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Old 04-21-2002, 12:07 PM
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Deltacom Deltacom is offline
Join Date: Dec 2001
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A word of caution about V8 oil changes

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A word of caution about V8 oil changes

On any Mercedes with the 116/117 engine (mainly of the 380, 450, 560 line), there is a procedure you must do after changing the oil. Draining the oil also drains the oil out of the timing chain tensioner. If the engine is started after an oil change, the tensioner takes a few seconds to build up oil pressure again. in these crucial few seconds, the timing chain is flopping around loosely. On a higher mileage, or even not so high mileage engine, this slapping of the chain has a tendency to break the timing chain guide rails, sending plastic shards into the oil pan, and possibly bending the valves by letting the piston hit the valves. I have seen so many inexperienced, or just uninformed, people make this mistake. When this happens, the heads and oil pan must be pulled off. The valves have to be inspected for damage, the timing chain has to be replaced, along with the guide rails obviously. And all the debris has to be cleaned out of the oil pan. The way to prevent this is simple. Once you change the filter and get the new oil into the car, unplug the ignition coil, which is on the wheel well just behind the left headlight. Then crank the engine until the oil pressure gauge on the dash starts to move, which usually takes a good 20 seconds. Plug the coil back in, and fire it right up! If you own one of these cars, I wouldn't recommend taking it to a Jiffy-Lube type place just for this reason.

With the coil unplugged, the only force on the chain is from the starter motor turning at a few hundred RPM's. This is opposed to the force of a 200-something horsepower V8 on a 1200 rpm fast idle. The difference is dramatic. You're right, the chain is still loose, but it doesn't do NEARLY as much harm as starting the motor would.
Deltacom ~ Absit Iniuria Verbis ~
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