1990 Honda Civic ... Overheats!

My husband has a 1990 Honda Civic … it has a strange habit of overheating BUT usually only first thing in the morning, after sitting all night. It will start to over heat after driving for about 3 to 5 miles. Sometimes the temperature will just fluctuate up and not get into the red and then after driving some more it will level out and be fine and sometimes it goes into red and he has to stop and let it cool off! We have had two mechanics work on it and it is now been at the dealers for three days and they can not find anything wrong with it.

What we have done so far:
Changed the thermostat twice - once with after market, then with a original manufacturers part
Changed the radiator cap
Replaced the lower radiator hose
And my husband and 2 other mechanics have tried to bleed the air out

It is NOT leaking antifreeze

Any thoughts would be GREAT!!!

Kindly, Amy

Are you sure it’s not leaking antifreeze? Sometimes you can get a pinhole leak in a small hose that doesn’t leak much antifreeze, but drops enough pressure to cause the system to overheat. By the time you pull over and get the hood open, the leak has stopped. If it’s small enough, it might seal itself once it heats up enough. There are a couple of very small diameter hoses just behind the engine that are kind of hard to see from the front, that sometimes do this.

Instead of throwing parts at the problem, your first step should have been to get the cooling system pressure tested by a qualified mechanic. Do that next.

The cooling pressure was checked and was fine. We have been told by two mechanics that there might be air pockets but it still has not gotten better and it has been over a year.

How about the fan thermostatic switch? I’ve never heard of them “sticking” before, but I imagine anything’s possible. (I’m talking about the electric on/off switch, in case there’s doubt)

The radiator is 21 years old. Over the years, crud builds up in the tubes through which the coolant flows to dissipate heat. The crud insulates the tubes, often totally blocking some of them. You can have radiators tested, but after 21 years I’d just replace it.

While you’re replacing the radiator you should replace the hoses. The inner linings can collapse and restrict coolant flow.

In addition, the impellars in the water pump, the “paddles” that pump the coolant, can erode, reducing the effectiveness of the pump. Unless you’ve been changing your water pumps when you changed your timing belts, this is another good possibility.

Honestly, I suspect the dealership really isn’t interested. As to the other two mechanics, they may have found one thing wrong (like a stuck T-stat) and fixed that without evaluating the entire system. On an old vehicle that wouldn’t be unheard of. Shops don’t want to hit an owner of a 21 year old car with a whopping bill.

amylemmon: “The cooling pressure was checked and was fine.”

What does that mean?

A cooling system pressure test is more than just testing the pressure of the cooling system. It involves pressurizing the system and looking for leaks, sometimes after adding a dye to the coolant.

I am with Mountainbike on the radiator. If yours is the original, either have it flow tested or just replace it, although I would be really surprised if you still have the original radiator after all this time.

If there are air pockets, your mechanic should be able to get them out of the system.

Your main problem, based on what you’ve written so far, is that you haven’t yet found a competent mechanic to solve your problem. You’ve got mechanics who give you “air bubble” excuses, and instead of doing proper trouble shooting and diagnosis, threw parts at the problem. Find a better mechanic, because the two mechanics you’ve had work on your car so far don’t seem to know what they are doing.

Thanks for your thoughts … I know that the first mechanic that we brought it to did a pressure check in the system and said that it was all functioning proper and that there were no leaks. I am NOT a mechanic, matter-a-fact I know little about cars … which is why I am seeking help!

As for a better mechanic … how does one go about finding a mechanic that is worth anything! It seems in my lifetime it depends on who you talk to … I am new to my area and do not know lots of people.

We have owned the car for about 3 years so I am not sure if it is the original radiator or not. I guess maybe we will just have to replace it BUT I hate replacing things that we can not find something wrong with!!!

…then have the radiator flow tested.

I suggest you look for shops that specialize in radiators and cooling systems. There aren’t many, but a google search or a look in the yellow pages might be a good place to start. You can also look here http://www.cartalk.com/content/mechx/find.html for a good mechanic.

I have had good luck with Goodyear for diagnosing and fixing cooling system problems, but make sure you go to a company store, not a franchise. Others will tell you, though, that they’ve had bad experiences with tire stores and other chains, so you may have a different experience. If you get desperate, you might consider going to a Honda dealership if you can’t otherwise find a good mechanic. Honda dealerships might try to rip you off, but at least they should be better at diagnosing the problem.

You’re right that a good mechanic is hard to find, but keep looking until you find one who is good at diagnosing problems without throwing parts at the problem. Throwing parts at problems like this one can turn a cheap problem into an expensive problem when it isn’t necessary.