# Take apart Graco 390ST fluid section?



## kdubya (Oct 2, 2008)

My 390 ST stopped building pressure today while I was cleaning it, it had been performing flawlessly moments before. I taped it with a hammer but no joy. So I'm trying to figure out how to tear it down, How do I get the pick up hose off the tube? looks like the collar might be a release but mine is full of paint. How do I take this off?


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## NCPaint1 (Aug 6, 2009)

Most likely some trash stuck on the upper ball in the piston.


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## NEPS.US (Feb 6, 2008)

hammer and wrench


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## nEighter (Nov 14, 2008)

the st's are a bit different. When you clean it you MUST keep the filter on, only after you have ran it through can you take the filter our and clean that out. It goes filter then the valve for purge or pump. Take the purge valve apart and clean it out. That is probably what it causing the no pressure.

Also.. did you just clean or did you repack it? I think that unit has 3 check balls, it has a little plastic cage that one of the check balls sits in. You need to make sure that is all cleaned out real good. But don't run it without the filter. I got brought one of those and it was solid. I charged $400.00 to get it running again. It was a major pain. Also there is an ST and ST PRO. The packing kits are different.

Good luck man.


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## kdubya (Oct 2, 2008)

ok got it torn down. Lotsa junk built up in the block, I think I want to soak it. How do I get the bypass valve off? I see 2 holes on the knob, is that a pin I can push out? nEighter I just flushed it, now I'm tearing it down for a better cleaning and inspection.


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## nEighter (Nov 14, 2008)

sweet. Have fun!


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## kdubya (Oct 2, 2008)

torn down and put back together, nice and clean, everything works again. But now It 's pumping out of the throat pretty bad. Tried tightening the collar, wondering if I damaged the throat packing in the process.


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## nEighter (Nov 14, 2008)

pics?


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## kdubya (Oct 2, 2008)

no pics, but its obviously pumping water and oil out of the cup right between the shaft and seal. If I have to tear this down again I'm going to repack it. Found aftermarket packing on ebay for $29 from Northwest compressor. The packing looked ok and I oiled it before reinstalling. geez did I install packing upside down? rounded side up in the throat. what else can go wrong to cause this? seems pretty simple but this is my 1st tear down on.


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## nEighter (Nov 14, 2008)

I am rusty.. I went throught that one like 3 times and each time something dislodged and was caught in a check ball. You will be a master once completed


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## kdubya (Oct 2, 2008)

nEighter said:


> I am rusty.. I went throught that one like 3 times and each time something dislodged and was caught in a check ball. You will be a master once completed


 Lord, give me patience...


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## mr.fixit (Aug 16, 2009)

if it is leaking out of the throat the piston is scored and needs to be replaced.
check your private messages I will try to help


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## kdubya (Oct 2, 2008)

torn it down again and discovered a damaged packing ring on the piston and 1 of my throat packing was on the ground oops. are the aftermarket repack kits any good or stick with graco? I assume pretty much all the same. getting good at this but a vice would make working on this much easier.


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## Workaholic (Apr 17, 2007)

kdubya said:


> torn it down again and discovered a damaged packing ring on the piston and 1 of my throat packing was on the ground oops. are the aftermarket repack kits any good or stick with graco? I assume pretty much all the same. getting good at this but a vice would make working on this much easier.


I always buy the name brand packing kits.


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