If the cap is off, slightly it doesn't leak coolant at all. If you can then park on a dry spot overnight, (assuming one can find a dry spot in England in February) then look carefully on the ground in the morning for moisture. Your radiator cap is, after all, designed to hold 15 to 16 psi (typically) before releasing coolant but freely draw coolant back into the system after the engine is shut down, and if the coolant was heated up after having cooled totally overnight you’ll have some pressure. Most cars these days have a translucent coolant overflow tank right next to the radiator. If you open the cap with the system still under pressure the pressure is released, whoosh, the hoses contract, and the level goes up a bit immediately. Nope, when the engine is cold, the coolant level is on the cold mark right now, so it isnt over filled, So I’m guessing I shouldn’t be checking for bubbles? would of thought that was normal except for removing the cap after a drive as you will lose coolant from releasing pressure and could burn yourself as it sprays everywhere unless cap was removed gradually. As will coolant. The engine temps were running normally on the run at … And as this happens it fills the radiator right to the brim. When the engine is cold, the coolant level should be between those marks. I don’t think this is something to be concerned about. Once the coolant reservoir tank is filled to the maximum level line you can reinstall the cap (clockwise) until you hear or feel the click. But other than that I’m at a loss. then had to release cap to let water rise bakc but a bit of water did get lost, Read similar threads on other forums and similar issues are pointing at headgasket or airlock in heater matrix? This is because the hoses expand slightly with normal running pressure. Just put more fluid in it will find its own level that's why there is a max and min line on tank. I am told it's very important to get all the air out of the cooling system with these engines, and that the easiest way to do that is to start the engine (when cold) with the radiator cap off and wait until the thermostat opens and let the coolant level sort itself out. Reading your coolant level. Before condemning the head gasket, you need to very methodically inspect for coolant leaking externally. As the pressure causes the coolant to get higher than the pressure cap, the excess coolant needs to be captured somewhere in order to prevent leakage. Opened my expansion tank to check coolant level and add water wetter, car was lukewarm after sitting for ~2 hours in the garage, small hiss. I got a 2002 mustang v6 and I hadn’t flushed the coolant since 5 years ago so I decided to take off the radiator cap off too check the status of the coolant. So I’m guessing I shouldn’t be checking for bubbles? Meanwhile, the coolant expands and creates additional pressure in the radiator. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register. My coolant tank was just replaced 4 years ago. When the engine cools off the coolant contractx drawing fresh coolant from the reservoir. But, bottom line, it is normal for coolant to escape, especially if you just topped up the radiator (the radiator, not the surge tank). Please help btw coolant is still green. What causing this? … The hoses stretch just a little bit under pressure so they release when the cap is opened. how do you release airlcok from the heatermatrix? JavaScript is disabled. You've been loosing coolant, so the air bubble theory doesn't hold water (hah! Apparently you do have a coolant leak somewhere in the system, based on what you have stated. Luckily it only takes a second to check your coolant level. It’s dangerous to remove the pressure cap from the radiator or coolant recovery system reservoir while the engine is still warm. Download this Cooling System Radiator With Cap Removed Showing Green Antifreeze Coolant Level Inside Concept Of Automotive And Lawn Equipment Maintenance And Repair photo now. Do not remove the spring cap of the radiator to check the coolant levels. I did find this - Coolant goes down, triggers alert, but bubbles back up when cap is removed Maybe the OP @Ondro05 can give us an update. Next you can close your hood and confirm its latched. The outside of your coolant tank should have marking indicating the recommended level of coolant for proper function of your car. I have not had a warning even when at min. does that sound a possibilty. Put the cap back on the radiator and check the heater radiator, coolant, cars, level, trucks, suv, chevy, mechanic, hot, how to, how long to waitYou should put antifreeze—more appropriately known as coolant—into your car immediately. So I have a 92 Plymouth Voyager with the 3 liter V6. What causing this? Is the heater core higher than the radiator cap? Paraoxically the hot level is different if you run engine until hot with radiator cap removed. The surge tank usually is marked with minimum and maximum levels. Hi all just after bit of advise after replacing coolant cap... and thats the first time ive taken the new cap off after a drive so i'm hoping the new cap has done something ? About the Author Stephen has been an automotive enthusiast since childhood, owning some of his vehicles for as long as 40 years, and has raced open-wheel formula cars. a pun). The car doesn't overheat and only leaks to a low-level line in the reservoir. The important thing it, if the coolant is at the seam when it was cold, then after getting hot and cooling again it's still at the seam, it's fine. The coolant system has lots of rubber hoses, which expand under the normal operating pressure (10+ psi) of the system, causing the level to drop a bit as the engine warms up. Check out the Drive’s Garage Guide for detailed instructions to check your coolant level. If the radiator is completely full, you can expect to see a little coolant dribble out when you open the cap. Any ideas on what agreed, this no longer sounds like an air bubble etc and much more like a head gasket breach that is over-pressurizing your coolant system slightly under certain conditions. Now, turn on the car, during the engine running (about 10 minutes) kept check the level of coolant be sure it still maintains pass the full mark level. Water will seek its level. When checking my coolant reservoir on my 2018 Escape 1.5 I noticed the coolant was low, when I released the pressure cap the reservoir filled almost back to the correct level. So, the radiator coolant overflow tank functions to serve this exact purpose. As the engine cools while parking the car overnight, the coolant in the overflow tank gets sucked back into the top of the radiator. Now, fill coolant to the top and put a new cap back on. You must log in or register to reply here. Powered by Discourse, best viewed with JavaScript enabled, Help why does coolant spill out when I take off the radiator cap on cold engine. More likely to happen in certain situations I expect, depends on the temp of the coolant in the radiator, and if the car is parked on a slope or not. Maybe plugging a laptop in will tell you what temperature your coolant is reaching so you can ascertain whether it’s at a safe level / within parameters We recommend keeping some coolant in the trunk in case you need to top off the coolant … If your car’s coolant levels are near or below min, it may be wise for you to add more coolant. It’s been reaching over 100F there this past week. The expansion tank and radiator are both under pressure at different times in the cycle: when the pressure in the radiator gets beyond a certain limit, an overflow valve releases coolant into the expansion tank - this lowers the pressure in the radiator, and increases the pressure in the expansion tank (assuming it is properly sealed and the cap is on tight). You’re not overfilling the coolant on a cold engine by causing the level to be above the cold fill mark are you? Most likely the coolant is leaking under pressure when the engine is operating. The first thing that you need to inspect is the coolant level sensor if your BMW has one. If not, and you want it done, ask your mechanic to do it. It's white plastic, but you can see inside to see if there's enough juice to keep things safe. The excess fluid flows into the overflow tube and goes into the overflow tank. I have heard some say it's how some cars are. Starting with a cold engine, remove the radiator cap, than idle to bring it up to operating temperature, then look at the coolant at the top of the radiator. Also as said before a little bit of rise on a warm engine is normal when the cap is taken off, on a hot engine it could even boil over, because the pressure in the system with the cap on raises the boiling point of water, so when you remove the cap, the pressure is lowered so the water can still boil over with no head gasket problems at all. Be surprising some coolant escapes when you remove the radiator cap is off, coolant started to slowly spill of! 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