thefutureisweirdT Hello! I'm providing a writeup on how I finally got the air pockets out of my cooling system. I'm hoping this helps others, and also gives myself a reference if I have to do it again. I know there are other writeups on here, but I did a lot of reading and never found a perfect step by step guide that worked for me. This video that is often recommended is nearly perfect ( ), but didn't go into enough detail for me. A little background on my situation: One day while driving out of state, my idler pully broke off and my water pump belt released while on the highway. I heard a clunk, but thought nothing of it. Luckily, within a couple minutes I got off the highway to get some gas. When I came to a stop, I noticed smoke from under the hood. I then noticed the temp gauge in the red. I switched my ScanGauge over to water temp and saw the number over 300. It quickly went down. I limped it to the gas station just a few hundred feet away. The coolant reservoir was pressurized and steam was making its way out of the hose neck at the reservoir. I found out that an Advance Auto 2 miles away had the tensioner and belt (minor detail: they didn't have the exact belt. I could only get a 4 rib belt of the right length, instead of 5 rib). I decided to let the car cool down and limp it to the Advance Auto. While limping it there, I saw the temp climb over 250, and did my best to keep the temp down turning the engine off at red lights. Turning on the heat did nothing since the water pump wasn't spinning. Once I got there, I swapped out the parts. Lastly, I checked the coolant level by removing the radiator cap. To my dismay, the radiator cap was broken. The spring had fallen apart, and the fill neck on the radiator was burnt up and misshapen where the radiator cap seal sits. I bought another radiator cap and hoped it would seal. Not knowing the special burping procedure, I did what I usually do: fill the radiator, and let it idle while continuing to top off the radiator as it goes down. I think I got really lucky here, because I was able to make it 6 hours home without any major issues. I did monitor the temp, and it never went over half on the dash. However, I would see the scangauge go up to 230 or more sometimes on the way. Eventually it leveled out in the 205 area. When I got home, I parked it and decided to check it the next day. The radiator had lost some coolant and the reservoir was empty too. I figured I would bust out my service manual and check the burping procedure. I saw that it had a special procedure. I decided I would buy the correct belt and a better pulley, and do the burping after that. I also decided to do a new water pump while I was in there. I followed the service manual step by step, and noticed the coolant reservoir would fill every time I poured coolant into the burping funnel/tube. The radiator fill tube was burnt up and the radiator cap was not sealing. I knew I had to get another radiator. So, I ordered one and went ahead and got a new thermostat and fan switch too. Just in case. So, I swapped all those parts, did more reading on the burping procedure, tried doing everything right, and....no luck. When I would check to see if the heat worked, it blew cold. I don't know what I was thinking, but I decided I would drive it down the road to see if it worked anyways. It immediately started overheating. Actually went to the red. I pulled over, let it cool down, and limped it home again. Note: I also tried using a head gasket test kit (the kind that you stick on the radiator fill port and draw air into fluid). It came back as OK, but these kits may be hard to get to work on our insights. When I did it, the thermostat likely wasn't open (it needs to be open for an accurate result). If you don't have an air bubble, you probably won't be checking for a head gasket. But if you do have an air bubble, you likely won't get your thermostat to open for an accurate test result. And we know the radiator cap can't really be open for the cooling system to flow correctly. I wouldn't recommend using one of these kits. Now, let's go over exactly what I did, and what key things I did differently to make it work: Key points: -Jack the front of the car up! The video that everyone shares on here, that is the first step (well, they pull the car up on ramps). For some reason, I always skipped that, thinking it was only to remove the undertray to drain or something. This step is not in the service manual. I think it is very important. Likely it helps get the coolant flowing toward the back of the engine into the heat exchanger so it can actually make it to the water pump. -I used a clear vinyl tube that was about 18 inches long for the burp tube. I would say go even longer. The coolant level will expand while you do the procedure. You want a long enough tube so that it stays above the burp port but doesn't overflow out of your funnel. You also want it clear so you can keep a really good eye on the bubbles and level. I was using a short, semi transparent tube before and it made things very hard. A larger funnel would be good too. Something a little transparent is nice so you can see the level from inside the car while you burp. -I used a spill free funnel on the radiator first thing to get coolant to actually flow out of the bleed valve. I couldn't get it to flow out before when I was only pouring into the radiator with a normal funnel). -Know how to actually open the heat exchanger. The service manual just says to turn heat to max. That's pretty vague. And if they mean turn the temp dial all the way to hot, that's not always going to open the heat exchanger (like if you're in auto mode). You want