This is normal. flush but it has never worked when they get that bad take the rad. Coolant Reservoir doesn't drain back into Radiator. Over time, the coolant reservoir can leak, become worn, and fail because it is used on a regular basis. Maintenance/Repairs. Coolant is under pressure so it does not boil, which make bubbles, bubbles do not transfer heat to radiator walls where it can be dissipated into the atmosphere. Overflow tank had filled and coolant had shot all over the front passenger wheel well in particular.. It should drop, and if you take the cap off the coolant should be filled to the top. The excess coolant goes into the reservoir. You need to check the level of coolant in the radiator as well. When you start the engine the water begins to warm. The hose could have small cracks at either end that would prevent a good seal. I replaced the radiator and thermostat on my 98 Subaru Forester but still when I drive it the temperature gauge reads over the hot line the heater doesn't work but the coolant doesn't seem to be circulating to where its supposed to be. The reservoir might be cracked so it leaks and when the radiator gets hot and it overflows all the coolant leaks out. This puts the outlet in coolant when at proper level. he put a chemical in the radiator fluid that is supposed to form a plug to stop a leak. Open the drain valve by turning the it counter clockwise. I noticed though that the overflow tank would fill but not siphon coolant back into the rad. There may be times that the reservoir radiator cap may turn out to be faulty. As the system cools down, the contracting coolant creates a vacuum that draws coolant from the reservoir back into the radiator. Coolant is pulled back into the radiator by a partial vacuum, as the radiator cools after driving. Coolant goes into reservoir but doesn't get drawn back into the radiator when it cools. This expelled coolant moves against the spring in your radiator cap. to a rad. Removing it and whether the fix will hold up under the average 15 psi pressure may impose challenges and risks to question the validity of the repair. If a valve is not available loosen the lower radiator hose and slowly remove it from the radiator to initiate the draining process. Have a fluid catch basin ready to catch the now draining coolant. Before coming home i topped up the rad again, and had overheat issues again after about 2.5 hours of highway driving. If you look at just about any overflow reservoir (not an expansion tank), the hose from the radiator run off goes to the bottom of the tank (or dips down to the bottom of the tank from the lid). The coolant would drain into the reserve reservoir, but would not drain back into the radiator, and I would have to keep refilling. However, upon cooling, it still put a bunch into the overflow, leaving my level way below the cap. With a couple of days driving the level returned to normal. The excess fluid flows into the overflow tube and goes into the overflow tank. If the coolant reservoir is completely empty, you can’t just refill it. If there are any leaks in the system, air will be drawn into the system via those leaks instead of drawing coolant from the reservoir. While this may seem to be a minor issue, it can lead to dire consequences. After ~5 months of waiting, still no plug…no change. When you warm up your engine, the coolant expands and builds pressure, then the radiator cap allows the excessive coolant at a given pressure to flow into the reservoir. Fill your reservoir with antifreeze up to the FULL line at the middle of the plastic tank, you don’t have to add water, because the water will evaporate in a few days and what is left is antifreeze which will not evaporate. - Answered by a verified Subaru Mechanic This excess coolant stays here until the system cools down enough to create negative pressure and draw the excess coolant from the reservoir back into circulation. The video above shows you where the coolant reservoir in your Contour is located and how to add coolant. As this coolant warms, it expands. 99 Toyota Avalon, 3.6 L engine, 160k miles The engine sends radiator fluid to the overflow reservoir but doesn’t suck it back into the engine when it cools. This allows for excess pressure to vent to the reservoir as well as any coolant. Be sure to check your owners manual to determine the correct type of fluid to add - for Fords, it will typically be in a section titled Fluid Capacities in the back of your manual. After this liquid passes back into the radiator, the reservoir will normally be left with only 1/3 of the coolant. The coolant won't "suck" back into the system until it fully cools. 