Overflow Tank Keeps Getting Fuller & Fuller....

[PredatorSniper]

So I bought my car a month ago or so. It did not have a coolant overflow tank. So after driving it around for a while it almost overheated cuze is spit all the water out of the radiator. So I bought a nice aluminum overflow tank with the capability of returning the water back into the system (there is a hose going to the bottom of the tank) So I filled the radiator to capacity, then put some coolant in the new overflow tank, maybe 1/4 full. Now its spiting out that overflow because the coolant level is maxed out in that. So I take the coolant out of the overflow tank down to the 1/4 level and now its almost full again?? So my confusion on this is there something wrong with my car, I've very familiar with cars and understand the concept of the factory overflow system on this car, but is it going to keep on doing this until it reaches a level in the radiator it is happy with or is there something wrong with my cooling system?

 

[dsmcurse]

No that's super normal for are cars. Its in relation to the thermostat being the highest point in the system. Mitsu shoulda mounted it lower in my opinioun. The radiator cap comes off and you fill that sucker till its plumb full huh? If you awnsered yes, which I know you did, stop filling it ALL the way. The system will always be a cup or two low on coolant.

It isn't untill the car parks and shuts off and the car cools naturally till the over-flow can will create a vacume and suck what's left of the bottle back into the system.

I used to worry about that a lot also. Just learned to accept the fact that it will always be about a cup or two from being trully full.

This is normal for our cars.

 

[My1GLaser]

It sounds like you might be pushing coolant, or have a weak radiator cap. How much boost are you running and what HG? How old is the cap?

My coolant level never changed til I started pushing coolant. I run a 160* thermostat and rarely see 180* so I know I'm not overpressurizing the system due to steam. Stock 13psi radiator cap.

 

[dsmcurse]

Where does your temp reading come from? A factory sensor or a aftermarket water temp gauge? I run a napa thermostat (can't remember the temp rating) and my autometer electric water temp says 180 and the water temp being logged out DSMLINK claims 200 ? 20* differance... I think the mitsu sensors read a tad hotter than what's really real. My best friends 97GSX has tha same issue with 2 differant readings.

He also has a system that will slightly puff a lil water out to the can. (Maybe cause we both clear 500AWHP on a dyno and both see 30PSI off a HX40 everysingle time we drive it.

I know my car indeed does NOT have a head gasket issue or anyother kinda engine issue. We just had to deal with the fact that a tiny bit a water is constantly goin back and forth from the system to the overfull can.

Been FOREVER since I've rocked a BONESTOCK 4G63. But I'm wantin to say back in my younger days when I did have a bone stock 14b equipt Talon that I had the same issue. Couldn't ever TRULY keep the coolant system plumb full to the max.

I've spoke with many others that say that they'll fill 'er up all the way and then check it a few days later only to find it about a cup low.

I'm sure a guy's actuall coolant to water ratio will play factor to the case of the missing water as well. If more mixed on water than coolant some will turn to steam and just disapear outa the system all together.

Oh and by the way, for some reason I'm a FIRM believer in the radiator caps that have the built in pressure releif lil flicker valve. Napa sells them and that's what I ALWAYS use. After a race or a hard dyno pull I always pop the hood and flick open that pressure releif on my readiator cap and vent all that hotness outa the system and into the overflow can.

 

[kchaazz]

Change the radiator cap first. It will cause your problem if its bad, and its also the cheapest, easiest thing to change. If the smaller of the two seals on the cap- the seal thats at the end of the spring assembly- is crumbling or otherwise looks old or damaged, its a dead giveaway that its time to change the cap. Ive had the same issue youre experiencing now where my tank was overflowing because the system couldnt suck the coolant back in and the cap was the problem. Of course, you could also have a headgasket issue, but the way youve described the issue youre having is indicative of a bad cap...

 

[Paintballaa5]

Oh and by the way, for some reason I'm a FIRM believer in the radiator caps that have the built in pressure releif lil flicker valve. Napa sells them and that's what I ALWAYS use. After a race or a hard dyno pull I always pop the hood and flick open that pressure releif on my readiator cap and vent all that hotness outa the system and into the overflow can.

Really? I always try to advise people not to get these, because of the MANY times mine have failed in a short period of time. Shoot, one barely lasted over a week. It usually tends to seep water out of the seals.

But, what you said about venting after running it hard does sound smart.

 

[goldeninja20]

i have a similar problem. My 420a seems to always stay full up to the cap. I took my cap off of my 420a and put it on my 4g63 and now it wipl.stay to the top.

 

[dsmcurse]

Ya, true, ill totally agree with you there that they don't last as long as a OEM style. But for as cheap as it is (like 8 to 12 bux) I can plenty afford a new radiator cap 3 or 4 times a year. The easy "vent of the hotness" after a hard pull is well worth having in my opinion.

Maybe if I were more stock and didn't produce like 3times the original HP than I'd rock a OEM style cap. But for the sake of protecting my investment I run overkill on all my cooling.

