Sealing gaps around radiator
 

Hello everyone, I have been working on a project that some of you may find interesting. As you can see, my 2005 Civic had pretty sizable gaps between the sides of the radiator and the radiator support. There are several problems with having gaps around the radiator:

1. Air takes the path of least resistance. The path of least resistance isn't through my trans cooler, AC condenser and dual row radiator. Sealing those gaps helps force the air through the radiators rather than allowing it to go around.

2. When sitting in traffic with the fans on, some of the hot air that the fans push into the engine compartment can go through those gaps and get back in front of the radiators, reducing their effectiveness. With the gaps sealed, the fans will only pull cool air in through the grill and can't recirculate hot air from the engine compartment.

3. Any air that gets into the engine compartment pressurizes it. This is bad because higher pressure on the back of the radiator and fans inhibits airflow through the radiators, decreasing cooling capacity. Ideally the engine compartment would be under negative pressure but realistically that won't happen, so we want as close to zero pressure as possible for the best airflow.

4. Air flowing through the engine compartment creates drag and should be minimized where possible for the best efficiency. If air is flowing through the engine compartment it should be going to good use (cooling the radiators).


My solution was to cut pieces out of a sheet of aluminium that I have and use self tapping screws to secure it to the sides of the radiator support. To prevent vibration issues and rattles, I left a small gap between the aluminium plates I made and the sides of the radiator and covered that small gap with foil HVAC tape. I also sealed off some other random holes with that foil HVAC tape while I was in there. Easy, simple, and free :thumbup: When I reinstall the bumper cover, I am also going to use a piece of foam to seal the upper grill to the top of the radiator so air can not go over the radiator.

Once I fabricate and install a shroud for my dual Spal radiator fans, I will be ready to put the bumper cover back on. But before I put the bumper cover back on, I am going to fabricate some ducting that extends from the radiator support to the inside of the bumper cover. This way all the air that goes through the grill openings will be forced through the radiators and can not go around and escape through the wheel wells, under the car, etc, which accomplishes nothing other than create drag. I know that probably doesn't make much sense, it will make more sense once I do it and upload pictures.

I am also planning on moving the radiator forwards about 1/2 of an inch so it is closer to the AC condenser and to give me a little more room to access the front of the engine. My understanding is that the radiator and AC condenser should be as close together as possible without touching for maximum cooling efficiency so the condenser doesn't deflect airflow around the radiator and so the radiator fans pull all their air through the condenser instead of being able to pull air around it.

I feel confident that all of these enhancements together (sealing the gaps around the radiator, installing ducting, and moving the radiator closer to the condenser) will result in a decent improvement in my cooling system's capacity, slightly better AC performance at idle, and a tiny decrease in aerodynamic drag. My intake air temp didn't increase either because I built a heat shield for my air filter to separate it from the rest of the engine compartment. As always, any thoughts or comments are always welcome and appreciated!

https://ecomodder.com/forum/attachme...9&d=1590798807

https://ecomodder.com/forum/attachme...0&d=1590798841

https://ecomodder.com/forum/attachme...1&d=1590798872

https://ecomodder.com/forum/attachme...2&d=1590798957

https://ecomodder.com/forum/attachme...4&d=1590799625

https://ecomodder.com/forum/attachme...5&d=1590799668

I like it. I did something similar with HVAC aluminium tape, foam, and leftover aluminium serving trays from an event. Helps. Needs some adjustment and repair now. Next time I have the bumper cover off....

Report back any improvement in cooling?

Subscribed.

Thanks. Honestly with my Mishimoto radiator my cooling system worked so darn well the way it was that I wouldn't see the improvement, even on a 100 degree day with the AC on the coolant temp sits right at the thermostat's temp of 182-186 degrees like it does in the winter. Without a thermostat, my cooling system would actually overcool the engine down to about 160 degrees even driving down the highway using the AC on a 100 degree day, which is darn good IMO.

I suppose once I finish my fan shroud, install ducting, and reinstall the bumper cover I will pull the thermostat out again and see if the cooling system could cool the engine even more after these mods, I think it will. Did you notice a cooling improvement when you did this?

I did think I noticed an improvement. My temps were better and I needed my fan less often. But it was not an objective test. Just my sense on my daily commute, which I have done the same way in the same car, on the same route all week for 11 years now. I felt confident it was a good mod.

A half inch between the radiators sounds right to me, btw.

That makes sense, if ram air cools the radiator more effectively after this mod then the fan wouldn't be needed as much to draw more air through.

