Water pump comparison

[siteunseen]

I had a small coolant leak I've been watching for the past year.  It was getting moved around by the fan and misting up my engine bay.  So today I put a GBM stamped impeller pump that was practically new.  I've always considered the OE cast impeller design to be better but after comparing the area of coolant passage in both I'm thinking the GMB has more movement. 

Any thoughts, opinions?  I'd like to hear from you guys please.

Doesn't a fan with no restriction on the back side flow more air?  

Edited February 6, 2018 by siteunseen

[Zed Head]

As I recall, people have identified three potential issues with the stamped impeller, but there's not a lot of evidence supporting the theories.  One is just having the stamped steel rust and wear away,  Another is cavitation, causing damage and wear to the impeller.  And the other is lower flow.  I've not seen solid evidence that the stamped is worse than the cast.

Some new engines use stamped impellers in the factory water pumps, I think.  But they were probably designed in conjunction with the housing design.  I think that the stamped GBM impeller is designed to fit in to a housing designed for a cast impeller.  Who knows if it matters.

On the other hand, here's a 2016 Camaro V6 water pump.  2016 and still cast curved blades.  http://www.rockauto.com/en/moreinfo.php?pk=7204964&cc=3353479&jsn=520

[Mark Maras]

 I've run both. I was watching for any change when I went to the stamped impellers the first time. I thought the stamped impeller pump looked cheap and flimsy. No change. IMO, they're both satisfactory for the street. 

[siteunseen]

Thank you both.  The stamped one I have has what appears to be a brass impeller.  I know outboard boat motors have a metal tab above the prop to ground out the electrolysis they create, otherwise they eat up the aluminium on the lower unit.  Hopefully that will not be a problem.

The cheaper stamped pumped actually has a little smoother feel when turning it by hand, felt like better bearings or seals?  Anyway we'll see today when I fill it up with coolant and go for a drive.  The cast pump puts the gauge needle dead on the far right leg of the M in "TEMP".  Maybe I can get it down to the left leg? 

Another thing I thought of last night, the cast impeller is more of a water wheel than an impeller.  It takes the water and moves it in the direction it needs to go, so the backside is irrelevant.

It feels good to work on the Z again, my back hurts but I have something for that. 

[Zed Head]

Never thought about the open back of the impellers on the stamped blade.  It is like a water wheel.  It probably does push less coolant but might not be a factor for a typical street car.  It would be neat to set two up pushing water against each and see which one wins.

Those cast impellers  are so purty though.  I'm surprised people don't polish or chrome them before installation.  Transparent plastic housing with a polished impeller inside.  A few LEDS...  Nice.

[siteunseen]

Another worry of mine on the coolant flow.

@240260280 mentioned running a bypass from the t-stat housing to the inlet for the radiator. I bypassed my coolant line through the intakes on my 240.

Is there any reccomendation on the hose size?  I'm worried too big will suck all the coolant at that bypass and short the supply through the motor.  Maybe 3/16" or 1/4" 5/16"?  I'm gonna go around the front of the head and use a Z inlet with the extra bung for the coolant line off the warming plate that 280s have.  Maybe it's metal line?  I can't remember, I've deleted all that.

Thanks for any advice, thoughts. These little things keep me up at night. 8^(

[siteunseen]

This is sitting in my garage, no airflow with a 180 thermostat.  It gets to 175-180 & opens.  The first picture is the cast iron impeller in an aluminum housing, 173.  The second one is a cheapo GMB from a local chain store, 164.

Well hell, I can't find the 173F pic.  It'll be hiding between healthy and heavy.

A follow up will follow.

 

[240260280]

[87mj]

I'm hurting my head thinking about this but assuming all other variables are correct, is it possible that the lower temp indicates that the new water pump is not moving as much water?  Can that mean water is sitting in the radiator and being allowed to cool longer rather than circulating through the block?

Shouldn't you take the temperature of the head or block instead?

[Zed Head]

So many ways to get variation in what you're measuring.  Cold weather, cold metal, where the point of the thermometer is sitting, etc.  I think that the only test for that new style of blade is a hot day, a long drive, and attempts to make it overheat.  That's just for cooling capacity.  You'll have to wait 10 - 20 years to test durability.

[240260280]

Set up a timing cover and pump with water source and water tower. Turn each pump at same rpm to see which pushes water higher.

[Dave WM]

like that idea of a water pump shoot out, target different RPMs to simulate idle, and 2-3k and then a 5k to see if the design lends itself to different performance at varied RPM.