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Discussion Starter · #1 ·
A friend has a 37 Chevy with a 350, aluminum radiator, and Derale flex fan (7 blades I think). There is absolutely NO ROOM for a clutch fan or electric puller fan between engine and radiator. Problem is the coolant temp rises to 200 degrees or more in slow traffic with the A/C on. Once the car starts moving, the temp drops to around 180. I know 200 isn't all that bad, but my friend wants a little insurance against it rising even higher in traffic jams, etc.

We were thinking about adding a pusher fan, but consensus on this forum is not to do it. I don't recall his water pump being anything special, probably just a stock replacement. So I'm wondering if using a better water pump could gain him a little insurance. There are lots of so-called "high-flow" pumps, but which ones actually live up to their claims? Also, would using a smaller diameter water pump pulley make a noticeable difference, assuming we can find one? Engine probably never sees more than 4500-5000 RPM, so fan and water pump speed would not be an issue.

Comments?
 

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I can't say for sure on some of the other high flow water pumps that is sold out there but I have a summit high flow water pump that looks like a stock replacement and I have run a regular factory regular volume water pump and I have honestly not had any difference in temperature on how my chevy s10 runs. I have issues with very low speeds and in stop and go traffic. The main thing is with high flow water pumps they recommend using a high flow theremostat instead of a oem one because the oem style hinders the flow and takes away the advantage of running a high flow water pump, but that is according to a company that sells them so I don't know how much truth there is to that.

I have used high flow thermostats and the oem ones and there is pros and cons in certain situations when it comes to cooling and your using a system that is not a factory setup that was normally built to run in stock trim without any fancy this or that water pump or super sized radiator etc. I can't say it hurts anything to run a high flow water pump as in my situation it has never done any different one way or the other. The difference for me has been my thermostat used but I have the pros of it and also the cons of how it is being done on my build.

If the ride does not go over 200 degrees and stops there I would not worry about it as many modern factory motors run around 210 degrees all day long in stop and go traffic. If it continues to rise past 200 and will keep getting hotter as time adds up then yeah I would be concerned. I don't know if some style high flow water pumps work better then others or not as I only have the experience with oem style looking ones. Hopefully someone else more experienced on the subject can shed some more info.
 

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High flow pumps aren't the wonderfulness that everyone says. They won't solve an overheating problem. You're limited by the physical properties of the coolant. It has a fixed rate at which it can absorb heat.

So think of it this way. Let's say the current pump flows 20 gpm and the coolant stays in the block for 2 minutes (not realistic numbers, just roll with it) Now replace it with a high flow pump. Now it flows 40 gpm, but the coolant is only in the block for one minute. You aren't moving any more heat from the engine to the radiator. Your problem is that the radiator isn't shedding enough heat.

You're right... 200 is not too hot, but if the temperature is rising, it means you have more heat going into the coolant than is being shed, and it might cause overheating in stop and go.

A pusher might help modestly when moving slowly, but it more often than not blocks too much free flow when you're cruising. You might trade one overheating problem for another. I would suggest trying one. You can maximize your chances of success by sourcing one that has as little blade real estate as possible so it doesn't block much free flow. Maybe have your friend keep an eye on FB or CL for a cheap used one so you're not out a bunch of money.

Heck, you might be able to simulate it with a box fan. Strap the fan to the condenser blowing back and run the A/C in the garage. See if it helps. Then unplug and go for a drive to see if the box fan causes overheating on the highway. Its certainly not an accurate test, but it might show you a trend and help make a decision before spending money.
 

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Maybe a high-flow t-stat is where we should start.
IIRC You are in North Texas. Its Hot during the Summer! I know, I used to get consistent readings of 135+F from any paved surface in July, and August.
How much coolant does your current radiator hold? Coolant volume comes into play also...

But if you are looking for a good HV Pump, go with Stewart for your application. You wont be disappointed, they make some fine quality products.
 

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This is an air flow issue over the radiator fins, a high flow coolant pump will be of no help as that is not the problem. You probably won’t find much nor lasting help from a high volume thermostat either. A pusher fan or more likely pusher fans ahead of the radiator will help especially if you use an array of smaller fans arraigned in the corners outside the diameter of the engine driven fan as without a shroud that encases and seals the core to direct the fan to pull air across the entire core then these outlying areas are doing no cooling unless forward vehicle motion is pushing air through these areas. This is evidenced by the 20 degree drop with doing nothing more than getting the vehicle moving. The downside of fans ahead of tge radiator is at sustained high speeds they start to impede air flow across the core. Which takes you back to the best solution is a shroud. Here is an example of do it yourself in a tight space yet maintain some streamlining for buffet free airflow inside the shroud.

