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Old 10-30-2008, 10:07 AM   #21
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As I understand, putting a restrictor on the lower rad hose limits the flow of water through the engine. If you put it on the upper rad hose, it slows down the coolant, making it take more heat away.

A lower pressure cap would mean it takes less energy to heat up the water, so that's not a bad idea. My cap is pretty stiff, 1.7 bar.

Last edited by Ben; 10-30-2008 at 10:25 AM.
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Old 10-30-2008, 11:43 AM   #22
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Restrictor in upper or lower has to limit the flow the same.


Doesn't a lower pressure cap just make the boiling point lower?

Olderguy, thoughts?
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Old 10-30-2008, 11:47 AM   #23
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Quote:
Originally Posted by Ben View Post
A lower pressure cap would mean it takes less energy to heat up the water, so that's not a bad idea. My cap is pretty stiff, 1.7 bar.
WOOT!! I had a good idea, maybe..
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Old 10-30-2008, 11:50 AM   #24
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Quote:
Originally Posted by Ben View Post
My cap is pretty stiff, 1.7 bar.
jeez, try a 13psi cap; still raise pressures enough to prevent boiling, but low enough to lower the overall efficiency of the cooling system and possibly bumping up the operating temps.
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Old 10-30-2008, 12:17 PM   #25
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Quote:
Originally Posted by paul View Post
Restrictor in upper or lower has to limit the flow the same.


Doesn't a lower pressure cap just make the boiling point lower?

Olderguy, thoughts?
that's i'm thinking, doesn't make it hotter
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Old 10-30-2008, 12:23 PM   #26
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Running the OEM thermostat? What other modifications? I personally would not use a restricter or lower pressure cap. Are you looking to get engine temp up faster or heater core more efficient?
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Old 10-30-2008, 01:20 PM   #27
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I'm running an aftermarket huge, very efficient radiator with a 1.7bar cap. Lowering the cap to standard pressure for winter time street use I'd think is a good idea. Sam, you get a cookie, and I'm kinda embarrassed I didn't think of that myself. It would allow the coolant to heat up quicker, and it would also lower the boiling point which isn't a big deal for this application.

Thermo is a brand new Mazda OEM. It's different than the one I just took out, which was also a Mazda OEM and not that old. The new design allowed the engine to come to temp faster than the old design. The old one opened up much earlier and much wider than the new one in a pot of water on my stove. I'm having the old thermo modified by my boss to open even more for summer time and competition type use.

Restrictor in the lower hose would limit the amount of water through the system. Restrictor in the upper slows down the same volume of water. As I understand, a restrictor in the upper could actually make the coolant temps drop if done correctly as the water will have more time to soak up heat from the motor.

Problem is the car has a tough time staying at operating temp in certain traffic conditions, like rush hour stop n go, now that it's like 35 in the AM. I'm going to be selling this car soon, and I want everything to be as up and up as possible for the new owner.
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Old 10-30-2008, 02:07 PM   #28
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Radiator cap pressure only affects how high the coolant temperature can get without boiling over.

If you are having trouble getting the engine warm in the first place, it will have zero effect. If the engine is still cold, you could run with a piece of cork as a radiator cap.
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Old 10-30-2008, 02:17 PM   #29
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Quote:
Originally Posted by KPLAFIN View Post
What about getting a cap rated at a different pressure, wouldn't that be able to reduce the overall efficiency of the cooling system for the winter months? I think Jay was referring to putting some extra stress on the pump, kinda like putting your thumb over the end of a hose and turning it on...increases the pressure/stress in the hose.
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Lowering the cap to standard pressure for winter time street use I'd think is a good idea. Sam, you get a cookie, and I'm kinda embarrassed I didn't think of that myself.
But, I suggested it...... According to other people here it may not help though, so maybe I shouldn't be taking credit....
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Old 10-30-2008, 02:55 PM   #30
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what is the fan story?

the system should be fine as it is. if the coolant gets cold, the thermo should close back up.
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Old 10-30-2008, 03:00 PM   #31
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Quote:
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what is the fan story?

the system should be fine as it is. if the coolant gets cold, the thermo should close back up.
He's just trying to get it to warm-up faster first thing in the morning. It will obviously stay at or above what ever temperature his thermostat is.
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Old 10-30-2008, 03:35 PM   #32
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Thermostat should regulate the temps by itself without any additional pinchpoints. The cap release pressure will have no effect other than raising the boiling point. My vote would also be that it there was no heater circuit the point where the flow of water is slowed down does not matter, whether it is in upper or lower hose, they both slow down the water and there still is same amount of water inside the head and the block removing heat.
Do you think the radiator is so efficient that every time thermostat cracks open, the water entering from radiator to engine is too cold and cools down the engine too much?
We used cardboard in front of the radiator to allow quicker heating and more comfortable cabin temps in Finland and also hotter thermostat. When changing winter tires, we changed higher temp thermostat (94 - 96 deg C, ~200 F) too.

