Air in pump when water heats up

[QuickShow]

Hey there. My water pump MCP655 with the speed adjust is acting funny now. When the water temp is within 10~30 degrees, pump is quiet and inaudible. As soon as the temp goes above 30 degrees, the pump starts to trap air and make lots of air bubble noises. If I disconnect the pump power and tilt the case, I can see a small air bubble float up from the outlet tube. If I let the water cool down and then warm up again, same thing will happen. No matter how many times I disconnect the pump power, there's always a small air bubble floating up. The 2 hose clamps at inlet and outlet are fully tightened. There's absolutely no air leaking into the loop from the inlet tube.

I'm using distilled water as the coolant.

Is this a faulty pump? What can I do to stop the air being trapped in the pump?

 

[amuffin]

Bleed out the air and add a bit more water.

 

[Motopsychojdn]

Disconnecting the power won't bleed the air out, you need to top up as Muffin suggested
could we get pics of the offending bubble?
and have you bled the loop properly? it may be the small bubbles are being pushed through from the rad or blocks
Moto

 

[Goodeggray]

It's called cavitation. You have get all the air out of the loop.

 

[QuickShow]

Since everybody thinks that I did not bleed out the air properly I decided to drain the old coolant and refill with the new one. Just for curiosity I removed the pump from the case and instantly I noticed a leak from the pump. It turned out that the tension ring on the MCP655 is very loose. I tightened the tension ring, put the pump back into the case, and refilled the coolant. I've been bleeding air since last night but the air still gets trapped in the pump.

 

[Motopsychojdn]

Rotate the Pc on as many angles as you can and shake it while you do,
this should force the bubbles from the pump through the loop but good job on finding the loose fitting, that would have been contributing obviously
Moto

 

[4Ryan6]

Since everybody thinks that I did not bleed out the air properly I decided to drain the old coolant and refill with the new one. Just for curiosity I removed the pump from the case and instantly I noticed a leak from the pump. It turned out that the tension ring on the MCP655 is very loose. I tightened the tension ring, put the pump back into the case, and refilled the coolant. I've been bleeding air since last night but the air still gets trapped in the pump.

My suggestion was going to be to check the sealing O-ring on the pump body.

Since you've discovered and done that yourself and still have a problem.

Would you please post a picture of your pump loop setup.

It is very important that the D5 pump has unrestricted and unlimited water entering into the intake, it does not have draw capability at all, it is strictly a circulating pump, (meaning it has to have the water to push the water), allowing any air into the intake at all will burn out the ceramic bearing.

You're extremely lucky you haven't burned it out already, increased water temperature is a sign of serious trouble.

Your D5 should be getting it's water to the intake directly from the reservoir itself, with the reservoir located above the pumps intake, with completely unrestricted or crimp impeded tubing.

 

[QuickShow]

My suggestion was going to be to check the sealing O-ring on the pump body.

Since you've discovered and done that yourself and still have a problem.

Would you please post a picture of your pump loop setup.

It is very important that the D5 pump has unrestricted and unlimited water entering into the intake, it does not have draw capability at all, it is strictly a circulating pump, (meaning it has to have the water to push the water), allowing any air into the intake at all will burn out the ceramic bearing.

You're extremely lucky you haven't burned it out already, increased water temperature is a sign of serious trouble.

Your D5 should be getting it's water to the intake directly from the reservoir itself, with the reservoir located above the pumps intake, with completely unrestricted or crimp impeded tubing.

Thanks for you reply. The O-ring and the ceramic bearing are in perfect condition, but surprisingly there is a small chip off the edge of the round core in the D5. I think this will mess up the flow but will it somehow produce bubbles in the pump? The reservoir is right above the pump and the tube in between is wrapped with coils so I'm pretty sure that the pump gets as much water as it needs, although the reservoir itself is tiny considering the size of the loop.

I can bleed out the air in the pump by disconnecting the pump power for a moment even when the water is @ 50 degrees, but then after about 2 minutes I can already hear the air being trapped in the pump. And meanwhile there is absolutely no visible air going into the pump from the inlet.

I'll post the pic later.

