Does This Debunk the "Coolant Can Flow Through the Radiator Too Fast" Idea???

[RustyRatRod]

I agree. But we aren’t talking earth moving equipment or junk like that.

If you radiator won’t cool and it’s aluminum, it’s not not cooling because of what it’s made from.

So my over simplifications aren’t really.

They are facts.

Almost no one disputes that two big cores will out cool four smaller cores. You aren’t building a radiator out of brass or copper or some mix of it that will tolerate two big cores.

Again, that’s a fact not a simplification.

If guys would figure out that skimping on cooling causes power losses because you can’t set and control engine temperature then they’d follow the simple rules outlined above.

I didnt make those up. Those came from the industry.

A few simple phone calls to a couple of places and anyone can learn what I posted.

Buying undersized junk **** and not grasping what it means when you have a 180 degree thermostat and the engine on hot days is running at 200 they should know their cooling system is NOT doing its job.

It’s failing at its job.

Guys will argue if it ain’t piking water out it ain’t hot and I call bullshit on that thinking.

Again, if you are 180 on the thermostat and 200 on the gauge it’s TOO HOT.

If that’s not too hot, get a 195 thermostat. Of course that’s not the fix for a piss poor designed cooling system.

I just don’t get why people don’t understand why the above scenario is wrong.

I've been talking to US Radiator off and on for the past couple of months, as I plan to plunk down probably about a grand for a copper/brass radiator for my truck, Gladys. I want very similar to what she had from the factory. She's an F250HD with the camper special package. Her original radiator was huge and a three row high efficiency core. US Radiator has echoed all of your talking points and then some. They've been at it a long time. I think they know what they're doing.

 

[Inertia]

I've often mused how raw water cooled boats (inboards and outboards too) running in various raw water temps from 32* melting glacial lakes, oceans, as some of my boats have been, how they maintain the 140* engine running temps that raw water thermostats run, (to avoid mineral (salt) crystalizing in the cooling system), - if somehow the thermostat didn't modulate the flow ?
Was there a valve I was supposed to adjust ?

 

[Newbomb Turk]

I agree, in our application if a car isn’t cooling it’s not because the radiator is aluminum


Actually it is again a wild oversimplification. Because if we’re talking about a 4 core brass/copper radiator and a large tube 2 core aluminum radiator it is NOT a slam dunk that the aluminum radiator will cool better. It simply is NOT a fact. You’d have to test those individual radiators, and the result would depend on the individual construction. It could easily go either way.

Saying otherwise is simply a wild *** guess.


Nope. Another simplistic over generalization.

Yes, the thermostat only sets the minimum temperature.

In general your cooling system should be able to maintain a temperature within the operating range of the engine. The thermostat has no effect on that, it’s out of the loop the moment it fully opens. So if your car maintains 180, or 190, or 200 once the thermostat is open that has nothing to do with the thermostat and everything to do with your engine, it’s tune, and your cooling systems capabilities. If you run a 160° thermostat and your car will maintain 190° regardless of the situation it doesn’t indicate an issue with the cooling system at all.



This is silly. Why are you worried about the “restriction” from the thermostat if your cooling system works well?

As for the amount of over or under drive it totally depends on the pump itself and the rest of the system. AC Mopars were overdriven at 30-40%.

As far and maintaining within 10°, sure, that indicates a robust cooling system, but that’s not a standard that indicates anything less is junk. If your car maintains 180° all day with a 160° thermostat you’ve got no issues at all.




Nope, not true. Pump speed is very important, and has to be matched. Again, Ma Mopar changed the speed of the pump by over 30% depending on the engine and options. It’s not the only thing, but it’s a thing. There are several threads here where members solved their overheating issues just by changing their pump drive ratio. Mostly after realizing they were unintentionally under driving their water pump.

Again, follow what I say and your cooling system will work.

I could get into why aluminum works better but nothing will convince you no one IN THESE CARS needs a heavy assed radiator.

If you read EXACTly what I wrote you would have noticed you said exactly what I said about thermostats.

The thermostat controls the MINIMUM OPERATING TEMPERATURE IF TGE ENGINE.

