Self-priming pump will not self-prime

  • Last Post 27 February 2018
rrnoseck posted this 29 December 2017

I’m trying to trouble shoot my Hayward Max-Flo 2 Pump.  Simply, it will not self prime itself every time it is switched on.  And, when it does prime, after a while it will loose it’s prime and will not prime itself again. When this happens it will run dry for a while, until i notice and shut it down. Do I need to replace the whole pump or maybe the impeller is melted/misshaped and needs replacement? Do you have any suggestions? If it needs replacement, could you suggest a 1 HP pump that would be right (as this pump is not in production anymore)?

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InyoRob posted this 03 January 2018

We would recommend replacing any Hayward Max-Flo II parts that look melted or misshaped. Pumps lose their prime when air gets into the system. Check the areas listed below.

Pump lid O-rings are a habitual offender of air leaks. The O-ring can expand or deteriorate over time and allow air to enter the pump. You can try applying a silicone or Teflon lubricant to see if it helps, but often times it needs to be replaced.

Plumbing fittings will also draw air. A popular technician trick is to use burning incense. While the pump is running, wave the burning incense near suspected areas. The smoke will be drawn in, if there is a leak. Check the fitting on the pump intake, the couplings and elbows. Cut out and replace any fittings that have an air leak.

Valves can be inspected like the plumbing fittings. Diverter valves will usually have internal O-rings. These O-rings can easily be replaced to fix an air leak. Simple ball valves are not usually repairable and need to be replaced, if there is a leak.

Drain plugs are found on most pumps. These plugs are usually used to drain the pump when a pool is winterized. They should be tightened firmly into the pump. Inspect the drain plug and drain plug O-ring. Replace them if they look decrepit.

SteveB posted this 04 January 2018

I’m having the same problem. I ordered and installed a new pump from you guys. I have a Sta-Rite 1 1/2 hp motor. It ran great for a year but now it will not hold prime. I did not use RTV and do not really know where to exactly put this sealant on. I guess it could be several things but I’ll check to see if any air leaks are present. It does get so so close to priming and getting ready to take.. only to fail. I crossed my fingers two times, then  gave up. It’s pretty cold here so I hope my skimmer lines don’t freeze, oh well. Nothing is easy it seems.

InyoRob posted this 04 January 2018

Steve - Check the same areas listed above and you should be able to find a possible air leak. 

SteveB posted this 04 January 2018

Ok, I’ll do that, but my leak seems to be at the bottom. I’m thinking the the seal plate and motor might be the reason. Thanks so much for the prompt forum reply!



InyoRob posted this 04 January 2018

You're welcome. If the pump is leaking near the seal plate and motor, I would recommend replacing the shaft seal and housing gasket/o-ring.

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SteveB posted this 24 February 2018

Ok, I replaced my shaft seal and then pump that I bought from you guys about a year ago just would hum briefy ( like 2 or 3 seconds) then stop humming. it wouldn’t start at all. So I called your help line and he (your tech supporting) guy said I needed a new start capicator, so I just installed it.  Btw, I did put some RTV on the shaft seal. I think I put it on the right place, but not 100% sure,.... but this would not be the cause of motor not starting and running.  

Well, it does the same thing happened again. I really to get my pump running again soon.

What do you think?

InyoRob posted this 26 February 2018

Hello Steve - If you replaced the capacitor and it's still not working, I would replace the motor. What is the model number of the pump?

SteveB posted this 27 February 2018


My pump is a A .O. Smith 1 and 1/2 HP square flange full rate motor. (item SQ1152)

i bought it from you guys  in the fall of 2016 and it ran good until now.

Guess I need to buy another one. i have nt replaced the "Run Capacitor" yet, just  replaced the "Start Capacitor" only




InyoRob posted this 27 February 2018

Steve - Try testing the run capacitor. That could be your problem as well. Check out our article titled "How to Test a Pool Pump Capacitor".