Is my cooling system operating normal?

[mopowers]

I have a hard time grasping the cavitation argument. How much time does an engine spend at high rpms (where cavitation would be an issue) under normal street driving conditions? I'll take the high flow pump any day over the low flow pump - even with over driven pulleys.

 

[Dana67Dart]

Some light reading...
Understanding Centrifugal Pump Flow Rate: Formula and Calculation

 

[Inertia]

I have a hard time grasping the cavitation argument. How much time does an engine spend at high rpms (where cavitation would be an issue) under normal street driving conditions? I'll take the high flow pump any day over the low flow pump - even with over driven pulleys.

You can run either pump at nominal speeds, the thermostat will regulate the flow to achieve the chosen temp .

 

[AJ/FormS]

I have a hard time grasping the cavitation argument. How much time does an engine spend at high rpms (where cavitation would be an issue) under normal street driving conditions? I'll take the high flow pump any day over the low flow pump - even with over driven pulleys.

Just so you know,
I run a Milodon HDHi-flo, 8-vane pump, with the anti-cavitation plate. (and yes with a hi-flo 195stat)
and it is underdriven, cuz
my engine, with a manual-trans, actually does spend a lotta time at higher rpms.
I run the 7-blade high attack angle bent-tips all steel fan on a thermostatic clutch. It's been on there like that since 2001.
No problems; and
system runs at 207*F, on a 195 stat, every day/all day, no matter how she's being beat on, including parading at 4mph with just 5* of timing advance, on the hottest days of summer.
For me, that big FORD T-clutch was a game-changer. It was new from the dealer in year 2001-ish, out of the parts book for an early 2000s pick-up truck. As soon as I heard that truck come into the shop I was working at, I knew I had to have one. By lunch it was in my grubby hands. By supper I was breaking it in. lol.
Just so you know.

 

[72bluNblu]

I have a hard time grasping the cavitation argument. How much time does an engine spend at high rpms (where cavitation would be an issue) under normal street driving conditions? I'll take the high flow pump any day over the low flow pump - even with over driven pulleys.

It's not just the highest rpm rating though, although even temporarily spinning a pump designed to max out at 6k all the way up to 8,400 could have catastrophic results even without cavitation, just like over-revving your engine. If the pump is trying to shove too much water through the systems small passages the resistance in the system goes up and the actual flow rate goes down. You can get a pressure difference across the pump, and if the intake pressure drops too much it will cavitate the pump even at low rpm. The speed of the pump is only one factor, with enough pressure differential you can cavitate the pump at idle speeds. Not gonna see something that extreme in this application, but in firefighting pumps it comes up frequently with poorly performing hydrants. That's not quite apples to apples because there can also be a volume difference at a level you wouldn't see in a closed system like the cooling system for these cars.

It's a complicated subject, and if it was as simple as just running the high volume pump with the overdriven pulley to get better cooling don't you think the factory would have saved the money on designing two different water pumps and pulley sets?

Some light reading...
Understanding Centrifugal Pump Flow Rate: Formula and Calculation

Exactly. There's a ton of factors that go into this, none of which we'll really have the specifications to run the actual numbers on. Even if you got all the pump numbers the resistance in the cooling system and rate of return would have to be known, and you'd have to measure that, because there is most definitely a maximum GPM for the flow through the system, and trying to pump more GPM through the system than it can handle just causes turbulence, increases resistance, and results in a lower actual flow rate.

That's another thing that comes up in firefighting. For example, a 175 GPM nozzle on an 1 3/4" hose. You attach that to a 1,000 GPM pump, but, past a certain point all that happens is the pressure in the line goes up and the pump works harder, you don't get more GPM out of the nozzle. In fact, you actually get LESS flow out of the nozzle. Assuming the line doesn't burst and the poor bastard on the line manages to hold on still. If you want to flow more, you need a bigger line and nozzle, not try to force more through the smaller line because that simply doesn't work.

You can run either pump at nominal speeds, the thermostat will regulate the flow to achieve the chosen temp .

You're giving WAY too much credit to the thermostat. Yes, they do regulate flow because they're not always fully open or closed, but, if you actually check the temperature range from fully open to fully closed it's not that wide of a range. If it's actually hot outside your thermostat is wide open more than it's not, and usually all of these cooling discussions are about operating temps in hot weather, not what's happening on a cold day when the thermostat might hang out at a spot where its barely open.