That’s not a ******* guess or an assumption. It’s a fact. You even agree with it and then tell me I’m guessing. That tell me you don’t read what I write.

So if engine temps are higher than the rated temperature of the thermostat the cooling system is at fault.

Whether it’s the radiator or a fucked up clutch fan or some whiz bang in gym shorts decided to slow the pump down, it’s the cooling system that’s wrong.

So again, whether you like it or not if anyone is getting ready to make enough power that you need to upgrade your cooling system follow these simple rules.

Biggest two core radiator you can fit. Even if the core opening isn’t as big as it could be. Get as big as fits.

A high flow water pump is a must. Arguing against that is just stupid.

Get a quality high flow thermostat.

A mechanical fan if it will fit. Most of the time an electric fan won’t pull enough air at low speeds to cool the engine. The good ones will but the power savings if they won’t do it costs more power because the temp can’t be controlled.

Cooling is about flow. Air and coolant flow.

Chrysler used up to 20% overdriven.

So get the pump and fan turning faster than the crank.

No guessing there. But once, cry once.

 

[HemiSSDart]

The ONLY reason OEM's use aluminum and plastic is that it is exponentinally cheaper than brass/copper! My 2001 2500 Cummins split one side of the plastic tanks while on a transport a couple years ago, NEVER had that happen to a brass radiator. Sure the solder has split on the top tank but it was simple to fix in a matter of minutes while on the road while the aluminum POS had to be replaced by me in a gas station parking lot after taking an Uber to and from a parts store that had one in stock and I barely got it together and on the road before dark. I have never had an issue with a brass radiator but sure have with aluminum, so this old fart will always err to the side of decades of service...

 

[Bewy]

Back to the original topic, coolant flow rate.

I think the best explanation is on this website: www.stewartcomponents.com

And it is really simple!

The cooling system is a closed system. If the coolant stays in the rad longer [ as some wrongly believe ], then that must mean the coolant is backed up in the engine for a longer period of time....& absorbing more heat. When this coolant arrives at the rad to be cooled, it is hotter...

 

[ESP47]

The thermostat controls the MINIMUM OPERATING TEMPERATURE IF TGE ENGINE.

That’s not a ******* guess or an assumption. It’s a fact. You even agree with it and then tell me I’m guessing. That tell me you don’t read what I write.

So if engine temps are higher than the rated temperature of the thermostat the cooling system is at fault.

The first sentence there is true. The last sentence is not. If your engine runs at 195-200* and you decide to throw a 160* thermostat in, your cooling system is not at fault because it doesn't stay at 160*.

 

[Newbomb Turk]

The first sentence there is true. The last sentence is not. If your engine runs at 195-200* and you decide to throw a 160* thermostat in, your cooling system is not at fault because it doesn't stay at 160*.

EXACTLY. YOU MADE MY POINT.

The cooling system SHOULD have the capacity and capability to maintain WHATEVER your thermostat opening is.

On my piece of garbage I use a 160 thermostat and it barely climbs to 168-170 on 100 plus degree days.

And I could drop a 195 in there and that would be as cool as it would get BUT it won’t get any hotter than that either.

Why?

Because my cooling system will maintain 160 degrees. If I take the thermostat out it won’t even get to 160 because the system will cool it.

I run a 160 degree thermostat because I drive it in the winter and I need a defrost.

So both statements are correct.

If you are using a 190 thermostat and you drop down to a 160 and it still runs at 190 then you KNOW your cooling system isn’t up to even par.

 

[Inertia]

If you have an infinate amount of cold water supply, you can put any thermostat temp you want in there, and it will continue to run at thermostat temp, as the thermostat itself modulates the coolant flow.
Some of you seem to feel the thermostat opens fully at whatever temp, and stays fully open, - nonsense.
If the thermostat is full open all the time, how can cooling ability increase as more heat is created by "work". ie hill, load, ambient temp .
It doesn't, the wax pill in the stat modulates the opening to increase flow, as more heat is created in the coolant.
Thermostats generally fully open once coolant temp exceeds a few degrees over stat rating.
If you have a 180* stat, and engine runs 200, your system has no reserve to "work".
Years ago I tried to get overheat issues diagnosed with a heat gun or pyrometer at the top and bottom rad hose, suggesting the difference should exceed 50*, and that 30* be a very min., suitable for a " lawn tractor".
Then, I suggested folks go shoot the temps on their daily driver to compare, . (It'll be 50* +)
Some have understood.
If you can't get the radiator/coolant to shed enuff heat,
SOMETHING IS DEFICIENT.
Radiator ability/capacity, and/or airflow .
Once you get the radiator to shed 50 + *, you then likely need a thermostat to slow flow.

