Mercedes 300D

[Dieselnut59]

I just got a 1987 Mercedes 300D with 240,000 miles. It is a good, straight car, well maintained but needs some TLC. It has been sitting for almost 5 years. Will need all new tires, battery, all fluids changed and a good "going over". Is there anything in particular I should be looking for?

I jumped it off and after waiting for the glow plugs, it cranked right up and runs very smooth.

The serpentine belt is taken off because the power steering pump went out and is removed. The engine stop solenoid is not working (have to kill it with the stop handle on the injection pump). Paint is faded, plastic around headlights is dry rotted and I believe it may need brakes. Interior is nearly perfect, except for a few small cracks in the dash. This is a car worth spending a little money on and fixing up right.

Any pointers of what to pay special attention to?

By the way, it is the inline 6, turbocharged 3 liter engine and automatic transmission.

 

[Skydiver]

While I am not sure about your 87 6 cly diesel there were major problems with the 350 sdl heads. I hope yours is the good 6 cylinder.

Check for compression leaking from the radiator cap after it is up to temp.



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Does the vacuum pump run off the serp. belt? That would explain the "no shut down".



I wish I knew more.

 

[TPasquali]

I think the engine has 5 cylinders not 6

 

[Dieselnut59]

I think the engine has 5 cylinders not 6

Definitely 6. This 1987 300D is just like my mother's former car which was a 1987 300SDL, only a little shorter. It is a inline 6, 3 liter, turbocharged engine. Must be a good engine, as it cranks and runs well after sitting almost 5 years!

I have all the filters on order, will change the transmission fluid, rear end lube, coolant and oil.

My question is more about the rest of the car than the engine. It has 248,000 ish miles on it. It has been well serviced, always by the dealer and the guy I got it from is the only owner. What things do I need to be aware of or look out for?

Thanks for the link Skydiver. It appears that forum is set up similar to this one. The Jeep Liberty one was sure helpful when I had questions about my Jeep.

 

[Royk]

If you lose vacuuum, the auto doorlocks won't operate.

 

[Skydiver]

These Mercedes are built well. Get a manual and you will find that they are not hard to work on, just a different breed.

The heater control valves were a problem as well as the a/c fan motor on my 81 300D. I took my fan motor apart, found some brushes,filed them down and made them fit. Saved me $183.

I had one rear wheel bearing go bad. That requires a special too to remove.

Speedometers are known for failing. As well as power antennas.

Always use touring tires. I once installed a set of Michelin xh high milage tires and the car handled like a boat. Wrong tires.

When changing the oil I would disconnect the oil cooler line right at the cooler and that would allow another 0. 8 quarts to drain.

These engines will not crank if one glow plug fails, below 50 degrees.

Check the tie rod ends, rear end fluid,turbo hoses.

After you get it all put back together, pull the oil cap while it is warm and check for blowby. My first 220d had major blowby but it cranked and ran perfect. Just used 1 qt every 800 miles. These engines will use a little oil and thats normal.

 

[WDixon27]

actually they have a electric pump to back up the locks if it makes a difference

If you lose vacuuum, the auto doorlocks won't operate.

 

[MOates]

I just got a 1987 Mercedes 300D with 240,000 miles. It is a good, straight car, well maintained but needs some TLC. It has been sitting for almost 5 years. Will need all new tires, battery, all fluids changed and a good "going over". Is there anything in particular I should be looking for?

I jumped it off and after waiting for the glow plugs, it cranked right up and runs very smooth.

The serpentine belt is taken off because the power steering pump went out and is removed. The engine stop solenoid is not working (have to kill it with the stop handle on the injection pump). Paint is faded, plastic around headlights is dry rotted and I believe it may need brakes. Interior is nearly perfect, except for a few small cracks in the dash. This is a car worth spending a little money on and fixing up right.

Any pointers of what to pay special attention to?

By the way, it is the inline 6, turbocharged 3 liter engine and automatic transmission.

Welcome to the club! Got an '87 300D myself, 143K miles, and a '05 Jeep Liberty Sport CRD as well.



If I remember correctly, Repair Manuals, Ford, Mercedes Motorcycle Honda - Manuals Unlimited - Automotive Repair Manuals and a couple other websites, you can download or order the CD with the entire W124 Class Factory Sevice Library. Worth it's weight in gold, actually shows and tells you how to troubleshoot and fix the car.



Also The Number One Source for You and Your Older Mercedes, We sell Solutions, not just parts! | MercedesSource.com has a lot of DIY manuals and kits for the more common problems with older MB diesels.



