ok I need help here. On friday I was driving home from school when I noticed that there was a trail of smoke following me. I looked down at the dash and noticed that my temp was waay high; almost to the red. I got the car home and let it cool down then opened the hood. To my surprise, the radiator cap had come off! so I added some water to the radiator (as I had no coolant). Now my car won't run without the temperature soaring to the red. I don't think I broke a head gasket as there doesn't seem to be any major leaks, only a few drops here and there. I did reuse the radiator cap that flew off. could that cause a the problelm?? maybe the water instead of coolant mix? I'm totally bummed out hope it is easily fixed. anyone help?

 

Try draining out all the fluid and put in a new mix of subaru coolant w/ distilled water.

 

okay.
A radiator cap can't cause something like this happen tho right? Anyone know?

 

The cap should never have come off to begin with unless it was loose or damaged. Take a good close look at the cap and the filler neck where it mounts.
You may or may not have done any damage to the engine, it depends on how hot it got and for how long. It's possible there is just trapped air in the system, you don't say what year WRX you have but if it's an 02-03 that does not have the second cap on the radiator it is imperative to follow the proper procedure when refilling the systm. If you just pour the coolant in you will definitely have trapped air and subsequent overheating. The later models with the second cap on the radiator generally avoid this problem as long as you fill them slowly with both caps off.
From empty, the cooling system should take almost 2 full gallons of coolant/water mix, if it appears full after adding much less than there is most certainly air in it.

 

yeah, I have the 02 WRX. There doesn't seem to be any damage to the cap or flange. So both caps should be off when filling the coolant huh?

 

If you have an 02 there will only be the one cap, on the engine, unless your radiator has been previously replaced with the updated one. I am NOT referring to the cap on the plastic overflow bottle.

 

You said that your radiator cap blew off...Right? Radiator caps are designed to hold a certain amount of pressure in the system, most cars are around 8-12 psi.. some are more.... This pressure allows the engine water temp to stabalize. If your cap does not hold enough pressure than it never allows the system to pressurize which would cause the overheating.. Check all hoses- check the radiaor fins for any noticable damage, rocks are big problem.. Check over everything very close.. Also you can run a pressure test on your radiator, see if there are any leaks that way.. very simple... Also a quick flush of the old coolant with some new would be a smart idea....

I hope that you get this fixed if you havn't already!!!

 

thanks for the tips. unfortunately, I have been busy with college and haven't had time. Probly this weekend I will do a thorough inspection and coolant flush. I should probly get a new radiator cap too I suppose. Just in case it was damaged.
oh, how can i test for pressure? Is it something i can do at home or do I need to take it somewhere?

 

You'd need to go to a shop that has a pressure tester, it's a device that replaces the cap and pumps air into the system to pressurize it. You then observe to see if the pressure drops and if there are any externally visible leaks. If there is pressure loss but no apparent leaks it's a sign of possible head gasket failure.