Electric Water Pumps & Rear Mounted Radiators

[ludacris]

Ok I have a rear mounted radiator and have a Davies Craig electric water pump aswell as the original water pump to help get the water to the front with all the extra piping.

I have been told to remove the electric pump as there may be to much pressure. And the water maybe flowing to fast.

The temp was getting a bit high on the dyno but I have removed the shrowed and added two more electric fans. Two fans pushing now and one pulling. The tempreture holds while idling but have not been able to test under load with the extra fans.

Has anyone played with the electric water pumps and have you had any issues with using them.

Cris

[Draven]

Ive never played with rear mounted rads, but I would have thought the thermostat would have slowed the water down more than enough ??

[ludacris]

Ive never played with rear mounted rads, but I would have thought the thermostat would have slowed the water down more than enough ??

That is what I was thinking.

Cris

[BushTuckerNed]

Do you have the digital controller with the pump to? Cant you adjust water flow with that?

[ludacris]

Do you have the digital controller with the pump to? Cant you adjust water flow with that?

No I do not have the controller but I can hook the water pump up to the thermo swithch but that may cut the water flow down to none when the pump / fans are not running.

Cris

[chimpboy]

There is no such thing as coolant "flowing too fast" unless your problem is that your engine is running too cold. Faster coolant flow = more cooling. Unfortunately there is a myth out there that coolant "has to sit in the engine long enough to pick up heat" or something but it is not correct.

The system is designed for pressure so "too much pressure" seems doubtful unless you are blowing a lot of coolant out from under the pressure cap.

I have heard that the davies craig pumps can be more hindrance than help to coolant flow but I have never used one.

[ludacris]

I have heard that the davies craig pumps can be more hindrance than help to coolant flow but I have never used one.

Ok this is interesting. I will definatly be doing some testing without the electric water pump if the truck does not hold temp with the extra fans under constant load.

Cris

[money_killer]

should have ur fans sucking not pushing. that may have something to do with it also

[ludacris]

should have ur fans sucking not pushing. that may have something to do with it also

The big one is sucking 2750 cfm and the other two little ones are pushing on opposite side of the radiator.

Cris

[chimpboy]

The big one is sucking 2750 cfm and the other two little ones are pushing on opposite side of the radiator.

Hmm, some would say that is possibly not as good as just leaving the small ones off as you could effectively be blocking more of the radiator off. What I mean is that wherever there is some fan hardware such as the fan centre up against the rad, basically you are removing that much of the radiator area from doing anything.

Is the puller in a cowl or is it hard up against the rad? Just personally I would try leaving off the two smaller fans and mounting the larger fan in a cowl such that it is pulling air through the entire radiator. It would be a bit of work though if you currently have it hard against the rad.

I would also try ditching the electric pump and just running the mechanical one.

And then I would kind of take it from there, but I would probably not have fans both in front of and behind the rad.

Just some thoughts.

[money_killer]

wat chimpnoy said. or run twin sucking in a shroud like a au themo setup.

[ludacris]

wat chimpnoy said. or run twin sucking in a shroud like a au themo setup.

If anything I will go to this setup and ditch the electric water pump. Will do some testing first.

Cris

[PJ.zook]

There is no such thing as coolant "flowing too fast" unless your problem is that your engine is running too cold. Faster coolant flow = more cooling. Unfortunately there is a myth out there that coolant "has to sit in the engine long enough to pick up heat" or something but it is not correct.

The problem with coolant flowing too fast, isnt that not to do with flowing through the block to pick up heat, but lies with not getting rid of it quick enough in the radiator, as the temp differential between the coolant and engine is much larger than the coolant and air flowing thru radiator?
If the coolants flowing too fast does it not have enough time to transfer the heat into the air?

[chimpboy]

There is no such thing as coolant "flowing too fast" unless your problem is that your engine is running too cold. Faster coolant flow = more cooling. Unfortunately there is a myth out there that coolant "has to sit in the engine long enough to pick up heat" or something but it is not correct.

The problem with coolant flowing too fast, isnt that not to do with flowing through the block to pick up heat, but lies with not getting rid of it quick enough in the radiator, as the temp differential between the coolant and engine is much larger than the coolant and air flowing thru radiator?
If the coolants flowing too fast does it not have enough time to transfer the heat into the air?

No, the faster the coolant flows through the total circuit the more efficient the cooling system will be.

