Differences Between Expansion Tanks & Overflow Tanks in Automotive Cooling Systems
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- Опубликовано: 26 авг 2024
- Overflow tanks are not pressurized, and simply hold what overflows from the pressurized side of the system when pressure exceeds what it noted on the radiator cap, typically 16PSI. An expansion tank expands the amount of coolant that the pressurized system can hold, and the top of the tank takes on the role of the previous design's radiator cap (expansion tank caps and radiator caps are sometimes the same exact part) for venting excess pressure.
What is a expansion tank in a car? How does a car expansion tank work?
The expansion tank takes in excess coolant and minimizes excess pressure in the engine cooling system. An expansion tank helps maintain a minimal pressure increase during the expansion of heated water, helps reduce coolant hammer, and helps protect the engine cooling system from stress, typically brought on by pressure and temperature changes.
What is the purpose of a coolant expansion tank?
The expansion tank is always located higher than the radiator and functionally becomes the top of the radiator, providing additional fluid capacity, with plenty of room for coolant expansion. This method allows the hood line to be low, as the radiator can be a bit shorter in stature and doesn't need to have it's own cap.
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Great video, no intro, jumped right into it, explained it concisely. Learned more in 3 mins then I did in 10 mins of google/forum searching lol
I just want to say thank you. I bought a car with an expansion tank and NEVER could find anything like your video to explain WHY I didn't have a radiator cap and what more, how each was used. Bravo! 👏❤
Good job on the explanation. Keep note that the bigger spring on a pressure cap is named pressure spring. Then, the smaller spring is named vacuum spring.
Awesome, thank you for the description. I've worked on cars for 2 decades but never had to do much on coolant systems, this helps a lot!
Great explanation. I had wondered by my BMW could have small hole built into the top of the coolant tank, when most websites I saw said that the coolant tank is pressurized and part of a closed system
Does your car have an actual radiator pressure cap on the radiator. If so the coolant tank is an overflow tank.
very informative, thank you. i was playing "The Long Drive," a driving survival game and was just curious how my coolant tank was working just by putting a liquid in it. i will be watching more of your videos, sir.
Thanks!
I like both driving and survival games, so I'll have to look into that one!
Good explanation
wow thank you for the valuable info, please consider explaining the internal chambers to expansion tanks as I have a 2018 Nissan Frontier v6 crew cab and noticed after playing with the levels in radiator and expansion tank that there are 3 different levels, or chambers in my whitish semi-transparent tank, first closest to line from radiator, a small rubber hose about 3/8 inch ID was about 2 inches above max line and only about 1/4 of tank area, then near the middle of tank a 2nd chamber that was about 1.5 inches above max line covering another 1/4 of the tank area, then a 3rd chamber in the remaining part of tank, the back half that was about 1 inch above max line. I have search high and low on the internet for this info, breakdown but have failed. I think you are more in tune with the proper resources to supply the explanation, I hope.
Just found this channel - not too sure how I've missed it. This was very clear, thank you. Subbed from London.
Marvelous way to break it down and to explain it
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Hey, an you explain why there is a return line on a expansion tank that sends coolant back to the pump? My tank has 3 connections, 1 to the radiator, 1 to engine outlet (behind the thermostat) and 1 connect just before the waterpump. Isn't there a bypass to the radiator in such a design? I'd like to understand why it was build that way and whats the purpose. Thanks!!
Very nice clear explanations, thanks for posting!
Very clear, the difference between the two designs. Thank you. Question, with an expansion tank design, can I gradually "change" the coolant by siphoning off the contents of the expansion tank and pouring in new coolant, say, once a week or per month? Thank you
Thanks!
As for your question, that would maybe have a slight effect on the condition of the coolant, but it would keep bad coolant in the system for a long time and you wouldn't get one of the major benefits of a full flush: clearing out the sediment.
Good question though! There are some service chemicals that get changed in a similar manner to what you described.
Do you know why my nissan frontier has a pressure cap on the radiator and the overflow reservior? How necessary is the overflow pressure cap?
Reason: I wanted to change my reservoir to the aluminum reservoir with the vertical tube that clearly shows fluid level.
