82 300SD engine diagnosis - PeachParts Mercedes-Benz Forum

anhydrous7 · #1 01-26-2006, 01:27 PM

I recently acquired a second 82 300SD. The disease has got me. The PO allowed this car to overheat due to possibly two reasons. The first is that he ran the car without the radiator overflow cap in place. He had it back on when I looked at the car, so I dont know how long he ran it like this. Secondly he lost the valve cover cap and ran with it off for a period of time. The car overheated, he said the temp gauge was pegged at 120°C (dont know for how long) so he pulled over and had it towed home. To make matters worse, he used a tube sock to cover the opening on the valve cover. As you may guess the sock got injested and was sent throught out the upper valve deck and down through the engine. Since I have had the car, I have dropped the lower oil pan and found the oil pickup screen to be completely clogged with sock material. I have cleaned this and placed fresh oil in the engine. I then started the car up and got it to run. Upon cold start up, the oil pressure pegs out at over three bar, and the engine temp looked good. As the engine warms up, say over a period of 10 to 15 minutes, I saw the engine temp move into the 100°C range. As this happened I slowly lost oil pressure. The oil pressure bottomed out at just around the 1 bar range. It should also be noted that as the car warms up, it loses power. Very slow acceleration, etc.

My question for those of you who have 617 engine is this:

I believe one of my next steps is to do a compression test to see what shape the rings are in. I believe the overtemp condition may have stressed the piston rings, I beleive this may be the reason for the loss of power when the engine becomes warm.

I have not dropped the oil pan a second time to see the condition of the inlet screen. Having said that, what else could be causing the drop in oil pressure as the engine warms up? Is it possible that the lack of oil caused damage that would result in low oil pressure over time and increased temperature.

The car is in pretty good shape otherwise, so I am looking for any advice or suggestions on what to do or look for to get this engine running correctly.

I think replacing the piston rings is in order, and would not mind doing that, but I am worried there are bigger problems with the dropping oil pressure.

Has anyone experienced a similar situation and brought one of these engines back to life after situations like this?

Thanks,

Rob