Vacuum pump removal

[crazy4diesel]

I'd like to change the gasket on the vacuum pump and check out it's internal diaphragm will I have it off. I have the engine out of the car and on a stand. I've read the wiki's and also the FSM on this, but what I'm looking for are tips and pitfalls here.

Should the crank be in a specific place?

Are there surprises when it comes off (springs flying, cams dropping, etc)?

The same questions to taking it apart to look at it, I know it's working, no issues with vacuum (other than the fact that the door locks don't work, but that's another issue I'm sure).

And finally, reinstalling it, any tricks there?

Thanks much!

[Simpler=Better]

Assuming you're talking about the 617, with the cam rollercoaster monstrosity, you just remove it nothing special.

Be prepared to buy new bolts, I had to drill out 3-4 of mine even though I had it on a stand.

Check the intermediate shaft for play as well when it's out.

[uberwasser]

From everything I've come to understand it's best to have the spring compressed when you open the pump up, at least if you're replacing parts.

Otherwise there aren't many "gotchas" in this job except to make note of orientation of the pump when you remove it from the engine, and of the cover on the outside of the pump once it's on your bench. I put the cover back on the pump one notch to the left and spent some time confused about why the power steering belt was now interfering with it...had to re-open it to correct this.

When re-installing depending on the position of the cam roller you may need to push against the spring pretty hard to get the pump to seat against the engine so you can start the bolts. A second set of hands can help there.

And of course the aforementioned potential for stripped socket head bolts.

On the topic of your door locks check this diagnostic guide I wrote up if you're in the mood to look at fixing them. It's not bad once you get in to it.

Mercedes W123 Vacuum Lock System Diagnosis Technique - iFixit

[Dan Stokes]

Reinstalling the pump is the sort of job that can be made easier with 3 or 4 studs in the bolt holes. Get them long enough to start a nut with the spring NOT compressed. EVENLY pull it down close to the gasket surface then install your bolts in the open holes, followed by removing the studs and putting bolts in those holes, too. If the studs don't appear to be in the way you can just use them as the fasteners in their positions.

An added benefit of the studs is that they'll hold the gasket in place so you're not chasing it around and will align the pump. It will just sit on the studs patiently waiting for you.

Most hardware stores will have a decent bolt section and they should have the studs (I think they're 6mm but don't hold me to that). Remember to get nuts and washers (in case you decide to leave them) so you don't have to run back to the store.

As I almost always work alone I often use the stud trick. It's how I got my pan back on my 617 and over the years I've used it a LOT.

Dan

[ROLLGUY]

When installing the pump, I always turn the engine so the roller of the pump is on the bottom of the ramp. It is only about 1/4 inch away from the mounting surface, and plenty close enough to line up the gasket and start at least 2 bolts. I put the remaining bolts in and tighten them evenly. If the roller is near or at the top of the ramp, studs will definitely need to be used. That is why it is easier to do with the roller at the bottom.

[Stretch]

Definitely the hex head sockets that fit on to your 1/2" ratchet handle

Push hard against the vacuum pump when you undo the last two screws to make sure the threads don't have a hard time being subjected to the spring force of the piston

[connerm]

Clean out the hex heads with carb cleaner and a q-tip so your tool fits all the way in.

[Junkman]

Tap the allen wrench socket in to get the best bite possible and shock to help break free of any rust. Use a bit of your favorite stuff to loosen loosen the bolt regardless of rust.

[sleepstar]

does anyone know what the bolt size is? checked the EPC for a part # but its confusing, and the one lead i tried to follow ended up NLA from dealer

[ROLLGUY]

Originally Posted by sleepstar

does anyone know what the bolt size is? checked the EPC for a part # but its confusing, and the one lead i tried to follow ended up NLA from dealer

It is 6mm X 15mm

[crazy4diesel]

Thanks everyone, I pulled it off, and replaced the gasket, hopefully oil will not longer leak at least from this one place. Since I had the glow plugs out, I just turned the engine till the lobe was at the lowest point, and had no trouble getting it back on.