Vacuflush system won't hold pressure

D

drprunner

Member
Dec 31, 2008
77
SE Florida
Boat Info
1997 400 Sundancer
Engines
Caterpillar 3116 300hp
Back to my favorite forum for help with another problem with my 1997 400 Sundancer. I turn on the breaker for my rear head and I can hear the vacuum pump running for a few seconds and then it shuts off, everything working fine. I turn on the breaker for my forward head, and the vacuum pump never shuts off. I've tried pouring the marine head sealant/lube down it and no help. I'm pretty sure nothing is hanging up the valve.
My question: is there only 1 pump for both heads, or is there a pump for each head? I'm trying to figure out if there is a separate pump for the forward head and it needs rebuilding.

Thanks
 
Start with new duckbills if they have not been done in awhile. Cheap (but unpleasant) place to start and may solve your problem. Toilet seal kit is also a 20 minute job on most units.
 
I did the seal kit and it stopped cycling, I have all the pum parts just no ambition to get in there and get it done.
Jon
 
drprunner said:
Back to my favorite forum for help with another problem with my 1997 400 Sundancer. I turn on the breaker for my rear head and I can hear the vacuum pump running for a few seconds and then it shuts off, everything working fine. I turn on the breaker for my forward head, and the vacuum pump never shuts off. I've tried pouring the marine head sealant/lube down it and no help. I'm pretty sure nothing is hanging up the valve.
My question: is there only 1 pump for both heads, or is there a pump for each head? I'm trying to figure out if there is a separate pump for the forward head and it needs rebuilding.

Thanks
Click to expand...
Does the water remain in the bowl if not could be duck bills
 
drprunner said:
Back to my favorite forum for help with another problem with my 1997 400 Sundancer. I turn on the breaker for my rear head and I can hear the vacuum pump running for a few seconds and then it shuts off, everything working fine. I turn on the breaker for my forward head, and the vacuum pump never shuts off. I've tried pouring the marine head sealant/lube down it and no help. I'm pretty sure nothing is hanging up the valve.
My question: is there only 1 pump for both heads, or is there a pump for each head? I'm trying to figure out if there is a separate pump for the forward head and it needs rebuilding.

Thanks
Click to expand...
drprunner said:
Back to my favorite forum for help with another problem with my 1997 400 Sundancer. I turn on the breaker for my rear head and I can hear the vacuum pump running for a few seconds and then it shuts off, everything working fine. I turn on the breaker for my forward head, and the vacuum pump never shuts off. I've tried pouring the marine head sealant/lube down it and no help. I'm pretty sure nothing is hanging up the valve.
My question: is there only 1 pump for both heads, or is there a pump for each head? I'm trying to figure out if there is a separate pump for the forward head and it needs rebuilding.

Thanks
Click to expand...
Chased this same issue for quite some time. 2 vacuum units, forward head's is located under the port exhaust near the waste tank.

If water isn't staying in bowl when energized, probably the bowl seals. If not, duck bills are the next logical step if no service records. Could be a faulty pressure switch too. There is also an O ring seal on the pedal flush that could leak vacuum.

If you are trying to diagnose and repair yourself, consider making a plug out of good sanitation hose and an expanding hose plug.

Remove inlet hose to vacu flush (put a rag or wooden plug in the incoming head hose too!) If it holds pressure, then you know the trouble is upstream. Move the plug to the the hose coupler and work your way back.
 
New complete pump is $900. I bought one as the marina wanted that much to look at my system. Once old one was out I rebuilt it with new motor and all the internal parts now I have a spare. So next time one fails I can fix it without effort and repair when I have time. I also replace the pressure switched in the accumulators one had a small hole in the flappy part. They are easy to replace if you are thin and have 5 foot long arms.
 
You can also place a cork or block of some sort, I have a tester just for this, in the intake where the toilet hose connects n crank it up. If pump runs, stops n holds pressure for an extened period, then duck bills are ok. If not then duck bills are probably toast. The pressure switch would be my last culprit.
 
Well it's not the duckbills :(

Replaced the 4 duckbills and re-installed the vacu-flush. Nothing's changed, bowl holds water, and pump cycles but never shuts off. I'm getting a vacuum at the bowl, when I flush it I can hear the vacuum/suction.

Any ideas??
 
drprunner said:
Well it's not the duckbills :(

Replaced the 4 duckbills and re-installed the vacu-flush. Nothing's changed, bowl holds water, and pump cycles but never shuts off. I'm getting a vacuum at the bowl, when I flush it I can hear the vacuum/suction.

Any ideas??
Click to expand...
Only other thing I can think of is the pressure switch mounted on the unit that shuts the pump down when proper vacuum is reached. Did you change that when you changed the duck bills?

Edit: you said the 4th duck bill was in the pump, did you change the bellows with the duck bills? There’s an O-ring in there that can leak if “a solid object, AKA a feminine product” gets sucked in there.
 
Ok mine is doing the same. This is what I found. Rebuild the bowl assembly. There are two gaskets between the bowl and the base. They go bad and are an easy fix. I ordered the parts for the base and the bowl valve

there is a company that advertises here that sells the parts. Sea something
 
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