Supra Forums banner

Radiator not pulling coolant from overflow tank

48K views 39 replies 14 participants last post by  350jz 
#1 ·
Hey guys, im stumped. this is my 3rd thread today with questions i just cant seem to answer...

my car has been running a little hot, especially after overheating at the track...but i dont think the track caused the problem, just excessive pulls back to back.

anyways, 95 na-t, bl stg 2 kit, 2.5mm hg, factory NA radiator, with a ghetto overflow tank b/c i had to get rid of the factory one to fit the IC and the engine cover....

im not sure what the problem is, i thought it was the thermostat, but i changed that today, as well as changing the rad. cap. brand new from toyota. car warms up just like needed, and stay cool, but after a while, start to build heat (this is after days and days of driving)... what im noticing is that the overflow tank fills more and more, and sometime when it runs hot enough even steams out of the top. but it never pulls it back in.... like today, after driving 20 miles, i let the car cool almost fully, opend my cap and saw no coolant in the rad, but the overflow tank was pretty much full, i fit half of the tank in the rad b/4 it filled up.... what in the world could be causing it?

could the tank be crap? since we pretty much found it from a junked car? or maybe the way i have it set up? is the tank supposed to be oriented higher/lower then the rad? does it even matter? here is a pic, and thank you ahead of time.

 
See less See more
1
#3 ·
First thing that came into my mind but I didn't want to be a harbinger of bad news :(

Still, if it IS BHG, it's not the end of the world :)
 
#5 ·
i have no other simptoms of a blown head gasket.... the tank isnt pressurizing, not bubling, just boiling with hot water. no wite smoke, compression still seems fine.... especially since i ran 4 passes after over heating, the last pass at the track was a 12.01.... so i doubt its the gasket... but how likely is it?
 
#8 ·
Im surprised no one has informed you yet on how an overflow tank works.
This is a one way setup that when the spring pressure is met in the cap, that the seal in the cap pushes open and relieves pressure and fluid into the over flow tank
Therefor, it will not flow back, nor do you want it to.

If it runs fine sometimes and overheats sometimes, i would maybe try burping the coolant system. maybe there are air bubbles. Also maybe try a heaver spring pressure in the cap.
You would likely see more symptoms if it was a headgasket issue.
 
#9 ·
hm.... i never even thought about it being a one way system, for some reason i assumed that once the coolant heats and expends, it overflows into the tank, and when it contracts, it gets pulled back. but now that i think about it, there wouldnt be a way for it to flow back ...... you sire are correct, i just rented some tools from autozone (compression tester, and also some sort of a rad. comp. testes to see if it pressurizes too much) so i'll run some tests and then try burping the system.

how easy is it to get air bubles into the system?
 
#10 ·
i take that back, you are wrong. olde cooling system were set up like that , it was called an "open" system, but the problem with it was that since the system is pressurized, once the coolant expands it leaks into the overflow tank, leaving lesser and lesser amounts of coolant to do the cooling, cauzing the engine to run more and more hotter, this problem was solved by combining both the open and closed system which adds an adition seal on the rad cap. once the engine starts to cool, it creates a vacuum b/c of all the fluid that exited to the overflow tank, this vacuum and the upper sealing seat of the cap allow coolant to be pulled back into the radiator from the overflow tank.

just wanted to clear that up.


but it is possible, and most likely, that i do have an air buble in the system.... or maybe the cap on the tank is just bad...
 
#13 ·
i just burbed the system, i saw 3 or 4 bubles come up out of the rad. and spill a bit of coolant out and then drop significantly...so i gues it was full of air?? i hope that solves the problem. the thing is that my cap has been opened so many times that it is possible that i got some air trapped in there really easy. im going to jack up the car and burp it once more just to make sure all of it is out like suggested.


i appreciate all of the help guys. i hope this solves the issues ive been having.


thanks again.
 