 

[mopowers]

It's not just the highest rpm rating though, although even temporarily spinning a pump designed to max out at 6k all the way up to 8,400 could have catastrophic results even without cavitation, just like over-revving your engine. If the pump is trying to shove too much water through the systems small passages the resistance in the system goes up and the actual flow rate goes down. You can get a pressure difference across the pump, and if the intake pressure drops too much it will cavitate the pump even at low rpm. The speed of the pump is only one factor, with enough pressure differential you can cavitate the pump at idle speeds. Not gonna see something that extreme in this application, but in firefighting pumps it comes up frequently with poorly performing hydrants. That's not quite apples to apples because there can also be a volume difference at a level you wouldn't see in a closed system like the cooling system for these cars.

It's a complicated subject, and if it was as simple as just running the high volume pump with the overdriven pulley to get better cooling don't you think the factory would have saved the money on designing two different water pumps and pulley sets?

I understand what cavition is. I only mentioned high rpm because someone brought up an example of 5,600 (or whatever it was) rpm with a 0.95 w/p drive ratio would run that pump at 8,400 with a 1.4 drive ratio. Not sure about you, but I've never seen or heard of an instance where cavitation was an issue at low rpms. If that's ever occurred, it almost certainly wasn't because they used the wrong pump or pulley ratio. There most likely would've been a catastrophic restriction somewhere in the system. Let's not over complicate things.

My original point was people throw the term cavitation around like it's some rampant epidemic. I've had zero problems running a high flow pump with overdive pulleys. Minimize restrictions by running a high flow thermostat, good quality radiator, etc. and the extra flow will be your friend. But then again, my junk isn't zinging it's guts out for hours on end either.

 

[Oldiron440]

Before you start spending money on a solution try losing the rear bolt on your hood hinges and raising the rear of the hood an inch or so. This will help with airflow in your engine compartment adding airflow across the radiator.
I’ve seen problems with the airflow problems when the airflow is interrupted by headers etc.
Sometimes adding a small lip below the radiator on the core support causing a vacuum behind the radiator.
I have a Champion radiator for one of my unlit projects that I bought several years ago and I have read several threads about problems with issues with running hot. As time gets closer to actually running my project I believe I will replace it with a higher quality part.
So you might have several things to look into before starting spending cash.

 

[67_Slimer]

Before you start spending money on a solution try losing the rear bolt on your hood hinges and raising the rear of the hood an inch or so. This will help with airflow in your engine compartment adding airflow across the radiator.
I’ve seen problems with the airflow problems when the airflow is interrupted by headers etc.
Sometimes adding a small lip below the radiator on the core support causing a vacuum behind the radiator.
I have a Champion radiator for one of my unlit projects that I bought several years ago and I have read several threads about problems with issues with running hot. As time gets closer to actually running my project I believe I will replace it with a higher quality part.
So you might have several things to look into before starting spending cash.

I have a lift off hood , lots of times I just take it off and cruise without it. Not going to lie , other than some odd stares from people , I enjoy it so much more. That hot air just dissipates into the air.

 

[67Dart273]

Already mentioned above, but I would be suspicious that the electric is actually RESTRICTING airflow

 

[Inertia]

You're giving WAY too much credit to the thermostat. Yes, they do regulate flow because they're not always fully open or closed, but, if you actually check the temperature range from fully open to fully closed it's not that wide of a range. If it's actually hot outside your thermostat is wide open more than it's not, and usually all of these cooling discussions are about operating temps in hot weather, not what's happening on a cold day when the thermostat might hang out at a spot where its barely open.

BALDERDASH ! !

if you have a vehicle with a tow package to tow a huge trailer, comes with a rad capable of towing up mountains in 100* ambient temp, there is a very good possibility that thermostat never fully opens in nominal weather.

Put that huge firetruck rad in a streetcar assuming it will fit, will that thermostat ever fully open, likely not, - because it has the capacity to supply the nec cold coolant .

I once referred to a raw water marine engine sucking in 34* mountain lake water, - how can that marine engine maintain 140* coolant. (raw water thermostats are usually 140*) , then dump that boat into a summer lake, and still maintain 140* ?

To think the thermostat opens fully, and the radiator is so custom sized that it'll run consistantly within a 10* range summer/winter, uphill/downhill, towing fully loaded/1 passenger, - - is absurd ! !.

The thermostat is as active as your gas pedal on cruise, - more gas pedal, more work, = more heat created, - more coolant flow required thru the rad, - fundamental. - you just don't get it.

Perfect situation is rad cools to ambient temp, thermostat regulates flow to maintain 180?*

 

[Inertia]

If you can't get your head around that, consider.

