1980 300SD vacuum problem (Full Version)

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1980 300SD vacuum problem

  

jim x 3 -> 1980 300SD vacuum problem (6/13/2008 9:49:05 PM)

I have a 1980 300SD with about 290K miles. I change oil and filters and do little else to the car. Recently the engine started making a new ticking noise. Before I identified the source, the ticking disappeared. Simultaneously, I lost all vacuum. I looked at the vacuum pump on the front of the engine and see that it has self-destructed. The case is cracked, with pieces missing. What is involved in replacing this pump? Is there another underlying problem that has caused the pump failure? Thanks.

  
ForcedInduction -> RE: 1980 300SD vacuum problem (6/14/2008 3:36:53 AM)

First of all, DO NOT START THE ENGINE AGAIN until you have removed the vacuum pump and are 110% sure you have retrieved every single piece that came off the pump. Failure to do so means a high risk of serious engine damage. If you can''t find all the parts you must remove the lower oil pan to try and find the missing pieces.

Its an easy R&R job, http://www.pauldrayton.com/uploadfiles/merc/Service/W123/w123CD2/Program/Chassis/43-618.pdf
Your main problem is that something inside has catastrophically failed which means that pump parts can puke into the timing chain area and cause major damage.
We can''t really know the failure cause until you have removed and inspected it. From your description the rocker arm or bearings have failed or the piston seized.

Good luck, I''m hoping you caught it soon enough.

jim x 3 -> RE: 1980 300SD vacuum problem (6/15/2008 10:49:22 PM)

I am having trouble posting and replying

ForcedInduction -> RE: 1980 300SD vacuum problem (6/16/2008 11:50:37 AM)

Me too, its something to do with the forum software. Keep trying.

jim x 3 -> RE: 1980 300SD vacuum problem (6/16/2008 3:57:17 PM)

i can''t reply except with short additions via edit

FI, thanks for the reply - good advice.

After removal, it''s apparent that the 2 8mm 8.8 grade bolts holding the cam plate to the timing chain sprocket backed out. One of these then slammed into the guts of the pump.  The head was battered and bent at a 30 degree angle.  The piston connecting rod, roller assembly, and half of the rocker arm were gone.  The large spring was distorted and pushing directly against the cam plate, galling it.  The aft (lower) spring retainer was fused to the spring.  It looks like the offending bolt head swept the pump parts around to the 7 o''clock position, where they were punched through the case of the pump. Some (but not all) debris was found on and around the tach sensor and AC compressor.  I figure I’ve left the rest on the road.  Timing chain sprocket and damper are in good shape.  I have not dropped the pan.  There was no evidence that any debris entered the timing chain cavity.  Top end of the pump – valves and piston (except for conn rod) are in good shape.  I have run the engine with no further trouble.
 
I need a new pump and probably a new cam plate.  And a couple of new 8mm bolts!

EOM - finally.  Jim  

  

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