'94 Honda Civic that is in great condition has started to overheat occasionally.

Question

The vehicle's engine was nicely rebuilt at about 190,000 miles, it now has 230,000 miles and has been running fantastically, I also just put in a new transmission and clutch about 5,000 miles ago. I tend to drive it between 80 and 90mph on the hwy, that's just how fast speed of traffic is here in California, and the other day it overheated. I let it cool down, put in coolant and drove it home nicely and it drove fine with no overheating. If I drive it nicely it does fine but any high rpm's and it starts to get hot. About two weeks ago I put in some radiator sealant because the A/C was leaking, I know that's a no no, but I didn't think that it would cause problems. Could it be plugging the radiator or does this sound like a thermostat problem? Any other suggestions? Thanks for your help guys.

Answer 1

You put radiator sealant in because the A/C was leaking ????

I guess that you meant not to say the A/C correct ????

Anyway yes......if you put any type of radiator sealant in, it will clog up the cooling system and this will need to be completely flushed out....and replace the thermostat and have the raditor flow tested..

Answer 2

If you're driving 80-90mph, that should allow plenty of wind flow to cool down the coolant at your radiator.  However, if the coolant is not circulating in your engine, it will prevent the delivery of cold coolant your engine needs to avoid overheating.

Try replacing your thermostat if you haven't already done so.  If it's faulty and sticks, it can block the cold coolant from entering your engine.  You can buy this inexpensive part from your local auto parts store with little difficulty in replacing the old one.

Also, replace your radiator cap.  If it is faulty and can no longer keep up with the high pressure, it will allow coolant to escape through the cap and you will lose coolant mysteriously and eventually overheat.  Very cheap and simple to replace.

Also, inspect your water pump if it hasn't already been replaced during your last timing belt change. If it's faulty, it can prevent the circulation of coolant in your engine.  However, it will take special tools to get to the water pump if you don't already have them (50mm crankshaft pulley hold tool, air impact gun, breaker bar, etc).

Good luck!