to press OFF, then press Mode. Press mode until you have the arrow pointing at the face. I like this one because if you turn the fan on, it blows right at you and you know really quickly what the air temp is doing. Turn the dial all the way to the right. You should hear the heat exchanger open. Sounds like a little servo. Turn it left and back right if you were already on the hot side, just to make sure. At this point, air will only blow out if you press the fan button. I waited to open the fan until it was above 195deg. Throughout the bleeding procedure, I used the fan speed to regulate the temperature until it was properly burped. I was afraid my radiator fan would not turn on, since it wasn't even above 200deg. The fan should kick on between 200 and 215, but the temp gauge and fan switch are on opposite sides of the system, so it's hard to tell if it should be on or not. -The idling portion of the burping procedure can take a while. I saw it take an hour for others on here, and it did for me too. Now the exact steps: 1) Turn the heat to max (KEY POINT. See above. Turn car on (do not start). Press OFF on climate control. Press Mode to dash vents. Turn knob to hottest. Turn car off) 2) Jack up the front of the car using jack stands or car ramps (KEY POINT; see above for explanation). Engage E brake for safety. 3) Remove the engine cover 4) Make sure the engine is cool, then open the radiator cap 5) Install spill free funnel (KEY POINT; See above for explanation) 6) Open bleed valve 7) Fill radiator until coolant constantly flows out of the bleed valve. 8) Close bleed valve. 9) Close spill free funnel and remove from radiator 10) Install radiator cap (make sure it is good and sealed!). 11) Open and fill the coolant reservoir to the max line. Close reservoir. 12) Open bleed fill port and install a long clear tube with funnel on the top (KEY POINT; see above for explanation) 13) Fill up the hose/funnel. You may notice some bubbles already coming up. Fill to the base of the funnel until it's stable. Or if you have a large funnel, fill up some of the funnel too. 14) Start the car and let it idle. You might see some larger bubbles early on, reducing the level in the funnel and tube. This can happen quick, so be prepared to add coolant as it drops. 15) Now, patiently wait for the car to heat up. This can take a while. Keep an eye on the bubbles and level in the tube. You want the thermostat to open. I do believe I did some light revving to speed it up. Revving also helps drive some bubbles out. 16) Once the temp looks to be up, it helps to press the fan button to check if heat comes out. If it does, the thermostat is likely open and flowing. This is also a good indicator that you don't have an air bubble in the heat exchanger. 17) Keep burping while you're up to temp with the thermostat open. Since you're idling, at least for me, you may see the temp get a little too hot (207 for me). Use the heater to help regulate the temperature (cycling between low and high fan speeds). High fan speed dropped my temp to 175. Low speed around 195. Again, I'm not sure that my radiator fan will come on by itself, so I didn't want to let it get high enough to see. Also, if the thermostat isn't open, the fan won't come on. If there is an air bubble, do not let it overheat and boil the coolant. 18) Continue revving periodically to check for bubbles. Also switching between cold and hot on the dial will confirm if bubbles are out of the heat exchanger. 19) Squeezing the radiator hoses could also help burp any air out of those. You can also make sure the both hoses are hot. My upper hose was hot, and the top portion of the lower hose was hot (near the thermostat housing). Bottom of the hose and bottom of the radiator was cool. I think this is normal. The radiator is doing its job. 20) Once you haven't seen any bubbles for a while, you should be done. 21) Turn the engine off. 22) Pinch the bottom of the burp hose, remove it from burp pipe, and immediately put the burp pipe cap and clamp on. 23) Take it for a test drive to see how it does. Keep an eye on that temp! 24) If all seems good, check the reservoir when you return while it's still hot. It should still be at the max line. It shouldn't be overflowing. 25) Let it cool down and check the reservoir. It should be between min and max. Mine was about 30% between min and max. If it's completely empty, you should probably do the procedure again, as air likely got sucked in when the reservoir went empty. I will update here if my problem comes back in the near term! So far so good. Let me know if this helped you, or if you have any more tips. I definitely picked up most of these tips scattered across the forum. #1 · May 17, 2021 (Edited) Hello! I'm providing a writeup on how I finally got the air pockets out of my cooling system. I'm hoping this helps others, and also gives myself a reference if I have to do it again. I know there are other writeups on here, but I did a lot of reading and never found a perfect step by step guide that worked for me. This video that is often recommended is nearly perfect ( ), but didn't go into enough detail for me. A little background on my situation: One day while driving out of state, my idler pully broke off and my water pump belt released while on the highway. I heard a clunk, but thought nothing of it. Luckily, within a couple minutes I got off the highway to get some gas. When I came to a stop, I noticed smoke from under the hood. I then noticed the temp gauge in the red. I switched my ScanGauge over to water temp and saw the number over 300. It quickly went down. I limped it to the gas station just a few hundred feet away. The coolant