Alternate cooling such as an engine oil cooler with electric fan and if this is an auto trans vehicle a similar stand alone ATF cooler are of great help, the down side is finding a place to mount them.

Bogie
 

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Take that flex fan.
Throw it into the trash.

Get a steel 7 blade truck fan with a fan clutch from a 80's chevy truck.
Use a shroud from the same truck and modify it to fit by cutting/grinding the outside.
195F thermostat.
Stock waterpump

My guess is that you have a 7 blade flex fan with no shroud. These flex fans are known for being poorly constructed and also will cut you up when working on your ride.

Here is how I test a coolant system. Start up the vechicle and then bring it up to 70mph (driving nice) for 5 to 10 minutes(watching it) then down to park and let it idle in drive for 3 minutes(watching it) then let it idle in park for 10(watching it). Now drive it hard (over 70mph) then park it and let it idle for 30 minutes(watching it).

Then shut it off, turn the key on and watch the temp gauge. It should rise no more then 10 degrees(staying below 220) before eventually falling if the system is properly pressurized.

If it boils (going above 220) when you shut it off check your cap(thats the reason a majority of the time) then pressurize the system to check for a possible head gasket failure.



I drive my piles hard.
I expect them to get up to 200 in under 5 minutes of driving.
I expect them to hold 200-210F for several hours of driving holding 3000 to even 4000rpm (no overdrive) during that unintrupted 1 to 3 hours of drive time.

A 7 blade truck clutch fan with a truck shroud has never failed to deliver. I do run 4 cores when possible with anything over 350ci. Under 350 ci I have ran 2cores with out issue under the same conditions. But if you can fit a 4 core then run one.
 

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O.p. stated he had no room for a clutch fan , one of these^^^^^^^ should fit , will help I think & isn't horribly expensive . until the temp gets 230-240° in traffic , I wouldn't worry , as has been said , a shroud is you friend !
 

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Curtis73 is correct about "pump flow rate". (Although heat transfer rates are generally "non-linear"). I had the same issue with "no room" for a fan on the water pump, and my distributor cap is about 1/4" from the firewall. The issue with configuring fans was solved by using two pullers on a fabricated shroud, with the water pump nose being right between the fans. Later, I added a "double" transmission cooler and put an additional pusher fan on the bigger cooler that is controlled only by the fluid temperature (I thought I had a cooling problem with my 700R4 causing elevated 4th gear shift points, till I one day I had no 4th at all - but I was wrong. It was the "sticky governor".. a whole 'nuther story).

If he's really worried about overtemperature, he could always install two pushers as large as possible on opposite corners of the radiator, and control them with a Davies-Craig (made in England and carried by Summit Racing), with an electronic temperature display and 10 second fan sequencing to take care of "dead spots" on the corners (the controller has replaceable standard plug in relays)... Also for what it's worth, (and this is just a belief) electric fans DO NOT degrade any measurable heat exchanger efficiency while driving fast on the highway. Think of it this way: fan performance is primarily affected by the static pressure that it's pushing through (air flow resistance through the condenser/radiator), fan RPM, and atmospheric pressure (altitude). All else being equal, when you are sitting still, the fan(s) won't push as much air through the radiator due to the static pressure it's pushing against. Sitting still is the worst case scenario for fan performance. So the faster you go, the higher the static pressure on the ENTERING side of the fan, therefore increasing the flow rate/fan performance. At some point of speed, there is a balance between the incoming air / blade speed, so at that point, the fan, though energized and running, is basically doing nothing to help flow the air. And for the fan to actually restrict the airflow, while it is operational enough to make any difference in "how well the engine is being cooled" it's just insignificant. That's my story, and I'm STICKIN' to it !!

Oh, I just thought, slightly off subject, but I saw some guy say that if you install a 40 amp relay, and wire the relay power circuit (10 Gauge) between your alternator output terminal and the input power circuit of your fans (with an auto reset circuit breaker - or fuse), with the relay holding coil wired between you "accessory" ignition wire and ground, you will get full alternator power to the fans and fan speed will be measurable faster, especially if your fuse block and battery is in the trunk... it works..

