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Gregte 07-20-2008 07:41 PM

Electric water pump
Just wondering if the belt driven water pump is ever replaced with an electric water pump?

It would seem that the only time the water pump needs to actually pump coolant would be when the engine's thermostat opens. This happens only periodically and not real frequently in cooler weather. The belt driven pump is doing work all the time whereas an electric pump would only need to do work when needed.

Or maybe the belt driven pump is doing very little work when the t-stat is not open and thus no coolant is flowing.

Daox 07-20-2008 08:48 PM

The pump really needs to be going nearly all the time to eliminate any hot spots that develop.

dremd 07-21-2008 12:13 AM

Well; you could run a controller on an electric water pump; and get away with running it much slower most of the time. Payback time? Maybe.

Duffman 07-21-2008 12:52 AM

The advantage of an electric pump would be that the pump doesnt drag more at higher RPM and can be held in the sweet spot constantly.

Gregte 07-21-2008 01:07 AM

Another thing that I had forgot about... the pump needs to be running continuously whenever you are using the heater.

Thanks to all for the input.

Tango Charlie 07-21-2008 09:37 AM

I think most thermostats have a small hole in them so they still circulate a small amount of coolant when closed. At least the thermostats that I've seen.

MazdaMatt 07-21-2008 09:45 AM

I had some overheating problems last weekend (tstat crapped out) and my friend/mechanic explained the cooling system to me. There is apparently a bypass for the rad so the water pump is always circulating coolant within the engine. When the coolant gets too hot, the tstat opens and it starts also coursing through the rad to cool it. You can't run without any water going through or your head would probably warp.

I know that racers use electric water pumps because they push the crap out of their engines, then have to turn them off while blistering hot. They run the water pump for a while with the car off to make sure it cools evenly and doesn't warp anything.

larryrose11 07-21-2008 01:09 PM

Hey guys,
First of all, I wouldn't undertake something like this if you are not comfortable programming a micro computer of some sort, like an Motorola HC11.
Your effots could be put in a better place, like switching over to a manual rack and pinion steering, or plug in battery w/ alternator field kill switch.

I know a bit about electric water pumps. They make sense, mostly on the HEV's I work on for my job. They can run at optimum speeds, instead of just engine speed. Typically coolant pumps on gasoline ICEs actually rely on cavation to limit pump flow!! in order to control e-pumps well, you need to know where you water temp sensor is, and the transfer function for the sensor. You set some minimum flow, say about 0.1 gpm. This will help the engine warm up much faster. There needs to be a target engine coolant temp, say 190F, but below the threshold for radiator fan operation. Use these as your bounds and tune a PID to run a small brushed motor controller that has a 0-5V input.

So here is the non-propriety data: The real benefit to using a E-pump is the elimination of the belt all together. Most modern HEV's already have e-power steering and e-Air Cond. In an HEV, the alternator is redundant, and not present, that leaves the water pump on the belt. The belt, all by itself uses 2-3 HP with no load on it, but that load is pretty constant and doesn't change. Switching to an e-pump allows you to shed that load.

ATaylorRacing 07-22-2008 06:52 PM

To gain more power out of the first car I drag raced I made a electric water pump set up. The car was a 81 Horizon and I bought an electric water pump called a "Water Guppy" that was used to circulate water in bass fishing boats. I had the water pump off of my car (due to bad leaks) and found that the thermostat housing had two bolts that lined up with two where the pump was. I simply bolted on an extra thermostat housing in place of the pump and then put the electric one in line with some longer radiator hose. I ran the pump with a simple on off switch in the car and in hot weather it worked like a dream. I never checked for gas mileage. A trick that a lot of drag racers use is to cut off every other fin inside the water pump. They have less drag, more power, more miles per gallon, and adequate cooling.

ATaylorRacing 07-22-2008 06:55 PM


Originally Posted by Tango Charlie (Post 45978)
I think most thermostats have a small hole in them so they still circulate a small amount of coolant when closed. At least the thermostats that I've seen.

