Sealing gaps around radiator

[me and my metro]

Correct, a thermostat is also used as flow control in a cooling system. Sometimes cars overheat due to the coolant not staying in the radiator long enough to transfer heat.

[EcoCivic]

Originally Posted by me and my metro

Correct, a thermostat is also used as flow control in a cooling system. Sometimes cars overheat due to the coolant not staying in the radiator long enough to transfer heat.

That is incorrect, a higher flow rate will always equal more effective cooling. With all else being equal. This is basic thermodynamics. Looking at the other side of that statement, the coolant stays in the block a shorter amount of time and picks up less heat as well, meaning it does not need to stay in the radiator as long to dissipate heat since it didn't pick up as much. The problem is that everything else is not necessarily equal without a thermostat.

For example, depending on the vehicle, there is likely a bypass hole behind the thermostat to allow coolant flow through the block while the thermostat is closed to prevent hot spots and allow for even warmup. The disc on the back of the thermostat pushes against that hole in the block to seal it off when it opens, forcing all coolant to flow through the radiator and not allowing hot coolant to recirculate into the block without flowing through the radiator first. If hot coolant is bypassing the radiator and recirculating directly back into the block, cooling efficiency will suffer.

Another problem someone may run into when running no thermostat is that there may not be enough pressure in the block to keep the coolant from boiling at hot spots such as around the cylinders. If the thermostat is located at the upper radiator hose, it creates backpressure in the block as the water pump tries to push coolant through it since it is a restriction even when fully open. The backpressure raises the boiling point of the coolant in the block, preventing it from boiling. If it boils, cooling efficiency will drop dramatically and damage may result.

Finally, depending on the design of the water pump, it may cavitate and lose effectiveness without backpressure. If the pump cavitates and loses effectiveness this will result in overheating because the coolant won't flow through the system fast enough to keep the engine cool. Again, the overheating would be caused by inadequate flow, not too much flow.

When people remove their thermostat and have overheating problems without a good understanding of thermodynamics and how the cooling system works, they often incorrectly jump to the conclusion that the overheating is caused by too much flow through the radiator without realizing the other variables that they are changing. If more flow through the system resulted in worse cooling, truck engines and other heavy duty vehicles wouldn't come with higher flow water pumps than lighter duty vehicles.

[Ecky]

Originally Posted by EcoCivic

That is incorrect, a higher flow rate will always equal more effective cooling. With all else being equal. This is basic thermodynamics.

This is one of those automotive myths that really drive me nuts. Thank you for the detailed breakdown.

I'd like to add to it that the amount of time water spends in contact with the radiator is *always*. There is always water in the radiator, conducting heat into it, and always water in the engine block conducting heat away from it. How fast your circulate that water has nothing to do with how much time water is in contact with the heating and cooling surfaces.

What's most important is the temperature delta. How much heat is deposited in the radiator is largely dependent on the temperature difference between water and radiator. By circulating coolant faster, you better distribute heat in the system - the water in the block is a little cooler, and the water in it radiator is a little warmer, which causes improvements at both ends.

There are also some effects caused by turbulence which improve cooling as flow increases which I won't get into, but suffice to say, it's entirely a myth (for practical purposes) that removing a thermostat decreases the cooling system's effectiveness *because* the water doesn't "hang around" long enough to gain or lose heat.

[cRiPpLe_rOoStEr]

Even if you don't "feel" any advantage of using the thermostat, it's better to have it all-year round. I see the point when some folks remove it during summer, but it doesn't mean there wouldn't be some temperature variations on a same day once the sun goes down.

Originally Posted by California98Civic

I did something similar with HVAC aluminium tape, foam, and leftover aluminium serving trays from an event.

Those aluminium tapes and foils, and the expansive foam, are more useful for makeshift repairs than it may seem at a first glance.

[EcoCivic]

Originally Posted by cRiPpLe_rOoStEr

Even if you don't "feel" any advantage of using the thermostat, it's better to have it all-year round. I see the point when some folks remove it during summer, but it doesn't mean there wouldn't be some temperature variations on a same day once the sun goes down.

As I said, I normally run a thermostat. I just ran without it for a few days last summer to see how cool my radiator could get the engine. That’s all. I understand the importance of proper operating temperatures.

[EcoCivic]

I have an update. It definitely does cool better with those gaps sealed, at least at idle. Yesterday I got stuck in traffic and idled for about 15 minutes with the AC running on a 90 degree day and the coolant only heated up to 193 degrees even though the radiator only has 1 fan on it with no shroud and the temp came down pretty quickly once I got moving. Last summer I was seeing coolant temps of around 195 at idle under the same conditions with both of my Spal fans on the radiator with no shroud. The only difference is that the bumper cover is off for now and it was on last summer. I can't see that making this much difference by itself though, I will test that. I know from experience that having 2 fans more than doubles the cooling capacity of the radiator compared to 1 fan, the difference is more like 3-4X. The reason for this is because with 1 fan, only half the radiator gets cooled off and coolant still flows through the side that isn't getting airflow, bypassing the side that is getting cooled off.

Right now I have the radiator out and I am almost done making an aluminium shroud for my Spal fans so they can cool off the entire radiator, that should help a lot too. I am also going to drill holes in the shroud on the surfaces that aren't covered by the fans and cover the holes with rubber flaps. The flaps will get sucked closed with the fans running at idle, but when driving down the road at higher speeds or without the fans on the flaps will open from the pressure in the shroud, allowing air to flow through a little easier since the air will have another path to escape the shroud instead of all of it being forced through the fans.

I doubt that the flaps will make a lot of difference since there isn't a whole lot of my radiator that's covered by the shroud, flaps are mostly used on shrouds that cover a lot of the radiator. Most of my radiator is covered by the fans, so I don't expect flaps to help a whole lot. Why not though, it would surely help at least a little and isn't going to hurt.

Hopefully this all made sense, it's almost 3 AM here and I'm exhausted lol

[California98Civic]

If you have pictures of your assembly and set up, they would be fun to see.

[EcoCivic]

Originally Posted by California98Civic

If you have pictures of your assembly and set up, they would be fun to see.

If you mean the setup of sealing the gaps, nothing has changed since the pics above with the exception of needing to put the sealing panels back since I needed to remove them to get the radiator out to install the fan shroud. Here's some pics of my newly built fan shroud though. Basically I made it out if 1 inch angle aluminium and a 1/16 inch sheet of aluminium. It isn't perfect, but it's quite functional and is therefore good enough for my purposes.

I have a question for you guys. I was very tired when I built the shroud and I forgot all about the flaps I said I was going to add to allow better airflow through the shroud while driving through the highway. The good news is the bumper cover is still off so it wouldn't be a big deal to remove the radiator to add flaps to the shroud if you guys think it would be a benefit?

[MeteorGray]

I don't think so. Most cars don't even need running fans when at speed.

[EcoCivic]

Originally Posted by MeteorGray

I don't think so. Most cars don't even need running fans when at speed.

That’s the whole point of adding flaps. At speeds where the fans aren’t needed anymore, say 40+ MPH, the fans and shroud could block the natural airflow through the radiator. The point of flaps with holes behind them is to allow natural airflow through the shroud when driving at higher speeds when the fans aren’t needed. The flaps get sucked closed when the fans are running when stopped or at low speeds and they get pushed open from pressure in the shroud when driving at higher speeds. I just don’t know if it would help much since there isn’t a lot of my radiator that is covered by the shroud, most of it is covered by the fans.