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I also thought this was the issue, I'm running a vintage air system - which uses a valve to block off coolant flow to the radiator. I opened the valve manually, and the car still over heated (unless I turned the heater on)
I did read a lot of people with the vintage air systems are not over heating with that valve installed, but there were a couple situations where I saw the valve was the problem. Sort of odd
I've read the same thing about it sometimes being a problem while others have no issues at all.
I have vintage air in my car with the shut off valve and I used the LOJ bypass block just so I knew it was operating as the factory intended it to work when the valve closes.
What you say is true to a point. Coolant can run thru a radiator TOO quickly to shed a sufficient amount of heat. It needs a certain amount of exposure time in the radiator to do this. This is one reason it needs to be of enough capacity to cool sufficiently. Too small a radiator lets coolant go thru too quickly to cool correctly. A large enough one slows the flow enough to get it done right. In other words, a radiator might be able to handle the flow gallons-per-minute-wise, BUT without letting the coolant be there long enough to cool sufficiently.
Incorrect.The amount of heat/energy transferred will increase with increased coolant flow rate. There is no such thing as moving through the radiator too quickly.
It is true that at a lower flow rate with more time in the radiator, the difference between the inlet coolant temperature and outlet coolant temperature through the radiator will be greater. I think this gives the false idea there is a more cooling going on. In reality you have taken more heat (higher temp change) from less coolant (lower flow). Higher flow rates,take less heat (less temp change) from more coolant (higher flow). It would be a zero-sum game (less heat from more coolant equal to more heat from less coolant) except you increase the thermal heat transfer at higher flow rates. Why? Because the temperature across the radiator remains higher across the area of the radiator (less temp change in the coolant), maximizing the temperature difference between the radiator and the air crossing over it. That difference of temperature allows more heat to be rejected to the air. A similar effect happens inside the engine. Also with higher flow rates, the velocity and turbulence in the coolant improves heat transfer (convection).
Imagine if the flow rate dropped to a trickle. The coolant would quickly reach air temperature in the radiator and never shed any more heat. The coolant would quickly reach engine temperature in the engine and not absorb any more heat. The result is very little heat rejected. There is a practical window where the system can capably reject enough heat to keep the engine coolant temperature stable without doing unnecessary coolant pumping.
No harm, no foul -- we all learn by testing the water. The dead giveaway is the fact that water pump speed increases with increasing engine speed (which is usually proportional to increasing load). That's because more flow through the radiator is needed. It's also very easy for the uninitiated to confuse "temperature" and "heat".....Clint's description gets right at the heart of this area of confusion.
I remember arguing with a buddy about something car related (don't remember what) - and as his perspective began to make some sense to me I said "I'm confused." He replied:
Confusion is the state of mind that exists just before I finally figure out that something I thought I knew is wrong. Clarity.
Related -- sometimes folks want to check the temp of something by touching it. Ever wonder why a piece of granite and a piece of plastic at the same temperature don't feel the same? The granite will always feel hotter or colder than the plastic. The reason is that our sense of touch isn't actually very good at determining temperature. But it's VERY good at determining how quickly something will transfer heat between our skin and the thing being touched. Turns out we can exchange heat much more quickly with granite than we can plastic. That's why the granite feels always feels hotter or colder than the plastic. It can lose or gain heat with our skin much more quickly than the plastic can. Same with most metals compared to plastics.
Ah - nobody cares.....LOL!
Last edited by Michael Yount; Aug 7, 2018 at 05:35 PM.
The new radiator (2 row, 1" tubes, 27.5" x 18.5" x 2" core) comes in Friday. I should know why this weekend if that fixed the issue. BeCool 12008 is the part number
My take away on Dexcool, formed over 20 years or so - 1) Dexcool changed regularly is fine; 2) I don’t mix antifreeze brands or colors regardless of any info about compatibility
My Dexcool story: bought a 2001 Blazer for my son a few years ago. Was losing coolant through an intake manifold gasket and got hot once (he ran it low), so I decided to replace gasket. Tried to drain radiator. Pulled the petcock... nothing. Tried to drain block. One side trickled, the other side... nothing came out with the drain plug.
Ended up driving a screwdriver in to both drain plug holes and eventually muddy coolant came out. Replaced the radiator outright. Flushed the system for 30 minutes with the garden hose running, drained, and then went back in with regular coolant.
Screw Dexcool. Truck ran very well after that, no cooling issues whatsoever.
Got the radiator installed, filled up. I have been sitting in my driveway idling with the AC on for 10 minutes, and the temp hasn't broken 180 degrees! Before, it would be at 230 degrees within 10 minutes
