Iwaki making a rattling noise
 

I have an Iwaki MD-15R given a vibrating sound inside, almost like rattling. I'm running it with two MCW-5000A, one MCW-50 and a Thermochill 120.3 all in series and the pump is too hot to touch.

I know the Iwaki pump bodies run hot, and I have read Cathar's advice to others regarding Iwaki pumps needing some sort of restriction to minimise cavitation. Would the stuff in the loop be enough restriction? Or am I expecting too much from my pump?

Seems to me there is air in your system. I have a 15R as well, and it is just about silent. The pumps do get hot, totally normal but what voltage pump do you have? 100V? If it is 100v (which mine is) you should use (I never did) a resistor to drop the voltage down. So, my guess is air in the loop or a faulty pump, but my money is on air.

since dogbait (like me) is in the UK (230V, 50hz) hopefully he's using something to convert the voltage if it's not a 220V MD-15.....

Ahhh, didnt even notice that, good point.

Try taking apart the front housing where the impeller is. Its possible something is messed up in there. Iwaki gives schematics and such so I'm pretty sure its safe to take it apart.

there should be enough back pressure in ur system to make it so there is no cavitation. im runnning the WMD-20 and there is no cavitation in my sytem and i got equvialent components running.

I cleared the air, (love that about Iwaki's...they clear the system so fast :) ), and opened the pump, it looked very clean inside, no problems that I could see, the ceramic bearing looked fine also, and the O-ring was seated properly.

The thing is, it's been running for almost a year like this, no worsening or lessening of the noise. The only time it is dead silent (just that turbine like whirr) is when I run it in a bucket with no backpressure at all.

Another thing to consider is any restrictions placed on the pump inlet. The pumps won't handle choked water flow into the inlet very well at all. They will cavitate like crazy.

Hmmm, well, with an MD-20R in the loop now, (the MD-15R feeding into the MD-20's inlet) I watched as the tube into the MD-15R slowly collapsed, heheh. So I had to wrap some spiral-wrap to reinforce the tube.

The MD-15R still makes a noise with the MD-20R in the loop. When I turn the MD-15R off, the MD-20R's still quiet.

Now surely the MD-20R's intake is restricted to hell with an MD-15R (switched off) in the way?

With respects to the MD-15R's intake, I have 3/8" ID going into 1/2" ID using an adapter between the two hoses. Would it make any difference extending the 1/2" ID intake hose so instead of 6" of 1/2" ID hose I'd have 1'?

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