Most of the older cars did not have that feature. I know that the first one I saw was on my 94 Plymouth Sundance Duster....reason for it was to not have as many head gasket failures due to the big temp differences of the water coming in when the thermostat opened up. Since 81 I used to always drill a couple or three 1/8" holes in mine.

MetroMPG 09-18-2008 05:00 PM


Originally Posted by larryrose11 (Post 46048)
I know a bit about electric water pumps...

That was some good info, thanks.

CobraBall 09-18-2008 05:49 PM

Electrical water pumps are common in auto racing.

They can be controlled electronically to adjust the rate of coolant flow "even after engine shut down".

Plan on purchasing an extra motor. You can get a engine driven mechanical water pump just about anywhere. Try to find the replacement water pump electric motor at your local Auto Zone.

I considered putting an electrical water pump on my '33 Ford but gave up the idea. Most electrical water pump mgfs. say they pumps are for racing only.

Simple is usually more reliable.:D

CobraBall 10-16-2008 02:25 PM

Excellent discussion for an Electric Water Pump installation. :thumbup:

EWP Installation

NiHaoMike 10-16-2008 02:30 PM

At the same time, a heating element in a pipe can be installed inline with the bypass and a simple control circuit used to make a crankcase heater.

95badbird 10-16-2008 03:52 PM

electric water pumps.

they work great on daily drivers.

they also work great on race cars.

I run one on my 95 bird....the beauty of it for me, is I can cool the car off(going from 190 degrees to 170 degress in minutes) in the staging lanes before the next race, with the engine off!

parasistic drag from any accessory hurts any kind of mileage or power.
depending on the vehicle make, some e-water pumps come with an idler pulley built in, so belt routing stays the same.

bikin' Ed 10-17-2008 10:08 AM

Efficientcy question
Ok, I like not having the drag on the belt driven waterpump on my engine. Since the E-pump will have to runn all of the time, how much more drag will be placed on the engine due to the alternator supplying power for the extra electrical load?:confused:

Since there are probably soooo many variables, let's limit replies to hypermiling road vehicles with a small V-6 or less ICE. Thanks:thumbup:

95badbird 10-17-2008 12:20 PM

the one pictured above, only has a 7 amp draw.

NiHaoMike 10-17-2008 09:13 PM


Hey guys,
First of all, I wouldn't undertake something like this if you are not comfortable programming a micro computer of some sort, like an Motorola HC11.
Your effots could be put in a better place, like switching over to a manual rack and pinion steering, or plug in battery w/ alternator field kill switch.
Isn't the PWM control just a matter of using a MOSFET controlled by a common PWM chip? For temperature feedback, just mount a sensor on a pipe and use it to increase the duty cycle of the MOSFET. And maybe also add a PWM circuit for the radiator fan as well, and perhaps a servo motor for opening and closing the vents.

BTW, a friend of mine showed me a "desktop supercomputer" she designed the cooling system for. It was complex enough that the cooling system, consisting of a 2HP BLDC scroll compressor, R-410a refrigerant, a large condenser, 9 PZEVs (8 for the main CPUs, one for compressor cooling), and 8 evaporators, had a 200MHz CPU just to run it! Of course, that was because the CPUs had to be kept below -40C to operate correctly. An automobile engine is nowhere near as sensitive to temperature variations as a high performance CPU.

Concrete 12-30-2008 10:22 PM

I don't think you have to build your own controller any more
check this out - I've been drooling about it for a while
EMP/Stewart Components E558AR - EMP Stewart Electric Water Pumps -

55GPH - 10,000 hrs estimated life - 8 amps - inline and small
I'm guessing with the box on the side & the reliability expected, the motor is brushless

only thing holding me back is the price:(

TestDrive 12-31-2008 12:09 AM


Originally Posted by Tango Charlie (Post 45978)
I think most thermostats have a small hole in them so they still circulate a small amount of coolant when closed. At least the thermostats that I've seen.