 

[Motopsychojdn]

**I can bleed out the air in the pump by disconnecting the pump power for a moment even when the water is @ 50 degrees**
How do you get the air out of the loop at that point?
Moto

 

[QuickShow]

**I can bleed out the air in the pump by disconnecting the pump power for a moment even when the water is @ 50 degrees**
How do you get the air out of the loop at that point?
Moto

If the I tilt the case toward the outlet side of the pump when it's powered off, the bubble naturally float up into the top rad.

 

[Motopsychojdn]

And you top up the water to get rid of the air then?
Moto

 

[QuickShow]

And you top up the water to get rid of the air then?
Moto

I tilt the case and give a shake to agitate the bubbles. As I mention above, my reservoirs is very small and sometimes a few bubbles got suck right back into the pump, but it cannot explain why the air accumulate so fast in the pump when the water is warm.

 

[Motopsychojdn]

Yes but when you get the bubbles to the top, do you top it up with water to push the air out?
Moto

 

[amuffin]

Did you put more water!?

 

[QuickShow]

Yes but when you get the bubbles to the top, do you top it up with water to push the air out?
Moto

Yes all the air is pushed out.

 

[QuickShow]

Did you put more water!?

Reservoir is already full.

 

[4Ryan6]

Thanks for you reply. The O-ring and the ceramic bearing are in perfect condition, but surprisingly there is a small chip off the edge of the round core in the D5. I think this will mess up the flow but will it somehow produce bubbles in the pump? The reservoir is right above the pump and the tube in between is wrapped with coils so I'm pretty sure that the pump gets as much water as it needs, although the reservoir itself is tiny considering the size of the loop.

I can bleed out the air in the pump by disconnecting the pump power for a moment even when the water is @ 50 degrees, but then after about 2 minutes I can already hear the air being trapped in the pump. And meanwhile there is absolutely no visible air going into the pump from the inlet.

I'll post the pic later.

It sounds like a micro fissure crack in the housing somewhere, allowing air to leach in, is RMAing the pump a possibility?

I'd go ahead and get a backup D5 pump anyway, and then at your convenience have the defective pump completely replaced, then the replacement RMA becomes the backup pump.

I'm only suggesting that because I have a backup D5 pump on hand myself.

The pump is the heart of the system and the only thing that shuts everything down when it fails, so having a backup on hand is just covering your bases, and ensuring you won't be down long for any RMA event.

 

[Motopsychojdn]

Yes all the air is pushed out.

Ok, I just wanted to clarify that point
I'd suggest Ryans course of action is the one to follow, but I'd personally be microscoping the pump and top to try and find any micro-cracks
Moto

 

[QuickShow]

Ok, I just wanted to clarify that point
I'd suggest Ryans course of action is the one to follow, but I'd personally be microscoping the pump and top to try and find any micro-cracks
Moto

Thanks for your reply. I'm pretty sure my pump is faulty and going to replace it with a new one and see what happens.

By the way, if there a crack somewhere, wouldn't it let water leak out instead of air leaking into the pump?

 

[Motopsychojdn]

The water leaks/evaporates out leaving a vacuum and nature abhors a vacuum so air will be pulled into the loop through the fissure
the pump will be playing a part by pressurising the loop, forcing the water out
Moto

 

[QuickShow]

The water leaks/evaporates out leaving a vacuum and nature abhors a vacuum so air will be pulled into the loop through the fissure
the pump will be playing a part by pressurising the loop, forcing the water out
Moto

Exactly. But in my case there's not water leak. There's only air somehow got into the pump.

 

[Motopsychojdn]

For the air to get in there is a hole, if there is a hole then water is getting out, otherwise the level would not drop, a vacuum wouldn't be present and air would not be pulled in,
it may be tiny molecules of water that then get blown out by the casefans so no sign of a leak is evident but if no water is getting out then no air can get in, basic physics
Moto

 

[4Ryan6]

Are you running the pump speed on 5?

Always start out the MCP655 on 5 for a freshly setup loop, then once all the air is flushed you can lower the pump speed.

 

[amuffin]

Are you running the pump speed on 5?

Always start out the MCP655 on 5 for a freshly setup loop, then once all the air is flushed you can lower the pump speed.

1-2 would be fine for "most" loops.

 

[QuickShow]

Are you running the pump speed on 5?

Always start out the MCP655 on 5 for a freshly setup loop, then once all the air is flushed you can lower the pump speed.

My pump is constantly running @ 5.