coolant overflow tank hoses on cap

[wesware]

Hi all,

Just finished a timing belt job on my 93 celica 5sfe. Filled the coolant up and burped engine. All seems to be well. My question is related to the coolant overflow tank. The cap has a hose attached on one end coming from the radiator and another coming out the other side that is short and L shaped. The L shaped hose isn't attached to anything and is open allowing air to either vent out or vent in to the overflow tank. There isn't any place nearby where the hose might attach to. Is this hose supposed to be "unattached" as it is now or should it be closed to create vacuum for the overflow tank to allow coolant back in to the radiator? I read in another thread that the overflow tank should be air tight so I'm wondering if I should plug this hose. Thx.

['88 All-Trac]

That hose is meant to be the "vent" line of the overflow tank. If the tank fills up, fluid squirts out of that hose.

Why on earth would you want an airtight overflow tank? That sort of defeats the purpose... Whoever told you that was smokin' something potent. The purpose of the overflow is to allow excess fluid from the radiator have a place to drain to in the event it gets to hot, but then it holds said excess fluid so the radiator can suck it back in as needed- at least, that's how my Suzuki works. I haven't had to analyze any of my Toyotas, as they behave themselves.

[wesware]

Thanks for the reply.

Well the logic (and it makes sense) is that the overflow tank and radiator must create vacuum so that the coolant can be sucked back into the radiator as needed. If not, then the radiator will suck in air instead of coolant and create air pockets in the system.

The hose in question appears to be in it's "natural" position being unhooked from anything as there is nothing close by that it could possibly plug into. I have never noticed this before so i can't say whether the hose is supposed to be "open" or not. i guess its possible that this is a vent hose and vacuum is still created within the overflow tank even if it is left open.

I should note that I just acquired this car and am still learning a bit about the mechanical setup.

Anybody else have an opinion on this?

[griggsfamily5]

'88 All-Track is 100% correct the hose is a vent for overflow in the case of over heating, and the extra cooland should be sucked back in as the engine and coolant cool back down.

[alltracman78]

There is a long hose that connects to the cap [basically an extension of the hose from the radiator], the bottom of this sits in the coolant. As long as the bottom of the hose is sitting in coolant the system is "sealed". When there is a vaccuum in the radiator it sucks coolant into the radiator [as long as the bottom of that hose is in coolant].
The "vent" elbow is separate from the radiator/reservior hose. If the reservior gets completely full it allows coolant to flow out of the res.