Hello! I am new to the forum and I look forward to attaining alot of information here! Thank you in advance!

My car has been shooting white steam from the radiator cap. Also, the temp gauge would go to half, but then go back down to cold even though I was driving the car. It was doing this for a while, so I researched and changed various things such as:
1. Radiator Cap
2. Thermostat X2
3. Water Pump
4. Changed coolant temp sensor
5. Finally Replaced Head Gasket

The shop that fixed it gave me a new cap as well. It was fine for a month, but now the coolant gauge barley moves and this morning after a 15 minute drive, if began to shoot the coolant out. No one has been able to answer this correctly for me and I'm all out of options.
Please help with any advice you have that may be causing this issue. Thank you very much!

Coolant bled of air properly?
Radiator fan coming on?
Radiator blockage?
Heater working inside cabin at idle and while driving?
Ever put a bottle of headgasket sealer in coolant system?

the steam might have eroded the plastic neck of the rad. wait til the engine is cold and pull off the cap to check for damage, new rad is pretty cheap and easy to replace

Coolant bled of air properly? Yes
Radiator fan coming on? Yes
Radiator blockage? No
Heater working inside cabin at idle and while driving? Heater is working fine
Ever put a bottle of headgasket sealer in coolant system? Never. Too scared to try.

Colin42

Is that something that could have been a common issue? When it first got fixed, the cap area did not steam up at all.

Coolant bled of air properly? Yes
fan coming on? Yes
Radiator blockage? No
Heater working inside cabin at idle and while driving? Heater is working fine, so is the A/C System
Ever put a bottle of headgasket sealer in coolant system? Never. Too scared to try.

Handy pic of steam erosion damage, but this one still has the residue from the boiled antifreeze (and maybe stop leak) kinda covering the eroded ring surface...Anyway, during a serious overheat event steam literally melts the nylon away so the (inner) rubber gasket of the cap no longer seals under pressure.

This example did not leak to the outside, but instead it would not allow pressure to build up in the radiator, it just vented directly into the reservoir all the time.

Yours could be all black with no antifreeze residue, but if the ring isn't smooth and flat, it's trashed.

pressure tested coolant system? cracked radiator?

ripped radiator hose?

Mine had a little damage, probably from overheating before. Does the white steam mean the engine is overheating?

I might need to check the hoses, but there are not leaks from the hoses.

I want to add this. Before, the small hose that goes from the radiator to the coolant reservoir used to pop off when I drive. But that isn't happening any more, but the steam(Coolant) still shoots from the radiator cap. Would built up pressure cause this to happen as well?

im just thinking .. escaping steam means theres a leak somewhere.. specially odd to escape at such low temps...as you said it never overheats.

I've seen the temp gauge read 1/2 and then when I idle, I can see steam coming from the hood. Sometimes the temp gauge reads C and it still steams. Not sure if the temp sensor is off, or if the car is actually overheating. I do remember that when my temp gauge used to act weird, it would always go to the H when the car was actually overheating.

Not if everything were sealed properly. The cooling system is supposed to run up to about 15 PSI before it vents to the reservoir

2 things that probably have nothing to do with it..

1. "used to always go to the HOT" keep a mental note head MAY be warped.
2. when this steam is coming up from... wherever... are your fans coming on?

What if the coolant reservoir is full?

How did it get completely full?

The steam is coming from the radiator cap. And yes, the fans work as they should. A/C blows cold and the Heater blows hot.

2 ways I believe. I used to put coolant in there. And before I got the car fixed, the head gasket was blown. I heard that when it is blown, it would cause coolant to go into the reservoir and fill it up.

i think i can guess what ezone is going to tell you your system is over full and to much pressure..

Reservoir is supposed to only be half full. See the MAX line somewhere along the side of it.
Level in the reservoir always changes a little as the engine heats up and cools down, but its level should always return to its starting point when the engine is cooled down.

Coolant is getting pushed out of the radiator into the reservoir.......is the radiator staying completely full or is its liquid level always dropping?

The reservoir is staying full, while coolant is shooting from the radiator cap.

its crazy because ive seen hoses pop...and radiators explode before caps fail... if you got low temperature steam escaping id assume you got the wrong cap.. idk sounds weird.

I've had a hose pop before. It's a hose in the back. A real pain to replace in my opinion. The first known cap I had with this car had a black covering on it.

i wouldnt trust the mechanic.. for my own piece of mind id go to autozone and have them look up the proper cap and sell it to ya.. might not fix it but you can rule out wrong cap.

Honestly this would be the third cap. I bought two myself and the mechanic got a new one as well. Now I'm on cap number four.

damn..lol.... the 2 you bought... did have them look up the proper one ? or off the shelf universals?

I had them look it up at Autozone. The only one that seemed to work was my original cap with the black covering on it.

i wonder if the part that the cap screws onto is cracked.. the radiator part.

Why can't the radiator cap seal? Inspect the radiator surface closely where the two cap gaskets have to seal.

Refill and dry everything, then start it up and WATCH to pinpoint exactly where it's leaking.