Cummins Marine Diesel Repower Specialists › Forums › Cummins Marine Engines › Fitting on underside of QSB6.7 Aftercooler
Tony Athens.
Hi: new-to-me 2019 QSB6.7 480s have the silver-look fitting on the underside of the aftercooler….see attached pic. It looks like a drain fitting with a hose barb….could someone tell me what it really is and how it should be used please? thanks
It is supposed to be an auto drain for the typical fresh water condensation that occurs in the cold side(input side of the aftercooler). In theory, when the engine is OFF or at very low RPM ( like idle or so) the auto drain valve is open and condensation should drip from it and you may even feel air escaping from it actually blowing out the condensation.<br />Once the engine load is increased, 1/2 to 1 psi or so of boost pressure, it is supposed to close the drain (in theory). If it was me, I’d pull it once a year, clean it to make sure it’s working as it should by blowing in both ways. Simple to check and nothing scary about it
On another note——— My 1st experiences with a condensation drain on a SWAC diesel was about 11 yrs ago when we installed 2 x Detroit Series 60’s in USCG Sut-Chapter T vessel. Detroit put a fitting on the aftercooler in a place similar to yours (lowest spot in the intake side) but did not use a “fancy valve” ( IMO failure prone) –They just used a hose barb and a 3/16″ hose to the bilge with a 1/16″ open orifice in the fitting , continuous “leaking” condensent and air/boost.
Condensation drain for the aftercooler. Just leave it as is.
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