Differences Between Expansion Tanks & Overflow Tanks in Automotive Cooling Systems
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- เผยแพร่เมื่อ 5 ธ.ค. 2020
- 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! 👏❤
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!
Just found this channel - not too sure how I've missed it. This was very clear, thank you. Subbed from London.
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.
Very nice clear explanations, thanks for posting!
Perfect explanation. Thank you for making this video
Great explanation! Thank you!
Thanks for that. Now I understands the difference.
Great explanation - thank you.
Many thanks , very good explanation.
Thank you ! great info!
your expansion tank explanation isn't correct. There is only (2) hoses on the expansion tank and one goes to the engine and the other goes to the top of the radiator (bleeder tube). Having (2) hoses going to nowhere makes no sense. And there is no expansion tank that leads to an overflow tank.
Love this explanation.
Excellent explanation....thanks
Nice video, thank you.
Thanks for the helpful video. Is there any benefit to one system verses the other?
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.
Excellent video.
Great explanation
Great thanks!
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!!
Good explanation 👍👍
Thanks man
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.
Great video
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!
thank you sir.
Hi
There are some special coolants that does not boil at around 100 degree celcius but boils at much higher temp like 160 degree celcius. If we operate with such coolants the radiator system does not work under pressure. In this case do we need expansion tanks?
Nice explanation
thanks
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!
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!
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 👍
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?
Been looking for a flow diagram for a cooling system with expansion type (specifically Hyundai Tucson). Can you help?
Can you flush and REFILL coolant through the expansion tank (top picture) because my car does not have a typical radiator cap??!
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?
If you have a low mount radiator with an expansion tank that links to a thermostat housing/fill neck - what PSI caps would go on the thermostat housing and expansion tank?
Eg if 16 psi cap is normal - would I do 8 and 8 in each location or 16 in each?
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
Is the Toyota hiace van (with 5L diesel engine) has an expension or an overflow reservoir.
Explain how it works.
Thx
Great 👌
very good video
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 have downflow radiator and stock overflow tank. Can i put a swirl pot sir? What are the benefit?
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…
So does placement of the overflow tank matter then? Or is it traditionally lower than the radiator
Hi, I have a race car with an expansion tank set up, however the expansion tank has a pressurised cap without a valve and the radiator has a valves cap. The valves cap on the radiator is vented to nothing which gets messy.
It didn't used to get messy but I'm getting overheating issues ( possibly head gasket) but not sure.
Have you seen a system like this before and am I a component missing?
Any help appreciated.👍
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?
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?
May I ask if hoe to bleed the expansion tank? Thank you for your time
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
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?
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
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!
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?
Bravo..
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
Question. Why does the expansion tank on a ford e350 have 4 separate compartments in it
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
How should i drain a traditional coolant system. I have a 2016 corolla.
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
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
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?
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
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 ?
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??
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.
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.
Does the expansion tank circulate with the radiator circulation.
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
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!?!?
Do 1971 Lincoln Mark 3 have overflow radiator container?
Can i install an overflow Reservoir to a system that uses expansions tank?
Is it possible to change from open to closed in any cooling system.
Whats the best method to clean the gunk out of them????
Very interesting! My 2016 Chevy has a different configuration. Both my radiator and surge tanks each have a pressure cap. When the dealer did a flush recently, when the car is cold, the fluid in the surge tank is all the way to the top. I'm concerned about what happens if it gets hot. Where will the excess coolant go?
It'll come out through the hole below the cap. It's VTA
@@BMR_WRLD Thank you! That's what I am concerned about. I wouldn't want the hot liquid going on wires or any electronic components. With your information, I am now doubly glad that yesterday I used an old Turkey baster and removed the excess.
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
Is it normal to see some bubbling in the reservoir with the car showing normal temps ?
'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?
What causes the expansion tank to be full with coolant and split coolant out leaving the radiator with less coolant thanks
How often should you top off coollent ? I live in desert thanks
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.
I have a sonic 1.4 and the reservoir tank cap say 20psi so if i use a 16 psi cap Is any problem with that or could be a good thing???
Does the overflow have to be vented or can be completely sealed?
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?
great video - thanks! question: my car's engine can't reach the operating temperature, even after some time of driving. I also don't see the coolant swirling in the expansion tank as it used to before when it start circulating through the radiator. What could be the reason for it? thanks!
Hope you figured your issue out already but sounds like you have a coolant leak that has reduced your coolant level to the point that there is now no coolant where your temp sensor reads the coolant temp. If you didn’t fix it I’m guessing you might have ended up with head gasket issues? Probably started out with a perishes hose somewhere in the system
Remove half the coolant place one cup of milk in and then 50 grams of rocks. You’ll be gtg.
@@alanhillyard1639 see my comment for the solution 👍🏻
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
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?
My 1985 BMW E24 635CSi has an expansion tank. The small diameter line from the radiator, and the large coolant from the motor to the tank are understandable. However; the atmospheric line just run to nothing, with the hose hanging down several inches. I can see clamp marks on the end of the atmospheric hose, but the diagrams I've seen do not show where it is supposed to connect.
The expansion tank cap is pressurized, with the atmospheric hose outlet just beneath it.
Suggestions? Solutions? I have yet to see where it is supposed to go, and I don't think that the engineers would have an open line out.
I have the same question and I hope this bumps it to the top to get noticed and a reply
during negative pressure how it will work
I have a expansion tank with radiator cap you described 1st. The water level never changes whether hot or cold and engine temp is fine & no leaks. So I'm assuming there's no flow between radiator cap and the cooling system. I see the hose that goes from cap to the overflow tank and that doesn't seem to be a problem. I'm pretty sure the radiator is full. Any suggestions? Thank you for the video. Very helpful knowing what I have.
If its not overheating and you've got hot air I'd say dw . Unorss you feel something is wrong. I've personally got cause for concern lol (my car )
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
hey man what happened if I put a little more coolant in flow tank?
If I have expansion tank the level of coolant increase or decrease when the car is running.
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 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.
Thanks so much for the video. I have a C7 corvette and am wondering how the engine cooling system gets pressurized. If it is so. Now in the expansion tank there is an overflow hose connected directly to the ambient. So, the pressure cannot increase in this tank. In any case there is a 20 psi cap. Maybe it's there for safety reasons. But my main concerns are with the pressurization of the engine cooling system. How can the pressure increase due to this venting in the expansion tank? What do you think?
In a pressurised cooling system (i.e. most cars), as the coolant heats up it expands, and pressurises the air inside. If the coolant level is high enough, so that there is little air volume the pressure will exceed that of the cap rating (typically about 15 psi) and the cap will release any air and/or coolant. If the coolant expelled is captured in an unpressurised overflow bottle, then some or none of it may be returned but this depends on certain conditions such as the height of the bottle, and whether the end of the pipe is in or out of the coolant. I hope that helps?
As for the expansion tank, suppose you siphon out all coolant and replace it with new fresh fluid: how long would it take for the entire content of the expansion tank to be replaced with old coolant from the rest of the system? That way one could replace all coolant over a period of time instead of causing a mess on the parking lot.
Put a tub under and empty the system properly you need to do this to clean out all the crap that builds up in coolant never let it just spil out on the floor the smallest ammount of coolant will kill a cat if it licks it up and cats do as they like the smell of the stuff.
My dog licked up spilled gas started running around my car outside then he started shaking uncontrollably and he dropped dead on the driveway .
He ran out of gas
Obviously a high octane dog dealing with low octane gas. You cheapskate, you! @@Foxtrotwilconiner1969
On the expansion tank, where does the lower hose go?