No to source to cite (other than myself), but it is an over simplification to think of an automotive thermostat as simply a two state (on/off) device.

If you take a new one and toss it in to a pot of cold water on a stove over low heat, you'll see it slowly open as the water temperature nears the thermostat's nominal operating temperature.

jtgh 11-10-2009 02:00 AM

you forget 1 problem.
the energy from the alternator , is wasted converting rotational power to electric.
lose 25% , then the electric motor , back to rotational. Double losses !!
so you'd have to have a very smart electric pump to compensate for that loss.
huge conversion losses.
no free lunch on that. ( no engine alternator creates free energy either )

you also under estimate the huge amount of wasted energy the engine expels as heat.
Even at idle , and cruise.
The water temp(coolant) must never drop below 150F. or the ECU will drop to warm up mode and while go rich AFR. Defeating the whole purpose.
so you must keep the temp between 150 and 195F.
there is a latency for this , you must not let it overshoot.
so long as you maintain good circulation, you will be ok.

I think the mfg wants to shorten the length of the car by taking out the pump on the front RWD. or on FWD cars a bigger motor fitting between strut towers.
lots of reasons, but efficiency? , sorry im just a skeptic,
show me. with hard data.
Lots of ideas, few , hard facts.

Those inefficiencies above are darn hard to overcome.

user removed 11-10-2009 08:17 AM

The key is to control the temperature of the coolant after it has passed through the radiator.

Thermostats control the flow based on the temperature of the coolant exiting the engine, but they do not control the temperature of the coolant exiting the radiator.

Radiator capacity is based on the "worst case scenario" of operation. In every other case it has too much capacity. As you reduce heat losses through hypermiling techniques, you will encounter lower coolant temperatures of coolant exiting the radiator.

When this happens the thermostat will restrict the coolant flow, but that will exacerbate the situation.

Test the temperature of the exit coolant hose in the summer and winter and you will see a huge difference in temperatures, as much as 100 degrees in coolant temperature.

One way to compensate for this is to reduce the effective surface area of the radiator, a radiator block, which has the effect of increasing the exit coolant temperature to bring it up to the temperature of the same coolant in the summer when its hot.

Two ways to fix this would be to have a thermostatically adjustable radiator block, or a thermostatically adjustable radiator bypass. Either solution would make the temperature of the coolant entering the engine constant regardless of ambient temperature or loads applied to the engine.

Basjoos does this by monitoring his coolant fan activity and adjusting his fresh air opening to allow more air flow when the coolant fan operation becomes more frequent.
Making this operation automatic by either adjusting the grille opening or bypassing the radiator would accomplish the same objective of controlling the coolant temperature as it enters the engine.

In his case since air flow through his engine compartment is much less than normal, he also benefits from warm air intake from the higher temperature of the under hood air available to the engine. This is recycling the engines radiated heat for higher efficiency.

I have personally used a radiator block on my Insight and seen a significant mileage improvement in the winter. I Have also completely blocked the lower grille openings on both my Insight and Echo, and it seems to have made a fairly significant difference in maintaining higher mileage as the weather cools down here in the fall.

I know this might seem off topic in relation to electric water pumps, but to me the real problem is not the water pump, but the inconsistency of temperatures of coolant entering the engine and its effect on mileage and thermal stresses.


jtgh 11-10-2009 06:02 PM

all well and good.
the thermostat controls the flow of the coolant based on the temperature of the fluid as it just exits the motor. "out of the book" and controlling the flow controls the temperature at the same point. It will never control the temperature of the water temp. as it leaves the Radiator. By Design.

nothing else need be worried , so long as the Radiator has cooling Overhead

Thermal shock? are you cranking blocks?

you forget to state the problem.

you must be discussing , living in the extreme North. in super frigid temperature.
it is SOP to block the Radiator in these locations. since the tin lizzy days. (im 62 just retired,mech)

i guess we need a variable displacement radiator.
but a computer controlled bypass is the only solution. and one more thing prone to fail.
cardboard works great. as do the variable louvers on MACK trucks.

my friend (heavy equip. op , mech) in Prudhoe bay AK , they spray the whole motors with instant foam insulation. Extremes have not limit , it seems.
most their equipment never gets shut off ( speaks volumes, no?)