Door and trunk locking system is a separate vacuum system with it's own electric pump under the rear seat. Main vacuum pump is on the front of the engine and driven off the engine timing chain. Might want to ask the PO if the main vacuum pump was ever changed out - these do have a tendency to fail with age, and if they grenade the shrapnel goes straight into the timing chain. If it still has the original pump with 240K miles on it, it would be a definite CYA move to go ahead and replace it. Unfortunately, unlike the '85 and earlier models, this style vacuum pump isn't rebuildable.



Engine stop is actually a vacuum actuator, with vacuum routed thru the ignition switch assembly and sourced from a small vacuum line that taps off at the check valve in the large black vacuum hose going to the brake vacuum booster. Could just be that the vacuum actuator itself is bad, or isn't getting vacuum for some reason. A good Mityvac hand vacuum tester and vacuum gauge from the local auto parts store is a definite must for troubleshooting one of these beasts.



With the power steering pump and belt already out of the way, might want to check out the idler pulley, and the belt tensioner with it's mini-shock absorber - another 100K plus wear item, bearings in the pulley and tensioner and the shock absorber itself wear out over time.



Major bugaboo with the '87's and early 603 engines is a cracked head - the early # 14 heads were machined a little thin in some areas, and if allowed to overheat can develop cracks. OTOH, if treated properly and the cooling system has been maintained, no reason to worry - plenty of '87's out there, including mine, still running with the original head. Just make sure it has the correct antifreeze in it - HOAT type - Zerex G 05, Mopar 5/100, Motorcraft Premium Gold, or from the MB dealer - and give it a good cooldown after a hard run, at least a half-minute recommended.



Ways to check for a cracked head - any oil or black sludge floating in the coolant tank? Does the upper radiator hose get hard immediately after starting the engine with the coolant system still cold? When you start the engine and pull the cap off the coolant tank can you see bubbles floating to the top? Mysterious loss of coolant level with no evident cooling system leaks? If the answer to all of these is "no", I'd be willing to bet you're golden and have a good engine.



Been sitting for 5 years, ie, never seen ULSD fuel in it - get the fuel tank drained flushed and cleaned out, pull the supply strainer out of the bottom (1 13/16" socket) and check it out - you can pull the fuel tank itself out easily as it's mounted between the trunk and rear seat. Replace all the rubber fuel lines - 5/16" ID for the main lines, 1/4" ID for the two small clear lines on the IP. Be ready for fuel leaks from around the delivery valves on top of the IP - 0-ring seals on these, easy enough to replace with the special whammerdyne splined socket.



Brakes and rotors are a fairly easy DIY job on this car. And if you do the brakes, might as well check out the front wheel hubs and bearings as well. Removeable hubs with roller bearings that do need to be adjusted and repacked with grease or replaced over time. My front hubs had nearly a 1/8" slop in them - once I repacked and adjusted the bearings, drove like a whole different car.



If you pull the wheels off for any reason, make sure those lug bolts get torqued to 80 ft lbs. NO EXCEPTIONS!!!!! The brake rotors are held in position with one small 5 mm set screw - the lug bolts not only hold the wheel on, they secure the brake rotors as well. And recheck them 500 miles down the road.



Other than the stock 195/65 tires, 205/70's will fit with no problems as well. Just put this size on mine a week ago - feels like this is the size tire the car was made for. Big improvement in ride and handling, engine can handle it no problem, and the car just looks better with larger tires under it. But, this will throw the speedo and odometer off by 5% low - speedo will read 1 mph low for every 20 mph of speed. But the advantage is I can run 65 by the speedo on the interstate, still be doing essentially 70 mph, and the engine is turning nearly 300 rpm slower (2500 rpm vs 2800 rpm with stock tires).



Basic specs - 2. 65 rear end, 4 speed non-lockup slushbox 1:1 in 4th, redline 5100 rpm, 145 HP at 4900, 200 ft lbs at 2400.



Been going over mine the last two years, an item at a time, and it's to the point it's knocking down 35 mpg rain or shine commuting to work.



Another couple forums - MercedesShop - Mercedes Benz Parts and Technical Information and www.schumanautomotiveforums.com .

 

[Dieselnut59]

WOW! Thanks for all the great info MOates!

I always loved mama's 300SDL and so did she, but she "acquired" it in the divorce with my father. She mainly got rid of the car to get rid of the memories and to buy a new one (no diesel available at the time). This 300D is almost exactly like hers, but one size smaller car. The interior looks exactly the same, except there is nowhere near as much leg room, especially in the back seat.

The beauty of this deal: My neighbor GAVE me this car and I paid him back the 50 dollars for hauling it on a rollback (had flat tires). I jumped it off and it cranked right up!

