is the water tank pressurized?

[b3master]

i was doing some work on the bottom of the car n forgot to put the bottom cover back on (the mud cover under the battery side) when i was on the highway i didnt realize the thud i heard was the water tank falling off, so i was pretty upset to loose it but i am wondering if the water in it is pressurized or not since ill have to get the watertank alone n then its cover alone, cant seem to find it at junk yard, is it okay to leave it with no cover?

[Dave M]

I assume you mean the coolant overflow resevoir? Is that what you mean by water tank? And by cover you mean the screw on cap? It's not pressurized but you need to keep a very close eye on your coolant level and engine temps until you get it replaced as you have no tank to allow for expansion during heat up. When the coolant heats up, it expands and some flows into the tank, when it cools down again it gets sucked back into the radiator as it contracts. It can't do that now so it will only suck back in air. Keep that up more than a few times and you'll be overheating your engine.

[Injuneer]

Is the V6 that much different than the V8's? The V8 coolant reservoir is also the battery support. What is your battery sitting on now?

[b3master]

yes i did mean the coolant overflow resevoir, its just the bottom resevoir itself that fell off, the car has had a wreck on this side so that peice i guess wasnt on too tight or too well, so if it isnt pressurized i can just buy a new one and fill it up n leave the cap off i guess. anything that wants to flow out can do so if it pleases as long as i dont have air getting sucked in the radiator..
i just thought it was pressurized, n thought they gave the coolant a bit of breathing room but i thougt under pressure it can control the amount of expansion hence under pressure can force the coolant not to get too hot, i know it sounds silly but i thought if u pressurize somthing that wants to expand upong heating that u can keep its temperature down since it has no place to expand, like stuff in fire extinguisher (sp?) n compressed air cans etc...... am i off here or what?

[Trash man]

look at ur radiator, see that cap? that what pressuriezes the coolant system. for every pound it pressurizes it adds 3.25* to the boil point of water at seal level. u can run no overflow tank without worries. the old cars never had one, when the car was fully warm the radiator was full and when it cooled down, it contracted. for now u can cut a small hole in water jug or something other like that if u want.

[Injuneer]

You need a reservoir of some sort, and the end of the hose that carries the overflow coolant from the radiator fill neck has to be submerged below the level of the coolant in the reservoir. If you don't have that, you will get air in the system. The coolant heats up and expands. Since its an air-free system, the cap needs to release a little coolant to counteract the expansion. When the system cools down, the coolant contracts, and pulls a vacuum on the system. The cap has a vacuum relief valve that allows the vacuum to pull the coolant from the reservoir back into the radiator, keeping it full, and air-free. You do NOT want air in a system using Dex-Cool. You will have sludge in a very short period.

[b3master]

without the coolant reservoir it expands n then sucks in about 2 liters of AIR! so i figure the coolant is expanding 2L over normal size, how can the system run the way older cars used to run!?
i think older cars had much more coolant in them the system was bigger and allowed for more expansion, i cant believe i can run this system pressurized if i wanted to cancel the coolant reservoir, i think the radiator will bust up much sooner than older cars did.

[Injuneer]

The "old" cars had air at the top of the radiator - but you're going back at least 30 years. The coolant doesn't expand all that much, so it doesn't need much free space. The newer cars can't run that way, because the system is designed not to include air. The heat transfer coefficient is higher when there's no entrained air. And, air causes corrosion.

Look at the reservoir markings.... they indicate the proper "hot" and "cold" levels. The actual expansion amount is less than that, and its not 2 liters.

Finally, just to clarify. There is NO pressure in the overflow reservoir. It operates at atmospheric pressure, not at radiator pressure. As noted in the earlier post above, the spring in the cap holds the pressure on the radiator. What gets past the cap just pees out into an open tank.

I'm still puzzled how the "tank" fell off.... I thought the combination radiator and battery support was blow molded out of one piece. Did the accident crack the reservoir and allow the bottom to break off.

If you're running at the track, you need a "catch can" of some sort, to avoid dripping coolant on the track and screwing up the traction for others.

[b3master]

yes during the accident the impact cracked the reservoir and the bottom was broken off. we just glued it on,obviously not too well, so couple of bumps without having the bottom mud cover on it fell on highway somewhere n im gonna try to find some cheap replacment for it and rig it on there, just wasnt sure if it was a sealed pressured reservoir or not, ill find some similar tank from some junk yard save me few bucks.