The gurgling sound is air bubles rushing through the heater core, and yes, the fill needs to be completed. With the engine cold, check the overflow bottle. The liquid will be its minimum level and should be above the "low" mark on the bottle. If not, add coolant until the bottle is half full or at to sligtly above the cold level mark. Here's whats supposed to happen. When the coolant heats up, it expands and should burp some some trapped air into the bottle. Then, when the system cools and the coolant shrinks, it draws fluid from the bottle into the cooling system, that is, if there is enough fluid in the bottle to keep the inlet/outlet in the bottom of the bottle covered. After about 3 thermal cycles, the system should have enough air flushed out. After that, keep an eye on the coolant level in the bottle for the next 3 to 4 trips. The "sealed" coolant systems on today's cars vary in detail such that no one set of descriptions fit all. However, all sealed systems perform the functions described above. The mechanical details do vary. In some systems, the overflow tank is pressurized to the same level as the engine coolant, while in others, the overflow tank is vented to the atmoshpere. This is what I'd do. With a cold engine, fill the overflow bottle to or slightly above its "cold" mark. Put the cap back on the overflow bottle. Warm the engine into its operating temperature range, then shut off and let cool. After cooling, refill the bottle. Do this until the liquid high and low level stablizes. Be very careful! Do not remove the cap of a pressurized bottle if the coolant (engine) is hot. Upon release of pressure, the coolant can flash to steam and geyser about half of the coolant out of the system. You could get scalded, not to mention the ensuing mess. Let it cool until you see the coolant being sucked out of the bottle back into the engine. Antifreeze can be purchased as full strength, or already diluted half water and half antifreeze. Look carefully at your antifreeze container. Do not dilute the already diluted antifreeze.

Thanks, I assumed it was a mfg and warranty expense driven item...I did wonder if just on the lower cost products, or all, by all or most manufacturers. Not an important point. From the end-user perspective: 1) I am concerned about wear-and-tear on the lower hose on earlier leaks there - suppose with a 5 year flush interval one should expect to replace the hoses on the second change anyway. 2) I read a discussion elsewhere that raised, even when using the lower hose removal method, the issue of the thermostat blocking drainage. Are these real concerns? With the drip-along spigots of the past I never noticed any reduced flow as the flow rate didn't overtax the air bleed-through,or whatever is needed. I of course have the radiator filler cap off. 3) Is there any support for the installation of a "reverse flush" in the heater hose? I have used this many years ago, and didn't have any problems, but I have not continued to use it in the past 20 years of car ownership.

the reason i say airflow is IF the OP's lives in an area like i do. we stay in teh 70-90% RH range most of the time and even a minor cold air leak WILL cause condensation on this level. my unit for the back of my house has done it in teh past. i noticed the backup drain had water coming out, so i figured the main was clogged. go in teh attic and see it is the plenum sweating and pouring water off it. i found the leak, a strap had come undone and allowed it shift a little. resecured the strap, sealed the leak and no more water. of course, if you live in a normal area that humidity is not so high this may not apply. regardless, those gaps should be SEALED.

I also am very happy to find websites like this. Never had a problem until 64 and doctor thought I needed some estrogen for "dryness" issues. I was on Estriol compounded as it is not sold in U.S. but is in other countries. 2 1/2 months had to stop using as it made me ill. I realized later it was ordered too strong . My Gyn was also an Ob and specialized in adolescent pregnancy. What was I thinking !! Started very disturbing symptoms about 2 months after the end of Estriol. Profuse sweating, followed by chills, rapid increase in heart rate (over 130), dizziness and nausea in the middle of the night, night after night. I was so exhausted I ended up passing out and in the hospital. First Cardiologist, then Endocrinologist and finally going next week to GYN specialist. Of course went through the "you must be having anxiety" talk. Did I mention I am a retired Major in the Army Nurse Corps and psychiatric trained Reg. Nurse. I only mention this as I was almost starting to believe them. Thank GOD, and I mean this, I started to do my own research. Hot Flashes and Night Sweats with severe vasomotor reaction, very common. Well I say with all my heart thank you ladies for sharing on sites like these. It has been 81/2 months and they are definitely less. I am using magnesium, Vit. E, watching sugar intake, doing deep breathing , trying to control stress and thinking about Remifemin. Good luck to everyone .