Swiftech MCP-35X stalling at low Duty Cycle?

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Nimisys

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I have a 3.5 year old Swiftech MCP-35X that has ran at more or less 20% duty cycle it's entire life and lately has been stalling out around 1600 rpm. I haven't had an issue when the duty cycle above 40%, but I really don't like running it that high as it is loud, and at idle, it is not needed for cooling. when stalled, adjusting the duty cycle to full and then physically tapping the pump is all that is needed to restart it, after which, the duty cycle can be lowered again. Fortunately my loop has a sufficient thermal capacity that even stalled for a few hours while away from the house, the temps never went more than 13C above ambient (or about 40C peak), but I like keeping this setup idiot safe. it is running off the motherboard header.

Anyone know of a solution, other than running it higher or replacing it? if replacement is in order, what is recommended? Loop is mixture of 3/8" copper tubing and 3/8" ID flexible, 2x 240mm radiators with about 1.5L total capacity. :
 
Number of blocks? Amount of water really isn't an issue, and restriction due to tubing is negligible compared to restriction due to waterblocks.

I would replace it with a D5/MCP655 variant. I have one that's been solid for 5 years now. And it was manufactured in 2005, so it's nearly 10 years old.
 
Replace it.

I had the same thing happen with my old 35x. Starts off as stalling and eventually the pump won't restart for long and longer intervals...minutes then hours then days.
 
3 blocks, all from the XSPC line of Rasa blocks IIRC, however they are ran in parallel.

Skripka: how long did it take to go from minutes to hours to days?
 
In parallel, your overall restriction would go down. That is right up the D5's alley, as it is a pump that has high maximum flow rates but lower head pressure compared to the 35x.
 
Nimisys said:
3 blocks, all from the XSPC line of Rasa blocks IIRC, however they are ran in parallel.

Skripka: how long did it take to go from minutes to hours to days?
Click to expand...

At first stalls were infrequent. And I could see the CPUFAN warning notifications in Windows. My pump was driving the equivalent of my sig rig (1 low restriction CPU block and a single GPU block), and lived its entire life at 1400RPM.

Took about a year in my case IIRC. Believe me I tried anything and everything. Unplugging the pump power and CPUFAN lead completely made no difference in getting the pump to wake up again faster (at first I suspected a bum fan header or mobo fan control software). Using a different molex power made no difference. Using a different PSU (completely unloaded) made no difference. Removing the pump and flushing it didn't matter. Heck I shipped it back to Swiftech, and Gabe couldn't find anything wrong with it, which was amazing as at that point it was taking 3-4 days before restarting....when it came back from Gabe 10 days after I shipped it, it spun up fine in my sink.

Once it started taking days to restart, I bought an Alphacool D5 with pump head/mount on sale, and didn't care anymore. D5 runs quieter at any speed and is a more durable design all around anyway.
 
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