[60_series_united]

There is no such thing as coolant "flowing too fast" unless your problem is that your engine is running too cold. Faster coolant flow = more cooling. Unfortunately there is a myth out there that coolant "has to sit in the engine long enough to pick up heat" or something but it is not correct.

The problem with coolant flowing too fast, isnt that not to do with flowing through the block to pick up heat, but lies with not getting rid of it quick enough in the radiator, as the temp differential between the coolant and engine is much larger than the coolant and air flowing thru radiator?
If the coolants flowing too fast does it not have enough time to transfer the heat into the air?

No, the faster the coolant flows through the total circuit the more efficient the cooling system will be.

you's both have a point, but its flowing throught the radiator at the same rate as it is flowing through the engine so it is still going to have the same amount of heat transfer as it would if it was slower, but then saying that with it being faster it shouldnt let it get up to a higher temp, if that makes sence
tyson

[GeneralFubashi]

Indeed it does, because slow flowing water picks up a lot of heat going though the head, then loses a lot through the radiator.

Fast flowing water may not pick up as much heat, but then doesnt have to lose as much to keep the coolant at optimal temp. Its just with faster flowing coolant you are distributing a set volume of coolant over a larger pickup area in the head thereby hopefully getting a better equalisation of coolant temperature. So you shouldnt be getting hot spots.

The coolant differential is correct too, but shouldn't have any effect for sustained running, yes the engine heats the water faster than the radiator can get rid of it, but only until the normal operating temperature of the engine is reached, and only because the thermostat reduces flow through the radiator until a certain temperature. Using air to cool fluid, as long as there is some forced air flow through the radiator, the air is always going to be flowing faster than the water in the tubes, so if anything you wont get the best cooling effect until water speed is increased to the point the air through the veins is picking up all the heat it can before being blown out past the engine, and while the engine fan blows, the differential remains pretty much at 87-35 or so (if you live in qld).

Sam

[its aford not a nissan]

There is no such thing as coolant "flowing too fast" unless your problem is that your engine is running too cold. Faster coolant flow = more cooling. Unfortunately there is a myth out there that coolant "has to sit in the engine long enough to pick up heat" or something but it is not correct.

The problem with coolant flowing too fast, isnt that not to do with flowing through the block to pick up heat, but lies with not getting rid of it quick enough in the radiator, as the temp differential between the coolant and engine is much larger than the coolant and air flowing thru radiator?
If the coolants flowing too fast does it not have enough time to transfer the heat into the air?

No, the faster the coolant flows through the total circuit the more efficient the cooling system will be.

i dont know where you get this dribble from , the radiator can only remove so much heat dependant on air flow going through the radiator ,and seeing as we are using thermo fans then the air flow is limited , just speeding up the flow of coolant through the radiator will only over run it with hot water or insufficiently cooled water will be re-entering the block , i keep hearing this falicy(sp) of faster flowing water is cooler , yeah maybe in a stream but wtf has that got to do with engine coolant under pressure ??? ( not saying this was said here , but i have seen it refered to before) yeah sure faster flowing coolant in the block is fine but the water pump will look after that as the coolant is constantly recirculated and held in the motor till the thermostat opens and allows the water pump to suck cooled water in from the radiator , the only ways to make a radiator more efficient at removing heat is to either ; fit a bigger radiator ( bigger radiator means it holds more coolant slowing the flow of coolant down through the fins ) , increase air flow ( uses more power ) , or increase the temperature difference between the coolant temp and ambiant air temp ( the bigger the difference the easier it is for the air to remove heat )

sorry but it gets frustrating when i see people say things that defy the laws of physics , seriously , if a radiator cant cope with the heat , how is speeding up the water ( hot ) going to help without increasing the amount of the air to absorb the heat ???

[chimpboy]

sorry but it gets frustrating when i see people say things that defy the laws of physics , seriopusly , if a radiator cant cope with the heat , how is speeding up the water ( hot ) going to help without increasing the amount of the air to absorb the heat ???

I am not going to have this argument with you again, you simply don't understand the topic and it isn't my job to teach you high school science.

The frustration is in continually hearing backyard mechanics saying, "nah the coolant hasn't been in the radiator long enough to cool down." I am referring specifically to the first post and the argument that the extra pump might be making the coolant flow too fast. That is clearly incorrect.

