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Rebuilding the Vacuum Pump on the 617 Engine

Introduction

The technical material for this FAQ (Frequently Asked Question) was provided by Raymond Ryel of Portland, Oregonwas edited by Richard Easley of Baylor University.

Please note that this procedure is specifically for the piston vacuum pump on the 1981-85 300SD (617.952 diesel engine) but is similar for others in the MB line . . .

[Note: If you have done the diaphragm type pump then please add to this or write up the process and share it with us!]

Using the categories of mechanical ability from the Mercedes-Benz Discussion List, you need to be at the level of "Medium Do-It-Yourselfer" at minimum, to rebuild the pump. If you are below that level, you may want to provide these instructions for someone who is at the medium level or beyond.

Parts needed:

1. Pump rebuild kit # 000 586 17 23

2. Gasket (pump to block) If you know the part number for this gasket, please send it to us for adding in this document.

Together, the above items cost about $50.

Tools needed:

Normal hand tools, wrenches and metric socket set with Allen sockets of 5 & 6mm.

Special assembly plate or build your own from a scrap of 10 inch square wood: see picture of mine below: note that the bolt positions can be determined accurately from the gasket or (after the pump is removed) from the holes in the pump.

Dental pick or automotive pick set used to remove the piston seal ring.

Rebuilding the vacuum pump

I removed the radiator but it is not required to remove the vacuum pump. If left in, it should be covered with cardboard to protect the surface fins from damage. The upper radiator hose and fan will need to be removed along with the shroud. The four 10mm bolts securing the fan are a pain to remove but straight forward as are the two spring clips holding the shroud to the radiator. Remember to leave the final fan bolt in place so that the pulley doesn't slip off. Your choice on beginning with the belt or the vacuum line; keep life simple.

Remove the vacuum line; lower connection on the pump and upper to the brake booster line. This picture shows removal of the vacuum line bracket bolt at the fuel filter.

Remove the power steering belt

Then, remove the 6 5mm Allen bolts that secure the pump to the block;.

Clean the old gasket off and prep surface for new gasket.

Remove the 7 slotted screws from the top cover, then the cover, gasket, 3 check valves and their gaskets;

Now you have something of a choice: the book says remove the self-locking nut from piston rod and remove disc (piston): but those springs are pretty strong so I suggest mounting the pump on the board thereby relieving the spring pressure. Now remove the 10mm nut and washer. The washer is reused; the nut is replaced, and is included in the kit. The book said I could remove the piston with a special pair of pliers but I had to remove the rod and spring assembly and then push the piston out the top. Note that in February ’83 the piston design was changed. Pictures are in the book, but it is no big deal. The later piston has a lower skirt.

7. With the pump off the board, remove the ‘closing plug’ bolt from the side and remove the pivot shaft with a needle nose pliers taking care not to scar the shaft and to remove the pressure on the shaft by light compression of the springs with your hand. The piston rod/spring assembly is now free to remove. Please note that this is the most critical component of the vacuum pump. If these bearings fail they can and will find their way into the engine with possible catastrophic result. The assembly is available but if there is question as to replacement I would suggest replacing the entire pump with a new unit. (your car, your decision). A note on the two spring washers: the center hole of the top washer (by the piston) is larger allowing more movement then the lower washer.

8. Now the fun part of cleaning everything, but you know how to do that. So begin re-assembly with putting the rod/spring back in and lubing the pivot shaft with 30 weight before slipping it in. Tighten the closing plug with only 8-10 Nm (that’s only 80 inch/lbs so be gentle folks) Remember your Loctite blue.

9. Now get the dental pick and remove the old seal from the piston along with the ‘O’ ring under it. Clean and replace with the new ones from the kit. Lube lightly with 30 weight. (I know…lousy picture). Note the three black rings in the upper right corner of the picture? Those are the seals for the check valves

1. Clamp the pump onto the assembly board forcing the piston-rod to its top position. Now center the piston on the rod and fit the piston into the bore. I had a difficult time getting the piston to fit in, so I applied heat to the pump body until it expanded. Then the piston slid in smoothly.

11. Replace the washer, put on new self-locking nut and tighten to 9 Nm (that’s 80 inch pounds) so keep it gentle.

12. With the piston in replace the three check valve seals, then the valves: note that the two go ‘crown down’ and the one goes ‘crown up’. Then place the new sealing ring around the top, fitting it around everything so that it does not get crimped.

13. Place pump cover on housing and screw in slotted screws to 2.5 Nm (22 inch/lbs) Remember your Loctite blue.

14. Dress the new block gasket with Hylomar and put the pump back on the engine.

15. Finish by re-attaching vacuum pipe, power steering belt, fan, shroud and hose.

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