If you have cold operation prob. post them.

thanks for your clear issues.

dwtaylorpdx 11-11-2009 02:11 AM

I work on a road race car with an electric water pump. with a 2.0 Liter ford OHC engine the pump runs at about 10% most of the time. and We take the thermostat out because the controller controls the speed of the water flow to the preset temperature. It takes surprisingly little water to cool the engine at speed. Oh, and the car has no alternator, we charge the battery between races, our sequential shifter solenoids use more power than the water pump. (We have full data logging on just about every part of the car....) I can correlate the battery charge at each turn...


Frank Lee 11-11-2009 03:53 AM


Thermostats control the flow based on the temperature of the coolant exiting the engine, but they do not control the temperature of the coolant exiting the radiator...

Two ways to fix this would be to have a thermostatically adjustable radiator block, or a thermostatically adjustable radiator bypass. Either solution would make the temperature of the coolant entering the engine constant regardless of ambient temperature or loads applied to the engine.
Is "too cold" coolant temp variation incoming to the block an issue?

Cuz if the thermostat says brrr I'm cold, it closes, then flow incoming to the block is restricted/stopped. The net result is pretty consistent coolant temp in the block pretty much whatever the coolant temp leaving the radiator is... right?

vtec-e 11-11-2009 07:29 AM

Sounds right to me. I'm interested in this thread because my block heater is an externally mounted one with connecting pipes to the engine. I have no choice in that. However, my temps never get up to much while the heater itself is piping hot. If i had a low wattage mains driven pump then i could heat the engine more evenly.


dremd 11-11-2009 10:29 AM

All depends on the run time of the pump AKA how much waste heat you have.

jtgh 11-14-2009 12:36 PM

race car , i wonder how that race car does in N,Dakota. in the winter?
Most ppl here?,expect it to work full time all the time. not on some track.

sure as i said, the temperature can be controlled at all times with flow and the rate of flow and with more than one sensor, when its really hot and when very cold.
a PIC processor and some tables. nothing more. ( with elec.pump)

Thermostat is a very reliable device and is gosh darn dirt cheap.
it regulates fully linear from closed to open (wax expansion)

one can argue that having simple system is better.
relying on the STAT and the belt. ( few parts)
the early rage for electric fans was.
low hood line.
and too small radiator was used for same, and now motor overheats at a engine kill.
so it kicks on ,parked key off at 225F or higher.

it for sure saves lots of fuel , when driving on a highway, that is for sure.
if the duty cycle is low. 10%
if the DC is high, it uses more energy (fuel) because of it's poor efficiency.(double conv)

keep in mind any extra piping is just more that can freeze.
same with external pump. (mind that antifreeze)

there must be this huge list of pros and cons
engineering is a compromise and must include bad weather.

ATaylorRacing 11-14-2009 01:01 PM

The 81 Horizon I had the electric water pump that I drag raced was also my dailey driver. I even used it several times a year during the winter when the cars the USPS used would not start....I never had a problem in the years I had it and neither did the second owner. I left so early for work back then that my car was the first out into the snow nearly every day...our area would never get plowed until later in the car was the plow!

dremd 11-14-2009 02:07 PM

I think it is safe to say that an electric water pump on a thermostat will save energy on just about any ecodriven vehicle. BUT if you are operating in conditions which create lots of excess heat, then the mechanical pump will win out.
However the time for the pump to pay for itself is very long.

I had a short talk with a manufacturer of an electric cooling pump last week at SEMA ad they estimated that run time was between 5% and 20% on a SBC depending on conditions.

gone-ot 11-14-2009 07:49 PM

...worst case E-waterpump scenario: (a) pulling a trailer; (b) up a steep incline; (c) with A/C-running; (d) on a hot summer day. case E-waterpump scenario: (a) lightly cruising; (b) flat road; (c) no passenger climatic loads; (e) on a cold winter day.