reservoir was pressurized and steam was making its way out of the hose neck at the reservoir. I found out that an Advance Auto 2 miles away had the tensioner and belt (minor detail: they didn't have the exact belt. I could only get a 4 rib belt of the right length, instead of 5 rib). I decided to let the car cool down and limp it to the Advance Auto. While limping it there, I saw the temp climb over 250, and did my best to keep the temp down turning the engine off at red lights. Turning on the heat did nothing since the water pump wasn't spinning. Once I got there, I swapped out the parts. Lastly, I checked the coolant level by removing the radiator cap. To my dismay, the radiator cap was broken. The spring had fallen apart, and the fill neck on the radiator was burnt up and misshapen where the radiator cap seal sits. I bought another radiator cap and hoped it would seal. Not knowing the special burping procedure, I did what I usually do: fill the radiator, and let it idle while continuing to top off the radiator as it goes down. I think I got really lucky here, because I was able to make it 6 hours home without any major issues. I did monitor the temp, and it never went over half on the dash. However, I would see the scangauge go up to 230 or more sometimes on the way. Eventually it leveled out in the 205 area. When I got home, I parked it and decided to check it the next day. The radiator had lost some coolant and the reservoir was empty too. I figured I would bust out my service manual and check the burping procedure. I saw that it had a special procedure. I decided I would buy the correct belt and a better pulley, and do the burping after that. I also decided to do a new water pump while I was in there. I followed the service manual step by step, and noticed the coolant reservoir would fill every time I poured coolant into the burping funnel/tube. The radiator fill tube was burnt up and the radiator cap was not sealing. I knew I had to get another radiator. So, I ordered one and went ahead and got a new thermostat and fan switch too. Just in case. So, I swapped all those parts, did more reading on the burping procedure, tried doing everything right, and....no luck. When I would check to see if the heat worked, it blew cold. I don't know what I was thinking, but I decided I would drive it down the road to see if it worked anyways. It immediately started overheating. Actually went to the red. I pulled over, let it cool down, and limped it home again. Note: I also tried using a head gasket test kit (the kind that you stick on the radiator fill port and draw air into fluid). It came back as OK, but these kits may be hard to get to work on our insights. When I did it, the thermostat likely wasn't open (it needs to be open for an accurate result). If you don't have an air bubble, you probably won't be checking for a head gasket. But if you do have an air bubble, you likely won't get your thermostat to open for an accurate test result. And we know the radiator cap can't really be open for the cooling system to flow correctly. I wouldn't recommend using one of these kits. Now, let's go over exactly what I did, and what key things I did differently to make it work: Key points: -Jack the front of the car up! The video that everyone shares on here, that is the first step (well, they pull the car up on ramps). For some reason, I always skipped that, thinking it was only to remove the undertray to drain or something. This step is not in the service manual. I think it is very important. Likely it helps get the coolant flowing toward the back of the engine into the heat exchanger so it can actually make it to the water pump. -I used a clear vinyl tube that was about 18 inches long for the burp tube. I would say go even longer. The coolant level will expand while you do the procedure. You want a long enough tube so that it stays above the burp port but doesn't overflow out of your funnel. You also want it clear so you can keep a really good eye on the bubbles and level. I was using a short, semi transparent tube before and it made things very hard. A larger funnel would be good too. Something a little transparent is nice so you can see the level from inside the car while you burp. -I used a spill free funnel on the radiator first thing to get coolant to actually flow out of the bleed valve. I couldn't get it to flow out before when I was only pouring into the radiator with a normal funnel). -Know how to actually open the heat exchanger. The service manual just says to turn heat to max. That's pretty vague. And if they mean turn the temp dial all the way to hot, that's not always going to open the heat exchanger (like if you're in auto mode). You want to press OFF, then press Mode. Press mode until you have the arrow pointing at the face. I like this one because if you turn the fan on, it blows right at you and you know really quickly what the air temp is doing. Turn the dial all the way to the right. You should hear the heat exchanger open. Sounds like a little servo. Turn it left and back right if you were already on the hot side, just to make sure. At this point, air will only blow out if you press the fan button. I waited to open the fan until it was above 195deg. Throughout the bleeding procedure, I used the fan speed to regulate the temperature until it was properly burped. I was afraid my radiator fan would not turn on, since it wasn't even above 200deg. The fan should kick on between 200 and 215, but the temp gauge and fan switch are on opposite sides of the system, so it's hard to tell if it should be on or not. -The idling portion of the burping procedure can take a while. I saw it take an hour for others on here, and it did for me too. Now the exact steps: 1) Turn the heat to max (KEY POINT. See above. Turn car on (do not start). Press OFF on climate control. Press Mode to dash vents. Turn knob to hottest. Turn car off) 2) Jack up the front of the car using jack stands or car ramps (KEY POINT; see above for explanation). Engage E brake for safety. 