The point is that the only flow-rate problem you could realistically have, that could possibly lead to high engine temps, in any likely situation, is flow that's too slow, not flow that's too fast. If you disagree with that then... I dunno what to say.

[its aford not a nissan]

sorry but it gets frustrating when i see people say things that defy the laws of physics , seriopusly , if a radiator cant cope with the heat , how is speeding up the water ( hot ) going to help without increasing the amount of the air to absorb the heat ???

I am not going to have this argument with you again, you simply don't understand the topic and it isn't my job to teach you high school science.

The frustration is in continually hearing backyard mechanics saying, "nah the coolant hasn't been in the radiator long enough to cool down."

LOL , i think you need to study a bit more , but hey its no skin off my nose , i know im not giving out bad advise , i really think you should re-read what you have written and have a think about it

[chimpboy]

sorry but it gets frustrating when i see people say things that defy the laws of physics , seriopusly , if a radiator cant cope with the heat , how is speeding up the water ( hot ) going to help without increasing the amount of the air to absorb the heat ???

I am not going to have this argument with you again, you simply don't understand the topic and it isn't my job to teach you high school science.

The frustration is in continually hearing backyard mechanics saying, "nah the coolant hasn't been in the radiator long enough to cool down."

LOL , i think you need to study a bit more , but hey its no skin off my nose , i know im not giving out bad advise , i really think you should re-read what you have written and have a think about it

I'm not going to bang my head against yours on this topic again, IIRC we've had this argument before. If people want to take your advice and slow their water pumps right down to 1/10 speed or something, because apparently it doesn't make any difference, then that's up to them!

[its aford not a nissan]

sorry but it gets frustrating when i see people say things that defy the laws of physics , seriopusly , if a radiator cant cope with the heat , how is speeding up the water ( hot ) going to help without increasing the amount of the air to absorb the heat ???

I am not going to have this argument with you again, you simply don't understand the topic and it isn't my job to teach you high school science.

The frustration is in continually hearing backyard mechanics saying, "nah the coolant hasn't been in the radiator long enough to cool down."

LOL , i think you need to study a bit more , but hey its no skin off my nose , i know im not giving out bad advise , i really think you should re-read what you have written and have a think about it

I'm not going to bang my head against yours on this topic again, IIRC we've had this argument before. If people want to take your advice and slow their water pumps right down to 1/10 speed or something, because apparently it doesn't make any difference, then that's up to them!

im not telling people to slow there water pumps down , it does its job just fine , but speeding it up wont help either, besides , the thermostat controls how fast the coolant flows through the radiator not the water pump

[Jacked]

you all have it wrong. a radiator is a great heat exchanger. it can get rid of the heat very quickly. its the water running through the engine that cant exchange heat fast enough.

if water is flowing too fast through an engine block it will not have sufficent time to absorbe heat from the engine. part of a thermistats job is to slow the flow rate of the coolant. alot of cars will overheat whilst cruiseing at 100 kph on the freeway but not at idle due to the thermastate being removed (to much flow).

fast flowing coolant systems will give a low reading on temp gauges (as will a guage that has no water around it) but it will not cool down hotter areas around the top of the cylinder head.

what you are saying defies all basic engine cooling princibles that are taught too a first year apprentice mechanic (spelling isnt taught there so dont even bother) if you think thats wrong chimp take it up with the automotive apprenterships board or whatever there called. they have only been teaching it for 60 years im sure they will want to listen too you.

water takes time to absorbe heat. if you have a thermostate in your cooling system this would provide enough restriction if you had 100 water pumps (not that it would increase flow by 100 times)

20L of water throwen in a hot cast iron pot for a minute will reduce the temp off the metal fuck all compared to 10L put in there for 2 minutes (provided the same surface area)

test it in the backyard for yourself if you dont belive me.

[rockcrawler31]

Jesus.

some of you love taking liberties with the laws of physics don't you.

Part of my job is understanding fluid dynamics and cooling isn't about flow rates it's about temperature differentials. Everytime i've taken the thermostat out it's run wayyyy colder due to the increased flow without the annular restriction of a thermostat. I've NEVER had it run hotter without a thermostat. We have to consider drill bit cooling when we design a drill string and pump rates. And every calculator i've ever used assumes higher rates of flow increase cooling.

As for the OP - i suggest maybe taking off the pusher fans. Laminar flow will always cool better and since air is a fluid, i'm thinking that perhaps the pusher fans are inducing turbulent rather tha laminar flow characteristics.

