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tidenumone 11-04-2012 08:20 PM

HVLP Gun Leaks

I recently acquired a Graco HVLP 4900 procomp in non-working condition. I have completed the rebuild of the unit and everything works great now…but one little issue. I am getting a leak on the gun at what I believe is called the “Packing Nut”. It where is the needle goes into the front part of the gun in front of the trigger.
I did perform a rebuild of the gun – did I install the parts incorrectly? What would cause it to leak here and what should I try?


joecaption 11-04-2012 10:21 PM

Just google the info you just posted on the make and model and look for a parts break down.
Is there burrs or a worn area on the shaft?

Tub Refinisher 11-08-2012 07:02 PM

The packing material in Graco guns typically consists of 5 plastic washers and a brass nut. The brass nut is adjustable, and controls the amount of drag on the fluid set (needle).
when you rebuilt the gun did you dis-assemble the packing and replace it? If not, you may just need to tighten down the brass nut a bit to take up the gap around the fluid set. Otherwise the old packing may be shot and need replacement. It's a pain to replace because there's 5 tiny plastic washers that are grooved and all have to fit together in the right direction.


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