Vintage Air and Griffin Radiator both recommend 1/4" to 3/8" of space between the condenser and the radiator with 1/2" as an absolute maximum. Makes sense to me. If the condenser is too far away from the radiator, the radiator's fans will pull a lot of air around it rather than through it and the condenser can deflect airflow around the radiator.

The only disadvantage to this mod that I can think of is that you may increase your intake air temp depending on how your air intake is set up and where it gets air from. I noticed no change in my IAT because my custom cold air intake draws air from behind the passengers side headlight and I made a heat shield to separate it from the rest of the engine compartment, but this is something to keep in mind if you are planning on doing something like this.

This is a great thread, thanks. I work on trucks mostly and need to blow out the straw and leaves the accumulate between the condenser and the cooling package on my trucks. The factory does a great job of sealing everything on the Ford trucks I work on. To the point of it being painful to get it right after replacing a radiator. To be honest I have not even looked at my Saturn to see if it would gain anything by sealing this.

Yeah I imagine much more attention is paid to details like this on trucks since they are designed to haul heavy loads, which creates a lot of heat that needs to be dissipated. On a heavily loaded truck running wide open up a long steep grade in 110+ degree heat, these little details could possibly be the difference between the truck making it to the top without a problem and overheating to the point of something failing. Not that I would ever heavily load my car up a steep grade... https://ecomodder.com/forum/showthre...gle-37994.html

Nice mod!

What's this about removing the thermostat though? Why would you do that?

I just took the thermostat out to see how well the radiator and cooling system worked, and I think the fact that it can significantly overcool the engine driving down the highway with the AC running on a 100 degree day means it works pretty darn well. I normally run a thermostat. Once I get everything finished and put back together I will redo that test on another ~100 degree day and see if it can cool the engine off more. If it can that means my mods worked.

As effective as my cooling system is, I can't judge its performance with the thermostat in since the coolant always runs right at the thermostat's setpoint of around 182-186 degrees all year, doesn't matter if its the middle of the winter with the heater on or a 100 degree day with the AC on.

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.

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

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.

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.


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

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.

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

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?

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.

Forced air will pass right through the fans and even turn them. If you had a way to measure, you would maybe see a little power generation. You're fine. I vote no flaps.

Considering what happens to some longitudinally-engined Volkswagens which have their radiator behind the left headlight, which tend to overheat more often when the radiator flaps are removed, seems like your idea of resorting to flaps at speeds which allow a natural air flow is worth.

Thanks, I guess I will pull the radiator back out and install flaps then. I don't see how it could hurt and it may help a little so why not. I also came up with the idea of adding flaps on the top and sides of the shroud to allow airflow through there at speed too, I could drill holes and cover them with rubber flaps. I wouldn't install flaps on the bottom of the shroud though since they would hang down and not get sucked closed when the fans are on.

I never thought about power generation. I may wire a multimeter to one of the fans and see how much voltage I can get out of it while driving down the highway. Totally useless information, but still cool to know (in my opinion anyways) :thumbup:

Not so sure if it would be so easy to find a motor-generator compact enough to drive a fan when required and to harvest energy while cruising with the fans off.

The fan motor already acts like a generator when spun. The problem is that adding a load to the motor would make it significantly harder to turn and would therefore create more aerodynamic drag as the air flows through the fans and would restrict airflow more, so the power wouldn't be free. Whether generating power with the fan motors would be more efficient than generating that power with the alternator I have no idea.

I have an update. I pulled the radiator back out and added flaps to the shroud just to be safe. I can not have this car overheating under any conditions, it is my only functional vehicle at the moment and it must be reliable.

I finished installing my new AC condenser and did some testing on my new fan setup to see how well it works and it is definitely a massive success. I ran the car for about 30 minutes bleeding the air out of the cooling system, recharging the AC, and doing testing and the highest coolant temp achieved was 186 degrees after 30+ minutes of idling with the AC on in a 100+ degree garage. 186 degrees is totally normal, the coolant runs between 182 and 188 when driving normally so 186 is great. The lower radiator hose wasn't very hot either, I could comfortably hold it. This tells me that the cooling system still had a good amount of capacity left even under those conditions. I plan to do a more scientific hot idle test on a hotter day, measuring ambient temp in the garage and such.

Also, while I had my AC gauges on it, I checked pressures with the gaps on the sides of the radiator open and closed and I found that the high side pressure seemed to be about 10 PSI lower with the gaps closed since less hot air from the engine compartment was getting back in front of the condenser through those gaps. I think that's a decent drop for such a simple mod and I suspect the difference may have been much greater with the hood closed and the bumper on since the engine compartment would have been under more pressure and the bumper may be under slight negative pressure, increasing the amount of hot air that gets pulled back through those gaps and ends up in front of the radiators. I didn't think to close the hood when I tested the pressures, but I will try that when I test this again.