Perfect explanation. Thank you for making this video
hello, thanks for t he video. it is very useful. On my 2004 acura is blowing off the reservoir plastic cap, This car has a spring loaded raditior cap. what could be reason. is it ok to drive without platic cap. Dealer asks 15 dollars for it?
Thanks for that. Now I understands the difference.
Is there a difference in pressure between these two systems? I know that the cap determines the pressure in the radiator but can you adjust your pressure with the expansion tank setup?
There’s a cap on the expansion tank
the radiator cap does NOT let coolant back in when its cool but as it cooled down it lets it in but NOT when its cold.
my nissan frontier has a pressure cap on the radiator and the overflow tank with a pressure cap, do you know why?
I wanted to change it to the aluminum tank with the clear tube showing levels.
Upon coming back to my car (did a 10 min. hywy run to local store) noticed Prestone near and under the driver's side of my 1976 Lincoln Continental Coup. I lifted the 900 lb. hood expecting to find a wet or steamy radiator, but lightly touched the unpressurized cap and accessed it was safe enough to touch. When I unscrewed the cap, Prestone gushed out of the coolant overflow tank - making me think that the plastic OEM container must have seen it's last day. After days of searching for a replacement, I decided to remove mine and see if I could "repair" it with GOOP. What I discovered was that the tank on this model is a "purge" tank. The coolant enters the overflow and purges it out of the car entirely! I had never heard of such a thing, but sure enough when I got under the car saw how the tank has a nipple which sits in a groove designed to allow the coolant out - right onto the road or wherever. Mind that it's not daily. Perhaps it's running hotter than when I drove it late winter.
Have you seen this before? I think you may have stated that some cars 60's - 70's may have not even had overflow reservoirs.
This experience also made me think about how or where would I ever get a replacement. Meaning, is there something universal?
Is it normal to see some bubbling in the reservoir with the car showing normal temps ?
I've got a 1.4 petrol corsa and my water tank has a return nozzle at the top but no pipe attached so what does that mean?
I made my own radiator overflow tank since I have a custom engine swap. My question is, should the cap be a tight seal or should it be vented? Currently I have an aluminum container with a twist on cap with a rubber seal on it
How does the coolant flow back into the radiator past the radiator cap when the pressure of the cap pushes down on radiator creating a seal?
I’m not comprehending the return flow from the reservoir to the radiator!?!?
Thank you ! great info!
Question. Why does the expansion tank on a ford e350 have 4 separate compartments in it
HI -
i have Chevrolet epica 2009 with 2.4 6 cylinders engine - i remove the old engine and install new Toyota Camry engine every thing is great but i want to know
Do i have to change the RAD system from the original one ( expansion tank ) to Over flow type ?
Thanks
theres a center valve in the caop that allows water to run back into the system, the vacuum created by the system as it cools..us what pulls the coolant back in from the overflow tank
Excellent video.
The drawing shows the two tanks place at two different levels (heights) but you didn't mention whether that matters. Are you familiar with the term "header tank"? My understanding is that a header tank contains a "head" of coolant above that in the radiator so that gravity plays an important part in its operation and is preferable to the two you have covered.
In an expansion tank system -is it correct that the coolant does continually circulate through the entire system (including the expansion tank) when the vehicle is at normal operating temp?
Nice video, thank you.
I have 2004 C5 Corvette no cool e leaks no dropping level in expansion tank but smell odor of coolen t after shutting car off hot top hose from expansion tank goes into radiator the cap says 15 psi now th does not sell 15 psi but 18 psi called th dealer 've said that is what it calls for is his a m flaw saying 15 psi Bettendorf o early so 18 psi looks like water pump had been changed and belt pulley rose color but not wet could the smell be the heat of technology belt burning off old coolent car not running hot 200 to 220 hot day in traffic any help On this
Great explanation and I really thank you for your time. I got a question: what happened if I just install an expasion tank instead of a overflow tank (radiator has already its cap) would it work as "overflow"? The issue is that I am rebuilding an old truck which has no overflow tank at all (there is just a hose from radiator to space) so I have to keep checking for the coolant level as it drops it when heats up, because of the place where the overflow tank supposedly fits it is kind of weird that only found an expansion tank that would fit in place .. let me know what do you think would ya? Thanks in advanced man. Atte MC.
