lawman2391

I have a 1998 Civic EX with a little over 200,000 miles on it. I live in Minnesota and the past 6-8 months I have been having various problems with temps in my Civic.

This past summer I was overheating and so I checked and replaced all fuses, replaced relay switch, checked cooling fan motor, replaced thermostat sensor switch, and replaced the thermostat itself (with a fail safe one that stays open all the time if it fails). None of that worked and so (stupidly) I checked the coolant level and it was very low. Once I did this the temp did not run hot anymore...chalk it up to experience and doing the easy thing first, right?

Anyway, being that I am in Minnesota and it has turned cold now I am experiencing a different issue. First of all, when driving, my temp gauge never rises above "C" on the gauge and the heater blows mildly warm, but not hot (as it used to - it used to be like a dragon in the dash). When at idle for a time (5-10 min or more), the temp will rise and it will blow warmer air. If I leave the heater off and let the temp rise, it will go above normal and get close to "H" on the gauge. Turning on the heater full blast, brings this down to normal range quickly. After extended idle and getting back to road driving, the temp drops back down to below "C" and heater is back to mildly warm again.

I have checked the coolant level once again and it is fine (not low). I have not checked anything else at this point and figured I would field suggestions from the forum as to where to start on this, as to not repeat my inefficient efforts this last summer. I have received a couple of suggestions from friends/neighbors on this, but figured this is a better place to get advice before diving in...THANKS!

Fliptard

letting the car idle, does the fan come on and go off periodically?

also, there is a valve the hooks to a coolant line, next to the firewall, coming from the heater core, as you change your temp inside from hot-cold, it opens and closes this valve as well, does this work? or is the wire broke the moves it and it's stuck closed?

you can also try putting a piece of cardboard with a hole in it in front of your radiator to keep it from getting too cold as you drive, to help warm up the car faster and keep it warmer as u drive, but don't let it idle too long if it over heats.

pjb3

Sounds like the thermostat is stuck open. In cold weather the themostat will prevent or reduce flow to the radiator allowing the engine and heater to warm up. If the thermostat is stuck open the flow thru the radiator will not let the car warm up. When you idle the lack of air flow thru the radiator allows it to warm up but when you drive the air cools it back down again.

Your fuel mileage should also be less than normal since it takes longer for the engine to warm up if it ever does.

It also sounds like you have a second problem. If letting the car idle will cause it to overheat you need to verify that the radiator fans are working correctly.

ezone

Head gasket breach-- check and verify
Coolant leaks
Factory thermostat
Bleed the airlock from the heater tubing
Inspect for proper operation of the water valve
Make sure the radiator fan actually operates when it is supposed to.
Check the accuracy of the gauge and sending unit

lawman2391

Thanks for the quick responses guys. I'm going to dig into it this evening and tomorrow and will post findings as I can.

This noob appreciates it!

Thanks again!

kdliberty

Replace the heater hoses. I just had to have this done myself. They looked pretty good until we got them off. One of them actually had a split on the bottom. It only leaked when it wanted to and was putting air in my system. I didn't figure it out in time. I ruined my heater core .