Can't vacuum out pool

[boardgamegeek31]

Hello
I've been having a problem with figuring out how to get the vacuum on my above ground pool to work. It has a 1.0 hp hayward pump with a sand filter. I replaced both O-rings already and have the filtration system working well. However, every time I go to hook up my vacuum hose, it provides really good suction for 5-10 minutes and then just dies - and after that, the filtration system won't go back to it's normal function either. I cannot for the life of me figure out why this keeps happening. My local pool store told me that I need to replace the pump entirely, but I'm skeptical. The pump is only 4 years old (according to the previous homeowner, who I respect and trust), and like I said, it runs fine when I don't hook up the vacuum. I would rather not shell out another $300 to replace the pump if I don't have to.
Any insight would be much appreciated. Or even alternatives to cleaning my pool out without using the clearly broken vacuum system.

[Denniswiseman]

How does the vacuum connect to your system?
Does the pump pre-filter collect air in it?
You're right to be wary of pool store advice, they are in the business of selling

[Teapot1]

As Dennis is suggesting, you are drawing in air when vacuuming. No you dont need a new pump.

[boardgamegeek31]

Okay, good to know. I figured the pool store would be a good resource for advice, but I see your point about wanting to sell the biggest item. So I've tried hooking the vacuum up a few different ways, with the same result every time. Primarily, it is supposed to hook up through the skimmer. I always take the basket out of the skimmer, but I've tried it with the hose connected directly to the vacuum plate that goes in the skimmer (as the previous homeowners showed me), I've tried it attached to the L-shaped connector thing that goes on the vacuum plate, and I've tried it with the hose connected directly to the skimmer (no vacuum plate).
If I'm understanding your second question correctly, I don't believe the pump is getting air in it when I don't hook up the vacuum, because it's been running perfectly fine and keeping the water nice and clear the last few days (I have the pump on a timer).
Do you think I just need to replace and/or repair the vacuum hose? How should I go about figuring out how air is getting into the system?

[Paul Land]

Are you pre-priming hose with pool water?

[Teapot1]

Yes its most likely a vacuum hose issue. Are you making sure you fill the vacuum hose with water prior to connecting it to the vacuum plate?