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Flaps are for highway speed air flow..

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First you should realize that everyone who has solved a heating problem has had different results when they tried the exact same thing that someone else did. Its hard to say that any one specific change will always be effective OR that a specific change never solved a problem for someone. So take all suggestions with a grain of salt.

The basic problem is contact time between the coolant and the engine head. Thats the hottest point in the system. People talk about how coolant can be made to flow too fast and not carry the heat away. Thats totally untrue........IF...........you have a continuous supply of coolant that is sufficiently cooler than the surface its rubbing against. The RUB so to speak in an automotive system is that you have a fixed amount of coolant rather than a never ending fresh supply, and it must give up the heat it absorbed by rubbing against the aluminum surfaces in the radiator and subsequently transferring that heat to the air. So looking back at the statement that coolant can't flow too fast,...........well yes it can. Its not only about coolant speed, but the area available to rub against.

To clarify that: If I take some boiling water and pour it in 2" diameter tube 1 foot long and just removed from my freezer, it will flow thru fast enough that it doesn't give up much heat and will still burn my hand as it flows out. On the other hand if contain the coolant and let it slosh back and forth, it will cool. So you either need more area or more time. Depending on how someone wants to view this or describe it, when you have an unlimited amount of coolant, it can't flow too fast (within reason) to cool. When you have a limited supply contained in a system, it may flow too fast to give up its heat. So is it flowing too fast or is there just not enough surface area ? Semantics........

In general, adding a high volume pump generally doesn't help because you are still caught in the same self contained system that isn't quite giving up the heat while its in the radiator. One solution some people use when they can't put a larger radiator in, is to either buy or convert to a multiple pass radiator. At each side of the radiator, a small plate is put in place that causes the flow to reverse and go across the radiator again. Basically the coolant flows thru the top 1/3 of the radiator, reverse and flows back to the other side in the next 1/3 and finally crosses a third time at the bottom 1/3.

It is always possible that a particular thermostat is not completely opening or closing or that some air might be trapped in the heads. Possibly the addition of an oil cooler or removing a transmission cooler from a radiator and installing a stand alone cooler might pull some heat from the radiator. At the very least, it is going to keep cooler oil flowing if the engine does get too hot. Sometimes coolant hoses collapse and reduce flow when running.Lots of little things that can make a difference.

Might wanna watch this video........https://www.youtube.com/watch?v=ZXdLgaFXZzs
 

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Yes, you have an air flow problem. If you have no room for bigger fans or as mentioned, a clutch fan, then you’ll have to make room, I don’t know if small blocks had “short” and “long” water pump version accessory setups. If they did, he could try going to short water pump accessory setup. Which is expensive if it even exists, scoot engine back, which would be expensive and a nightmare, or scoot out the core support if the grille would even accommodate it.

A flex fan isn’t ideal, but with a proper fitting shroud, it will work. It’s a clutch fan without the clutch, they’ve been used forever, that would be a lot of overheated cars all over if they didn’t work. Another thing to think about, what avenues does the air have to escape the engine bay? That can help. Louvres in the side panels can evacuate heat or not using them at all. Ever heard of the take the hood off trick.

He‘s not in major trouble, but it sounds like he’s at the point of having to work on each part to gain a couple degrees here and there, if you catch my drift, one part may mean a three degree drop, another may mean five degrees. And, with ac, you have another restriction for air to go through, take the condenser off, might just drop the temps.

Here‘s the deal with high flow pumps. If you purchase a pump for an ac car, or one marked “heavy duty”, guess what, it’s a higher flow pump. But, they won’t be the miracle cure all. As far as heat transfer, air bubbles in the coolant cause more harm than too fast flow, bubbles cut the surface area down, which means less heat transfer.
 

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Discussion Starter · #14 ·
Take that flex fan.
Throw it into the trash.

Get a steel 7 blade truck fan with a fan clutch from a 80's chevy truck.
Use a shroud from the same truck and modify it to fit by cutting/grinding the outside.
Thanks for all the comments and pictures, but there is no room for a clutch fan between the water pump pulley and radiator. The owner has an electric fan that's about as shallow as you can get, and even it doesn't fit. Hindsight is 20-20, but if he had a do-over, I'm sure he'd move the engine back another couple inches.