#16 ·
yea ure right, i was just thinkin about that myself, lol.

but i think i know how this problem started. i had a faulty radiator cap which busted and allowed all of the hot coolant to overflow into the tank, evetually i was running so low that i overheated a bit at the track. and i gues between filling in the coolant, changing the thermostat, and all that stuff i got some air bubbles....

im just glad it wasnt my gasket, even though i was sure it wasnt since i had absolutly no symptoms of it.


i am going to burp the system one more time with the front end jacked up right now to see if there is any air left in there.


and PM, we learn something new everyday :) hell, atleast i do
 
#18 ·
First thing I would check would be to make sure the siphon tube(SP??) in the overflow tank is not bad(or make sure its even there). Then check for air in the system. I recommend this since the first is the easiest to do, and neither will cost you any money. If its still doing the same thing, post back in here. Goodluck
 
#19 ·
well only thing is that i dont ahve the factory tank, this one only has one tube that goes in, not two like the supra, so i couldnt have reversed the lines, it wents the air through a special vavle in the cap.


now i burped the systemwith the car jacked up, but now im doing it with the heater on also, b/c i got another pretty big air buble out as soon as the heater turned on.


when i test drove it everything was fine for a couple of pulls , but when i started coming to a stop the heat began to rise again. but then i realized i didnt top off the fluid in the radiator when i burped it, it lost quite some fluid from the 3 times. and i also forgot to put the heater on, im doing that now.


good news is that after the water expanded into the ove flow tank, it started sucking right back in as the engien was cooling, thats already a major progression with my problem. i hhope this last time fixes it period.


thanks
 
#22 ·
i think i figured it out guys....... i dont think that it was my coolant system that was at fault.... i just noticed ...well just now started really payin attention to my AFRs and boost levels... i was only tuned to run at 16 psi, and even at that my injector duty cycle was at 85%... so imagine what its doing at 17 and 18 psi.... or even worse, when i hit 20psi on the way back home today. my afr was 13.3, i belive thats whats causing my coolant to start boiling into and out of my overflow tank, and then went its time to pull it back in, since it boiled out as hot vapor, there is a shortage, so after a couple of cycles like this, i start to be low on coolant...

so now im off tryin to figure out how to get a bit more fuel w/out retuning my car...
 
#26 ·
yea so slither redid my map for me in the trouble areas and now the AFRs are down to a 12.2-.3 at 19.4 psi, which is A LOT better than the 13.3 i saw last night.

now, i tink that is definatly my problem causing the engine heat... a long 3rd gear pull at 12.3 AFR insteal of low 11's would obviously cause the coolant to start boiling, correct? (please correct me if any of my assumptions are wrong..) so the boiling coolant overflows into the thank and eventually out of it, b/c i see spilled coolant all the time, i can start with it empty, do a few hard pulls and it will fill up to the top. so when it comes time to pull it back in, it starts running short after each of these cycles.... i gues thats whats wrong.. im looking for a leak down tester and will also do a compresion check to see if the engine is healthy...

any ideas where i can rent one? autozone didnt even know what i was talking about, the guy said "well what you are talking about is a compression tester, this right \here" so i just left
 
#27 ·
interesting discovery..... so i just loged a pull, we got teh AFR down pretty good, but still a bit lean, its all we can do with teh fuel pressure and inj. duty cycle maxed... but anyways, i loged the coolant temp... and during the 3rd gear pull, it only changed 1 degree.... 30 secs after the pull it was still like that... but after a few mins of driving it started raising to 180, 190, and eventually stopped at 210ish.

all of the coolant is in the system, but mostly in the overflow tank. and i felt the pipe at the top of the rad. it had some pressure in it.

now, could that possibly mean that i have a small leak in the head gasket? b/c obviously the engine didnt heat that much during the pull and 30 secs after.... so could it possibly mean that at high psi im leaking some pressure into the cooling system which in turn is pushing hte coolant into the overflow and causing me to run hot?


or is the fact that all of the coolant gets pulled right back in after it cools say other wise? b/c if there was indeed a gas pocket there, the coolant couldnt possibly go back.....??
 
#30 ·
come again?

a leak down test shows you if you have a worn exhaust valve, air coming thorugh you exhaust, a worn intake valve, air coming from the intake mani, or bad compression rings, air coming from the oil pan/dipstick hole.

none of those are in any way shape, or form related to the cooling passeges. or atl,east thats my reasoning.

anyways, i have made in excess of 15 HARD pulls after suspecting a blown hg, my car now is running stronger then ever, and spools even faster with slither adjusting the lower end fuel curve.

anyone with a blown hg would be suffering when it came to good spool up, and im not one bit.
 
#31 ·
leak down test will show you all of those yes plus if you have a bad hg you will see it leak out or hear it. Compression test is not the best way to goo, I had the same problem like you after racing a bike, first 2 pulls where good then it started to over flow just like you. The car ran great with no problem. Everything on my list checked out great but i still decided to take the head off and bamp my hg moved a little over time and caused my coolant to over flow every time i get on it hard.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top