issues see the Repair Links. Also note that with the exception of the Oil Pressure Sending Unit your Engine Mechanical stuff is the same as the Turbo Diesels in the 82-85 300Ds.
Repair Links
DIY Links by Parts Category - PeachParts Mercedes ShopForum

The best way I have found to locate where a leak is to degrease the whole Engine.
PeachPartsWiki: Do It Yourself Articles - Mercedes Vehicles

I think the easiest way to find an Oil Leak is to degrease the Engine. I had a major Oil leak that I thought was the Rear Main Seal and it turned out to be the Valve Cover Gasket.

Typical Oil Leak Areas.
The Valve Cover Gasket
The bottom of the Turbo Darin Tube
The Rear Main Seal
The Front Crankshaft Seal
The Crankcase Breather Drain (if you have one)
The Engine Block to Oil Filter Housing Gasket
The Oil Cooer Hoses


Rubber things that need to be inspected.
Oil Cooler and Transmission Cooler Hoses.
Upper Control Arm Bushings and Boots
Lower Control Arm Bushings (they have to be extremely bad to actually see a problem)
Engine Mounts (on My Year and Model if the Motor Mounts get squashed enough the Power Steering Belt can cut through one of the Oil Cooler Hoses)
Transmission Mount
2Rubber Flex Discs on the Drive Shaft (When a Flex Disc comes apart it tears stuff up and People have lost the whole tail end if the Transmission. The Front one is hard to see so you may need to support the Transmission and remove the Plate Under the Back to see the Flex Disc.)
The Drive Shaft Support
The 4 Boots that are on the CV Axle
The Differential Mount

While under the Car look for rusted through spots with special attention to the Rear Trailing arms.

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84 300D, 82 Volvo 244Gl Diesel

The Idle shaking issue can be a bunch of things by themselves or to gether.

The idle speed should be with in 750-800 rpms; but, some Engines can differ slightly. If the rpms are to low the Engine is going to shake. Ther Should be an under-the-Hood Sticker that has what your Idle Speed should be.

There is also an Rack Damper/Governor Idle Pin adjustment that may or may not help. You should back out the Rack Damper/Governor Idle Pin when you adjust your Idles Speed and turn in the Rack Damper/Governor Idle Pin to take away some shaking. If you turn in the Rack Damper/Governor Idle Pin and it it starts to have lot of effect on your normal Idle speed the Rack Damper/Governor Idle Pin needs to be repalced with a Gold Colored one and/or you have som other issue/s.

On mine Doing a Valve Adjustment and rebuilding the Injectors took away the bulk of the of the Shaking.
Changing the Motor and Transmission Mounts helped somemore.
Note that an Air Leak on the Suction side of the Fuel Supply/Lift Pump can cause shaking and besides the Hoses if you have a Hand Primer that has a Shiny Aluminum Body old ones become a source of Air Leaks.

After all the above stuff was done the new Rack Damper/Governor Idle Pin was able it take out a tiny bit more of the shaking.

Note that the Engine has one or more Shock absorbers. The Mounts on those are expansive but can also go bad. There is a way to replace the rubber inside with another rubbery type Uretshene (spelling?)

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84 300D, 82 Volvo 244Gl Diesel

Do you know if this vehicle had standard rubber transmission cooler lines from the factory? It has the newer style with the spring-style housing. I'm guessing they were replaced at one time.

On My 300D the Original Hoses has no Springs. The Replacements have Springs. I don't think My Repacement Hoses are made by Mercedes as I did not get them at a Dealer.
Maybe someone can give an aproximate Year when they started useing Springs on the Transmission Cooler Hoses.

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84 300D, 82 Volvo 244Gl Diesel

How about some pics of the SD.

Mais bien sur !

There looks to be wetness near the back of the engine on the driver and passenger side. The valve cover gasket may be leaking slightly, but that wouldn't cause the amount of oil that I am finding on the ground overnight. The oil that I took out was thinner than the 15w40 that I put back in, so I'm hoping that helps some as well.

I fixed another problem too. My windshield wiper fluid was not spraying. I assumed it was the motor. Turns out that the battery was pinching the line. I cable tied it to prevent it from getting pinched.

Concerning the Valve Cover Gasket. A lot of People with leaking Valve Cover Gaskets try to tighten it more resulting in a stripped Nut or Stud.
If using the correct torque does not stop the leak then you need a new Valve Cover Gasket or to use sealant on the old Valve Cover Gasket (a lot of People say no ot sealant).

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84 300D, 82 Volvo 244Gl Diesel

I wanted to report back that the oil leak is a lot less severe than I thought. After changing the oil, I only found two minor spots on the cardboard this morning. My guess is that the oil that was in the vehicle was a thinner weight.

That being said, I still need to find the cause for the leak and also replace the cooler lines.

if they need replacing.I have 350,000 miles on my 83,and same cooler lines.Your car is in awesome shape.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

Could someone provide the part number for the breather hose? On the 300SD, it's a two piece setup. The plastic piece that connects directly to the valve cover, then there is an L-shaped hose that connects to that and into an elbow on the intake. I need the L-shaped hose that goes into the elbow.

Also, that little trim piece around the ignition (looks like there is a rubber neck too), does it just pop out? Looks like someone replaced mine with a piece of black wood and some screws.

What are the best windshield wipers for this car? The standard metal ones or the one piece units?

Lastly, is it safe to spray the bottom of my engine with soapy water from one of those DIY car washes? I'm hoping that will remove most of the oil and grease so I can see where the leak is coming from.

FWIW, I need synthetic oil to start in the relatively mild TN winters. I don't need to plug in with synthetic. Without it, I get stuck and end up driving another vehicle.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

I adjusted my valves and replaced the cover gasket yesterday. I am still getting a slight leak. There is a lot of wet oil in the black area circled. Maybe oil filter housing gasket?

There also looks to be some oil leaking behind the starter on the passenger side.

There is gunk on the front of the engine, but I don't see any wet oil.

I still need to degrease. Will purple power and a car wash pressure hose work?

The vibration sounds like it is resonating through the chassis, so my estimation would be a failed mount somewhere. The trans mount would be a good place to check. It will be obviously deteriorated to cause that much noise in the cabin.

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1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge