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Old 10-24-2004, 12:11 AM
Coming back from burnout
Join Date: Jun 1999
Location: in the Pacific Northwest
Posts: 2,274
Has anyone actually rebuilt a 85 300D vacuum pump?

Has anyone out there actually rebuilt a 85 300D vacuum pump?
Yes I did do a SEARCH but found conflicting info. Also just what parts do I order to rebuild one....
My cars vacuum pump is gone, once in awhile it wont shut down and the vacuum locks are sluggish, and I am losing oil..and now I am hearing the stranges sound Larry Bible mentions..
Needless to say the car is down for Repair
I checked Shop Forum for a Reapir Kit and they list a "Valve" kit at $72 and a Rocker Arm kit at $275....Is a 85 300D vauum pump actually rebuildable?
I remeber Steve Brotherton pHD once said parts of it cant be fixed.............

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Old 10-24-2004, 01:51 AM
adamb's Avatar
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Join Date: Jul 2001
Location: Chapel Hill, NC
Posts: 321
I had attempted to rebuild my 85 300D pump and all was going well until I overtightened the 10mm nut holding on the piston. I broke the threaded portion that holds the center of the piston diaphram and decided to just throw down 220 and get a new pump.
I have since rebuilt 2 other pumps with success, and they are working well still. The one-way valves often will go bad perhaps your piston sleeve won't need to be replaced.
Good luck, Adam B
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Old 10-24-2004, 02:24 AM
Ara T.'s Avatar
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Join Date: Sep 2004
Location: Santa Rosa, CA
Posts: 2,075
I'm curious as to how the locks actually work with no vacuum whatsoever... and why the engine only occasionally doesn't stop running?
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Old 10-24-2004, 12:32 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Vacuum is low, not gone all together, or the brake booster wouldn't work either.

That pump vents into the crankcase, so you will only be burning excess oil if it's really blowing hard enough to physically overwhelm the oil separator in the air filter housing.

1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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Old 10-24-2004, 06:00 PM
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Join Date: Sep 2004
Posts: 8,731
One of the more common reasons for vacuum pump failure is not the pump itself, but the check valve. It is located where the vacuum line attaches to the pump. A bad check valve will cause intermittent problems like you describe. The good news is that you can replace the check valve while the pump is still installed on the engine. If I were to rebuild the pump, I would replace the check valve on principle, anyway. (It is not included in the valve kit.) The pump is very rebuildable, unless the housing is cracked, broken or otherwise distressed. You will not know for sure which O/H kit to buy until you remove the pump. Most likely you will need only the valve kit, unless the rocker arm assy is in obvious distress. The rebuild is not difficult, although getting the rocker spring compressed during assembly can be a challenge.

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