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Old 09-11-17, 05:39 PM
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So irritated...

Sadly, Mazda waterpumps have been NLA for years now, and they no longer supply remans at any rate.

This leaves us two options...

One, you buy a new patent-part waterpump.
Two, you buy a shady reman. waterpump.

I chose the new route, but I am here to discuss the consequences of either choice...

Part manufacturers go on about how their new or reman pumps are equipped with the latest impeller designs. What they actually mean by that is to say that they are designed for more efficient 'pumping' of the coolant.. ergo, faster coolant flow.

This is a problem. By speeding up the flow of coolant through the system, it does not remain in the radiator quite as long as a good OE pump with an OE impeller. The consequence of this is lack of heat dissipation, and that my friends means warmer coolant temps.

My old OE pump, comparing datalogs between it and the 'new' aftermarket pump, averaged 5 to 10 degrees cooler across the range.

My temps have risen a majority average of 10 degrees. The temps are more sensitive to even light loads or short bursts of medium to high loads even as ambient air temperatures have dropped significantly.



Before anyone anyone asks, I replaced the pump immediately upon spotting that there was a tiny leak. The car did not run any hotter than its usual 185, there was absolutely no measurable loss of coolant, and I stopped driving the car when I spotted the signs of the tiny leak. After replacing the pump with this patent part, I (as anyone should anytime the cooling system is opened for service) pressure tested the system to ensure the new pump or gasket was leaking. It held pressure just fine.

The difference between the impellers is pretty significant. The new part is much taller and does not have anything like the same taper of the blades. The design of the impeller viewing it from the top appears very similar, but the blades have much more surface area due to the extra height and lack of taper.

I am not amused..

I'm thinking of calling the parts manager of my shop's Mazda vendor armed with part numbers to see if the seals and bearings for the OE pump are still available so I can rebuild my OE unit.
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Old 09-11-17, 06:55 PM
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I would guess that both the seals and bearings are standard metric. You need to get the original ones out and look for a number on all parts and cross reference. If there is no number, ID and OD on the seal and bearing will lead you to a replacement.
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Old 09-11-17, 07:58 PM
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I do not doubt/question your results but this:
" By speeding up the flow of coolant through the system, it does not remain in the radiator quite as long as a good OE pump with an OE impeller. The consequence of this is lack of heat dissipation, and that my friends means warmer coolant temps. "
...is sheer nonsense.

IF the coolant spends less time in the radiator and therefore does not shed as much heat, the coolant is ALSO spending less time in the engine and therefore not picking up as much heat to shed.

Your new impellor design is the root of your issue, maybe it's less efficient, maybe it cavitates...who knows?
But it's not because the coolant is rushing through the radiator.
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Old 09-11-17, 08:10 PM
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Im going to agree with clokker on this one. If a anything i would have thought faster flow would have a better chance of controlling hot spots and keeping an even temp through the whole block. The coolant is spending just as much time in the rad when you consider its passing tjrough there more often. The problem with too much waterpump speed is risk of cavitation at the impeller.
Fwiw there are after market waterpumps all over the place. Quality and design could be a minefield though..
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Old 09-11-17, 08:26 PM
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As long as he's using the stock pulleys, the speed of the pump hasn't changed.
Impellor design could be less efficient, but it's spinning just as fast as the OEM pump.

First thing I'd do is dump a bottle of WaterWetter in the loop and see what happens.
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Old 09-11-17, 11:15 PM
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The impeller may be spinning at the same speed, but a difference in the design of it to move more coolant wouldn't require it to spin any faster.

I also believe its a lot easier for the coolant to pick up heat in the 'bowels' of the engine and turbo than it is to shed that heat in the radiator.

There could be something to the cavitation theory, but I can't think of a way to compare the pumps in that regard.

I can't imagine a manufacturer would have altered the impeller design that would move coolant more slowly than the original and call that an improvement.

Without hard data, and having compared the two visually, I'm going to stick with more surface area/larger blades = more flow rate.

Regardless, this is very irritating.

Water wetter should not be necessary now where no problem existed before.
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Old 09-12-17, 12:10 AM
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Im confused, Mazdatrix and Atkins Rotary still sells Mazda Water pumps
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Old 09-12-17, 12:16 AM
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Both vendors list the OE part number, but that does not mean you're getting a genuine mazda part, unless specified.

I'm sure someone out there has NOS parts, it's a matter of hunting them down.
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Old 09-12-17, 06:43 AM
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Atkin's also has OEM pumps
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Old 09-12-17, 10:10 AM
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"This is a problem. By speeding up the flow of coolant through the system, it does not remain in the radiator quite as long as a good OE pump with an OE impeller. The consequence of this is lack of heat dissipation, and that my friends means warmer coolant temps"

Common internet myth.
Increased coolant flow in a closed loop system provides an increase in cooling capacity, not a decrease.
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Old 09-13-17, 06:03 AM
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You're going to have to back that up with something, because if it is an internet myth, then it's been around since before the internet.

