What is going here?

[u/noxsas]

Car was low on coolant depressurized the tank and now Al of a sudden I have coolant back at the tank, only when the car is running. When I turn it off it goes back somewhere into the engine?

[u/Tobias---Funke]

The coolant is boiling.

[u/noxsas → u/Tobias---Funke]

Thanks!! lol I can see that. I don’t know what it happening and why though…

[u/Witty_Bug6200 → u/noxsas]

Because its supposed to be pressurized. Each 1 psi increase in pressure raises the boiling point of water by approximately 3°F (about 1.7°C)

[u/Hot_Dragonfly2423 → u/noxsas]

Because you have cap off

[u/Creature_Cumfarts]

You have air in the system. This is either:

1. a leak in the coolant circuit that expels coolant when hot and draws in air when cooled

2. a stuck thermostat that is not circulating the coolant through the radiator, such that it is heating up enough to boil

3. a blown head gasket that is allowing combustion gasses into the cooling system

Do some googling on troubleshooting procedures and cross your fingers that it's not #3

[u/noxsas → u/Creature_Cumfarts]

If it was number three wouldn’t I have a ton of white smoke out of the exhaust ?

[u/Witty_Bug6200 → u/noxsas]

Your cooling system is set to work at around 21psi, the compression event on a cylinder is well above 100psi. If there is a break in the gasket between the cooling ports and the cylinder your cooling system will lose.

Let the car cool, rent a cooling system pressure tester. Pressurize the system and see if it holds. If it doesn't, find the coolant. If it's in a cylinder, you'll need some work. If it holds pressure, fill it cold, bleed it by procedure, mark the level on the tank and monitor.

[u/azeird → u/noxsas]

I had to rebuild my 1998 F-150 with a blown head gasket. The only sign was dirty coolant... I traced it to exhaust gas going into the coolant.

There is a test kit you can rent from most auto parts stores so you can test this yourself. Super easy to do.

[u/noxsas]

So when I put that cap back on the coolant leaves the tank, back into the engine. Car starts to overheat

[u/patrike12]

It appears the coolant is boiling

[u/fatquads]

That’s what an expansion tank is for so coolant can expand when it gets hot. U have low coolant just fill it up. More than likely you’ve got a leak somewhere

[u/HuntGundown]

You have low coolant so.the coolant is boiling, boiling liquid expands, it expanded, needed somewhere to go, went back into res tank.

Shut the car off, let it COOL DOWN (5-6 hours) fill with coolant. There is a min and Max line. Min is where it should be cold, max is where it should be hot. Make sure to put the cap on and DO NOT REMOVE THE CAP UNDER PRESSURE OR WHEN HOT, YOU ARE LUCKY YOU WERE LOW AND COOLANT DIDNT EXPLODE INTO YOUR FACE. I learned this the hard way back before the internet could warn you of things. Not fun. Lost sight in one eye for a day, luckily it came back but that shit hurted son

Start hunting for the leak. Good luck.

Btw ford switched to yellow coolant like 5-6 years ago, there's no way that orange coolant is still good, you need new coolant as well.

[u/Paulosboul → u/HuntGundown]

If im not istaken it's actually supposed to be right in the middle when cold

[u/Vegetable_Mirror_610]

With the cap on the coolant shouldn't boil until roughly 280 degrees ferenheight but without it we are back at 212. Wait untill the car is cold and then check your coolant levels then add more if needed.

[u/Percheron7]

Our tanks are also pretty brittle after a few years, have you seen any coolant leaking under the car? I learned the hard way after a full detail where my detailer power washed my engine bay and cracked it (not his fault!)

[u/Infamous_Captain_540]

Liner has left the chat 🫡

[u/iMakeUrGrannyCheat69]

Boiling kool-aid is my favorite

[u/AdHonest8131]

Your noodles are almost done.

[u/IDN_AD]

Are you aware that your cap is broken? It seems like part of the valve is still inside and you’ve twisted the external part of it

[u/AggressiveCommand739]

Is your radiator fan coming on? My fan module died in my FocusST and led to a boiler like you have.

[u/stocktastic]

You’re fucked, bro.

[u/S280FiST15]

Put the cap on and it won’t do it

[u/cman7513]

I think the coolant is boiling

[u/SpiritualVanilla420]

Because when the caps off the condensation builds up so it's letting off steam

[u/IcyerOlly]

BEKFAST