...somewhere between those two extremes has gotta be some hidden FE numbers!

dwtaylorpdx 11-14-2009 11:19 PM

Worst case scenario, electric water pump moving water through the system with 10% the load of the stock mechanical pump. Everything happy.

Best case Cruise on the interstate on a blue sky 50% day, electric pump pulling like 2% of the original systems load, still have a happy ending to the story... :)

I'm going to try and find the specs on the pump I've been working with.
Its a SMALL unit and keeps up with a engine running way beyond design limits.
Gotta be some good data somewhere.

Its worth about 2 effective HP on the race car, if it could maintain that
in a highway situation it would not take long to pay for itself. Plus the
benefit of being able to cross connect it and a block heater for pre-heat use.
As I recall it was about 180 bucks for the unit and the controller was 75


Nerys 11-24-2009 11:49 PM

I am thinking something like a Variac where you simply "adjust" the speed of the pump yourself. IE "YOU" be the computer so to speak.

electric rotational conversion is NOT EQUAL. yes the alternator is very inefficient but if your going epump your also going sans alternator so irrelevant.

also the conversions are NOT EQUAL electric motors are VERY VERY efficient approaching 90% some over 90% electric GENERATORS (ie alternators) are very inefficient.

I am thinking something like a dimmer switch where I "learn" what settings are good for my commute based on outside temps and I "mark" the knob with the temps. get in the car its 60' out turn the knob to the 60' mark and "tune" if needed.

I would add an audible alarm to the temp gauge so if it started to rise (or fall) too much I would get an alert kind of like the sensor telling the actuator to adjust ie the sensor (buzzer) would tell the actuator (driver) to adjust the knob :-)

Can I retrofit an electric motor directly to the existing water pump or would that lose a lot of efficiency?

bluevet 11-25-2009 03:40 AM

where to purchase
where can i find an electric water pump for the 99 metro? (if they even make one)

2speedranchero 11-29-2009 01:16 PM

Something like this maybe

Mr. Gasket 4333 - Mr. Gasket Electric Water Pump Drive Kits
Mr. Gasket 4333 - Mr. Gasket Electric Water Pump Drive Kits - Overview -

basslover911 12-05-2009 10:59 AM

Just get a 12 volt dc (probably 1000 watt) electric motor of ebay and put it either 1) in place of the pulley ie in front of the pump or 2) with a pulley and a belt connecting the motor to the water pump (so you dont have to mess with "modding" the water pump at all).

Nerys 12-05-2009 11:46 AM

I was not sure if that would be efficient or not. I may try it though because I can use an AC bracket to mount the motor too and this way LEAVE the water pump and alternator in place as is. So if something happens I can pop the regular belt on and be on my way stock.

basslover911 12-05-2009 02:36 PM

Exactly... sure its not the MOST efficient way but if you rather pay $150 for an electric water pump, find a way to mount it, route all the lines, and remove the oem water pump then you can do that also :D

Nerys 12-05-2009 04:38 PM

I was thinking LEAVE the oem pump in place and I figured a replacement pump would have an IN and an OUT which I could simple insert into a cut in half radiator hose. Done. No mounting hassles no running lines no removing the oem pump (that is an issue will water flow ok if the oem pump is left in place and not spinning? I have no idea on that one.

Remember I want to go alternator free as well so power consumption is pretty critical. a 1000watt motor "seems" to my gut check to be seriously over kill.

smokeyj 12-07-2009 02:07 AM

Here is a company that makes electric water pumps for cars, including a controller.
Kind of expensive but nice little video explaining the benefits and savings.

You can get with or with out the controller.

They are targeting 3L V6 type car. They claim a benefit.

I am interested but hoping someone else will give it a go.

Davies Craig

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