KHowe

I searched on replacing the coolant and got some good info, still have a few questions though so any help would be appreciated. This is on a '99 Civic EX.

I am going to swap the coolant in my car, as the temperature gauge seems to be rising all the way up on long car rides and I have ruled out the fan.

Anyway, I've never done this before. I did search, and from what I gather, I take out the plug at the bottom of the radiator and let the fluid drain. After plugging this back in, do I have to drain the coolant from the engine by undoing the bolt/plug near the oil filter, or can I simply replace the coolant in the radiater, let the car run, and let the old coolant go into the radiator while the new fluid goes into the block. What is the ratio of coolant in each?

If not, and I drain the coolant from the block, I then refill the coolant in the radiator and run the car with the heat all the way up, and continue refilling the coolant as needed?

How do you go about bleeding the air out so the car does not overheat in the future?

Lastly, is there a specific coolant I need to use on my Honda or are they all the same? Thanks for the help.

Loserkidwac

well you can pick up some coolant flush stuff at the auto parts store, the instruction on the bottle will help you, pretty much drain the rad then refill with the flush stuff and water run the car and repeat till the coolant is out, I doubt you'll be able to get the freeze plug loose to drain the block but I wouldn't even try, the flush will work fine...while you are draining the system I'd suggest you replace the thermostat too...it most likely is the reason you are over heating and also the rad cap, these items are cheap and are def worth replacing if you haven't...you can use regular automotive coolant GM's are usually the cars that use the weird stuff, I prefer to use the premixed stuff but if you have the owners manual I believe it will tell you what percentage of coolant and water to use...probably between 50/50 to 70/30 coolant/water...oh there is a bleeder on the upper coolant neck off of the head...follow the upper rad hose to it..>i personally preffer to just start the car and let it idle with the rad cap off, turn the heater on full blast and let the car warm up to operational temp and add coolant as needed...HTH

KHowe

Thanks for the fast reply, man. I will do it that way then, not worry about the drain plug on the block.

I'm going to search now on replacing the thermostat, hope it's easy.

whereiscarmensandiego

your car should never be overheating even if the coolant in your rad was 5 years old..and i doubt replacing it will solve your problem..u need to find the cause of the problem.. ie bad thermostat, bad head gasket cloged radiator any number of things could be wrong.. but this needs to be corrected or u will still overheat.

KHowe

I will replace the thermostat when I replace the coolant; hopefully this will fix the issue.

KHowe

Well I replaced the coolant (which still looked good), as well as the thermostat. The car was overheating on the way to work today (which is a short 5 minute commute), before it only overheated on long highway trips...

It is possible there are still air bubbles in the coolant, I will do my best to bleed them out today.

I noticed the fan hasn't turned on though when the car got up to temperature (where it usually sits, halfway between hot and cold), though I read it should. When I came home from work for lunch, the fan still wasn't on. Is this normal, or should the fan have kicked on? It's probably the coolant did not heat up significantly, and so the fan didn't kick on. Should I look into replacing the fan temperature sensor? Is this an easy/cheap thing to do? Thanks in advance.

Loserkidwac

Well first check to see, its possible that there is still air in the system, make sure it is completely bleed, sometime an air bubble will get caught behind the thermostat so if you didn't let it open when you bleed the air out originally you might have to top it off again...the fan is really easy to check, the system consists of the fan itself the coolant sensor on the thermo stat housing and a relay...check all those to see which is the culprit...also replace the rad cap if you haven't just some added security...if all those things check and you are still overheating there is probably a more serious problem...