91 civic LX, 1.5
Just changed engines, changed timing belt, water pump, thermostat, all air and water hoses. Am losing about 1 cup of antifreeze per 100+ miles. Can't see any dripping from hoses, no white smoke, oil is fine, no oil in antifreeze, car runs fine, normal temp. Where is the anti-freeze going? Should I change the head gasket or wait to see if leak gets bigger?

 

I'd wait... It's very possible that where ever it's coming out, it evaporates quickly enough that you wouldn't see any fluid. Look for a tiny stream of steam. Or wait until someone else suggests something better.

 

You you are saying the antifreeze could be leaking out of a hose connection and I am not seeing it? If so, I'll tighten down the connections to be sure.

 

when the car is cold start it up and pop the radiator cap (it won't spray as the engine is cold)...look for bubbles in the coolant to see if you have a headgasket leak...you could have a very small one and burning a little bit of antifreeze (enough that you won't see smoke)

also i'd put the car on a clean surface and start it up and let it get warm ~ about 5 minutes should do (turn on a/c etc to make it run hard to it gets warmer than usual idle)...move the car and look for leaks on the ground

 

How soon after I start car on cold start would I be seeing bubbles in radiator?

 

should be immediately if you have a leak...they maybe small or big depending on the leak

i forgot there is also a dye you can put in the antifreeze that will show up when leaking on dark and dirty surfaces...if you have a small hose leak or seal leak you can find these b/c they'd discolor the area even when it would evaporate

 

yeah. sometimes things that seem like a huge problem can be really small

 

I just checked and no air bubbles came up on cold start. After about a minute, antifreeze level started rising up and going into the overflow tank.

 

yeah. one time I was losing a tiny bit of fluid to the overflow hose connection. but of course this is different. On the plus side since you have varying levels, you can easily add some water wetter and make your existing fluid a little better.

 

Well, at least this way, I'll always have fresh antifreeze in my car. Before I changed my engine, I had to put in over a quart of oil a day (220 mile round trip). It was my Exxon Valdez on wheels. I was going thru 3 of the 5 quart Walmart oil containers every two weeks.