[its aford not a nissan]

you all have it wrong. a radiator is a great heat exchanger. it can get rid of the heat very quickly. its the water running through the engine that cant exchange heat fast enough.

if water is flowing too fast through an engine block it will not have sufficent time to absorbe heat from the engine. part of a thermistats job is to slow the flow rate of the coolant. alot of cars will overheat whilst cruiseing at 100 kph on the freeway but not at idle due to the thermastate being removed (to much flow).

fast flowing coolant systems will give a low reading on temp gauges (as will a guage that has no water around it) but it will not cool down hotter areas around the top of the cylinder head.

what you are saying defies all basic engine cooling princibles that are taught too a first year apprentice mechanic (spelling isnt taught there so dont even bother) if you think thats wrong chimp take it up with the automotive apprenterships board or whatever there called. they have only been teaching it for 60 years im sure they will want to listen too you.

water takes time to absorbe heat. if you have a thermostate in your cooling system this would provide enough restriction if you had 100 water pumps (not that it would increase flow by 100 times)

20L of water throwen in a hot cast iron pot for a minute will reduce the temp off the metal . all compared to 10L put in there for 2 minutes (provided the same surface area)

test it in the backyard for yourself if you dont belive me.

water is a great heat exchanger , its the air that isnt so good , thats why you need 3000 cfm of air flow to cool 30 cfm ( estimate ) of coolant

the thermostat only controls the flow of coolant through the radiator , it has no control on the flow of coolant through the motor, the water pump constantly recirculates the coolant in the motor whether the thermostat is open or not , and the water pump controls the speed of flow in the motor

fast flowing coolant reads the same temp and is the same temp as slow moving coolant ( no matter what planet anyone lives on )and the temp sender will read it the same unless there is air in the system

water does take a bit of time to absorb heat , but not that much , and the reason the water pump recirculates the coolant in the motor is to keep an even temp in the motor and not have hot spots

[its aford not a nissan]

Jesus.

some of you love taking liberties with the laws of physics don't you.

this also makes me laugh

Part of my job is understanding fluid dynamics and cooling isn't about flow rates it's about temperature differentials.

exactly , but flow still plays a part


Everytime i've taken the thermostat out it's run wayyyy colder due to the increased flow without the annular restriction of a thermostat

which is what normally happens untill the motor starts to put out more heat than the given airflow through the radiator can remove


. I've NEVER had it run hotter without a thermostat.

your just lucky

We have to consider drill bit cooling when we design a drill string and pump rates. And every calculator i've ever used assumes higher rates of flow increase cooling.

limit the amount of coolant in the calculations and watch the coolant temp rise

As for the OP - i suggest maybe taking off the pusher fans. Laminar flow will always cool better and since air is a fluid, i'm thinking that perhaps the pusher fans are inducing turbulent rather tha laminar flow characteristics.

[Draven]

Maybe its not to do with flow at all...Is the radiator upto the job ? Blocked maybe ? Did it work when it was mounted in the front ?

[-Scott-]

The internet - still the world's best source of incorrect information.

There are people posting in this thread who clearly have little knowledge of physics, and even less understanding of how a typical engine cooling system works.

Ludacris, I don't know how your setup works, but my understanding is that an electric water pump typically removes the thermostat and controls pump speed to regulate temperature.

I've also read a long thread on another forum in which Davies Craig were unable to configure a system to keep an LS engine cool.

Have you looked into measuring coolant flow, to see if that gives you any hints about what's going on? I'm not sure how you'd do it, without buying some expensive instrumentation...

[ludacris]

Maybe its not to do with flow at all...Is the radiator upto the job ? Blocked maybe ? Did it work when it was mounted in the front ?

It is a 4.2 diesel radiator and has been flowed tested recently. I just removed the shrowed and added the two little fans pushing with the big one pulling still after the dyno run.

The truck was holding temp idling but on the dyno it got upto 103 and we had to take a break to let it cool. I will only be able to test the truck this Sat under load to watch the temps. I will test with the electric water pump and without to see if that makes a difference.

If it does not hold temp I will use a good alloy radiator and grab some falcon fans.

Cris

[chimpboy]

Itsaford... on reflection I am not sure whether what you think I'm saying, and what I'm actually saying, are the same thing. If you look at the original post, Ludacris got advice that the "the water maybe flowing too fast", causing his engine to get too hot. I am saying this advice is wrong and suggested he should be looking at his airflow.