Does the expansion tank circulate with the radiator circulation.
Do 1971 Lincoln Mark 3 have overflow radiator container?
Hi I did a coolant flush on my passat b8 and put in 4 litres of coolant. I realised it wasn't enough but my mechanic said its fine you can drive it. It covered 2 inches of the bottom of the expansion tank but after 10 minutes of driving I realised my expansion tank was empty. My engine fan did not turn on my car did not show signs of overheating on the temperature gauge. Is there a chance that I have damaged my engine?
Whats the best method to clean the gunk out of them????
during negative pressure how it will work
I have question what If I filled the resovoir with one jug a pure antifreesze and did not mix.Can I still fix the mix to get right ratio?
You might be able to if there's enough room for the water. Most personal vehicles I can think of don't have two gallon reservoirs, though. You may have to drain/extract some of that full strength stuff.
I have a 454 everytime i use it for bit then turn it off it always leaks water I always have to fill up the radiator w/ water b4 i use it, it doesn’t drain all the way just a bit after a couple uses it gets pretty low any ideas on what i need
'05 Town and Country 3.3L Overflow tank fills but doesn't seem to ever return any liquid to the radiator. Radiator level decreases. What would be a fix for this? I've changed the cap, no apparent result. Could there be a leak in the cooling system?
i replaced the radiator, with a new one the water pump and thermostate in my 09caravan
coolent level drops and does not get sucked back into the radiator, i must add coolent to radiator to keep it from overhaeting. no white smoke no coolent in oil what should i be looking for van has 149k i am thinking vally pan gasket
Many thanks , very good explanation.
Great explanation - thank you.
My exspansion tank or so I think it because there is no radiatorcap on the radiator, will not pressurize at all but if I put the cap on it will throw out some antifreeze. I don't know what's going on? Plesae help. I tried to text it with a pressure gauge but it won't take any. I don't see a hole or a crack in it at all.
And one of the things people take for granite. I remember the days in the 60's and 70's where you didn't have the expansion tank. You strictly add coolant to the radiator cap and there was a hose next to the cap when there was expansion and the excess would fall to the ground. Hopefully no animals like dogs would be around to drink that green sweet Preston antifreeze!
For sure! I have read that coolant will mess up people and animals pretty badly. Pretty much guaranteed that you'll need a stomach pump ASAP.
should I take it for limestone instead?
@@executive or take it for concrete!
Granite 😝 ... it's granted. "take for granted"
Corian or maybe Silestone. Some of those look like granite. Lol, don't you just love Google auto correct.
I have a 2012 GMC sierra. Does the coolant circulate through the expansion tank is my question… Just added some coolant after I fixed a radiator leak and I want to make sure that the proper ratio is flowing through the system. It still looks like pure coolant on the expansion tank, even after driving for a while…
Sir can I ask something about my ford ranger expansion tank. I went into a shop to check my ford ranger because I am losing significant amount of coolant and they haven't fount any leak. They said that my expansion tank is not generating pressure and that the coolant evaporates and i need to replace it. Is it possible that i have a faulty coolant expansion tank? Thank you
One question. Is the level of warm coolant higher or lower then cold coollant. Because the level in the expansiontank looks as it is rises at warm temperature en lowers at cold temperature. Is this correct?
On every one I've seen, that has been true (that the warm level is higher). Not every tank has high temperature and low temperature marks, but it will still work that way, marked or not.
I have a lengthy question. On my 5.3 swap in my 64 C-10 I installed the surge tank from the 03 Tahoe the engine came out of but not the radiator. I also installed the correct heater hoses to the surge tank. My problem I essentially have two radiator caps now and I can't seem to get the air out of the system. Running the vent line under the radiator cap of my LS swap aluminum radiator to the outlet on the surge tank that normally goes to the stock Tahoe radiator. I'm doing this via a reducer in that line. Thank you for taking the time to read. Great video BTW 👍
My golf v has a wire inside the expansion tank. When I overfilled it I used a cloth to soak up and pulling it out it bent the wire up. I bent it back. What is it for and will it cause a problem later?
