I put a Flow Kooler on my car and it ran hot in stop and go traffic with the A/C on. Using the "factory pullies"  a 4 core aluminum radiator with two electric fans. I know some don't like electric but I'm thinking of ditching my water pump for a stock pump because I've been told that the flow was to fast there fore not getting cooled down as it went through the radiator. I'd give my pump to some one if that fixes it.

For serpentine systems I've been happy with a GMB pump I got through Summit for $77.  Its the exact same pump as a Milodon one I bought for $108.  Only difference was an anti cavitation disc welded to the impeller.  Ten minutes, some scrap steel, and my MIG solved that for free.  Here's a link:

https://www.summitracing.com/parts/gmb-125-1560p/year/1989/make/ford/model/mustang

I've heard the "high performance water pump moved the water through the system too fast to cool it" before, but after a good amount of research I'm going to call that one debunked.  There may be some extraordinary case where someone used grossly mismatched pulleys or something, but in the case of a typical car that's overheating; its not being caused by a high performance water pump.  Here's why: thermal transfer occurs fastest at the greatest extreme, so if the ambient temperature is 100 degrees and the coolant coming from the engine is 220 degrees most of the reduction in coolant temperature occurs within a few seconds, where it might drop 20-30 degrees.  After that it only drops say 5 degrees in the next 20-30 seconds, and then it might take 2 minutes to drop another 5 degrees (the rate of reduction is actually an exponential function).  The closer the temperatures of the two mediums the slower the heat transfer from hot to cold and vice versa.  So even though in order to get the higher GPM ratings the coolant is going to move faster through the system there's a benefit in removing heat because it simply reduces the lag time between temperature extremes.  The coolant spends less time in the block and radiator, but in so doing actually removes more heat because the difference in temperature between the points of exchange are maximized. 

The myth seems to have started, like most do, with some truth.  Before cars had pressurized cooling systems it was indeed possible to move the water through the system too fast.  Its kind of like the idea that setting a battery on concrete damages or discharges it.  Its a leftover from before batteries had plastic cases.  Old steel cased batteries could be drained by being left on concrete. 
 

Correct, and also acting as a restriction as well, which increases pressure inside the block and reduces the chance of the formation of steam pockets. 

Water pumps are passive pumps, not positive displacement pumps. That said, they can only move as much water as the thermostat allows through it.  Once a thermostat is fully open, it still maintains some flow restriction.

It is my opinion that most overheating issues are NOT water pump related, unless the pulley ratio is wrong and, again, that is pulley related, not pump related.  I honestly believe any pump will do the job to move the water through the block sufficiently, and if it still overheats, look at block internal condition or one of the other myriad things that can cause overheating.

I think more cars overheat from inoperative distributor advance mechanisms than overheat from water pump malfunction.

Would it be true that a higher pressure radiator cap does not reduce the temperature, it only gives the water a higher boiling temperature?  In other words, it may run 240 degrees, but won’t boil over when doing it.  I have always used the original spec 13 psi cap.

I've used stock cast and Flow Kooler pumps no difference. Bigger rads. 3 core 4 core with little difference, plus electric fans with clutch fans. If it's hot out there and your just sitting in traffic with the a/c on its going to get hot. In most cases a standard clutch is never going to cut it. HD or more clutch makes a difference and buys time before it boils

red351 wrote:

I've used stock cast and Flow Kooler pumps no difference. Bigger rads. 3 core 4 core with little difference, plus electric fans with clutch fans. If it's hot out there and your just sitting in traffic with the a/c on its going to get hot. In most cases a standard clutch is never going to cut it. HD or more clutch makes a difference and buys time before it boils

Yes, at some point you have to move air through the system.  The air around the radiator begins to get saturated with heat and starts to become a barrier to cooling.  Bigger radiators just extend the amount of time it takes to reach that point.  A good fan is the best bet in those situations, but even then, the air a fan moves pales in comparison to how much moves through the radiator when the car is in motion. 

BTW, since mid 90’s ditched 13# and went to 16# cap after replacing radiator.
Heater core was replaced prior as well.

With 289/c4 and internal and external transmission coolers:
16# with 3 row high fin count copper brass
180 thermostat
289 cast iron pump

Currently 5.0/t5 internal cooler not used:
16# with 2 row 1” tubes aluminum
190 thermostat
5.0 stock replacement aluminum pump

Last edited by Nos681 (2/20/2020 2:21 PM)