If you think that Ludacris's engine may be getting too hot because his water pump(s) are flowing too much coolant, please say so as otherwise I am not sure what the discussion is.

if water is flowing too fast through an engine block it will not have sufficent time to absorbe heat from the engine.

This is dead wrong. PLEASE show me the page in your textbook where it says this.

We are not talking about a case where the thermostat has been removed. Sure, an engine with the thermostat removed may have cooling problems. However they are not because of "too much flow", they are because the design of the engine requires a thermostat to be present to control where the flow is happening. A better example would be a thermostat that is stuck open, which will always result in the engine running cooler (or as hot, but not hotter) than it would with a working thermostat (all else being the same).

(Obviously I don't mean "more coolant flow but without worrying about whether the flow goes through the whole water jacket like it's meant to".)

To say "water takes time to absorbe heat" in the sense you are saying it is just incorrect. Water (or air, or whatever) will absorbs heat at a rate per second, or a rate per microsecond, or a rate per nanosecond, but in the tiniest fraction of a second it will absorb some heat and if it then flows along to the radiator to shed that heat, it doesn't matter because the next little bit of water has come along to absorb some more heat. The difference is that when it is moving faster the system as a whole becomes more efficient.

20L of water throwen in a hot cast iron pot for a minute will reduce the temp off the metal . all compared to 10L put in there for 2 minutes (provided the same surface area)

I'm going to assume we are not talking about a pot that's over boiling temp, because that would be boiling off water which is a different thing.

I am not sure about your example but let me tweak it a bit to show something that I am sure about and that is more relevant.

Here goes: if you put 20L of water into your hot cast iron pot for two minutes, it will shed more heat in the first minute than in the second minute, more in the first second than the next second, more in the first 1/10 of a second than the next 1/10 of a second. The best microsecond of heat transfer is the first one, when the temperature difference between the pot and the water is at its maximum.

That is why it will initially cool quite noticeably, then the cooling will taper off and the last bit of warmth in it will take a while to dissipate.

Anyway, how about we go into my backyard and do a different experiment, using an old Mazda wreck I have sitting there. Here's the experiment:

1. We will give the thermostat a whack with my big shifter so that it is stuck fully open.

2. We'll replace the stock water pump with an electric one that has an adjustable flow rate... just a big dial from zero to 10, zero is no flow, five is about the same as the stock pump, 10 is twice as much flow.

3. We'll put the electric fan (there's no mechanical fan) direct to the battery so it's always running.

4. We'll conduct our experiment in constant weather conditions just to be extra careful.

Then we'll start the motor and let it run at, say, 2500rpm for an hour or so at each of the eleven different settings on the dial and plot out what the stable temperature ends up being with different coolant flow rates.

What do you think will happen? At zero or low flow rates the engine will overheat and die. At some flow rate, say around 4-5, the engine will sit at roughly it's normal operating temperature. At higher flow rates it will run cool, approaching a limit based on the radiator size, fan performance, and ambient air temp.

In fact, it will do something like this:



I understand you think I am wrong. Fair enough. So, what do you think would happen instead?

ps just for kicks, this is what it would do with the thermostat working:



If you are in the left side of the graphs, you need to look at your water pump. If you are in the right hand side (but still having overheating issues) then your blue line is too close to your green line (or is above it) and you need to look at air flow, rad size, etc.

[rockcrawler31]

If you are in the left side of the graphs, you need to look at your water pump. If you are in the right hand side (but still having overheating issues) then your blue line is too close to your green line (or is above it) and you need to look at air flow, rad size, etc.

This is what led me to think about the rad. All the water is doing is moving the heat to another spot, flow rates or otherwise.

If the engine produces more heat than the radiator can cope with it will over heat.
If the rad is larger than the heat produced it will cope with the heat load until something else reduces efficiency. Blocked rads, airflow, sticking thermostats reducing flow, positive air pressure pockets limiting flow and so on

As an aside, is the temp guage working properly? i recently thought the motor was running hot but the VDO guage or sender wasn't working properly (so much for VDO being the ducks guts.) It was reading 104 and when i put a laser temp reader on the rad it was reading 75 degrees and at the back of the block (traditionally the hottest part of the 1HZ and where the sender is) was reading 84 degrees.