Overheating with A/C on, 99 Civic
 

Hey there. I just moved from Oregon to the much hotter state of Texas. Previously my car never exceeded the halfway mark on the temp gauge. Today, while driving with a/c on, i noticed the air felt warm when driving, and then went cool again while idling at red lights. Then, i looked and noticed the temp gauge was close to the red (about 7/8 maxed out). I turned off the a/c and the temp dropped pretty quickly.

i have looked at a few threads regarding this issue, and hope someone can help me troubleshoot mine. I recently did my timing belt and water pump and filled the radiator with Honda radiator fluid (all about 2000 miles ago). I just verified that the radiator is still topped off, as is the reserve tank. I also verified that when the car gets hot, the radiator fan kicks on, and when the a/c is on, the condenser fan turns on. I do not notice any bubbling in the reserve tank when the car is running. Finally, i had a compression check about 5k miles ago and everything was fine.

I'd be much obliged for any suggestions!

First thing I would suspect is a bad thermostat. Did you change that when you did the t-belt and had the system drained?

I did not change the thermostat unfortunately. Would that be the first step?

Yep, should be a cakewalk to replace it if you just did your t-belt yourself.

I kinda get the feeling the radiator fan is not turning on when it should. Right now when it is near red it is not on, though it was earlier today... Could i have a bad fan or radiator or harness or something?

Could be one of the coolant temperature sensors that engages the fan. I've never messed with them before, but is definitely another possibility. I know there's one beneath the distributor.

Would think if it were a harness issue the fan wouldnt work at all.

If the thermostat is stuck closed, the fan will not come on. Replace thermostat first before you do anything else. Any time you have drained and refilled the coolant you have to top it up with the engine running and the radiator cap off to get all the air out.

If it still overheats, you can jump the fan switch on the thermostat housing, which will make the fan run all the time the key is on (if it doesn't, something is wrong). Test drive with the fan running all the time. But first replace the thermostat.

Thanks much for the helpful advice guys. I'll replace the thermostat as you suggested. I will say that when I refilled the radiator, it was up on jacks and I poured until it was full, and then filled the reservoir about halfway or so. I made sure the heater was all the way up. Just that alone consumed the entire jug of Honda radiator fluid. I ran the engine with the radiator cap off, but it didn't require any extra fluid for topping off. I don't know if I did something wrong and that maybe there's still a bubble or two in there?

Also, I just looked in the radiator and coolant reservoir and noticed there's a little bit of debris which I don't recall seeing previously. I'm hoping this is just normal crud, and not bits of head gasket or something crazy like that... maybe one of you guys can confirm? There does not appear to be any oil in the fluid...

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When I've refilled my cooling system, with the radiator cap off I always saw a sudden drop and then "burping" once the engine got up to temp and the thermostat opened.

As for the crud, what kind of coolant did you have in there before? Ever use tap water?

I never got that burping that I've read about, and even after 2k miles driven, I never had to top it off... Could it be that I have a bubble in the system? Maybe I'll replace the thermostat and redo the radiator fluid or something?

As for the crud in there, I never put water in it, but I don't know if the previous owner did. I had the car between 120k and 155k which is where it's at now, and the fluid was always a clean green previously. Now I have the blue colored OEM fluid... and cruddy looking fluid, at that. Hope I didn't wreck something.