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Water pump recommendations

AlaskaBill

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the AC Delco pump from a 2000+ 6.5 will get you all the updates that GM did balancing the flow. This will get you the spin-on style pulley where you will need to use a different clutch. two good options here. If you go with the Hayden thermostatic clutch you will need ether the 9-blade steel fan (I have one available) or the d-max plastic fan. the second option and one of my favorites is the electro-viscous fan clutch coupled with a Hayden electric fan controller. Just lookup the application for a 2010-11 3500 express van with the d-max engine for both the clutch and fan blade.

Credit is due to @ak diesel driver for this as he put this together for us on our trucks. I can get you the part numbers if you need them, everything is available on RA using all AC Delco parts except for the fan controller. this setup will allow you to set what temp you want the clutch to engage and also have ether an override switch in the cab or have it wired into the AC system when the AC needs a fan but the truck might not be up to temp and a normal fan clutch wouldn't help. all of these mods are direct bolt on and no molesting under the hood required, allthough it's highly recommended to plan on installing new motor mounts and possible trans mounts due to the larger fan blade possibly contacting the fan shroud.
There is a different WP for 2000+ 6.5's that balances flow? I would be interested in any information on that!
 

SnowDrift

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I think if you read over this entire thread, including the embedded links, you'll find that it has been thoroughly covered. There is a question as to whether the later pump versions are different in terms of flow. One point which was made is that they're essentially the same internally so they flow the same, but another point is that there is an additional fitting in the bolt on type (non spin on) that might cause enough disruption in flow that it doesn't really balance the flow into the engine.

From what I can tell the spin-on version is probably worth me putting onto mine when the time comes.

Welcome to the forum, incidentally. If you fill out your signature line, it is helpful to those wanting to help on a given situation. Different years and options, along with modifications factor into decisions and responses.
 

dbrannon79

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not sure about the balance flow but iirc the best pump was deemed as the AC Delco 25-1603. it's shown on the 1999 and 2000 6.5's on RA's site. 98 shows a Delco 25-1590 which I am not sure what the differences are between the two.
 

dbrannon79

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Correction: the 98 pump 25-1590 is a bolt on hub for the clutch and has two ports on the pump the 99+ 25-1603 is a spin on hub with pulley and only has one port. I need to look at mine, but I think mine came with two ports and a spin on hub.

it wouldn't surprise me if the hubs could be swapped since they are both press fitted on the pump shaft


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AlaskaBill

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I think if you read over this entire thread, including the embedded links, you'll find that it has been thoroughly covered. There is a question as to whether the later pump versions are different in terms of flow. One point which was made is that they're essentially the same internally so they flow the same, but another point is that there is an additional fitting in the bolt on type (non spin on) that might cause enough disruption in flow that it doesn't really balance the flow into the engine.

From what I can tell the spin-on version is probably worth me putting onto mine when the time comes.

Welcome to the forum, incidentally. If you fill out your signature line, it is helpful to those wanting to help on a given situation. Different years and options, along with modifications factor into decisions and responses.
Thanks SnowDrift!
 

AlaskaBill

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If you search the flow kooler threads here- you’ll see we spoke about them and I called them up asking about the balanced flow issues. They knew NOTHING of it.
They have their twist on a pump impeller design and are making replacement units for all kinds of engines in cars and trucks with that impeller.

In the threads here you’ll notice when in their ads the LATER ADD about balanced flow. Sales pitching without actual testing anything.

Worse sales pitching to customers that haven’t worked around pumps professionally:
And they still have the thing about high head pressure. It an issue in the laws of physics.
“Head” pressure is just pressure on the output of a pump. But there is positive displacement pumps like your oil pump or fuel pump, and there is non positive displacement pumps like a car water pump which uses an IMPELLER not a PROPELLER. Technically pumps don’t create pressure. They create flow, and the resistance to that flow creates the pressure.

So actual head pressure is measured when you completely stop the flow of the fluid, then while at its median speed measure the pressure. And since this is an impeller- that number will be zero. The impeller is designed specifically to not allow pressure built from the pump. Here is why:
Engine cold, no pressure. Remove thermostat also remove radiator cap, start engine- no pressure only flow. As engine gets hot no pressure can build and at 212 you boil water away. If you add the cap- THE HEAT builds pressure like a pressure cooker on the stove.
You have a 15 lbs cap- and the engine gets hot enough with this engine to make 14 psi all by itself. Now- imagine if all the sudden you add a water pump that can add 1,2,3 psi pressure. POP goes the cap and water on the hiway!

