Ive got a 95 civic cx with a b16 in it, ive been driving it back and forth to school for the past few months. The past week or so the temp has been going up. The first day i added some coolant and then it was fine for another week. Then as i was driving to school one day the temp sky-rocketed, i turned the heat on just to make it to school and the temp went down and everything was fine. I check the coolant again and it was low again with lots of air. Ive had mechanics as well as my self check for a possible head gasket problem and they said theres no problem there. A friend said my t-stat is bad but i just replaced it about 5 months ago. The water pump is new and not making any noise or leaking. The top radiator hose gets super hot and the bottom only get a little hot. Is it the thermostat? wheres all the air coming from? thanks guys

 

Well, if you don't have a leak then the missing coolant is getting burned off in the combustion chamber. You may have a very tiny leak at the head gasket especially that you mentioned that it has air in the system when you removed the cap. If it doesn't overheat with the coolant level filled up then the thermostat is probably fine.

 

I would suggest that you start by replacing the thermostat and radiator cap, and then by bleeding the cooling system:


1) Park the car on an inclined driveway with the front end higher than the rear.

2) Push the dash heater lever/**** to MAX heat.

3) Follow the directions in the diagram below (hint: the bleed bolt is located where the upper radiator hose connects to the engine):

 

bleed bolt.. cool.
You could just leave your cap off your radiator.. Any air will come up through your radiator... and coolant will drop when fan kicks on, and increase when engine is fully warmed and all hoses etc are filled, it expands.

As for the bottom hose not being hot, if you were to run your car from cold with the hood open for 30 minutes bleeding your coolant, the bottom hose would only get luke warm if warm at all........ Hondas dont produce much heat, and having your hood open on a cool/cold day will take forever to heat up! the bottom hose only really gets used when your engine is completely at operating temp.

 

ok so today i drove the car to school, it heated up and then cooled down about 15 times, not to the point of overheating but the needle jumped alot. Before i came home i filled the rad with coolant/water and left the overflow bottle cap loose. It had no issue coming home, needle didnt move. Im buying a stat, rad cap and more coolant tomorrow. Well see how it goes. btw i did all the steps to bleed air out of the system everytime i have had any kind of issue.

 

do any of you guys think it could be something within my heater core? i smell anitofreeze sometimes when i run the heat. do you think it might be a head gasket? because when it gets hot ill check my overflow bottle and itll be full of coolant, more then it had in it before and the radiator is filled with air.

 

Hopefully the leak is around the heater core and not the head gasket that is blown. Check around the passenger floorboard for any wet spots. I would get the cooling system pressure tested to see if it holds any pressure and if you can find any leaks.
Good luck!

 

what about like i said before about the overflow bottle? it doesnt suck any coolant out of it, it adds it into it and then theres air in the radiator. is that a head gasket?

 

Yes, I had the same problem about the coolant not drawing back into the radiator when the engines cools down. It was my head gasket. When the engine was at temp and running, I could see very small bubbles in the coolant reservoir coming from the overflow hose. On the following morning, if I opened the rad cap, you can hear some air rush out the radiator.

 

so i bought a stat and a new rad cap today. i had a greddy high pressure one before. i put the new one on topped the car off with coolant and even with the heat off the car ran perfect today. weird as hell.

 

Sounds good. Just keep an eye on the coolant level.

 

sounds like a bad head gasket. check out your heater core before you doing anything related to taking the head off. cuz if its ur dd thats gunna be all bad. if you smell anitfreeze when you run the heat good chance its something around the heater core.
Good luck

 

so it wasnt your head gasket?

 

any update to this???

 

i had same symptoms, replaced head gasket and the shop also did a valve job which is pretty much required when the gasket gets replaced. my engine has 140,000 miles on it when it got done. the shop also recommended a timing belt/water pump since it was all off the car anyways. now my baby is running smooth and quiet.