I have repeatedly tried to explain the thermostat modulates the opening to regulate flow thru an adequate cooling system to maintain the desired temp.
If you think the thermostat just "opens", - watch the video.

Good Luck !

 

[Brooks James]

I was considering a hi psi pump, went to high volume and a fat radiator

 

[Newbomb Turk]

I was considering a hi psi pump, went to high volume and a fat radiator

Who makes a high pressure pump?

 

[ESP47]

EXACTLY. YOU MADE MY POINT.

The cooling system SHOULD have the capacity and capability to maintain WHATEVER your thermostat opening is.

On my piece of garbage I use a 160 thermostat and it barely climbs to 168-170 on 100 plus degree days.

And I could drop a 195 in there and that would be as cool as it would get BUT it won’t get any hotter than that either.

Why?

Because my cooling system will maintain 160 degrees. If I take the thermostat out it won’t even get to 160 because the system will cool it.

I run a 160 degree thermostat because I drive it in the winter and I need a defrost.

So both statements are correct.

If you are using a 190 thermostat and you drop down to a 160 and it still runs at 190 then you KNOW your cooling system isn’t up to even par.

This just means you have an overly robust cooling system that keeps your engine cooler than the factory service manual recommends. That's fine as long as you know that there are drawbacks to that.

The cooling system isn't going to just keep the temperature at whatever the thermostat opens up at. What happens if you use no thermostat? What about a 100* thermostat?

 

[Newbomb Turk]

This just means you have an overly robust cooling system that keeps your engine cooler than the factory service manual recommends. That's fine as long as you know that there are drawbacks to that.

The cooling system isn't going to just keep the temperature at whatever the thermostat opens up at. What happens if you use no thermostat? What about a 100* thermostat?

I posted that already. Without a thermostat I can’t get to 140. If it was a drag car I’d love it.

But I already know that temp or colder won’t defrost the windows. BTDT.

Plus the wife bitches about the heater not blowing hot enough air. BTDT too!

So that’s why the 160 thermostat.

Since I run more compression than most I can’t afford to gain 10 degrees of coolant temperature. It will make it much closer to detonation.

At 180 it would be worse.

So you’d be correct saying I overbuilt the cooling system. For those reasons.

Me personally I’d rather overbuild the cooling system and let the thermostat do what it’s supposed to do.

 

[ESP47]

I posted that already. Without a thermostat I can’t get to 140. If it was a drag car I’d love it.

But I already know that temp or colder won’t defrost the windows. BTDT.

Plus the wife bitches about the heater not blowing hot enough air. BTDT too!

So that’s why the 160 thermostat.

Since I run more compression than most I can’t afford to gain 10 degrees of coolant temperature. It will make it much closer to detonation.

At 180 it would be worse.

So you’d be correct saying I overbuilt the cooling system. For those reasons.

Me personally I’d rather overbuild the cooling system and let the thermostat do what it’s supposed to do.

Right on, I missed that part. All makes sense now. I'll be picking your brain if my new build starts over heating for sure. Take care man.

 

[clementine]

 

[Bewy]

Some have the wrong idea of the purpose of having a t'stat. It serves two purposes, but only one purpose needs a stat:
[1] It ensures the engine does not run too cool, which is inefficient & causes wear.
[2] It is the restriction in the system, that builds up pressure in the coolant in the engine; the pressure suppresses air bubbles in hot spot areas [ nucleate boiling ] inside the engine; air is a poor conductor of heat & you do not want it in your cooling system. You could use a washer instead of a stat for THIS purpose.


The number on the stat is the opening temp; fully open takes another 20-30*.

