Sooooooooooooo, are you still experiencing a noticeable loss in coolant?

Or...............??

 

Ok not a sealed system you say the cap when working correct is sealed before the threads look at one,it has a over flow hose but with the cap sealed it cant let out fluid unless the radiator is warm and letting coolant flow through the lower hose or if the radiator cap is open only other then that it is like google says it is a sealed system.From my point of view on this new one I just installed because mine was broken at the top where it seals with the cap and now does properly with the new one.Factory OE#15075570

 

Google is wrong. Sealed systems operate at cooling system pressure and therefore there is no need for a cap on the radiator.

 

This will be my last post in this thread... If replacing the overflow container fixed the problem, great, good on ya mate! (or however they say it )

Anyway, the pressurized part of the coolant system, i.e. the engine and the radiator, use the overflow container to deal with the expansion of the coolant as it heats up and builds pressure. As pressure builds up, the spring in the radiator cap retracts allowing coolant to enter the bottom of the unpressurized overflow bottle. The coolant has to go in the bottom of the overflow bottle to avoid allowing air into the system. As the engine cools, a vacuum is created pulling the expelled coolant back into the radiator.

Now, like Les said, some vehicles use a pressurized tank in addition to the radiator. None of the GM products I have owned use that setup. My thought is maybe there is some misunderstanding between the terms pressurized and sealed on the site you found on Google. I will go so far as to say the coolant in the overflow bottle creates a seal for the vacuum that forms as the engine cools thus drawing the coolant back into the radiator.

However, the system itself by definition is not sealed. The definition of sealed used here means closed off to the passage of gases or liquids. The overflow bottle being open to the atmosphere allows the passage of gases. The overflow bottle being open to the atmosphere will also allow the passage of coolant should the level of coolant reach the opening.

 

Captain why don't you tell Les Myer that the over flow system is a sealed system you out of all people should know that when the cap seals before the threads on the over flow container not even hooked up water cant escape from the sealed system out either hose because of a thing called vacuum lock.So if you dont want to believe me Google it yourself or if you want proof yourself take a new one fill it with water wile it is leaking out the two drain holes put the cap on and snug it down then try telling me it isn't a sealed system.By the way I haven't lost a drop of coolant since I replaced it.

 

You are absolutely and without question wrong. This will be my last post on the subject.

 

A "sealed system" must be capable of retaining coolant during normal levels of coolant expansion. Typically they do not have a cap on the radiator. They use a pressure regulating cap on the expansion tank, which pressurizes the entire cooling system, including the expansion tank. The expansion tank is designed with an area above the coolant level to allow for normal coolant expansion. If the coolant level is correct, and the tank becomes over pressurized, the cap blows off air, not coolant.


Although your theory with vacuum, (negative pressure) is correct, it doesn't "hold water" on the "closed system" used in our Blazers. The entire cooling system is pressurized by the radiator cap, with the exception of the coolant reservoir. The drain hose releases positive pressure in the reservoir to prevent pressurization.


If you fill the radiator and overflow reservoir right to the top when the engine is cold, provided the radiator cap is good, the coolant level in the reservoir will eventually drop to where it should be. Where does the coolant go? Out the overflow hose.

 

Sorry but the sealed system is sealed until the radiator cap opens to the over flow hose due to pressure expansion to allow coolant to expand into the sealed coolant over flow canister. then while cooling vacuum from the radiator draws the coolant back from the sealed system until the radiator is once again full.And now that I have replaced the over flow canister I haven't lost a drop of coolant due to evaporation or what ever happens to hot coolant exposed to the atmosphere.When the faulty cap isn't doing its job in sealing the system.And that's my story and i'm sticking to it.

 

Sealed, or pressurized is a bit different. My 99 Alero has a pressurized system, with no radiator cap, but has only the one on the overflow tank. The Bravada (99, I'm guessing not too different from yours) has the radiator cap. I can take the overflow cap off of the Bravada while hot without any problems. Can't say the same with the Alero. It volcanoes out if opened while hot.

 

It seems that know one would believe me on my coolant loss due to the overflow canister threads at the top of the canister were buster up.That's all no visible leaks even after pressure testing with dye still no visable leaks but since I couldn't find the source of the coolant loss.I went ahead and replaced the overflow canister in my 2003 blazer L/S 4.3 liter.Before replacement coolant loss was about from the full mark when hot down about 3/16 every week or two and would have to be added to get it to stay on the hot mark when warmed up well with air on as well. Now going on three weeks no coolant loss at all fill it up to the full when hot drive for about a hour with air on to make it heat & expand more it stays rite on the hot mark. then as its cooling like it should it draws fluid back into the radiator to keep it full to the top at all times.It just go to show that it can be something small like the over flow cap that may be over looked by many who think it cant be that because they say its not a sealed system but google says different and so far they haven't let me down with their true facts.