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Old 05-20-2012, 07:58 PM   #1
Docsuby79
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Default Coolant flow direction

I know this sound stupid, but, I've had an argument with my mechanic and I want to verify I'm right. The engine coolant flows from bottom to top, or top to bottom. Meaning does the pump pull or push the fluid from the radiator.
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Old 05-20-2012, 08:28 PM   #2
UK-Wagon
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coolant flow is ALWAYS top to bottom in the radiator. The hot fluid is cooled as it goes down the radiator tubes. The Water pump is is there to create flow direction. Its neither a push or pull, those two are the same in a way lol. Coolant flows by tempature and pressure. The water pump just directs that flow of fluid. When water or coolant gets hot it expands, causing pressure, when it builds pressure it moves faster. So the water pump is there to direct that flow of fluid pressure. Therefor the WP really isnt pushing or pulling....

If you think of cold coolant, the water pump pulls fluid from the radiator and then pushes it through the engine. So its sorta both until it warms up.

All radiators flow the same for just about anything, hot comes in the top, cold goes out the bottom. Let your car warm up, touch the top hose, itll be really hot, then touch the bottom, itll be warm.
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Old 05-20-2012, 11:44 PM   #3
WhiteBgeye02
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as said it pushes and pulls at the same time. it pulls water from the in hose and pushes it out the outlet hose. i am unsure what makes me think this but i was told i should put the water coolant temp in the bottom hose since its off engine temp while the top hose will give me a reading but will be cooler. i honestly would have to look to verify which way it goes.
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Old 05-21-2012, 01:54 AM   #4
UK-Wagon
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Quote:
Originally Posted by WhiteBgeye02 View Post
i was told i should put the water coolant temp in the bottom hose since its off engine temp while the top hose will give me a reading but will be cooler. i honestly would have to look to verify which way it goes.
wait what? no the bottom hose will be cool, the top hose will be hot. You want the sensor at the top to give you the engines actual temperature. Putting it in the bottom would give you the cooled down radiator temp.
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Old 02-20-2021, 08:55 PM   #5
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i've been having this discussion with several very knowledgeable engine builders and technically both schools are correct, kinda.

Its a cooling management philosophy really. Hear me out.

One school (the most common) is that you want to use the TOP hose to see what coolant temp is exiting the engine and kick fans on accordingly. Hence why the OE temp sender is in the block. Right? Kinda...
.
The second school of thought is about MANAGING engine temp with proper airflow and assuring the radiator is doing its Job effectively. Again hence why the old "sure fire test" is top hose should be almost too hot to hold with the bare hand and the lower should be warm, This is foundation of the @nd school of thought, which I tend to build my engines and systems this way.

By placing the temp sender in the lower hose or, if available in the jacket around the water pump area if possible, you are reading the Radiator/Fan combination's ability to MANAGE temperature.

The Prosport in hose coolant sender adaptor instructions say in the UPPER hose Which is great. Im installing mine in the lower exactly half way in the hose. With both my Prosport gauge sender and my 2ndary fan temp override.

Now I have BOTH. I've owned my 04 WRX Sport wagon going on 11 years. I've been through 3 radiators, 1 water pump and T-stat, 2 sets of fans. I know where the car runs best on the factory water temp gauge. Now I will be able to dial in a fan override depending on temps and outside/weather conditions. I live out side Dallas, TX and temps can get well over 100* and I also travel 40+ weeks all over the US all continuous 48 states all 4 seasons. The WRX through Death Valley in the Summer, -23* with a wind chill of -43* in Fargo, ND. and everything iun between.

Just last Xmas time I left Crested Butte, Co at 7am with temp -8* and wind chill of -25* by about 2pm I was crossing into NM and temps were nearing 30-35* and at the end of a day 1/2,14 total drive, It was nearly 63* at home.

Heat inside the cabin of the car was never a "problem" but early in the trip it would have been nice to hold the fans back a little while watching top and bottom temps.

the opposite driving through Death Valley, I would have wanted the fans on earlier than the factory settings because the car did run warmer for sure.

Just recently at 300K the aluminum Koyo rad I put in at about 78K took a chunk of road debris and the damage was about a 1.5" whole in the fin/tube area low near the bottom tank. I found a killer deal on a Mishimoto rad. In the process it damaged BOTH factory fans. So I ordered slightly larger fans and aluminum shroud and a Grimmspeed rad cover plate. Full Monty upgrade. Just received the Matching Prosport Oil/water temp premium gauge and an extra sender and an extra sender harness, and the hose sender adapter, and a Dearle adjustable electric fan controller with full on override capability. I plan to use a switch and a relay to use ONE Temp gauge to be able to toggle between oil temp and h20 temp.

Just like My Prosport Oil Pressure gauge is already set up to handle toggle between Oil Press and Fuel Press, just flip a rocker switch.

~Rob
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