Now think about that thermostat when it is put back in. Engine is cold, thermostat closed. Big 2” radiator hose feeding that water and it has to circulate somewhere or blow a hose off. So the impeller is designed to let the water “slip past” so that it doesn’t build pressure while cold. Most of us have seen the waterpump backing plate and noticed the pitting- its all chewed up like it is rusting away. That is not rust. That is cavitation. When you increase the flow it increases that cavitation linear. But when you increase pressure it reduces the cavitation. Why did gm go from 97 to 127 (not really the 100-130 estimates we round off to) snd not go to say 140 gpm? The cavitation is in reased dramatically. It isn’t hard to change impeller angles and counts. It doesn’t cost ten times more to do that. They had to pick how high they could go without creating a new problem.
And adding back in that thermostat- does that change the pressure that is created by the engine heat? Nope. That pressure when the thermostat is open and the cooling is really needed- what is the system pressure- is it magically higher head pressure for an advantage? Nope- it is what it is from temperature changes.

All engines of every manufacturer has always only used an impeller water pump for this reason. They cannot run a pump that is positive displacement UNLESS they control the speed based on heat and pressure generated. A modern design that would be great is a positive displacement pump, no thermostat, heat sensors in a few spot on the engine as well as water pump that feed a computer to tell the pump when come on and go off as needed for cooling.

Yall remember me talking about the testing I did years back? We removed the belt driven waterpump and used two electric driven pumps to replace it. This was on an engine stand. And we did 2 pumps not one because we didn’t have electric motors that were strong enough to drive a single pump. That electric water pump idea should sound perfect- no wasted energy, better control of cooling- even one side vs the other!
And so long as you use a honda generator in the bed it would work.
Look up electric water pumps that can move 100 gpm and notice the hp they use. You are not driving that on 12 volts anytime soon. You need a Toyota starter motor running non stop for that much power. Water pumps steal a crap ton of power even without the fan. Thats why our old school drag cars had restrictors inplace of thermostats and the electric belt driven pumps- free hp. Just enough cooling to keep it alive then cool it down in the pits. They talk about the 130 gpm now from reading forums. But never learned the actual GM spec of 127 or would have referenced it. Then they never say what gpm their improved unit is. Just “It achieves greater flow rates, higher head pressure and a more efficient flow.” Ok, last claim of more efficient? Lets say sure- because they don’t say more efficient at what drops per revolution while using less fuel? More efficient at moving money from one store into theirs is most likely.

One last thing about their snake oil slinging speak- “color is due to Type II Class II military grade surface coating” ok- plenty of military folks here. Anyone know where to look that up? That is some bs there. I mean- they already are trying to argue against the laws of physics so why not the military nomenclature as well. Look at the pic and see what is meant. Then tell me who here had their impeller wear out as the issue why they replaced their 6.2/6.5 water pump. Instead of the front seal failure that sends coolant out the weep hole so you don’t seize the bearing and have your fan be the giant ninja star of death.
View attachment 78755

If that coating is all that and a bad of chips- why aren’t they selling it on the backing plate which actually surfers the damage they are trying to protect against.

Look- I am not saying this can not work, or that it can not work better.
But a couple folks said they tried it and had less results than the AC Delco.
And this company has done some shady advertising at minimal.
And they did admit to never having run a 6.5 on-a dyno or in a truck to do comparisons testing. They said they did tests on a small car engine (I can’t remember which right now) and the “technology” proved itself so well they started making pumps for many other engines including the 6.5.

Last take a look at what year vehicles this works on and doesn’t work on. They don’t even know the interchange years.

With the known problems that experimenting with 6.5 cooling has brought about- no way can I afford to blow up an engine verifying what they think will work with what we know works- after GM spent millions trying to figure it out.

It just pisses me off when any company wants to pedal snake oil and and acts like it is king daddy when they haven’t even actually tested it on that engine enough to see their holes don’t even line up. Yeah if you do remember that part- ya might search it - but to be fair that might have been hummer forum not here.
Greetings Will L,

I can understand that you are passionate against the FlowKooler, you may be right, I have no experience with them. I try to stay with OEM unless it has been substantiated that something else is better, like turbos and open down pipes.

As to “head pressure” I think FlowKooler is trying to say the higher flow would produce more pressure to move coolant through the head. I don’t think they were trying to say you would get higher pressure (total) including pressure rise due to heat in a closed system. Centrifugal or impeller type pumps do not build a lot of pressure, but to be sure there must be differential pressure between inlet and outlet or there is no flow. This is the result of cavitation, impeller still spinning but little to no flow. Manufacturers specify “Head Pressure” and it has to do with the pump’s ability to lift a column of water so many feet. The head pressure is the PSI that can lift the weight (mass) of water in the hose, or move water along in a very long hose which would take more force, unless going down hill.

