Mighty Vac pump rebuild.

So one of my tools I had since 1994 has not been working correctly.

Success, holding vacuum now. 

My Mighty Vac hand pump stopped holding vacuum a year ago and I have been to lazy to do anything about it.   This is a metal body one, not the plastic one, so I was reluctant to throw it out and buy a new one.

After searching Amazon.com I found a rebuild kit that seemed like it would work correctly for my pump.

I purchased the Mityvac 4100 Silverline Pump Maintenance Kit for about $20 use.

It worked great.  All the parts were there in the package.  It included a paper sheet showing where all the parts go, but no step by step instructions on the process of rebuilding.  So I had to think about it and come up with my own step by step.   Feel free to enjoy the pictures.

I split the body parts from each other and started on the body one way valve.  I removed the handle then the plunger cap. 

Removed the little one way valve at the end of the bore.  There was build up on the body preventing it from sealing and letting vacuum leak out.   I cut some small pieces of fine sand paper and used my finger to scrub out the valve sealing surface and the bore of the body.  Be very gentle and very fine paper or you could gouge the surfaces and they will not seal. 

After a long time of gentle scrubbing with fine grit paper, the bore and the wall feel smooth to my touch so I think they will seal with the new rubber parts. 

Cleaned the body surface with fine grit paper.

Installed the new valve into the bore with some grease and pulled it  through the center hole.

Removed the old plunger and plastic pieces from the metal rod.  These are on tight so it takes some force to remove them.  

I installed the new plastic pieces with a deep socket until they snapped into place.   It takes some force but they will snap into place.  Then install the rubber part. 

Plunger with new plastic body and rubber ring.

Then add the spring plate. 

Installed the new large spring.

Installed cap and new short screw.

New short screw installed.

Re-attached the pump handle.

Removed the top pressure valve. 

New one way pressure valve installed. Old one on the blue napkin

Be sure to match the screws removed to the new screws so you don't pick the wrong ones. 

Cleaned the front half of the body and the groove the o-ring seals against.

Bleed valve assembly

The order of how the bleed valve is assembled  

Removed the o-ring then cleaned the surface with fine grit paper.

New small o-ring with grease. 

Some debris on the ring mating surface needs to be removed. 

Some very fine sand paper to gently clean the mating surface for the new o-ring.

Installed the new spring from the kit. 

Compress the new spring with the original cap. 

Installed long bottom screws.

New Oring from kit with some grease. 

Assembled the two body halves with the new short screws. 

Success, holding vacuum now. 

I'm pretty pleased with the parts kit and the simplicity of the tool.   The quality of parts seems to be pretty good.  They matched what was already in the tool.   I would recommend the rebuild kit as long as you have a metal bodied pump.  I don't have confidence in rebuilding plastic units.



Tools used in this post - Phillips #1, Phillips #2, grease, deep socket.

Parts used in this post -

 

 Let me know if you have any questions or would like more detail. Thanks for reading.