Any pictures of the actual flaps you made? How big were your cutouts? How much overlap around the edges with the rubber?

Unfortunately I didn't think to take pictures while the radiator was out of the car, it was almost 4 AM by the time I was done. Basically what I did on the top and sides of the shroud is I drilled large holes and covered them with rubber flaps I cut out of an old bike inner tube and secured them with self tapping screws. I did this along the entire top of the shroud as well as on the sides. I wasn't able to do much on the front because there simply isn't a lot of shroud covering the radiator and the corners were too small to add flaps to. Also, as you can probably see, there is a bar that goes between the fans, so putting flaps behind that bar would have been pointless. But what I did is I used a thin sheet of flexible clear plastic to cover the holes and secured it with self tapping screws. I did this on the top part of the shroud between the 2 fans, but I couldn't on the bottom because of the support bar. I didn't cut too much out because I didn't want to weaken the shroud or suck the flaps in.

It doesn't seem to be more efficient.

Now that I think about it, I wonder if Honda may have designed the radiator support to have gaps on the sides for a reason such as to allow fresh air into the engine compartment to cool the transmission or oil pan. I'm not worried about it since I have nice engine and transmission oil coolers and my temps are always good, I watch coolant temp on my Scangauge and I have gauges for transmission and oil temp, I'm just curious. I think it's more likely that the gaps are just there since this is a mass produced economy car and not an F1 car, but something to think about.

I think perhaps you are attaching too much to what appears to be sloppy engineering of a osfa mount.

It would depend on how the air flows through the engine bay, but I wouldn't hold my breath for it to lead to any improve on transmission and oil pan cooling. Unless the transmission case and oil sump had fins like the air-cooled engines.

Neither has fins. I was just wondering if Honda may have intentionally left gaps on the side for a reason, but I don't think the gaps were intentional and I don't think they do anything positive. I didn't notice any increase in trans temp, oil temp, or intake air temp since I sealed them off, but like I said I have nice coolers for my engine and transmission oil and I put my air filter in its own heat shield box to keep heat off of it so I wouldn't expect to see any differences in any of these areas. Not sure how any of these areas would have been affected in stock form.

Presumably the cost of filling those gaps :D

I finally mostly finished my radiator ducting and reinstalled the bumper cover. What I did is I cut sheets of plastic out of an old storage bin I had and cut them to fit tightly between the radiator support, bumper bar, and bumper cover, which was actually a huge pain since it needed to be cut pretty precisely to fit tightly enough to stay in place without being so tight it bends or breaks, but I got it done. I still need to use some Gorilla tape to seal the little gaps and some expanding foam to fill in the ends of the hollow bumper support bar so air can’t escape through there. I also need to get a piece of foam to seal the top of the upper grill to the top of the radiator so air doesn’t go over the radiator. This solution certainly isn’t sophisticated, but it should be effective. I feel pretty confident that I now have a more effective cooling system that creates less drag than it otherwise would have. I’m also moving my trans cooler to the back so it isn’t blocking and preheating the airflow to the condenser and the radiator.

I have an update. Since I sealed those gaps off and put those plastic plates on the sides of the radiator against the bumper cover, I noticed that bugs and other debris now seem to get forced deeper into the fins of the AC condenser, which would seem to indicate that the air speed through the radiators has increased. In stock form, bugs would barely get stuck to the condenser's fins and would usually fall off from barely touching it or rinsing it off with a garden hose. However, since I performed these modifications, bugs now seem to get forced between the fins much deeper and needs to be picked out rather than just brushed or rinsed off. Not scientific, but it does indicate that my modifications seem to have increased airflow through the AC condenser and the radiator.

The other thing I noticed is that the car seems to feel more stable at higher speeds now. It always drove well at high speeds, but it just feels a little bit more stable and predictable at speeds of above around 70 MPH than it did before. I don't know enough about aerodynamics to why this is, but I'll take it :)

Would a bug screen around the radiator and AC condenser be out of question?

Probably. I like the idea though, some type of screen may help prevent my AC condenser from being punctured by debris a second time. The problem I see with that is the screen would block quite a bit of airflow since it would need to be pretty fine to be effective.

The other problem is that the screen would still need to be cleaned periodically just like the condenser does, so it wouldn't really solve the problem. I think my best bet is to just live with it and clean the condenser every month or so as I usually do, it only takes a few minutes to clean it off

It's still likely worth to try. As you mentioned an increased air speed around the radiator and condenser, most likely it wouldn't do much harm.


Having an easily-detachable screen in order to clean it may be worth too.