I have a 1995 Toyota Corolla and last night while driving on the freeway, every time I pressed the gas pedal, the car would make a very noticeable sound. I pulled over and, as soon as I did, steam started coming from under the hood. After opening the hood it appeared the steam was coming from the radiator cap. Unfortunately I forgot to check the temperature gauge on my dashboard.

I had the car towed and, after inspecting it today, there appears to be a white residue around the radiator cap and on the radiator. I checked my oil, which was about halfway between the full and low mark, and it appeared to be clean. My coolant is also halfway between full and low, but I am not sure what it was before this happened. I did not notice this earlier, but my car looks like it is leaking some sort of fluid onto the street, possibly before this all happening.

I will probably end up taking it to a mechanic, but I was wondering if you could shed some light on what it could possibly be so I am not going in uninformed. If you need any more info, please let me know and I will try to deliver. Thanks guys!

Edit: here is a pic of my radiator cap. I am assuming this is a problem. Note, the metal part in my hand simply came of like this, I didn't force it off or anything. radiator cap

  • How long since the last oil change? Even if the oil looks fine it can break down and cause excess friction and heat. Did you remove the radiator cap, (only when cold), and check if the coolant fluid was above the radiator fins? The coolant in the reservoir can be filled to the correct level but fluid in the radiator might be low after steaming like that. Check that the radiator cap is functioning. I've had caps be the cause of radiator issues in the past.
    – Seminecis
    Sep 9, 2013 at 2:31
  • About 4500 miles which I know is longer then the recommended 3000. Also, check my edit about the radiator cap. Sep 9, 2013 at 4:50

2 Answers 2


Definitely replace your radiator cap. When mine gave me trouble it wasn't closing when it should which made fluid steam out which made the car overheat. If you're lucky it's all that's wrong and you can refill your radiator and move on. Mine didn't give me any more trouble after I replaced the radiator cap.

I'm sure you can guess that I also recommend changing your oil and filter.

  • 1
    I will definitely get on the oil change. Question though, do you know how I would go about removing the bottom part of the cap. Its pretty wedged in there. Also, are the caps pretty standard from model to model? Sep 9, 2013 at 6:47
  • @pistolpete333 It might need to twist out, sorry I'm not sure about that. Mine remained in one piece and just wasn't working. Like other components, there are different radiator caps for many models. An auto parts store will be able to tell you which part is correct and they aren't very expensive.
    – Seminecis
    Sep 9, 2013 at 9:52
  • I would also replace thermostat. Maybe it's stuck closed and is the cause of this overheating.
    – elv
    Apr 18, 2014 at 12:05

Assuming your radiator cap is of the correct p.s.i. your radiator given age may be full of scale and could be overdue for rodding out/replacing core/or replacing entirely.A pressure test will obviate leaks not the condition of your radiator internal condition.

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