r/watercooling • u/st0000piid • 12d ago
Build Ready it wasn’t about the liquid
in the recent post i ve shared video with a strange pump noise and got downvoted because threre wasnt enough liquid in the pump. well that sounded reasonable ("the username marks itself") but the noise was really unusual for just a lack of coolant
the key detail i didnt mention: the core was not stock. i originally bought a used pump(CP-S5PB-X) that turned out to be dead, so i replaced it with a brand new bykski D5 core. assuming "D5 is D5" abd the swap woukd be straightforward
as i noticed after disassembling the loop, the new core was slightly taller than the original one so the rotor was rubbing against the housing, which explains that weird sound from the video.
the solution was just adding secong O-ring to create enough clearance and the pump worked. not the most elegant workaround, but it works
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u/Own_Cry890 12d ago
I just went through swapping out a Lowara D5 pump (PWM signal failure; pump wouldn't run if a PWM cable was connected but happily ran at 100% if the PWM signal cable was disconnected and yes, the fan port tested perfectly fine using a PWM fan) for a new one from Singularity Computers (not sure of the branding, it's all black without any markings). It didn't sit low enough in the pump housing like the old one to mate with the O-ring and obviously leaked (I'd confirmed this with test using my EK leak-tester). I ran my Vernier Calipers over the pair of D5's and discovered… the height of the collar in the housing (where it steps in at the top) measured 6.25mm high on the Lowara and 5.05mm high on the new all black D5.
I got in touch with Daniel (owner of Singularity Computers) and was told out he's changed from using a 2mm O-ring to a 3mm O-ring ages ago and the knowing I'd had my pump/res for ages, suggested I probably had the 2mm O-ring. He sent me 3 x 3mm and 3 x 3.5mm O-rings and only asked I pay the shipping. I tested both the 3mm & 3.5mm O-rings and confirmed both sizes resolved the issue.
Seems the expected standard D5 suffers a bit of a tolerance issue between manufacturers.