I like the idea of moving coolant out the back of the head then to circulate, but with the thermostat(s) closed, I don’t know how best to accomplish that.

I didn’t know about the 99+ water pump with pressed on pulley and spin on clutch. Wish I knew if it is actually better than the 130 gpm pump, and what all needs to be changed. For now I am using the 130 gpm pump, twin thermostats, 9 blade steel fan, KD lower temp clutch and Mishimoto radiator.

On a side note, I thought 130 gp(m) was a typo, I’m trying to imagine filling up 2 and 1/2 55 gallon drums in (1) minute!!! And is that at something like 4000 rpm?

Anyway thanks for the post, I don’t think anyone will venture to try the FlowKooler even if available.
 

dbrannon79

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Lol I start scratching my head trying to visually see the flow pattern in these blocks with and without the thermostat. I have that 6.2 mounted up on the stand with the pump still attached. one of the days I might just mock up a clear container to it with hoses from the pump and heater outlet, chuck a drill to the pump hub and watch things. maybe even play with the block off plates on the rear of the heads too. it would be interesting to visually see just how much water flows out of each head.

I always wished someone could do this mockup and video it for all to see. maybe someone better and more knowledgeable than I could do this and in several ways. maybe even removing the thermostat crossover and adding two hose bibs one on each head with a hose or even left open to see flow streams from each side.
 

Will L.

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I'm getting a bit lost about the various water pumps. I always thought the 1997pump was the 130 gpm pump and was the best one to buy. Can someone explain the various pumps? "Balanced flow", "spin on", and "H.O." get me confused. It is all very interesting though.

One point, using the heater hose at the back of the right head for flow wouldn't work if you also run it to the heater core as it is throttled (flow control valve).

Just put a new pump on my 95 with an expensive Mishimoto radiator, a front transmission cooler deleat, and twin oil coolers and AN-10 hoses. Looking to keep coolant and engine oil cool towing heavy.
AC Delco 88894035. The current spin on pump from GEP/ AM General is the same unit.

There are tons of knock off parts - many of AC Delco items included Nd they
Greetings Will L,

I can understand that you are passionate against the FlowKooler, you may be right, I have no experience with them. I try to stay with OEM unless it has been substantiated that something else is better, like turbos and open down pipes.

As to “head pressure” I think FlowKooler is trying to say the higher flow would produce more pressure to move coolant through the head. I don’t think they were trying to say you would get higher pressure (total) including pressure rise due to heat in a closed system. Centrifugal or impeller type pumps do not build a lot of pressure, but to be sure there must be differential pressure between inlet and outlet or there is no flow. This is the result of cavitation, impeller still spinning but little to no flow. Manufacturers specify “Head Pressure” and it has to do with the pump’s ability to lift a column of water so many feet. The head pressure is the PSI that can lift the weight (mass) of water in the hose, or move water along in a very long hose which would take more force, unless going down hill.

I like the idea of moving coolant out the back of the head then to circulate, but with the thermostat(s) closed, I don’t know how best to accomplish that.

I didn’t know about the 99+ water pump with pressed on pulley and spin on clutch. Wish I knew if it is actually better than the 130 gpm pump, and what all needs to be changed. For now I am using the 130 gpm pump, twin thermostats, 9 blade steel fan, KD lower temp clutch and Mishimoto radiator.

On a side note, I thought 130 gp(m) was a typo, I’m trying to imagine filling up 2 and 1/2 55 gallon drums in (1) minute!!! And is that at something like 4000 rpm?

Anyway thanks for the post, I don’t think anyone will venture to try the FlowKooler even if available.
Yes, rated flow was crazy high- I can’t remember but probably was 4,000.
And technically was 97 and 127 free flowing.

@Twisted Steel Performance
I would think so. But companies advertise and make it sound flashy- people buy up whatever it is without any evidence. All they care about is money, not if they are actually helping people or hurting them.
 

Hink

Overkill Is Underrated
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Nothing against Hink but he got most of his info here

Yessir, and I try to credit the people here as much as I can along with referring people to the forum itself.

And @SnowDrift nailed it as far as putting it all in one place. That was one of my main goals along with being able to change the articles as new info comes out, having detailed pictures, video, and writing in a way geared towards the new guy learning to turn their own wrenches.

(BTW, @ak diesel driver , I'm still trying to get up there and visit you. Maybe it'll happen this year!)
 
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