# Airlessco LP540 highboy not holding pressure



## ChristhePainter (Aug 30, 2014)

Well I got my Lp540 repacked and changed the piston. Whomever owned it before me really put it through the ringer and didn't take care of it; bad scoring on the piston, old, dried paint blown out of the top of the packings. So after the re-pack it wasn't holding pressure. It would lose about 20 - 30 psi every few seconds and re-pressurize. Now I've changed the piston. It's not as bad but still doesn't hold pressure completely. Now it's about every 10 or 15 seconds the motor cranks over about a half turn or so and re-pressurizes. And the motor sounds a little funny like a slight grind inside... very light and not very noticeable but it's there.

It's an older LP540 highboy, probably a 2006 or older. I read in the field troubleshooting section of the manual that the upper seat could be worn and to replace it. What is the upper seat and where is it located? Could it be the suction nut not being tight enough? A loose fitting somewhere? I've changed the suction seat o-ring. Or since the previous owners took horrendous care of it, could the prime valve be leaking slightly but still work? 
And could the brushes in the motor be bad and cause a grinding problem? I'm sure they worked the motor over time by running with bad packings. How often does anyone change the motor brushes in their sprayer?


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## two fingers (Sep 28, 2014)

Sounds like the smart box


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## driftweed (May 26, 2013)

We just got one from H.D. and tested it the other night. Our purge valve doesn't close, so I need to get another. Have you checked to see that yours is staying closed? I leave my purge line outside the paint bucket in another bucket and thats how I noticed it. 3 gallons later, won't close at all. First it was a dribble, then eventually it just gave out. It will pressurize if the valve is in just the right position though.


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