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Old 02-26-2004, 05:13 AM
skleutz skleutz is offline
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Join Date: Feb 2004
Location: Redondo Beach, CA
Posts: 15
Exclamation 87 300D loss of oil pressure

OM603 owners take note,

Purchased 300D about two years ago with great enthusiam since the car was the smoothest running diesel I've owned. During the test drive I noticed excellent oil pressure, better than I had ever seen. After purchase, I became aware that the oil pressure gauge would go to 3 bar with the just the key turned on, engine not running. Purchased new oil pressure sender and installed. Oil pressure indication was now where it should be at idle and rose to max pressure accordling with higher rpm. However, at idle the needle would jump around and fluctuate erradically. A couple of weeks later the gauge started doing the same thing, going to 3 bar with the key on, engine off. I assumed another bad sender and knowing I had good oil pressure, ignored the gauge problem.
On Thanksgiving day, my son and I were cruising around 70 showing about 3000 rpm, when there was loud knock from the engine and immediate loss of power! After getting towed home, I drained oil with chunks of metal and ball bearings coming out. Removed oil pan reservior and found oil pump chain and sprocket jammed up between the crankshaft and timing chain cover. Found oil pump chain tensioner in half with broken piece still in oil pan. Failure of the oil pump chain tensioner ($4 part) determined to be the culprit. Without tensioner, chain was sloppy causing the oil pump to pump erradic oil pressure, hence the erradic indication. The sloppy chain eventually caused the sprocket bolt to shear, with the resulting catastrophic failure. I assume the sender failed the second time from being pulsated beyond its normal range. I failed to sense the problem (I had oil pressure, who cared about the indication, these diesels last for ever, right), now I have an engine upside down on the engine stand getting ready for rebuild. Cam appears OK but the crank rod journals are groved and will hopefully be suitable for regrind. I will update condition of components and progress of rebuild with associated costs. Moral of the story:Oil pressure indication must be smooth from idle to max pressure. Donot ignore oil pressure indication problems.
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