I use a Huge 4" thick intercooler, Huge front mount engine oil cooler (increased my oil fill point from 4qt's to 5qt's), front mount powersteering cooler, nice Fluidyne aluiminum radiator with two SPAL electric fans, custom stainless steel tig welded metal radiator hoses.

Got a pretty solid set up. Have put a lil over 10K miles on my build. It clears 500AWHP on a heart breaker dyno, no engine issues ever. I do have recent pics in my profile.

I'm sure the OP is fine, for as cheap as a new cap is I'd recommend he just try buyin a new one.

 

[TallestHERETIC]

You only need to put a gallon of coolant in it. The extra space is for expansion.
It should only go up to the "full" line when the engine is cold.

I did that to mine and it stays consistently at around 160 degrees.

 

[PredatorSniper]

I have a new cap on it. The overflow is aftermarket so no "Fill Line" maybe it will step once it reaches a level it wants I guess. I'm running and HX35 at 25psi but this happens under normal driving conditions.

 

[kchaazz]

Regarding the capacity of your aftermarket tank, just put "some" coolant in the tank, and make sure its got a little in it after driving the car. If the tank goes dry, put a little more coolant in the tank, and after letting it cool down first, take the radiator cap off and add coolant to get rid of the air there as well. Drive some more and check it again. You just dont want the tank to go dry because if it does, it will allow the system to draw air in, which will cause cooling issues, so the idea here is to get just enough coolant into the tank so that the system can draw in coolant and not air, and leave enough room in the tank to allow the system to expel hot coolant under expansion into the tank without puking any out of the overflow. This is of course assuming a properly functioning cooling system, so let us know whether or not replacing the cap fixes your issue.

 

[JacksonAuto]

It's not normal. There is a malfunction somewhere. Unless the tank that you've installed has a capacity which is not sufficient to collect the coolant when the engine warms up.

 

[PredatorSniper]

It's not normal. There is a malfunction somewhere. Unless the tank that you've installed has a capacity which is not sufficient to collect the coolant when the engine warms up.

So when the engine is hot it will collect the coolant in the tank. I hardley drive this car, but every time I do I have to take some coolant out of the overflow tank. I'm hoping it will reach a level its happy with, if not what could be wrong with my cooling system? I have a new cap.

 

[JacksonAuto]

When the engine warms up, the coolant expands. Since they system is full when cold, there is now too much fluid in the system. That's what the overflow is there for. By design when the engine then cools down a slight vacuum is created in the water jackets which draws the coolant from the overflow tank back into the engine. Please ignore this info if you already knew that, but many folks don't.

Now if you've got an excess of coolant after the engine has cooled, that means that for some reason there is too much coolant going into the overflow. The system may become pressurized if the head gasket is compromised somewhere.

Another scenario that I've seen in the past is that there is an air leak in the hose that runs from the radiator to the overflow tank. If this is the case the fluid wont be drawn into the radiator.

To further diagnose the problem you'll want to perform a pressurized coolant system test. Pressurize the system to just under the rating of the radiator cap and it should hold that pressure indefinitely.

 

[PredatorSniper]

When the engine warms up, the coolant expands. Since they system is full when cold, there is now too much fluid in the system. That's what the overflow is there for. By design when the engine then cools down a slight vacuum is created in the water jackets which draws the coolant from the overflow tank back into the engine. Please ignore this info if you already knew that, but many folks don't.

Now if you've got an excess of coolant after the engine has cooled, that means that for some reason there is too much coolant going into the overflow. The system may become pressurized if the head gasket is compromised somewhere.

Another scenario that I've seen in the past is that there is an air leak in the hose that runs from the radiator to the overflow tank. If this is the case the fluid wont be drawn into the radiator.

To further diagnose the problem you'll want to perform a pressurized coolant system test. Pressurize the system to just under the rating of the radiator cap and it should hold that pressure indefinitely.

What are the chances of a blown head gasket? Its a cometic MLS on low boost. How do I pressurize my system to test it?

 

[nickk90]

My car would push coolant into the expasion tank until it was full but the cap was bad so it wouldnt pull it back into the system when the car cooled down.

 

[WES_393]

What are the chances of a blown head gasket? Its a cometic MLS on low boost. How do I pressurize my system to test it?

Did you have the head AND block resurfaced before install? If not, it's highly likely. But there are multiple tests for a blown head gasket. You can find them by searching.

 

[PredatorSniper]

Did you have the head AND block resurfaced before install? If not, it's highly likely. But there are multiple tests for a blown head gasket. You can find them by searching.

I think I just figured out the problem. I just bought an aftermarket overflow tank because the car didn't have one right. Okay, so I took the overflow hose off of the block housing by the engine and tried to suck some coolant out of the aftermarket overflow tank, and it leaked, I could not pull and coolant through that line, so that has the be the problem.