3) Remove the engine cover 4) Make sure the engine is cool, then open the radiator cap 5) Install spill free funnel (KEY POINT; See above for explanation) 6) Open bleed valve 7) Fill radiator until coolant constantly flows out of the bleed valve. 8) Close bleed valve. 9) Close spill free funnel and remove from radiator 10) Install radiator cap (make sure it is good and sealed!). 11) Open and fill the coolant reservoir to the max line. Close reservoir. 12) Open bleed fill port and install a long clear tube with funnel on the top (KEY POINT; see above for explanation) 13) Fill up the hose/funnel. You may notice some bubbles already coming up. Fill to the base of the funnel until it's stable. Or if you have a large funnel, fill up some of the funnel too. 14) Start the car and let it idle. You might see some larger bubbles early on, reducing the level in the funnel and tube. This can happen quick, so be prepared to add coolant as it drops. 15) Now, patiently wait for the car to heat up. This can take a while. Keep an eye on the bubbles and level in the tube. You want the thermostat to open. I do believe I did some light revving to speed it up. Revving also helps drive some bubbles out. 16) Once the temp looks to be up, it helps to press the fan button to check if heat comes out. If it does, the thermostat is likely open and flowing. This is also a good indicator that you don't have an air bubble in the heat exchanger. 17) Keep burping while you're up to temp with the thermostat open. Since you're idling, at least for me, you may see the temp get a little too hot (207 for me). Use the heater to help regulate the temperature (cycling between low and high fan speeds). High fan speed dropped my temp to 175. Low speed around 195. Again, I'm not sure that my radiator fan will come on by itself, so I didn't want to let it get high enough to see. Also, if the thermostat isn't open, the fan won't come on. If there is an air bubble, do not let it overheat and boil the coolant. 18) Continue revving periodically to check for bubbles. Also switching between cold and hot on the dial will confirm if bubbles are out of the heat exchanger. 19) Squeezing the radiator hoses could also help burp any air out of those. You can also make sure the both hoses are hot. My upper hose was hot, and the top portion of the lower hose was hot (near the thermostat housing). Bottom of the hose and bottom of the radiator was cool. I think this is normal. The radiator is doing its job. 20) Once you haven't seen any bubbles for a while, you should be done. 21) Turn the engine off. 22) Pinch the bottom of the burp hose, remove it from burp pipe, and immediately put the burp pipe cap and clamp on. 23) Take it for a test drive to see how it does. Keep an eye on that temp! 24) If all seems good, check the reservoir when you return while it's still hot. It should still be at the max line. It shouldn't be overflowing. 25) Let it cool down and check the reservoir. It should be between min and max. Mine was about 30% between min and max. If it's completely empty, you should probably do the procedure again, as air likely got sucked in when the reservoir went empty. I will update here if my problem comes back in the near term! So far so good. Let me know if this helped you, or if you have any more tips. I definitely picked up most of these tips scattered across the forum. See less See more Sort by Oldest first Oldest first Newest first Most reactions #2 · May 21, 2021 Thanks for the write-up. Changing the coolant is on my list of things to do. It's so easy to ignore it until you have a problem. Was the pully getting noisy before it failed? I have an EP3 Civic Si that I just changed the pulley and that thing was making a racket before it was replaced. #3 · May 21, 2021 The pulley did get noisy about 30 miles before. I heard it, but I had no idea what it was. Funny thing was I heard it while I was coming into my weekend destination (6 hours from home). The insight sat all weekend, then when I started driving home, it broke. If only it had broke right before, then I would have had all weekend to fix it! #4 · May 21, 2021 In step 1, "turn car on," that doesn't mean the same as step 14 "start the car." Correct? Maybe clarification needed. #5 · May 21, 2021 Correct. I've updated it. Thanks for pointing that out. 0Reply #6 · Aug 22, 2021 (Edited) For those of you who experience coolant spitting out of the funnel when purging, this is most certainly a symptom of an air bubble in the system causing the coolant to boil over. If you experience this, my suggestion would be to shut the car down, let it cool off for an hour +, remove the radiator cap slowly and carefully and add more coolant directly to the radiator. Then try the bleed/burp procedure again. I have no experience with a head gasket failure, so if that is the issue, my suggestion may not work. #7 · Aug 23, 2021 Engine oil breaks down at between 240~275 deg F depending on the oil. If you get your engine really hot most likely your engine oil is going to get really hot. After you cook the goose it's not a bad idea to change the oil. Tim #8 · Aug 21, 2023
For those of you who experience coolant spitting out of the funnel when purging, this is most certainly a symptom of an air bubble in the system causing the coolant to boil over. Click to expand...
