I've changed o-ring at pump basket lid, cleaned all baskets and filters, had the Hayward pool vac internal parts all replaced and can't get pool pump to **** enough pressure to run pool vac....

Look at your pressure gauge. If it is reading high, you have a clogged filter. Open filter and clean out or replace sand.

If it is reading low, you have a pump/ suction issue. Check the o-ring on the pump basket lid and make sure it is lubed and has no cracks. Check your basket for cracks. The pump impeller could be clogged. The pump may be pulling air in through a suction fitting or a small crack.

no big deal. turn pump off, clean basket, check lid o ring and put lid back on. turn on pump

if you are getting a suction noise at the skimmer then that means you need more water in the pool. Also if you have anything in the skimmer basket like tablets then take out the basket when you are using the vac. the only other thing I can think would be the problem would be the filter is clogged. I know you have back washed it but I would do it again to be sure it is not dirty. good luck

Try replacing or lubricating the seal on the basket lid. Pool pumps rely on a completely sealed system to work properly. If there is any air getting into the system on the suction side the pump will surge.

unscrew the lock ring and pull, the lid should come off with the lock ring. If not, line up the notches in the ring with the slots on the lid and pull. You should then be able to access the basket to clean it.

it fits around clear basket cover put all the way up hope it helps

Manual or Automatic?

Usually the problem is a worn out Strainer basket oring. With the addtional strain of trying to draw water through 40ft of vac hose it is easier to draw air from a worn out strainer o ring. My suggestion is to reverse prime, replace o ring if leaking and make sure you lube it with a silicon based lube.

If you notice bubbles in the water returning into the pool from the eyeball/discharge, or water in the strainer basket is visibly swirling (bubbles visible) odds are you need you replace the o-ring on the lid of the strainer basket in the front of the pump. This basket may also be clogged with debris, which also effect pressure. Could also be a cracked or warped strainer lid. Should be easy to see when you remove to check o-ring. Once you remove the strainer o-ring make sure you lube it with a good silcone based lube.

Failure to fill the basket completely means you have an issue at the pump basket (gasket), connection from the pump front to plumbing (threads need re-tightening or tape) or some other condition allowing air into the system between the pump and pool. This problem cannot be caused by the filter head. The problem is on the "suction side". From the top of the pump out all the way to the pool is the "pressure side" and would cause another condition such as leaking water. Examine and tighten everything before the pump and check the pump lid for possible gasket replacement. Rob