Hey guys I own a 2000 civic si with the b16a2 and I have a quick question... I might be losing antifreeze but I can't tell and I can't find it anywhere so I'm not sure ... But my question is and I don't know if civics are different from other cars, my over flow tank stays the same all the time and sometimes gets more full... If my car is on and I look at it, it will be at the same level.. Isn't it supposed to suck into the radiator when the car is on and go back when it cools down?

 

Coolant can only do one of two things - leak, or burn. Go to your local parts store and buy/borrow/rent a block testing kit, and use it. It'll include instructions. That will tell you if it's being burned. As for leaking, you'll just need to get your eyeballs in there and look. Carefully inspect all of your coolant lines, as well as your thermostat housing, rear coolant tube, and water pump for leaks.

 

Are you losing coolant or not?

 

I'm pretty sure I am but it is a slow leak and I can't tell where from

 

The one place you can leak coolant and not be able to visually find it, is if the heater core is leaking. If it's a small enough leak it can evaporate long before dripping to the floor and your coolant recovery tank will slowly dwindle (go low) over time until you top it up.

To answer your other question as it seems you don't have an understanding of how the coolant system works. You stated it backwards..... When the car gets warm/hot/operating temperature, the coolant/fluid expands and your coolant recovery reservoir gets fuller. Then as the car cools the fluid contracts and it sucks it back into the radiator. That's why that reservoir has a max line that is several inches down from the top. This leaves room for the expansion of the fluid without overflowing.

I hope that helps your understanding of how the system operates.

If the level of your recovery reservoir is not going down overtime and your car is not overheating, then I would say it's safe to assume your coolant system is operating normally and you are not burning or leaking coolant.

 

I never thought about it like that, about the whole expanding thing. Interesting.

 

Wow thanks a lot ... That was exactly what I was confused about and yes I do understand now. If I see fluid getting lower I will check the heater core immediately

 

Ummmm, that's not what you were supposed to take away from this.

The heater core was just one area you can have an issue with, but is more difficult to pinpoint visually.

If your fluid is going down you pressure test and also check all hose etc for obvious signs of leaking.

Your heater core, you can smell it when you run the heat.

I was providing additional information in the event your coolant was going down and you could not find signs of an obvious leak.

Pressure testing is your best tool for finding if your coolant is leaking. Then your eyes, then your nose.

Please don't just assume it's your heater core.

There are steps you go through to test and diagnose the problem. You just don't throw labor and parts at it and hope it works.

 

I understand I'm just noting that it will be the first place I look for fluid leak... One of my friends has a pressure tester so I'll start from there and I still haven't ruled out the water pump

 

The pressure test is the first thing you should so. You understood nothing.

If your heater core is leaking you probably would have smelled it by now.