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Old 10-30-2008, 04:00 PM   #33
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Quote:
Originally Posted by Ben View Post
I'm running an aftermarket huge, very efficient radiator with a 1.7bar cap. Lowering the cap to standard pressure for winter time street use I'd think is a good idea. Sam, you get a cookie, and I'm kinda embarrassed I didn't think of that myself. It would allow the coolant to heat up quicker, and it would also lower the boiling point which isn't a big deal for this application.

Thermo is a brand new Mazda OEM. It's different than the one I just took out, which was also a Mazda OEM and not that old. The new design allowed the engine to come to temp faster than the old design. The old one opened up much earlier and much wider than the new one in a pot of water on my stove. I'm having the old thermo modified by my boss to open even more for summer time and competition type use.

Restrictor in the lower hose would limit the amount of water through the system. Restrictor in the upper slows down the same volume of water. As I understand, a restrictor in the upper could actually make the coolant temps drop if done correctly as the water will have more time to soak up heat from the motor.

Problem is the car has a tough time staying at operating temp in certain traffic conditions, like rush hour stop n go, now that it's like 35 in the AM. I'm going to be selling this car soon, and I want everything to be as up and up as possible for the new owner.
If your heater core is still in the original circuit and the water has not been rerouted, I would do the cardboard thingy.
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Old 10-30-2008, 04:05 PM   #34
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I was looking for a more elegant solution, but so be it. cardboard/aluminum/whatever in the front it is.

First, I'm going to remove the extraction hood. I'm curious to see how much coolant and intake temps will rise with the original hood.
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Old 10-30-2008, 04:10 PM   #35
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Restricting airflow through the rad is a pretty common thing done here in the winter. We get into the -30C range regularly in the winter months. All the large tractor trailer type trucks have vinyl covers across the rad opening that can change the airflow by opening and closing panels.

If the problem is the rad being too effective, reduce the effectiveness of the rad. Get a piece of Plexiglas that is about the right size and start drilling holes into it with a hole-saw until you find a happy medium.
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Old 10-30-2008, 04:11 PM   #36
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I know. I see trucks all winter with cardboard or plexi affixed to the front grill. I was simply hoping to find something I found to be more elegant.

In the long run, it really does not matter too much. There are no problems with the way the car runs or drives. I just want to be able to toss over the keys to someone and say, "yes, here she is, 100% ready to go and problem free."
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Old 10-30-2008, 05:22 PM   #37
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Quote:
Originally Posted by Ben View Post
Problem is the car has a tough time staying at operating temp in certain traffic conditions, like rush hour stop n go, now that it's like 35 in the AM. I'm going to be selling this car soon, and I want everything to be as up and up as possible for the new owner.
Quote:
Originally Posted by KPLAFIN View Post
He's just trying to get it to warm-up faster first thing in the morning. It will obviously stay at or above what ever temperature his thermostat is.
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Old 10-30-2008, 06:23 PM   #38
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LOL

No I can make it get up to temp by letting it warm up for a few minutes then drive it on the interstate. It comes to temp fine, but then when I hit the stop and go, it drops down too low. I think HRK is correct in his theory that the thermostat can not close down fast enough with this new radiator.

I drove it at lunch time today, in 55 or so ambient, and it came up to temp quickly and held.
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Old 10-31-2008, 09:59 AM   #39
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not a good idea to block water flow from the lower radiator hose. There is a reason upper radiator hoses are smaller than the bottom hoses. By placing a plate in the lower radiator hose the pump builds pressure all the way up through the radiator which causes you to dump water out the radiator cap during high rpm. Upper hoses are smaller so the pressure is in the motor and the pump sucks from the radiator avoiding the above mentioned problem. The pressure were talking about here is not pressure from heat, its the current pressure from the pump.
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Old 10-31-2008, 01:09 PM   #40
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Ben, just get a higher temp thermostat. does someone make a 205?
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