My information on the subject comes from old men who do the american muscle car thing, and technicians at several different dealerships. It's pretty well accepted info.
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Old 09-13-17, 06:53 AM
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"I also believe its a lot easier for the coolant to pick up heat in the 'bowels' of the engine and turbo than it is to shed that heat in the radiator.
"You're going to have to back that up with something, because if it is an internet myth, then it's been around since before the internet. "

If you want to relitigate fluid dynamics and physics because some old guy with a Camaro told you to, feel free.
That set of conditions leaves you but two options...
-Either find an OEM pump, which should return you to the acceptable temps you saw before, or...
-Increase the size of your heat exchangers.
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Old 09-13-17, 07:28 AM
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Grumpybutt returns!

Yes, an oe pump design would put my temps back where I had been before. Having to upgrade a radiator to make up for a poor water pump impeller is a little silly.

And these old camaro guys' have more than likely built and raced more engines than you've owned, so, nice stab, but it's unwarranted.
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Old 09-13-17, 07:45 AM
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Originally Posted by Acesanugal View Post
Grumpybutt returns!


And these old camaro guys' have more than likely built and raced more engines than you've owned, so, nice stab, but it's unwarranted.
Possibly (although I do have nearly ten years in racing...) but my experience and their experience combined does not trump science (see what I did there?).

Perhaps you'd explain the mechanism that allows your coolant to take on heat efficiently in the engine block but lose the ability to shed the heat in the radiator.
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Old 09-13-17, 07:57 AM
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Physics and fluid dynamics aside, advertizing is advertizing. Their better impeller design means "cheaper to make" and it may not flow as well or cause cavitation at the speed it's running in the pump. Otherwise, it works great at low speeds but may be spun to fast in the RX7 application. I know a bit about manufacturing and they'll use the same impeller in as many pumps as possible. This goes for just about everything.


Out of curiosity, is the impeller cast like the original or is it stamped steel?

Last edited by TonyD89; 09-13-17 at 08:06 AM.
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Old 09-13-17, 08:10 AM
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I agree that the impellor design is probably at fault but this: " Otherwise, it works great at low speeds but may be spun to fast in the RX7 application."
Is somewhat misleading because the pump is spinning exactly as fast as it always has been.
The impellor design may be less efficient at higher rpm (very likely/possible) but engine speed isn't the problem, the design is.

Last edited by clokker; 09-13-17 at 08:39 AM.
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Old 09-13-17, 08:19 AM
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My point was if the impeller is somewhat generic and used across different applications, it may not be spun as fast in the other applications. I agree, the pulley ratio did not change.
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Old 09-13-17, 09:20 AM
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It is a cast impeller.

I'm no science major. I am simply describing my experiences and giving my theories on why the change has occurred. I am basing some of it off of conversations I've had with experienced engine builders (albeit not rotary), what I've read on this forum, and information I sought out on my own using the internet (obviously). The argument of coolant flow vs. heat absorbtion and dissipation seems to go either way... regardless of whatever technical jargon people use to defend either theory or what kind of physicist or thermodynamic engineer these people all claim to be.
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Old 09-13-17, 09:24 AM
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How does it look compared to the factory one? There was a thread in the first gen (I tried, couldn't find it) where someone noticed the impeller on his replacement water pump didn't run as close to the housing as his old one and set out to fix it. He felt it was hurting it's cooling ability.
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Old 09-14-17, 02:36 PM
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Originally Posted by Acesanugal View Post
You're going to have to back that up with something, because if it is an internet myth, then it's been around since before the internet.

My information on the subject comes from old men who do the american muscle car thing, and technicians at several different dealerships. It's pretty well accepted info.
google broken?

http://stewartcomponents.com/index.php?route=information/information&information_id=14

Last edited by scathcart; 09-14-17 at 02:38 PM.
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Old 09-14-17, 03:18 PM
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Of course google isn't broken, don't be ridiculous. It's not unreasonable to ask you to provide reasonable proof to back up your opposing theory.

So maybe these 'improved' impeller designs are slowing the flow of coolant rather than speeding them up.

Either way, hotter coolant temps vs. the OE pump's results are not a good thing.
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Old 09-14-17, 05:06 PM
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If the company you're buying from is claiming an impeller is more efficient isn't claiming it moves a higher mass flow, its claiming it uses less energy for a given flow than the stock design.
Most of the aftermarket pumps I buy claim to "meet or exceed" oem specifications, which would, of course, meet a flow requirement.
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Old 09-14-17, 05:48 PM
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i have a few remans that have stock impellers, and they haven't leaked.
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Old 09-14-17, 11:15 PM
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OK. Atkins is OEM for certain. Unless they're printing Mazda stickers which would be pretty dirty.
Impeller design could increase flow. Increased flow is basically guaranteed to raise efficiency. That's how convection works.
It's hard to measure flow :/.
Maybe you could take the hose off the BAC and floor it and test it that way. See which one gets closer to the garage door haha. Just keep the dog in the house.
If you buy one and your temperature moves then you can come back here and tell us all about it.
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Old 09-15-17, 06:15 AM
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I will be hunting down an OE pump at my earliest convenience. Stupid aftermarket. There's a reason I do everything I can to not order aftermarket parts at work.
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