Maybe that Speedway 7-blade fixed fan is worth a try, but it might sound like a B-29 at mid-high RPMs! Also, maybe the idea to run a small pusher at a corner of the radiator might help. That could be do-able.
 

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I been there. What you need to do is not use one big puller. You need to use 2 smaller ones.

This will let you put the waterpump in between the two fans (ideally). Now with a horizontal (rectangle) radiatior this is easier. You have more room to have one higher then the other and can usually get it so those waterpump pulley bolts are dang near a inch off the radiatior fins.
But with a vertical radiatior everything is right down the middle and if the engine is to high or low then you need to adjust. Ideally you would want two equal sized electric fans as big as will fit above and below the waterpump pulley.
But in the real world compromises need to happen and you may find yourself using a larger fan on the top and a smaller fan on the bottom. Or vice versa.
Now your still pulling that entire radiatior using 2 fans because you have the thing shrouded. 2 fans(of the same quality) can often out pull a single fan(not always).

Two fans will require more amps and I would install a 2nd fan controller so one comes on followed by the second coming on 5 degrees later to lessen the initial load you would have if both came on at once. I would also run a cs130 in place of a si10/12 alternatior to give me more amps for those fans to pull while idling in traffic.

Radiatior hoses actually hold heat. I have installed copper and aluminum pipes in place of rubber hose with short sections on the ends to allow for engine movement. Not only can these be polished to look nice. But they shed a surprising amount of heat. Just be mindfull of this before putting your paw on the thing when its hot.

Now I dont know how orgional he wants the thing to look. But I have ran my heater hoses through the dash(to the heater) and instead of going right back to the motor I made a dual pass heat sink out of copper tube and aluminum. I just took two 40" sections of copper pipe soldered 2 90's on the end so it made a U then used a junk condenser cutting it down to 3"x36" to place the aluminum against the copper with bolts above/below the tubing.

The thing sat on the outside of the frame rail and the hose ran back to the motor. If I had a longer flat section of frame I could have ran a longer one.
This adds capacity in the amount of around 1/2 to 1/3 of a gallon. If the car is sitting low it can easily go unnoticed. Your brake/fuel lines and exhaust should be on the inside of the frame and placing this on the outside lets it vent easier then if it were on the inside. The downside is if they can see your frame they will see that shiny aluminum finned contraption. But if that was the case a louvered or such piece of aluminum could be used to draw the heat from the copper while looking nice.
 

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Something else to consider since you mentioned the problem occurs when idling with the A/C operating. Sometimes the electrical supply isn't totally sufficient when idling because the alternator used doesn't provide enough current when idling. The fan may be turning slower than desired because it isn't receiving a full current flow.
 

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Yeah, running plumbing clamped tightly to the frame is a common trick be that copper or ordinary steel plumbing material. This adds capacity in volume of coolant and uses the frame as a heat sink. It’s pretty effective and easily concealed.

For any build the builder should strive for as much engine setback as the firewall clearance and exhaust system will permit. This not only gains space between engine and radiator but also massively improves handling by reducing to eliminating the overhung moments induced by those parts of the engine ahead of the front able.

Bogie
 

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Did I miss it, or no one mentioned a fan shroud? The OP does not mention it, but really, this should be the first thing to do. The other problem I see is the flex fan, it should probably be replaced by a OEM steel fan (without clutch).
 

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What the world needs is a pump driven fan that doesn’t need but could optionally use a fan clutch along the lines of the S-10/Colorado that is stiff reinforced plastic with 11 blades.

If there is space for a thermal clutch and one is using reverse rotation serpentine drive the GM fan is unbelievably effective at moving air. What I’m suggesting is there is a market for a clockwise rotating version that can or not exploit the choice of a clutch or not.

Bogie
 

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Before adding anything electrical to his system, I would put a few pieces of wire in front of the radiator and attach some thin paper strips to them so they flap when air is pulled through the radiator. Then let the engine idle and notice how much they are moving. Next, run the engine to 2,000 rpms and see if there is any change in how much they are moving. If there is a noticeable difference, then the cooling fan is turning slower at idle due to a shortage of current from the alternator. Costs nothing to check this, and eliminates one possibility..........
 
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