Coolant Overflow Tank Vent, Extra Spigot Going Nowhere, Missing Clamps?

[YoshiMoshi3]

I'm looking at a 2005 Camry, whose cooling system has a coolant overflow tank with a single tube (i.e., not a resevoir with an inlet and outlet with two tubes coming out of it). This got my thinking, why is there a need for what appears to be another "spigot" (not sure of the technical term) in the original cap that came with the car, where a second hose could be attached to? The car is supposed to come this way. Is it just to share caps among various models? With this extra spigot that has nothing connected to it, isn't the coolant resevoir essentially open the atmosphering air and pressure? I don't understand the purpose of this extra spigot and what function it has.

Interestingly, there doesn't appear to be a clamp where the hose connects to the spigot, but looking at the parts diagram online, it looks like there is supposed to be one. Considering it 20 years without it, I guess it doesn't really need it?

Interestingly the part diagram clearly shows only one spigot going on the coolant resevoir. But looking at the part number for the resevoir or the cap, 16470AA020 and 16471-AA010. I guess this may just be an error in the parts diagram for this vehicle?

Thanks for help in understanding the function and purpose of the second spigot, and if those hose clamps are really necessary or not.

 

[whateg01]

You have a cap on the radiator that maintains system pressure. The overflow doesn't have or need pressure. I'm guessing the second ****** doesn't have an opening in it, right?

 

[KnurledNut]

If the tank is overfilled it drains out there. And also acts as a vent.

 

[ericg]

That is an overflow for the coolant tank.

 

[YoshiMoshi3]

I've always wondered how an overflow tank works, but I think these things are related here. There's an overflow tank, but there is no pump to move coolant from the overflow tank into the raidiator, so how does the coolant move? It seems to be what your saying. The raidiator is pressurized, while the coolant resevoir is vented and at atmosphering pressure. The difference in pressure, results in coolant getting sucekd up from the resevoir into the raidiator, no pump is needed. Does this sound right? Not sure about the OEM one. But I have an aftermarket Dorman one, and looking under the cap, the second spigot is definantly open, one side of the spigot is to the atmosphere, and one side is to the resevoir. I was going to install the Dorman one, but then had these questions.

Any idea on if the clamps are necessary? I don't think I have seen them on cars before to the resevoir to radiator cap. But I haven't looked at several hundred cars.

 

[Wrench97]

I've always wondered how an overflow tank works, but I think these things are related here. There's an overflow tank, but there is no pump to move coolant from the overflow tank into the raidiator, so how does the coolant move? It seems to be what your saying. The raidiator is pressurized, while the coolant resevoir is vented and at atmosphering pressure. The difference in pressure, results in coolant getting sucekd up from the resevoir into the raidiator, no pump is needed. Does this sound right? Not sure about the OEM one. But I have an aftermarket Dorman one, and looking under the cap, the second spigot is definantly open, one side of the spigot is to the atmosphere, and one side is to the resevoir. I was going to install the Dorman one, but then had these questions.

Any idea on if the clamps are necessary? I don't think I have seen them on cars before to the resevoir to radiator cap. But I haven't looked at several hundred cars.

When the system heats up it pushes extra coolant out of the radiator to the overflow tank, as the system cools down it creates a vacuum to **** it back out of the tank into the radiator, the radiator cap regulates both of these functions.
If the hoses fit tight no clamps are really needed, if desired you could put a tie wrap on the hose to tighten it up.

 

[Beerhippie]

There would usually be a short hose on that barb fitting just to direct any overflow out of the engine compartment.

 

[ericg]

 

[YoshiMoshi3]

Thanks for the help! Ok I think I got it. So the overflow tank is at atmosphere pressure, the extra spigot ensures this and is open to the atmosphere. The overflow tank is not pressurized, so in theory you could open the overflow tank while the vehicle is hot? I was also wondering, if there should really be a hose on the extra spigot on the cap. But I see it must be open to atmosphere pressure in order for the system to work properly. So if you have to much coolant, it just gets shot out into the engine bay. Were would a better spot for it be. Like just attach a hose and put it underneath the vehicle so it goes onto the ground instead? Probably to much work, and it's just better to tell people not to overflow their coolant and put to much in it.

Also makes more sense to me why coolant lowers in the resevoir. Not only could get consumed or leaked out some how, but it can just simply evaport as it's literally open to the atmosphere, and will eventually evaportate away, even if you didn't drive the car. Kind of like if you just left a cup of water outside, eventually it will evaporate away.

 

[Radio Flyer]

I'm looking at a 2005 Camry, whose cooling system has a coolant overflow tank with a single tube (i.e., not a resevoir with an inlet and outlet with two tubes coming out of it). This got my thinking, why is there a need for what appears to be another "spigot" (not sure of the technical term) in the original cap that came with the car, where a second hose could be attached to? The car is supposed to come this way. Is it just to share caps among various models? With this extra spigot that has nothing connected to it, isn't the coolant resevoir essentially open the atmosphering air and pressure? I don't understand the purpose of this extra spigot and what function it has.

Interestingly, there doesn't appear to be a clamp where the hose connects to the spigot, but looking at the parts diagram online, it looks like there is supposed to be one. Considering it 20 years without it, I guess it doesn't really need it?

Interestingly the part diagram clearly shows only one spigot going on the coolant resevoir. But looking at the part number for the resevoir or the cap, 16470AA020 and 16471-AA010. I guess this may just be an error in the parts diagram for this vehicle?

Thanks for help in understanding the function and purpose of the second spigot, and if those hose clamps are really necessary or not.

I have a 2005 Camry in the family fleet. Yes, it’s vented to the atmosphere. It may have a 90* on it, but I may be confusing it with one of the other Toyotas. It’s too cold outside to go check.

 

[YoshiMoshi3]

I have a 2005 Camry in the family fleet. Yes, it’s vented to the atmosphere. It may have a 90* on it, but I may be confusing it with one of the other Toyotas. It’s too cold outside to go check.

How do you like the car? Yea the OEM one has a 90 in it. Aftermarket ones just have a straight 180 degree in the cap. If I'm understanding correctly, you can pop the cap off of the reservoir even when it is hot or the car is running (but still leave the tube submerged), because it's already at atmosphere pressure? Removing the cap off the radiator is an obvious no go, but the reservoir cap in an overflow tank type of setup is completely fine?

Also does yours have those clips on the hose going from reservoir to radiator? Mine are not on there, and I think it may have come from the factory that way

 

[Beerhippie]

How do you like the car? Yea the OEM one has a 90 in it. Aftermarket ones just have a straight 180 degree in the cap. If I'm understanding correctly, you can pop the cap off of the reservoir even when it is hot or the car is running (but still leave the tube submerged), because it's already at atmosphere pressure? Removing the cap off the radiator is an obvious no go, but the reservoir cap in an overflow tank type of setup is completely fine?

Also does yours have those clips on the hose going from reservoir to radiator? Mine are not on there, and I think it may have come from the factory that way

You don't need to leave the hose submerged unless the engine is cooling. The cap on the pressure tank has two valves built in: one for over-pressure which bleeds coolant to the overflow tank, one for vacuum (PVRV), which ***** the fluid back in as the engine cools. If everything is filled correctly, you haven't badly overheated the engine and you don't have a blown head gasket, you very rarely need to top up the coolant--which is done at the overflow tank. Evaporation is negligible due to that tiny barb fitting being the only vent.