Great explanation
So here is my problem i have a 2006 Daihatsu sirion and it had a coolent reservoir like the upper one but without a connection under it so it has one tube on the cap and that's it and i don't understand it
Great vid. My Cap seal broke and fell into the radiator, causing my overflow to leak a lot of water. Should I worry about the seal being stuck in radiator and obviously I need a new radiator cap? Thanks!
Excellent explanation....thanks
In the first illustration of the pressurised radiator with an expansion tank at atmospheric pressure, how can the coolant be drawn back into the radiator against a seal with a strong spring?
has a type of valve on the radiator cap that lets the overflow coolant back in as the cooling of the coolant cools it causes a vacuum that makes the pressure inside your sistem lower than the air pressure outside, and this push's the coolant back through the valve in through the radiator cap back into the system, this valve lets pressure out of the system when it gets to about 15psi ish to 18psi ish but about 0 pressure needed to push the coolant back into the system, well not zero but its 14.6 witch is our atmosphere pressure, so it wants to return to 14.6psi this is why it push's it back in and not sucks it back in
May I ask if hoe to bleed the expansion tank? Thank you for your time
Can you flush and REFILL coolant through the expansion tank (top picture) because my car does not have a typical radiator cap??!
Been looking for a flow diagram for a cooling system with expansion type (specifically Hyundai Tucson). Can you help?
On the bottom design...As the coolant heats up and pushes past the seal on the radiator cap, how does the coolant get past the seal on the radiator cap when it cools back down?
Good question! Definitely something I wish I included in this video. I'll end up taking one of those radiator caps apart sometime for a future video, but on some of these radiator caps there's a small sealed way back in that has a small spring holding it shut. As the coolant in the working part of the system cools down, the pressure can get low enough to overcome the spring and pull the excess coolant back in. When the cooling system is at a neutral pressure, just the spring seals the cap, and when the system is pressurized, the pressure and spring are both keeping that return path pressed closed.
When adding coolant to an expansion tank while the engine is cold, do you fill until level is at min, max, or in between the two?
Love this explanation.
In the upper system with the main cap on the plastic bottle can i add another tank to match the other system and to refill the the system if needed
Hi!
Is there a problem if I go to a higher pressure coolant tank cap?
For example the cap on my car (a4 b9) has 1.4 bar and want to change the whole coolant expansion tank with a new cap that has 1.6 bar release pressure.
Thank You!
Why does it say on the manual not to add coolant if the expansion tank is empty. Air could enter the cooling system and damage the engine. What are the chances of that happening?
I think u were so fast in the explanation but it's a nice video. The complete system would had been best
I recently replaced the radiator on my ‘19 Chrysler Pacifica. Afterwards, I burped the coolant with a big funnel, but now the coolant level on the expansion tank is a bit high. Soon as I open the cap it makes a whoosh sound and the coolant level drops about 1.5 inches. The coolant temperature ranges seem to be ok 195-225, depending if it’s seating idle on traffic or moving. Do you think I may still have air in the cooling system? Should I repeat the burping process??
I have downflow radiator and stock overflow tank. Can i put a swirl pot sir? What are the benefit?
Nice explanation
I am thinking, for the pressurized system, if I release the pressure when coolant is hot with care, then when coolant is cool, it'll create vacuum. Next time it gets hot again, the PSi won't be as high as usual. Is this a good idea to have constant vaccum in coolant line? I've seen coolant hoses got blown holes in them. The goal is to prreserve the coolant hoses. Thanks
What causes the expansion tank to be full with coolant and split coolant out leaving the radiator with less coolant thanks
You got the expansion tank vent location wrong. It’s rarely connected to the high point on the radiator since the expansion tank is the high point. It’s always plumbed to the suction side of the circuit ie upstream from the pump and in many cars other points. These systems function very differently. One is actively part of the cooling circuit and the other is as you rightly described as available after the car cools. An expansion tank will solve a lot of cooling issues in hot cars. All modern cars use an expansion tank.
On the expansion tank explanation, you mentioned that some systems have a return line. I'm wondering if you have any examples of systems that don't have a return. Seems like across the board if they have an expansion tank they have a return to somewhere just before the pump.
