The other day when I started my car the temperature warning light/buzzer came on after about 5 seconds. I refilled the coolant and it took about 2 litres, so I think it was about 3/4 full to begin with. I also noticed a small amount of coolant on the ground after refilling, but I'm not sure if it was from overfilling or a leak. Regardless, the light/buzzer still comes on when I start the car.

I tried adding just a little bit more coolant to see if I could find a leak, and when I poured it in it backed up right away out of the overflow tank, leaking onto the ground. There is a puddle on the ground bigger than the amount I spilled, so there is either another leak or it slowly backs up out of the overflow tank as the car cools down.

I read the big fat FD3s cooling thread, as well as a few other posts, but I couldn't find out what was most likely to be the problem. I think it's possible that it is the coolant line from the AST to the overflow tank not holding vacuum, but it might also be a pressure cap failure or something else. Fwiw I do have an aftermarket cap that came on the car when I bought it, but I don't know how old it is. What is most likely to be wrong? What order should I trouble shoot in?

Thanks all!

 

Did you put coolant into the overflow tank or into here:



The above spot is where you need to add coolant when you are low (when the car is cool/cold that is).

 

Embarassingly I added it to the overflow tank, but I just checked the radiator filler neck (that is what the circled part is called right?), and it is almost overfull when the car is cool.

 

When filling with coolant, first fill the ast. Then fill the filler neck. By filling at the overflow tank, you leave no room for coolant to expand in to it.

If your engine has many miles, or is old, you may be experiencing the first symptoms of coolant seal failure.

 

You most likely have the system overfilled right now. Go ahead and start the car and let it run for 10-15 minutes (take it around the block or something). Once the dash coolant temp gauge moves near the middle, go ahead and shut the car down. It will probably expel coolant from the overflow tank onto the ground. There is a vent hole in the overflow tank neck and coolant will flow out of that if it's too full. Once it cools down, check your level in the filler neck that is circled in the above picture. If it's full and you are getting the low coolant buzzer, do the bubble test.

 

Is this the bubble test you are talking about? I don't get any smoke at startup fwiw, but I will go do the test. In the thread linked the poster says to do the test "with pressure released". Does that mean with the pressure cap off? Or just the filler neck cap? I am looking for bubbles like this right? Thanks.

 

Yes, but I would recommend using a funnel or something similar so coolant isn't spilling all over the place. Here's what someone else did:

http://www.youtube.com/watch?v=4p5wlc6Ec6o