Lotta import vehicles have the thermostat on the lower hose, and won't let radiator cooled/stored coolant into the engine, and meters the amount of cooled water entering to maintain desired temp.

Sometimes a different perspective.

Cheers
I bet DMs are flying now, lol

 

[72bluNblu]

I understand what cavition is. I only mentioned high rpm because someone brought up an example of 5,600 (or whatever it was) rpm with a 0.95 w/p drive ratio would run that pump at 8,400 with a 1.4 drive ratio. Not sure about you, but I've never seen or heard of an instance where cavitation was an issue at low rpms. If that's ever occurred, it almost certainly wasn't because they used the wrong pump or pulley ratio. There most likely would've been a catastrophic restriction somewhere in the system. Let's not over complicate things.

My original point was people throw the term cavitation around like it's some rampant epidemic. I've had zero problems running a high flow pump with overdive pulleys. Minimize restrictions by running a high flow thermostat, good quality radiator, etc. and the extra flow will be your friend. But then again, my junk isn't zinging it's guts out for hours on end either.

Yeah, that was me. If you turn 6k rpm with a 1.4:1 overdrive you’re spinning the water pump at 8,400 rpm. With a .95:1 ratio that’s only 5,700. Impeller diameter will affect the maximum RPM rating for the pump. Sure, if you never drive the car hard that never comes up, but that doesn’t mean it can’t be an issue.

Cavitation can be an issue. It’s not as big an issue as just having the wrong pulley ratio for the pump you’re running and that mismatch creating a cooling issue, but dismissing it because you’ve never seen it in an extremely limited application doesn’t mean it doesn’t happen.

It wouldn’t be my first concern for a car, but, saying it’s not a thing because you haven’t personally seen it isn’t a valid argument.

I have a lift off hood , lots of times I just take it off and cruise without it. Not going to lie , other than some odd stares from people , I enjoy it so much more. That hot air just dissipates into the air.

Running without the hood can actually hurt cooling because it disrupts the air flow through the radiator. That’s why there’s typically a seal between the radiator support and the hood. The heat stored in the engine compartment is a relatively minor factor in engine cooling.

BALDERDASH ! !

if you have a vehicle with a tow package to tow a huge trailer, comes with a rad capable of towing up mountains in 100* ambient temp, there is a very good possibility that thermostat never fully opens in nominal weather.

Put that huge firetruck rad in a streetcar assuming it will fit, will that thermostat ever fully open, likely not, - because it has the capacity to supply the nec cold coolant .

I once referred to a raw water marine engine sucking in 34* mountain lake water, - how can that marine engine maintain 140* coolant. (raw water thermostats are usually 140*) , then dump that boat into a summer lake, and still maintain 140* ?

To think the thermostat opens fully, and the radiator is so custom sized that it'll run consistantly within a 10* range summer/winter, uphill/downhill, towing fully loaded/1 passenger, - - is absurd ! !.

The thermostat is as active as your gas pedal on cruise, - more gas pedal, more work, = more heat created, - more coolant flow required thru the rad, - fundamental. - you just don't get it.

Perfect situation is rad cools to ambient temp, thermostat regulates flow to maintain 180?*

I didn’t say thermostats didn’t regulate flow at all. I said you’re oversimplifying the rest of the cooling system and giving entirely too much credit to the thermostat. Which is still true. And now you’re oversimplifying what I said to make your argument easier.

Again, most of the issues talked about here are cars running too hot, and in those limited circumstances the thermostat is pretty much guaranteed to be wide open. This thread certainly isn’t about what a thermostat does when the water is colder than the thermostat temp, and almost nobody complains about their car running too cold on this forum anyway.

Radiator cools to ambient?! LOL. Not even in a perfect world. Not even close in the automotive world. Most of the time a temp drop across the radiator of between 10 to 20° means it’s good to go.

Seriously, if the thermostat is never fully open what good is a high volume pump? Just run the standard pump and let the thermostat open all the way. A half open thermostat would cut the flow volume more than a high volume pump would increase it.

No DM’s are flying. This is just another cooling thread full of old wives tales, misinformation, and irrelevant examples.

 

[slantsixdan]

160 degree high flow thermostat

Might want to rethink that thermostat selection. Other than that, your cooling system sounds like it's doing better than fine. The thermostat sets the engine's minimum operating temperature, not its maximum. Read this to understand the cooling system better.

 

[67_Slimer]

Might want to rethink that thermostat selection. Other than that, your cooling system sounds like it's doing better than fine. The thermostat sets the engine's minimum operating temperature, not its maximum. Read this to understand the cooling system better.

Thank you