Coolant Tank stealing water

[JapaneseAutox]

i'm a bit puzzled on this, hopefully someone can help me out. i'm not leaking anywhere (or at least i hope not, been pressure testing the cooling system and it holds fine). my reservoir tank fills up when the engine is hot, and when the engine cools down, it stays filled up. i thought it was the radiator cap but i'm using a brand new cap and it still does it. when you look inside the radiator the top is empty (the missing coolant in the reservoir tank). umm.. help?

[SiI40sx]

oh wait wait!! when the engine gets hot, open the radiator cap!! hahahahhahahah

[sylsevilsis]

oh wait wait!! when the engine gets hot, open the radiator cap!! hahahahhahahah
and then? :confused:

[idlafie]

i'm a bit puzzled on this, hopefully someone can help me out. i'm not leaking anywhere (or at least i hope not, been pressure testing the cooling system and it holds fine). my reservoir tank fills up when the engine is hot, and when the engine cools down, it stays filled up. i thought it was the radiator cap but i'm using a brand new cap and it still does it. when you look inside the radiator the top is empty (the missing coolant in the reservoir tank). umm.. help?

For those of you who don't understand how the cooling system works, click on the attached link:
http://auto.howstuffworks.com/cooling-system.htm

The usual cooling system problems I've seen, (what year is your car again??), are usually due to 1). Clogged radiator...when was the last time you serviced it - that is had it drained & filled with new coolant? Ever had the radiator chemically flushed?? 2). Stuck thermostat - not allowing your coolant to properly circulate in your engine, 3). Bad water pump - usually you'll see water dripping from a weep hole underneath the pump. And 4). air pocket in the coling system - you didn't properly bleed all the air out of the cooling system when you refilled it with coolant. KA motors are notorious for this. All four will usually cause your coolant temperature gauge on your dash to rise towards the "H" mark on your gauge - seen that happen lately??

Anyhow, these are usually my experiences when working on KA powered S13's & S14's. Let me guess...you've got an SR under the hood?? hehehe..
ID

[nightkid86]

Hot water is less dense BTW

[g2ic02]

try replacing the hose that runs from the top of the radiator to the over flow. It sounds like when the coolant gets colder, the vacuum created by the contracting fluid isn't pulling in coolant from the overflow. If the hose is cracked air would be the only thing going back into the radiator.

[boosteds13]

try replacing the hose that runs from the top of the radiator to the over flow. It sounds like when the coolant gets colder, the vacuum created by the contracting fluid isn't pulling in coolant from the overflow. If the hose is cracked air would be the only thing going back into the radiator.
I'm pretty sure coolant only comes out, not back in. When the pressure goes down, the plunger on the cap will go back down as well sealing off the coolant tank from the rest of the system.

[g2ic02]

"When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank. This arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled. " This was taken from how stuff works. I also work as a technician

[shayrgob240]

"When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank. This arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled. " This was taken from how stuff works. I also work as a technician

yup. BUT he did say that he's not leaking.

TO the original poster, can u verifty for sure that you don't see any remnants of a leak? If you do, then that line that g2ic02 is talking about could be the prob.

[krustindumm]

you can get leaks that only leak under vacuum, and a leak anywhere in the system could cause it to not pull in coolant from the overflow.

how high did you pump it to when you pressure tested it? I generally go 150% of cap pressure.

[JapaneseAutox]

i pumped it to 19lbs. the system was stable and no drops were seen leaving it pressurized for about 15 minutes. i was researching and heard that rumor about the tube between the reservoir and radiator being cracked so i immediately replaced and clamped it down (what g2ic02 was reffering to). the radiator is new, the thermostat is new, the water pump i have yet to check (however there are no noticeable leaks around the seams). i bled the system on a jack while opening the bleeder screw to allow all possible air to escape. although i pretty thoroughly bled the system, i figure any small pockets left should be rid of after a bit of driving through the pressurized system (since that is a point of the reservoir right?). my power fc doesn't show the car overheating. i'm going to fiddle with it more and test it again. anymore ideas?

[g6civcx]

Did you bleed the heater core?

[LA_phantom_240]

oh wait wait!! when the engine gets hot, open the radiator cap!! hahahahhahahah
What, and humiliate urself in public like u did? lol

[JapaneseAutox]

i'm running an sr with looped heater lines.

[shayrgob240]

oh wait wait!! when the engine gets hot, open the radiator cap!! hahahahhahahah

? what are u talking about