1900 subaru legacy wagon. just undo the small clamp (usually jsut needs a pair of pliers) around the hose on the radiator end and let it drain. Hey Victor, A radiator overflow tank collects the expanding coolant that is heated by the engine and recycles it back into the coolant system once it loses enough heat. To release pressure, the radiator cap allows some coolant to escape out, stored in the reservoir. I subsequently poured it back into the reservoir (it was low, but not completely empty) with the coolant vent valve open, until I got coolant coming out of it. Look at the level in your radiator in the morning for a few days without adding any coolant to the reservoir and if it does not go any lower this might be your problem. If the crack is on the inside, then any drainage would go back into the reservoir and not spill out on the ground, but it would break the vacuum that would draw coolant back into the radiator during the cooldown. While the engine is off, your coolant reservoir should be about 30% full. The radiator cap is designed to allow access to fluids in a ‘closed' system. So. Coolant in the radiator is 100% full. Once the engine cools down, the extra coolant flows back into the engine through a vacuum system. It spills back into the reservoir tank (plastic tank attached to the radiator) then it spills out onto the engine and everywhere else. It must not be the case that upon cooling the system is overpressurized and that is why it puts coolant back into the overflow, because with my wifes vehicle, I don't think it ever sucked it out of the overflow to begin with (probably a leaky cap like everyone mentioned). If that's not happening, it means that you've got a leak in the radiator, or a hose, or in the engine itself, and you're losing that vacuum, and leaking coolant out of the system. When you turn off your engine, and the cooling system starts to cool down, then there is a vacuum drawn from the radiator and the coolant in the reservoir is sucked/drawn back up the line into the radiator. The coolant expands and contracts as it is heated and cooled. So, the radiator coolant overflow tank functions to serve this exact purpose. The reservoir is where excess coolant collects when hot and then is sucked back into the radiator when cold. Once the driver parks the vehicle and turns off the engine, the heat dissipates which causes the coolant to not be as hot anymore. Here’s how to do that: Wait until the radiator has cooled. If you have a leak somewhere it will draw in air instead as the coolant cools. A new hose is cheap. Got it all back in with the reservoir level at most an inch above top line. Check your owner's manual for proper cap replacement. Seems that its not holding pressure or there is AIR in the system. Step 1. the small hose that goes into the overflow tank (reservoir you're talking about) runs to the top of the radiator right below the radiator cap. the cores in you're radiator are very small and in time get pluged and the water does not circulate causing pressure so then it pushes the water into the reservoir so then you have only air in the cooling system I have tried rad. Therefore i am constantly topping up the radiator when it has cooled down. There is signs of coolant in the top tank when i top up - so the radiator is not dried up. The radiator cap comes in different pressures. I replace new cap and radiator and I still have the same problem. Some coolant should push into the reservoir when hot and go back in as the engine cools. This did not fix the problem. This overflowing coolant passes into the reservoir where it is stored until the engine cools. In normal circumstances, the coolant gets ousted out from the reservoir overflow tube, the moment the engine starts warming up. noticed that the coolant overflow bottle is filling up and not returning the coolant back into the radiator. So you'll want to mark where the coolant level is when hot, and then come back when the car cools down and see if it's dropped. The coolant reservoir on your Accord is connected to the radiator, and allows coolant to flow back and forth between the two as it heats and cools. Once you are done driving, the coolant will slowly cool down as the engine does and the radiator cap will allow the coolant stored in the reservoir to flow back into the radiator. Mix the coolant with distilled water so that you have a combination of 50% coolant and 50% water. I also "burped" a few of the hoses as I was refilling. The coolant used to cool the engine does so at maximum efficiency when kept at specific pressure. My mechanic replaced the radiator, cap, and hoses…no change. When the system cools down, the radiator pressure reverses and coolant is siphoned from the reservoir back into the radiator. This leakage is visible and may result from bad reservoir cap. shop and have them flush it or just replace it Without a coolant reservoir, the expanding coolant would be pushed out of the radiator cap and allowed to spill on the ground, which is an environmental hazard. Your problem may simply be a loose or damaged cap not keeping coolant where it needs to be. Coolant is not very dirty No leaks (checked with a pressure tester too) Have bought 2 radiator caps and tried an old one (tested those too) Radiator is a year old And i know for sure it is coming from my overflow drain tube because i set the tube in a place that i could see it was draining and the tube and that area was wet. when it cools off the radiator level goes down a bit but never goes any lower. A cracked or leaking reservoir can easily be diagnosed and fixed. When the system chills, the coolant stored in the reservoir is pulled back into the radiator by the reduced pressure. Most car's have a radiator drain valve that will be visible at the bottom tank or on either side tank. I went back to town and replaced the rad cap. The hose could have small cracks at either end that would prevent a good.! 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