 

[BillGrissom]

The "if overheating, add a restrictor in the coolant flow" tip has been around for decades and won't die, with many auto hobbyists literally spitting on their keyboard as they argue such with engineers. Strangely, the thermostat works the opposite way (opens more as coolant warms above its setpoint). Any engineer who hears this myth snickers (me, 72bluNblu, a few others here), especially an ME/ChE since they specialize in heat transfer and fluid flow. A Robertshaw engineer ran across this myth and traced the origin (1930's engines), which they now explain in a tech tip: Tech Tip #3: Thermostats & Restrictors - Stewart Components

 

[BillGrissom]

Some have the wrong idea of the purpose of having a t'stat. It serves two purposes, but only one purpose needs a stat:
[1] It ensures the engine does not run too cool, which is inefficient & causes wear.
[2] It is the restriction in the system, that builds up pressure in the coolant in the engine; the pressure suppresses air bubbles in hot spot areas [ nucleate boiling ] inside the engine; air is a poor conductor of heat & you do not want it in your cooling system. You could use a washer instead of a stat for THIS purpose.


The number on the stat is the opening temp; fully open takes another 20-30*.

True. The T-stat opens progressively as coolant temperature increases. In engineering terms, it is a "proportional-only controller". The temperature does not run exactly at the designed "setpoint". To give more cooling, it must open further, which requires a higher coolant temperature. The is termed "proportional droop". Thus, it is normal for the dash reading to be slightly higher at higher loads (ex. driving fast up a long grade). But, as mentioned, it might take ~20 F higher for it to open fully. If you see higher than that, the T-stat is likely already pegged full-open.

Some have a higher "gain", i.e. open more per deg F increase. One in my 1985 M-B when tested in a pot of water against a thermometer and other T-stats, opened slightly late and more importantly opened sluggishly, requiring a higher temperature to open fully. Swapping in a new one cured my "running too hot" issue.

Some here have stated that the T-stat is constantly opening and closing as you drive. That is how your house HVAC works (on-off control), but would surprise me if true for the engine coolant control. A proportional control loop can oscillate if the feedback gain is too high. If the T-stat truly operates oscillating, you could measure that in the flow similarly varying. Robertshaw surely measures those variables on test benches and doesn't mention such.

 

[kmccabe56]

There is a thread on FABO now about a thermostat gasket leaking. One contributor mentioned that he installed a Flowcooler high flow water pump and his leak started then. I had never heard of Flowcooler High Flow water pumps, so I went to their website. I read the "Common Questions about High Flow pumps" section on their website. It was very interesting. It is a short read.

Considering how many comments/threads/problems we hear about engines running hot, I think this is a very good thing to read. My engine runs a little hotter than I would like. I think I might try one of their pumps. I am not easily convinced by high pressure, phony sales claims. The data in this short article make a lot of sense to me. One thing I found interest was this:

" Hold on...doesn't the coolant have to have more time in the radiator to cool? No. But a lot of people still think so. We have come up with some explanations for the Doubting Thomas."

What they said was very interesting. Please take a look at it.

Commons Questions about Hi Flow Pumps

Not buying what they're selling. Too much self contradiction.

 

[clementine]

My recent test has been to replace the water pump with a high flow (flow cooler) and over drive the pump. I tested the 180* thermostat and put it back in. The stat opened in hot water, when it opened and if it opened fully is tough to say as I cannot find my temp gun, so I’m not being scientific per say…..

But I can report my temps have gone down.

The gauge read 200* and the sniper screen reads 195*

This is an improvement from 210* running to, at one point 217*.

I have yet to put in the hood to rad support seal, and my electric fan is only 2400 cfm.

I will probably try a 160* stat.

I am playing with some aluminum/cardboard to build a couple air dams to help air not travel through the hood/top of rad to have a place to put tools while working and maybe not put seal…dunno just playing around.

Also, I have a stock fan but with no shroud and running a sniper setup I tried the electric because I could. There is not a lot of room up there with the BB.

I have another project that might do better with this derale fan with the flat shroud.

I have a 3 core stockish rad and the water pump pulley is so close to fan that I can’t change the belt…. So there is that as well.

I’ll report back with what happens if anyone is interested.

