Order of repairs for 1976 300D

I have a 76 300D. I plan to adjust values, purge engine, replace fuel filters as well as fuel tank filter. In what order should this be done? I would also like to experiment with running bio-diesel. I have heard this cleans out old sludge in the fuel tank. Should I run a few gallons through before I change filters?

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Diesel Engine Specific Aid

Chassis Model Number

W115

doctors #1 rule: do no harm

This might be more info than you are looking for, but I recently purchased a 1978 300D with 088,000 miles on it for conversion to a single tank veg oil ride. Looking back, I wish I had spent a couple tank fulls simply driving the thing first. If the car is otherwise road safe, you might consider this. Mainly just to evaluate the performance of the car as to appreciate what happens once you start working away. Also, to minimize confusion and mis-diagnosing any problems which do occur. If you are new to diesels, you will have to forget a lot of assumptions you may have from gasoline engines. If you are new to Mercedes-Benz, you may have to forget a lot of assumptions you have from other car manufacturers. With that in mind - first things first, like - how many miles are on the car? Depending on the age, you can presume some things are less likely, or more, in evaluating the cars performance. All that aside, here are some good ways to simply evaluate the condition of the car: 1) how quickly does it fire up when cold? Without waiting for the glow plugs to warm up, shouldn't take more than 8 to 10 seconds to turn over (not talking Winter cold starts, that's another issue) Quick starting = good compression 2) how quickly do you get from zero to sixty? Takes my 300D about 20 seconds, turbos should take around 15 seconds. 3) how quickly does the engine quit after you turn off the key? sputtering indicates poor vacuum pressure, a quick, smart stop is what you want. 4) Is there a lot of smoke at startup after sitting over night? Valve stem seals might need replacing 5) What color is the exhaust? Blue, white, black? How much smoke? 6) What temperature does the car usually run at? Should be around 80C/175F. Also, how long does it take to get up to temperature (around town vs. highway)? 7) Once the engine is warmed up, does the engine oil pressure indicator peg up to 45 (or 3 bar) quickly from an idle? At a red light for example. Should peg out pretty quickly once the light turns green and you press the accelerator. 8) how does the idle sound? When cold and once it has warmed up? Unlike gas engines, where you can tell A LOT about the engine health from a simple compression test, I have found that practical evaluations of these older Benz diesels will tell you most all you need to know. This is not to say that you shouldn't test the compression on a diesel, but unlike a gas engine, it wouldn't be my first place to start - also a leak down test is much more informative. Unless you have the original maintenance records, then your first job is to get the car back on it's regular scheduled program of maintenance and service: 1) Change the engine oil and engine oil filter - check the level every week to find out how quickly it burns oil. It will. It is better to chase the minimum mark than to top it off to max. 2) Replace the brake fluid - especially if it is dark brown (I would recommend if the car has a lot of miles that you take it to an M-B mechanic to have the brake lines, pads, rotors and such checked professionally. This is one area of service where I don't mind paying a pro!) 3) Drain the transmission, torque converter and tranny cooler lines, replace the transmission filter. 4) Drain the engine coolant. Is it green? Shouldn't be - get the proper coolant, the orange stuff. While citrus flushing or draining, take the thermostat, a regular thermometer and stick them in a pot of boiling water. If the thermostat doesn't open when it should, replace it. Or just replace it. But test the new one the same way before throwing it in the engine to make sure it works! 5) Replace the air filter 6) Replace the fuel main filter and pre-filter (some people I know fill the new main filter with ATF prior to installing - it acts as a conditioner to the fuel pump and is usually more readily available than diesel fuel - mostly just means less bleeding out air with the hand pump) 7) Replace the power steering filter and renew the power steering fluid. Sacrifice a turkey baster to get the fluid out... 8) Check the tire pressure 9) Consider performing a diesel purge with Lubro-Moly (Also called Liqui-Moly) - I assume that's what you meant by purge the engine? - to clean out the fuel injection pump and injector nozzles. 10) Adjust the valve clearances. Specs should be printed on a card at the front of the engine compartment. 11) Lubricate the throttle linkage - ATF and a Qtip works fine 12) Check the belts for tightness and wear, and check the rubber coolant hoses for wear. 13) Italian tune up - drive an hour or so around 70mph. Safely. 14) Wash 'n' wax so your ride looks swank! Now put some miles on her - . After your first tank full, check all the fluid levels and tire pressure. See any gunk in the pre-filter? If it is your first time adjusting valve clearances, re-check them after the first tank - just to make sure everything stayed put. NOW it's a great time too consider your first tank full of bio-diesel. There is a lot of talk about biodiesel eating away the old rubber fuel lines. It won't happen right away. Personally, I like clear fuel lines, but that's me... If they are the original fuel lines, it's time to replace them anyways. Take a look at the braided injector return lines and see if they are weeping fluids. Good time to replace those as well. Biodiesel is a solvent, so yes, it will clean out any sludge in your tank. Diesel fuel tanks are susceptible to having algae (actually a fungus) growing in them. Consider using a Biocide, or biostat to kill it - I had a bunch in my tank which caused the tank to "run out" with 5 gallons left in it! You can find the stuff pretty easily at West Marine or other boating stores if not at your local Autozone. As you fuel your ride with biodiesel, keep an eye on the pre-filter, but plan to replace both fuel filters after your first tankfull or two of biodiesel. I would wait on replacing the tank fuel filter 'til after you've gone through a tankfull or two of biodiesel. At this time, you may also want to remove and clean up - possibly repair - the fuel reservoir and tank level send (accessible under the first aid kit). When you switch to biodiesel, you might notice the level indicator jumping around. For both of these, it's best to drain the tank. This is also a great time to swap out fuel lines - send, return, vent and the various fuel lines at the pump and filter in the engine compartment. If you are gonna go all the way with the tank screen and fuel send, you will also want to make sure the fuel's hand primer pump is working properly. If it leaks fluid when you pump, it needs to be replaced. You'll need it working, though, even if you are just replacing the fuel lines. 'Course, having said all that, you can just go ahead and pour in some biodiesel - providing it is ASTM. I would be a little more cautious with the home brew stuff. Either way, get to all the normal maintenance stuff soon and you'll have a sweet ride! Best, -Patrick Kennedy