How to rebuild vacuum pump?

[theman53]

I am wondering. How to do it. I have 2 the one in the car isn't working correctly, the one out of the car has an egg shaped drive for the oil pump. I want to rebuild one or take the gears off and switch them. Never looked at them internally, just want some advice before opening them up.

[Quantum TD]

It's covered in the Bentley under Brakes I believe.

If you're talking about the rotary-style pump, you just remove all the slotted screws, install the new diaphragm, and then PRE-TENSION the diaphragm, and install all the screws again. Bentley says to remove the circlip from the piston, leave the diaphragm loose, etc. If you do it that way, you'll be rebuilding it again in under 10k. Just pretension the diaphragm and you'll be fine.

[Wayland]

It's really worth finding a later vane-style vaccum pump. Install it and you'll never have to worry about it again.

[theman53]

I should have stated it is a later vane style pump at least I think it is. It is pictured here.

[Wayland]

Yes, that is the later style vane type. Have you tested it on the car with the engine running? This style of pump requires oil pressure from the oil pump in order to produce vaccum. I had one which I thought was a dud, which I was testing on the bench by spinning w/ an electric drill. No vac, so I tried one I knew was good. No luck with that one either. That's when I realised they need oil pressure to work.

[theman53]

It is in the car and works, but sometimes it won't work until you rev it up a ton or drive it a 1/2 mile. I have the other one that works, but the oil pump drive in the bottom of the gear looks bad. It looks like a bow tie instead of a rectangle. I won't have time to mess with it until later in the week. I don't know if I will have my bentley until then.

Ideally if someone could tell me "just take this off and pull this then the gears can be swapped" I just don't want to ruin my good one to find it out or take that chance. Let me know.

[theman53]

I guess this is my deal. Would you use that vacuum pump pictured? I didn't want to as the oil pump drive looks bad. Especially considering my other gear is perfect. I do know that this vac pump does work on the vacuum aspect.



If you all think it is fine I might run it and pull the other and attempt a rebuild. Then pull this one and keep it for a spare...it just looks scary to me though.

[theman53]

Yeah, I know. I am just thinking of where is all that metal going and I have a fresh build. I suppose I can't hold its hand forever. I may just give it a pull this weekend and test it.

[fatmobile]

The vane-style pumps aren't as dangerous to run.
 The old diaphram type had a brass bushing above the gear.
 
So it didn't wear as a bowtie,
 it wore as a ramp,
 pushing harder against the brass as it machined it's way upward toward the pump.

 To remove the gear on the old ones; a pin needs to be ground and removed before it can be pulled apart.
 The "ramped" shaft end would probably need TIG welded and ground back into shape.
 The worn bushing can be swapped with the unworn/matching bushing inside the pump.

You are going to change that seal inside the gear

[theman53]

I do have an old style one too somewhere in the barn, but I am going to stick with the new style one. I will probably just pull the one in the car stick the bowtie in until the rebuild of the good geared one is done.

[fatmobile]

You are going to change that seal inside the gear

 Just asking again, some people don't know there is a seal inside the gear.

[theman53]

I have no clue on how to fix the pumps. If there is a seal in the kit that is left over I will start looking on the gear. Ideally I try to have parts left over so that I know I did it correctly

If I have time I will try to take pics of what I see inside. I need to get a kit yet as well.

[fatmobile]

The gear seal doesn't come with the kit.

[Earwig225]

Just pretension the diaphragm and you'll be fine.

Can you explain what you mean by "pretension"

Thanks!

[rabbitman]

Just pretension the diaphragm and you'll be fine.

Can you explain what you mean by "pretension"

Thanks!

Make sure the diaphram is stretched when you tighten the screws around the edge otherwise it'll stretch every stroke rather than just flap back and forth.

I think they make 'em too tight.