Vacuflush Pump rebuild technique?

First thing i should do is listing everywhere to hear vacu leaks. From my experience you can hear every vacu leak. You can also take off the hose after the vacu tank and put your hand on it, when the vacu is enough the pump will stop. Then you know there is a leak after the vacu tank.

When you put your hands on the 2 openings of the body you can feel the vacugeneration. Did you try that on the bench?

I hope you didnt adjust the vacuumswitch in the vacuumtank. This is factory set and when you adjust it then its bad. A dometic guy explicit sayd to me not to mess with that switch.

Again i would point you to 2 o-rings on the shaft in toilet. Listen good at that area, you can hear it leaking but only when the pump generats enough vacuum.
 
Jaybeaux said:
What about the O-rings? #7?
Click to expand...

This!!!

Problem solved. O-ring #7 had become dislodged when I first assembled it. Reinstalled and generating vacuum. I cant get a good enough seal on it here on the bench to get the switch to turn off ( and did not adjust the switch, that was one of the first $$$ lessons learned!), but I can feel and hear it pumping air. The toilet seals/orings were replaced and working well last year.

This was a preventative Maint rebuild while this was removed for another project. It would run fairly long last year, and I suspected old duckbills. A couple were deformed open, so I think it should be good for several years.

I'll reinstall in the boat next week.
 
dtfeld said:
This!!!

Problem solved. O-ring #7 had become dislodged when I first assembled it. Reinstalled and generating vacuum. I cant get a good enough seal on it here on the bench to get the switch to turn off ( and did not adjust the switch, that was one of the first $$$ lessons learned!), but I can feel and hear it pumping air. The toilet seals/orings were replaced and working well last year.

This was a preventative Maint rebuild while this was removed for another project. It would run fairly long last year, and I suspected old duckbills. A couple were deformed open, so I think it should be good for several years.

I'll reinstall in the boat next week.
Click to expand...
Happy that you found it David, good job.
Enjoy weekend and let us know when you reinstalled everything.
 
dtfeld said:
This!!!

Problem solved. O-ring #7 had become dislodged when I first assembled it. Reinstalled and generating vacuum. I cant get a good enough seal on it here on the bench to get the switch to turn off ( and did not adjust the switch, that was one of the first $$$ lessons learned!), but I can feel and hear it pumping air. The toilet seals/orings were replaced and working well last year.

This was a preventative Maint rebuild while this was removed for another project. It would run fairly long last year, and I suspected old duckbills. A couple were deformed open, so I think it should be good for several years.

I'll reinstall in the boat next week.
Click to expand...
Happy that you found it David, good job.
Enjoy weekend and let us know when you reinstalled everything.
 
Back in the boat with a new pump body, bellows and duckbills.

Works like a charm. I think that should do it for s couple years...or until someone puts something that doesn’t belong in the system!

B72A44F1-DDBC-48DD-A27B-B3424CFD0C0F.jpeg
 
IMG_4230.JPG
dtfeld said:
I tried it on the bench and in the boat...small amount of vacuum generated. I pulled it and brought it home to adjust. So far new body, bellows (#10) and 4 duck bills.

Pump never stops running.
Click to expand...
Do you you mean it never stops running when you have it installed in the boat and have a good seal in the toilet bowl? The pump assembly could be fine now that you have repaired it, but you might have a seal someplace else that is sucking air from having taken things apart. Verify the whole system is sealed up tight. The company has a pretty good trouble shooting procedure outlined in their literature. Go through that in a systematic way and you will find the problem.
 
IMG_4230.JPG
Oops. See you solved it. Good effort.
 
new inlet with grommet.PNG
I wrestled with mine for a while. Turns out there was a big enough vacuum leak that the pump ran non-stop when it decided to, sometimes for up to a week, as I typically leave the head system on, even when away from the boat. Eventually the #7 o-ring gave out, and started leaking there (that's how I saw that there was a problem). Then, the pump was binding, wallowed out the bushing in the plunger, got cockeyed, and burned out the pump with dead spots where it would stall.
We never really heard it because the generator or engines or both, or crowd noise drown it out. Wasn't until one day it wouldn't pump at all that i discovered all this mess.
I pulled the whole unit including the vacuum generator tank, and replaced the pump with the new "upgrade kit" that included the bellows parts. That is a great thing to do.
https://seacoastservices.com/whisper-motor-upgrade-kit-12-volts/
All new duckbills, yada-yada. I made a DIY pressure/vacuum tester with my engine vacuum gauge, and some other parts, to test. Definitely building up 10 lbs, and stopping. Then every minute or so it would cycle. I figured my tester wasn't perfect, so I installed the whole tank, hooked the hoses back up, and tested. It was still cycling every minute or so. In and out a couple more times to check o-rings and proper seal between the pump and the outlet of the vacuum tank. Still leaking somewhere. As I removed the hoses ONE MORE TIME, I noticed that the intake neck (molded plastic into the tank) was collapsed a bit around the lip. That was it! The neck, under vacuum was collapsing inside the hose. Tightening the hose clamp just deformed the neck even more. Researched, and discovered that the tank had been "re-designed" a long time ago, with a simple hole cut into the tank without the molded in neck, and then a separate neck insert that the inlet hose attached to. Now I know why. I wrote Dometic about this, and asked if I could just cut the neck off and buy one of the insert parts. They never responded. A new tank is a few hundred dollars. I think I am just going to do it anyways.
So, if you get a vacuum leak and have this "older" style (mine is 1998) tank, pull that inlet hose and see if the neck is deformed in any way. Might save you a week, and 300-400 in parts.
 
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