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Old 04-09-2020, 02:47 AM   #1
Mauricemonge
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66 Bug with ej20g

Default Donít flame!: thermostat eliminate/heater core question

Iím sorry if someone has asked this question already, but Iíd be surprised to be honest. If this in the wrong category, mods please move

Background:
I have an ej20g swapped mid engine vw bug and Iím working on my cooling system. I recently removed my thermostat, not knowing most vw swap guys do this anyway. My temps dropped after so Iím not going to be talking into putting it back in - it doesnít run too cool, just takes forever to warm up.

Iím still working on dropping a few degrees from my spirited driving temps, and my buddy put a thought into my head.


Question:

I am not running a heater core, I bypassed it to control the thermostat. But now that I donít have one, am I recirculating hot water through the engine block when I could be sending a bit more through the radiator?

Im really only looking for another 5 degree drop and want to max out everything I can before spending more money. Iím worried that my solid temperatures now in the cool 60 degree part of the year arenít going to translate well to a 100 degree track day.


Written with a lotta ethanol consumption
-Maurice
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Last edited by Mauricemonge; 04-09-2020 at 02:48 AM. Reason: Clarifying my post
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Old 04-09-2020, 07:14 AM   #2
rtv900
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Quote:
Originally Posted by Mauricemonge View Post
am I recirculating hot water through the engine block when I could be sending a bit more through the radiator?


-Maurice
when you say you 'could' be sending a bit more through the radiator do you mean heater core by that?

I doubt you'd see any real difference by adding back in a heater core, plus you'd have to leave the heat on all the time for it to do anything anyway

if your concern is 100 degree summer weather obviously that isn't an option anyhow as the car would be downright miserable to drive
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Old 04-09-2020, 09:26 AM   #3
Scuby04STi
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I am curious to the current configuration in the car? Seeing that will likely dictate what is logical.

But if I was in the position and wanted to minimize cost I would just add anytype of cooler on the heater core loop and toss a fan on it, hell you could even have it kick on at a specific temp if you like.

Likley I would just tear into the heater core until your down to just the part you need and just mount it away from heat as best you can on a vw.
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Old 04-09-2020, 12:56 PM   #4
Mauricemonge
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I think I didnít explain it well.

The 5/8Ē hoses that would connect through a heater core - which I donít have - loop hot water back to the water pump area without ever passing through the radiator. Its used to control the thermostat, but since I donít have one, Iím wondering if Iím missing out on cooling benefits by having them still connected.

I do like the idea of adding a heater core in with a fan to help cooling!
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Old 04-09-2020, 01:00 PM   #5
Mauricemonge
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Quote:
Originally Posted by rtv900 View Post
when you say you 'could' be sending a bit more through the radiator do you mean heater core by that?

I doubt you'd see any real difference by adding back in a heater core, plus you'd have to leave the heat on all the time for it to do anything anyway

if your concern is 100 degree summer weather obviously that isn't an option anyhow as the car would be downright miserable to drive
Unfortunately track days and drag strips here (California) get very hot during the summer. Many track cars donít run AC, and Iíve spent many a day during my youth in aircooled vwís in some serious heat. I just want to make sure the car will hold up longer than I could in the heat.

Iím also building a much more powerful engine so Iíll need as much cooling as possible for it
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Old 04-10-2020, 09:56 PM   #6
Mauricemonge
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Default Update

I found a oilcooler I had bought 15 years ago and ran it under the car with the heater core lines. Itís hard to say how much of a difference there was considering weather and how much calmer I was driving it, but it seemed to be a good 5 degrees cooler across the board. Some of that might be having a restriction in that line that sends more water up front instead of through an unrestricted line. Pretty happy with the result!
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Old 04-11-2020, 08:09 AM   #7
Scuby04STi
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Good, always nice using a part you have just been sitting on forever. Lol
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Old 04-11-2020, 09:16 AM   #8
spoolinsti05
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A lot of cars actually run an auxillary water pump into the heater core. Helps keep air from getting trapped in the system.

What are coolant temps with no thermostat? You can hard wire the fans to run with accessory power.
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Old 04-11-2020, 11:31 AM   #9
Mauricemonge
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So coolant temps ran between 180-195 at freeway cruising 65-80mph. It climbs higher when around town but I think itís because there isnít much water flow to get it to the engine. It climbed towards 200 when I was behind a large vehicle and stopped getting air, but dropped pretty quick when I turned my fan on and popped out from behind the van. When I did warm it up on slower roads in boost, the temperature came down quicker than before. The outside temperature is cool though - 60-67. I know the engine is runnning a bit on the cool side but thatís what I want to see with these outside temps.

Iíll retest with spirited driving, but at first I was seeing 225 and actually boiled over once. Then I remade my ducting and removed the thermostat and and saw 217, sealed off the front better and it dropped more. Iíve got a more powerful fan in the mail to help with around town summer weather. I think it should be enough to keep it cool.

My fan comes on around 195 and I have it on its own circuit with the sensor at the motor.

Last edited by Mauricemonge; 04-11-2020 at 11:43 AM.
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Old 04-11-2020, 12:11 PM   #10
spoolinsti05
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I wonder what the coolant temp reading taken from the heads vs block would change as far as how soon and long the fans are on for.
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Old 04-11-2020, 04:39 PM   #11
Mauricemonge
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Quote:
Originally Posted by spoolinsti05 View Post
I wonder what the coolant temp reading taken from the heads vs block would change as far as how soon and long the fans are on for.
I think the outgoing water temp is fine to read temperature from. The fans take a minute to actually cool down the water temperature anyway, so just a generic reading is fine.
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