I don't really know why they need a return, but it has to be doing something. Maybe keeping some small amount of flow up and through the tank continuously purging air?
My tank has a med to large hose to radiator then I have 2 small hoses from tank to radiator 2:31
Thanks for the simple explanation. I tried to find out the design of expansion tank of VW polo which, for me, doesn't have expansion tank cap. I just wonder how this works to control the system pressure. Aside question, if such expansion tank spit coolant when the vehicle stops, what that would be a sign of? Thanks again for your time to help people
Most of the newer Volkswagen stuff has a regular cap but also a pressure release valve on the underside of the reservoir
what would cause water to boil in the system, new thermostat fitted
Does the position of the overflow tank matter? let's say i want to move the one that came with the car, do I have to put it higher/lower than the radiator or can i put it wherever? Thank you!
On the expansion tank, where does the lower hose go?
Hi just wondering on the top picture , should the cap be Return or Non Return cap ? Thank you as I thought it should be Non Return but the shop is saying should be Return , where I thought it should be Non Return …. Thank you 0:22
Can I convert an expansion tank style to an overflow? I ask because I have a Power Stroke with an expansion tank (degas bottle) in a very inconvenient spot.
Hi from Australia. I own a 2005 Toyota Altise. Coolant is leaking from the Reservoir/ over flow tank. Mechanic has adjusted the hose and placed a clamp on the hose next yo the reservoir tank. Why is it leaking?
Can i install an overflow Reservoir to a system that uses expansions tank?
Steve if you have an older model vehicle and extra coolant, would it make sense from a preventive maintenance standpoint, to extract some or all of the overfill coolant and replace with new coolant, pre Summer?
Even if the coolant was being replaced directly from the radiator in the amount the tank has, the old and new coolant still mixes into a less ideal mix, and very little of the sediment that needs to get flushed out will be removed. An overflow tank being drained and filled with fresh fluid would be like that but the mixing would occur much more slowly, potentially not at all if there is an issue with the cooling system.
It wouldn't hurt, but it would be much better to just drain all the old stuff out and put in all new fresh coolant. Plus you avoid potential coolant compatibility issues.
@@CarsSimplified yeah you must be right because I've never heard of anybody doing it thanks for the feedback
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Om fixing a 1988 Cadillac. There is a little bit leak om waterpump, and the owner told he check the owerflowtank often. But Wien i checked the radiator, i filled it up with 2 gallon. So why did the coolant not go to radiator from the owerflowtank?
Hi
Thank you for making these videos
I have a question about my car, the coolant is in the minimum before using it, and dropped a little bit after using. It retains that level until morning and when I opened the cap it came back to min level.
Is that normal?
i hope someone made animation about cooling system with expansion tank
thank you sir.
Great explanation! Thank you!
So it bleeds itself?
Great thanks!
So does placement of the overflow tank matter then? Or is it traditionally lower than the radiator
hey man what happened if I put a little more coolant in flow tank?
Question, my truck had an expansion tank from factory and switched to an over flow style tank from a 90s-2000s mustang. Since there is no way for the pressure to be released could this be the reason for coolant pushing past the overflow tank cap and spraying out when I am racing for one consecutive long time/run? Doesn’t over heat or anything just pushes past the cap when i do lets say a 60-130mph runs.
I see in my mom's Hundai Starex it has an expansion tank system built to it. I suppose it's normal to see the coolant boils while the engine is running, correct?
Great video
I have put a Zzr1100 motorcycle engine in a kit car and mated the radiator of a honda Jazz to it. It has the fan of the honda Jazz and a temperature sensor. The piping from the bike has a pressurized cap. The radiator feeds to an overflow bottle. When the car gets hot, it's sucks all the coolant out into the engine, boils over and forces it back out of the expansion tank pipe over flow pipe. Then when it cools down, what's left drains back into the expansion bottle. This causes air locks, loss of coolant and massive heat problems. The thermostat is fine and the cap works fine. No air locks. Could it be that the expansion bottle is too low ?
Is it possible to change from open to closed in any cooling system.
Is the Toyota hiace van (with 5L diesel engine) has an expension or an overflow reservoir.
Explain how it works.
Thx