One more thing to add: disconnect and short your fan switch. Coolant systems don't always get hot enough to trip the fan unless they're sealed under pressure (e.g.). Burping coolant does not require the coolant to get hot -- it just has to be moving quickly, which requires some real RPMs, which generates heat. I'll also add that running all the fans at full blast means that you will know very quickly once your coolant system has started working -- see above in linked post from my engine replacement thread. If you are burping on your own using the throttle cable, a bluetooth-based OBD2 scanner + a stat reading app is not misplaced -- you might not feel it but you will see temps drop like a stone once your coolant loop is purged of bubbles. #9 · Aug 23, 2023 (Edited) Or you can skip all the above and use an inexpensive vacuum coolant bleeder tool. #10 · Aug 23, 2023 Got a "LINK" for the newbies? #11 · Nov 30, 2024 Heater core closed, This is what it looks like when the temperature control is hard left (cold). Note that the cable is exposed a bit. .. Heater core open, this is what you want when you're bleeding the system. The temperature control is hard right (hot). Note that you do not see any exposed cable. .. Funnel with section of clear hose to observe bubbling action: #14 · 28m ago (Edited)
Adria said: Heater core closed, This is what it looks like when the temperature control is hard left (cold). Note that the cable is exposed a bit. View attachment 112776 View attachment 112775 .. Heater core open, this is what you want when you're bleeding the system. The temperature control is hard right (hot). Note that you do not see any exposed cable. View attachment 112778 View attachment 112777 .. Funnel with section of clear hose to observe bubbling action: View attachment 112779 Click to expand...
@thefutureisweird post is extremely helpful! I've worked on cars for 58 years. "Burping" was not required the last time I changed coolant, but I bought a no spill funnel (attaches to the radiator) at O'Reilly's and eagerly watched the bubbles. I did NOT get an 8 mm hose to attach to the bleeder but when I open the bleeder coolant came out. I followed the instructions for heater settings. During a short test drive it seemed that I started to get a little heat. It is still winter in Wisconsin so my plan is to drive some more to see if I get intense heat. 0Reply #12 · Oct 24, 2025
thatdellguy said: Or you can skip all the above and use an inexpensive vacuum coolant bleeder tool. Click to expand...
Willie Williford said: Got a "LINK" for the newbies? Click to expand...
https://www.harborfreight.com/cooling-system-test-and-refill-kit-64985.html I’m about to do a bleed of mine, so been doing the research and reading forum posts. It looks like the above kit is what that user was referring to, figured I’d share it here for posterity. The reviews make it seem like a worthwhile investment at least, would be great to hear from anyone here with experience with them? #13 · Oct 25, 2025 (Edited) This is what I purchased. Amazon.com: YSTOOL Radiator Pressure Tester Coolant Vacuum Refill Kit 28PCS Automotive Cooling System Leak Test Pneumatic Water Tank Purge Fill Tool Set with Gauge Adapter Cap Universal for Auto Car Airlift : Automotive Update: Used it this weekend to replace my Insight radiator. Its not the best made tool but gets the job done. If you don't need all the adapters go with the Harbor Freight one. Insert Quotes Post Reply
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