Open to suggestions as well. (Put the stock setup responses must come with a free shroud/rad that will fit just kidding, I’d love to know the depth of a stock setup so I can compare. I have about 5 1/4” from rad support to front of pulley)

Sorry if this is considered a hijack but I figured this is applied vs theory.

AFRs have been in the 12-13s running/idling

 

[Inertia]

Some here have stated that the T-stat is constantly opening and closing as you drive. That is how your house HVAC works (on-off control), but would surprise me if true for the engine coolant control

My reference to "modulation/oscillation" is in the context of a gas pedal maintaining a constant speed by slightly adjusting the opening and closing of the throttle on a hilly road - not slamming totally open/close as a HVAC being turned on or off. Hence the vid.
Thnx Bill

 

[trapster]

I guess if water can go too fast through a radiator, than so can air.

 

[mopowers]

The best way for me to think about it is that heat transfer rates are not linear. The radiator dissipates more heat when the difference in temp between the coolant and ambient is greater. In other words, the sooner you can get the hot coolant to the radiator, the better. Plus there are diminishing returns the longer you keep the coolant in the radiator. Flow is your friend in this case.

 

[BillGrissom]

The best way for me to think about it is that heat transfer rates are not linear. The radiator dissipates more heat when the difference in temp between the coolant and ambient is greater. In other words, the sooner you can get the hot coolant to the radiator, the better. Plus there are diminishing returns the longer you keep the coolant in the radiator. Flow is your friend in this case.

The engineering explanation is that there are multiple variables involved in engine cooling - flowrate, coolant properties (conductivity and heat capacity), temperature difference between metal parts and coolant, temperature difference between coolant and radiator tubes, heat convection from radiator tubes/fins to airflow. The later is the major bottle-neck in the series of heat flows. Most public with no science education can only think in terms of one variable affecting one outcome.

 

[BillGrissom]

My reference to "modulation/oscillation" is in the context of a gas pedal maintaining a constant speed by slightly adjusting the opening and closing of the throttle on a hilly road - not slamming totally open/close as a HVAC being turned on or off. Hence the vid.
Thnx Bill

I wasn't referring to your comment, indeed didn't even see it. No, others on this forum imagine the T-stat is constantly opening and closing, since how their experience with other devices which have simple on-off control.

 

[BillGrissom]

My recent test has been to replace the water pump with a high flow (flow cooler) and over drive the pump. I tested the 180* thermostat and put it back in. The stat opened in hot water, when it opened and if it opened fully is tough to say as I cannot find my temp gun, so I’m not being scientific per say…..

But I can report my temps have gone down.

The gauge read 200* and the sniper screen reads 195*

This is an improvement from 210* running to, at one point 217*.

I have yet to put in the hood to rad support seal, and my electric fan is only 2400 cfm.

I will probably try a 160* stat.

I am playing with some aluminum/cardboard to build a couple air dams to help air not travel through the hood/top of rad to have a place to put tools while working and maybe not put seal…dunno just playing around.

Also, I have a stock fan but with no shroud and running a sniper setup I tried the electric because I could. There is not a lot of room up there with the BB.

I have another project that might do better with this derale fan with the flat shroud.

I have a 3 core stockish rad and the water pump pulley is so close to fan that I can’t change the belt…. So there is that as well.

I’ll report back with what happens if anyone is interested.

Open to suggestions as well. (Put the stock setup responses must come with a free shroud/rad that will fit just kidding, I’d love to know the depth of a stock setup so I can compare. I have about 5 1/4” from rad support to front of pulley)

Sorry if this is considered a hijack but I figured this is applied vs theory.

AFRs have been in the 12-13s running/idling

View attachment 1716281780

View attachment 1716281781

Robertshaw sells special "high-flow" T-stats. That refers to the restriction when fully-open. It only comes into play when over-heated, i.e. T-stat is pegged full-open so lost control authority. Avoid a "fail-safe" T-stat. Those jam open and then never shuts, after a single over-heat. It then becomes like running with no T-stat, which is only for racing.

A 195 F T-stat shouldn't measurably decrease coolant temperature if it is running >210 F since it is already as full-open as a 180 F T-stat would be. Operating around 195 F should give better mileage and less engine wear in cold weather, plus less pollutants. That is what I use in my old Mopars.