The Mercedes 126 is capable of astronomical mileages if properly maintained. To maximize the life of your vehicle and postpone costly repairs, it is essential to frequently make oil and filter changes with the proper lubricant. Although similar to the procedure used for most cars, there are some more subtle points that owners should remember. Let's look at the procedure for V-8 engines:
- Not more than 3000 miles after the last change (and ideally before), take the car for a nice run to get good and hot oil. The hot oil flows quickly from the drain plug, carrying suspended sediment. Drive the car on ramps.
- To ensure proper drain plug flow and avoid vacuum formation, remove the oil filter first. Place your drain pan under the filter housing to catch the drops. (There will not be much, it's a much sleeker design than hard-to-reach screw filters on most modern cars.) Remove the hose from the sprinkler. air inlet facilitates access. I also like to loosen the oil filler cap and remove the dipstick.
- With your drip tray ready, remove the oil sump cap with a 13 mm socket. Cover your hand with a store cloth to protect yourself from hot oil as the plug is removed from the last two wires. Allow the oil to run off as long as possible. The night is ideal, but 2-3 hours are usually enough. No, it's not Jiffy-Lube!
- While the oil is dripping, replace the oil filter. Filtration is crucial and filter modification is part of the rationale for frequent oil changes. Even if you use high quality synthetic oils that could theoretically last over 3,000 miles, you do not want to leave the same filter too long. The best filters are made by Hengst, with Mann and Mahle behind them. Use the new O-ring for the filter cover and the new steel washer for the long retaining bolt, tightening securely with a 3/8 drive.
- When the pan has stopped flowing, replace the crush ring drain plug provided in the filter kit. (There is usually a bigger copper ring in these kits that you can ignore like for the 107 SL cars.) Make sure the plug's wires are clean; replace the plug if it has burrs and does not rotate freely.
- The oil capacity is 8.5 quarts. At this point, add 8.0 quarters. The owner's manual contains a viscosity guide for different climates. Choosing the right oil brand has become more difficult in recent years; I discuss these issues in another article.
- With 8 liters of oil in the sump, and the filler cap at least partially tight, we are almost ready to start the engine and push back the ramps. But there is a vital step that we must take first. To protect the long timing chain, we need to create some oil pressure in the chain tensioner before turning on the engine. Disable the ignition by unplugging the green wire (TD) from the ignition control unit. (You can simply pull the spark plug coil wire, but this will send sparks to the ground.This method prevents the formation of sparks.) Then, run the engine for 20-30 seconds to increase the oil pressure. Once done, reconnect the TD cable and start the engine
- With the car on the ramps and level, add the remaining half-quarter. It will take some time for all the oil to flow into the sump. Whatever reading you have then on your gauge represents the full capacity. The gauges may be inaccurate. you can not always trust the min. and max. markings. Whatever you do, do not overload. Too much oil in the crankcase will emphasize the crank joints. When the rear main seal fails, you will have drops; when the front crank seal fails, you will have more than one drip; neither one nor the other is particularly easy to repair.
Check for leaks in the areas you have repaired and continue to monitor your oil level every week. Opinions vary, but I believe that one must check the cold level after the car has passed the night. I measure the old oil collected in the drain pan to see exactly how much the engine is using. Older cars tend to have a variety of external oil leaks, but will also have internal leaks beyond valve stem seals and valve guides. Monitoring consumption will help you decide when these major repairs can no longer be avoided.