Hello I have a 1994 Honda Civic LX. It has a new 4 month old radiator and the fluid level is good. When I do in city driving I have no real heat to speak of. But when I get on the highway the heat kicks back in. Anyone have any ideas, please? Thanks
The first thing that I would check for is air that is trapped in the heater core. You or your mechanic should be able to “burp” the system and then add additional coolant if this is the problem.
Also–was the thermostat replaced when the radiator was replaced?
Thermostats can fail after a few years, and if the thermostat in this 17 year old car is the original one, or even if it was replaced once or twice already, it is possible that it is stuck in the fully-opened position.
In addition to VDCs great suggestions (the air “burping” and the T-stat) I would recommend the following: On our '95 Civic LX there is a Summer/Winter valve under the hood which allows you to switch it over to more or less heat through the heater core. It’s easy to locate . . . just follow the heater hoses until you get to it . . . on the firewall kinda in the center. It’s easy for this valve to slide to midway (I don’t know how it happens but it does) and your heat then is about lukewarm in the cold weather. Squirt some penetrating oil on the valve while you’re there. I’d try this first since it will only take a minute, then go to the “burping” and T-stat change VDC suggests if that doesn’t work for you. Good luck with that Civic . . good little car! Our '95 gets great mpg and runs great at 225,000. Rocketman
A restricted (dirty) heater core will have poor output at low engine speeds and perform better at highway speeds. Measure the heater output tempurature at idle then at 2500 RPMs, if there is a significant difference you have a restriction.
Just to make sure…some people mistake the lack of heat for the lack of the fan blowing out the air. When you turn on the fan can you hear it run? Is air rushing out while you’re doing the in town driving, but its just that the air is cold? Or does it just seem that not much air comes out of the vents unless you’re going faster?
Thanks to all I will try these this weekend and let you know.