It still has the "trap oxidizer" device between the exhaust manifold and turbo. Not sure if yours still has this or not, but I speak from experience on mama's that they WILL come apart and lodge in the turbo inlet. I "hallowed out" mama's, then Mercedes had a recall. The notice is in the dash of my neighbor's car, but he never had it done obviously. The recall includes installing a pipe in place of the current "trap oxidizer" and installing a catalytic converter (much like our Libertys) on the downpipe after the turbo. I will just "hallow out" mine, as I did on mama's.

I replaced her belt tensioner/shock absorber thing one time because it had started rattling. I will also check out that vacuum pump. I have found with vacuum pumps, you can prolong their life, possibly "indefinitely" by putting air tool oil into the hose occasionally. It is basicly a air "compressor" where the inlet is being utilized instead of the outlet.

I can't wait to get this thing going!

Interesting that you have the performance specs of the engine too. What a gutless wonder by the numbers, but it is plenty to make these cars move and do it efficiently. It is a shame it does not have a lock-up torque converter...

 

[MOates]

The performance specs are factory WITH the trap ox - once you get rid of it, those numbers are "noticeably increased" from what I've been told. Certainly feels like it on mine, it had the recall done on it long before I acquired it.



From what I've heard, MB will STILL honor the recall on the trap ox and do it free of charge.



But if you let them do the recall, they install a conventional cat in the exhaust system underneath. From what I've heard of people that simply hollowed out the original trap ox instead of doing the recall, they were able to hit 38 mpg highway with these beasts!



Another performance tidbit - the '87 300D was rated for 120 mph from the factory, fastest diesel production car in the world when it was built.



Factory headlight bulbs on mine flat-out SUCKED - couldn't see 40 feet down the road. A set of Silverstar Ultras and getting the headlights aimed gave it a set of high beams that rival those searchlights on the Jeep.



Shocks and struts are probably long gone as well. Separate struts and springs on the front. Easy DIY job front and rear, and if you follow the procedure in the FSM you wont't throw off the front alignment either.



Might want to get one of those cheap voltmeters that plug into the cigarette lighter, to see what the alternator is putting out. Brushes on the regulator do wear out, and besides that the factory jobs were set to only put out 14 volts even - which drops like a rock when you pile the load on that 70 amp alternator. Easy to replace, aftermarket regulators are set to 14. 6 which keeps the battery happy and everything else working much better.



A 110 amp or 150 amp alternator from a late 90's 420 is a direct bolt in, have to swap the pulleys and replace the cables running from the alternator to the terminal block. Haven't done this on mine yet, but if you search the forums I mentioned you can find the how-to well documented.



Fuel primer pump - minimum spec is 4 1/2 psi at idle measured downstream of the cartridge filter before the IP. Cheapest place I've seen for a replacement had them for $130.



As far as the EGR and Air Recirc Valve - some neighborhood kids sneaked out one night and jammed metal BB's in the vacuum lines to both, such that they don't operate any more. For some reason , just haven't gotten around to taking them out.

 

[WDixon27]

my 300sdl was a slug till they did the recall and after that in the rain it would break em loose when the turbo spooled up, bin the kitty for sure, if i had kept that car i would of eventially killed off the trap they put under the car inplace of the factory unit but it was time to shake it before something major crapped, i hate working on mercedes cars, the engines are ok though

 

[Royk]

What exactly is this recall? I was driving my in-laws 84(?) 300D yesterday and it was wierd. Is it normal for it not to move at idle when shifted into drive, and to have to really start depressing the pedal pretty far before the car begins to move? I thought the emergency brake was applied! The thing is a total dog until turbo spools up, then it wants to go bigtime and I have to let up off the throttle. My in-laws bought it used and probably never received any recall notices.



Roy

 

[WDixon27]

it was only on the cars with a trap oxidizer between the head and turbo, 87 300sdl's had them and california cars had them, it's a huge cylinder by the turbo, i've only seen one of the 85 and older cars with the california crap on it in 12 years of salvaging mercedes but we are a good way away from the land of rainbows and fruits

What exactly is this recall? I was driving my in-laws 84(?) 300D yesterday and it was wierd. Is it normal for it not to move at idle when shifted into drive, and to have to really start depressing the pedal pretty far before the car begins to move? I thought the emergency brake was applied! The thing is a total dog until turbo spools up, then it wants to go bigtime and I have to let up off the throttle. My in-laws bought it used and probably never received any recall notices.



Roy

 

[MOates]

Hey Dieselnut, take a look at my post in the "mercedes benz diesel" thread over in the "Other Vehicles" section. Been doing some tweaks and trying out some dfferent ideas on the old girl - this past week she knocked down 180 miles by the time I hit 3/4 tank, in other words pushing close to 45 MPG!!! Don't know if it was just one thing, or a combo of what I did, but these '87's ARE capable of some serious fuel mileage.