With the car hot and turned off, you should be able to see or hear it.

 

No I haven't seen a leek besides the one I fixed. I'll try to check it out again.

 

your radiator is probably leaking. it is a common problem.

 

How or where should I check the radiator? I don't see any obvious leeks. What should I look for?

 

Have u noticed any smoke? Also if u cant see the leak u may want to try a pressure test.

 

Haven't noticed any smoke. I'm about to do an oil change to make sure there isn't coolant in the oil.

 

Remember milkshakes are bad!

 

Also, check your radiator cap. Mine went to 4 bars during city driving then back to 3 on the highway. I changed the cap that I think was about 6 or 7 yrs old with a new one. Problem solved.

 

Ok, so this might be a bit stupid, but could my problem be coming from dirty oil? or dirty oil filter?

I pretty much did nothing to the car except an oil change. I wanted to see if 'the worst' was happening and i had coolant in the oil. Nothing there. The oil was quite black though and the filter felt pretty heavy. Its been about 4k mi since my last oil change and it had been about 3k+ when the problem first presented itself.

anywho, after the oil change the car hasn't heated up again like it did. i'm still keeping an eye on it since i think it might still return. :/

BTW i'm using Mobil 1 synthetic with a Mobil 1 filter.
should i switch to OEM filter? I want to say the OEM is bigger isn't it?

 

So I thought the problem had gone away, but no luck.
Since I hadn't really done anything, I went in an changed the thermostat.
Well, there was no thermostat. Only the outer seal. Seams like the previous owner cut the thermostat out.
Could THIS have been the source of my problems?
I was only heating up at high speeds on the freeway.