Loosing vacuume after duck bill replacement

W

wayne0

Active Member
May 4, 2014
568
Newburyport, Ma.
Boat Info
2000 340 Sundancer
Engines
Twin 7.4 ltr.V-drives
Cleaned out a clog and replaced duck bills while in there. Vacuum builds fine and pump shuts off, but starts again after a few min. I can hear a "hiss" near the vacuum tank end. I greased the rims of the valves when I put them in. Should I have put tape on the threads?
 
You are likely going to have to take it apart and redo it to check the seals and o-rings. Cone of the connections might not be tight enough. I have not used tape on our system but would perhaps use the paste type.
 
Mines loosing vacuum also. I was checking it out a couple of days ago, and the hose going to the head is leaking down where it bends and outnof reach.
It's weathered pretty good, so that's a project that I get to do pretty soon.
 
I rebuilt one with new duck bills and had to redo. Do not use pliers and tighten the connections with the duck bills as tight as you can. Hand tighten and let the rims on the duck bills act like o-rings. Over tightening them will deform the seal and they will leak. Took them back apart, regreased them, and hand tightened. No more leaks.

Bennett
 
bbwhitejr said:
I rebuilt one with new duck bills and had to redo. Do not use pliers and tighten the connections with the duck bills as tight as you can. Hand tighten and let the rims on the duck bills act like o-rings. Over tightening them will deform the seal and they will leak. Took them back apart, regreased them, and hand tightened. No more leaks.

Bennett
Click to expand...
I will try that. The only problem is that when I go to re-bolt the pump to the tank, the holes don't line up unless I really tighten the connectors.
 
My buddy bought a 1997 370 express that vacuflush was cycling every 5 minute started with duck bills then the main hose and finally rebuilt the pump the orings were bad around the bellows.
 
It also could be leaking by the gasket on the toilet.
Does it hold water? If not, you can try cleaning the gasket.
 
If you have the J Series vacuum generator which has the pump on top of the vacuum tank and the duck bill valves down below the pump you have to get those set just right with the spacer so the retainer groove on the spacer and little ridge on the lip of the duckbill are engaged. Otherwise, the rubber will slip out and it'll leak. I also found out they need to be put together dry and clean. Also, that seal ring between the pump and tank needs to fit just right. If everything is done right that pump should sit flat, level, and right down on that ring. The bolts will simply pull it down compressing the assembly about 1/8 inch.
School of hard knocks and tearing mine apart no less than five times....

If you have the S Series where the duck bill valves are on the inlet and outlet, again, clean and dry fit. Tighten only hand tight so the rubber seal area doesn't extrude out or you crack the pump housing.
 
It's an s series. I'll take it apart and try again.
If I don't tighten the fittings on the vacuum tank side enough, the mounting holes for the pump don't line up. Maybe I will leave them out and try it.
 
Ok, so I went down to the boat today and took the duckbills out twice and reinstalled them. Still won't build vacuum. I said f**k it and ordered the bellows and o-rings as well as different duck bills. The last ones were cheap.
We'll see how it turns out.
 
I just had my vacuum generators rebuilt. I have the J Series. Since we were 3 days from leaving on a big trip, I had the technician do it. Since the pump has to come off of the accumulator tank anyway, we went ahead a did the bellows too. The tricky part there is pushing the top on evenly as not to roll the o-ring. Also, you have to make sure the bellows connector lines up to the top plate where the motor goes. You really can’t, nor shouldn’t, spin the bellows when it’s all back together. I haven’t seen the bill yet.

Jaybeaux
 
That's a shitload of work and sounds like a pain in the ass...

Someone had to say it.

Following this one closely as the toilet seals as well as a duck bills have been replaced on mine but it's still cycles every hour or so

I replaced the sanitation hose on my 3780 Regal all the way back through the firewall, that was not fun. I did find an old screwdriver or two when tearing out cabinets, obviously left behind at the factory.
 
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