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Coolant/radiator issue?

I cannot figure this out. My car was starting to over heat and I wasn’t getting any heat thru the vents. Thermostat was replaced and so was the radiator cap. The coolant reservoir is still topped off, and doesn’t seem to be getting sucked thru to the radiator. If I pour coolant directly into the radiator, car temp stays even, and heat eventually does come thru vents, better while driving. But, I still get steam/smoke coming from radiator cap. I cannot be buying and pouring coolant into the radiator everyday. Any help or suggestions will be much appreciated. Thanks in advance!

What make/model/year/miles?

You have a coolant leak, does anything drip out? If not, you might have a blown head gasket - does your car put out lots of white smoke? Does the oil on the dipstick look normal?

I have a 99 Mitsubishi Eclipse with approx 140xxx miles…
I see nothing dripping under the vehicle, and it always tended to put out alot of smoke. But I have checked the oil a few times and it appears normal becuz I have also considered a blown gasket

You may have a bad radiator cap. They are rated to hold a certain pressure, but get weak with age. And, the attached seals get weak, cracked and leaky. Just replace it, since it is cheap and easy.

PS - Oops, missed the part where you changed it. Yeah, it could be a head gasket. Sometimes they don’t pollute the oil. Just over-pressurize the coolant system. A cooling system pressure test is in order. If it doesn’t maintain pressure up to the cap rating, look for the leak, including the intake or exhaust or through the spark plug holes.

You also could have a blown head gasket…Today, shops have a hydrocarbon tester to quickly spot this…

A bad head gasket doesn’t necessarily affect the oil.
All depends on the path of the breach.

“it always tended to put out alot of smoke”

Age/mileage when you bought this car?
It may have had a head gasket problem when you got it and now it’s just gotten worse.

Hey AprilEclipse,

I also would have to assume blown head gasket due to the amount of white smoke you describe. Not always will your oil become contaminated when your head gasket is blown but if your are having to replace the antifreeze constantly to keep your radiator topped off and you see no clear spot where it is leaking out of it tends to limit possibilities. When you smell the smoke does it seem kinda sour/sweet? Quite often thats a clear indication that its coolant being burned in your exhaust. At the moment that sounds like the most feasible cause for your problem.

Hope that helps narrow your list of causes,
let us know what you find out.

Well that could make sense, but I’m still confused as to why the coolant isn’t even going to the radiator… The new thermostat seems to be working, and I have no issues when I top off the radiator directly… Its just that I manually have to put it there… Would that also be becuz of the head gasket? Or maybe a pump issue?

A breach to the cylinder of the cooling system would over-pressurize the cooling system, and force coolant to be ejected from the cooling system. Most caps hold between 13-20 psi, and combustion gasses getting into the cooling system will jack it way past that easily.

It says that its 13psi… And I have noticed that even when the car is not over heating, there is smoke/vapor/steam (whatever u wanna call it) coming from the radiator cap. That’s why i replaced it, but it still occurs with the new cap. (altho I noticed the new cap felt snugger and had a better fit, so not a complete waste of $7.99) I do like to try to repair my car myself, hence why I’m hoping this isn’t a head gasket issue lol

If there’s a cooling system leak the cooling system pressure won’t get low when the engine is cold, which is when the coolant is pulled into the radiator from the reservoir. So your leak keeps the coolant in the reservoir from doing you any good.

Replace the radiator cap, step 1

But I don’t see anything on the ground under my car…

@Barkydog… I already did that…new radiator cap, new thermostat as well. ‘‘steam’’ is still coming from the radiator cap, even when car is not overheating… Coolant is just not being pumped into radiator, but if I pour coolant directly into radiator, car runs fine (except for the steam, of course)

You likely have a blown head gasket. Do you have a mechanic?

In the overflow tank, is the tube that goes from the cap to the bottom of the reservoir still there. If it falls off the cap, it won’t draw coolant back into the radiator. If hte reservoir uses a molded tube on the side of the reservoir, make sure the bottom isn’t plugged up with debris.

Is it possible the seat for the radiator cap is bent? Not likely but should be checked for flatness anyway. Coolant is not pushed from the reservoir to the radiator but is pulled into the radiator as it cools. When the radiator heats up, the pressure opens the radiator cap and pushes the excess coolant to the reservoir again. So if the radiator is getting low, its not being pulled back in again due to a leak in the system somewhere which would depressurize the radiator, OR combustion gases are creating a bubble and pushing the fluid out of the radiator. Once the fluid level is low, you won’t have heat unless at high speed. I think you really have to look for a head gasket problem and do a pressure test on the system.

Yeah, from what u guys are saying, I’m assuming a head gasket issue… I do have a mechanic, sort of, but Idk if he wants to help right now. I’ll see what I can do. Thanks for yr help guys…

Yes, both tubes for the coolant tank are present…

‘‘steam’’ is still coming from the radiator cap, even when car is not overheating"

It is possible there is a small crack in the radiator filler neck or debris preventing a proper seal. I have heard if when cold you remove the radiator cap and warm up the engine, bubbles of air are indicative of a head gasket leak, of course a pressure test on the engine (leakdown test), and cooling system are the conventional ways to Wear safety glasses.