How can I tell if it is the hose, or the thermostat?



I recently got a new radiator for my 2000 honda civic est. 160,000 miles.

the two hoses I bought did not fit the best, and so only 1 new hose was used and I kept using the older hose.

there are smaller little hoses (I think), but they were not replaced.

today my car overheated and started smoking. there is still coolant in the reservoir, but it is at the minimum level. there was some type of leaked fluid on the front right side under carriage.

the fan for the radiator would not come on even though the temp was above the middle mark.

how can I tell if it is something simple like a little hose or a bigger hose that needs to be replaced, or if there is something wrong with my thermostat?

I am on a budget and cannot afford to pay for estimates right now.


Start by assuming all your problems are separate events.

  1. Why was the radiator replaced?
  2. Find the source of the leak
  3. Find out why the fan does not come on.
  4. Test the thermostat.


the radiator was replaced due to age and the fact that it was leaking from all over (except the hoses!).

Thank you for the suggestions, I hope it is just a simple hose.


if the fan doesnt come on at all it is going to over heat. a thermostat is very cheap and is fairly easy to replace. and the leak could have been from the overheating.




Does this thing have a Bleeder on the themostat housing?? Just a small bolt going vertically into the top of the housing. I’m not familiar with hondas but many smaller engines require the housing to be bled while refilling a drained engine. This can cause big headaches as the themostat can remain airlocked and not operate properly. The temp sensor is usually located in the same housing which - guess what - controls the electric cooling fan! I learned a long time ago to drill a small hole in the thermostat flange to prevent airlocking.
If you need more info on bleeding a cooling system just ask. Just remember don’t screw around with a hot engine! I’ve seen hot engines blast off a cap and shoot scalding coolant 20 feet in the air!
Good luck.


Well, it wasn’t the hose (even though we did tighten them just to be sure).

There is a plug-in item near the radiator and radiator reservoir that is not receiving the right electrical output from my car. A friend bypassed this problem so that i can drive without letting my car overheat.

What is the plug-in object? I apologize as I don’t have a manual. We tested the electical output on the receptor of the object, and the plug-in part of the object. there is electrical output from the receptor, but not coming from the plug-in part. Is this something to do with the thermostat? what could be the issue?




No, he made a switch option, so I can manually turn the radiator fan off and on. I know it isn’t the best option, but he was not able to determine why there isn’t electricity running to one part of the plug input. In the meantime until I can get to a repair shop, I have a manual switch that I can use.


The plug like thing is probably the engine coolant temperature switch. When the coolant temperature gets high enough, the switch closes and lets the radiator fan relay send power to the radiator fan.
The radiator fan should only come on if the engine coolant temperature GETS HIGH ENOUGH. For some cars, that temperature is somewhere between 220F and 240F degrees. Your engine coolant temperature SENSOR, which feeds the dash temperature gauge, might not be getting the true temperature of the engine coolant; or, it might be. A direct measurement of the coolant temperature would reveal which is the case.


I think this is the part I was talking about.

the relay switch for the fan. what causes it to stop working?


My fan usually only comes on when the temp gauge is just below the middle mark. if i turn the fan on only once the car is warmed up, does it harm my car or battery in any way?


So from the advice of the very intelligent folks at Cartalk, I am guessing that there is something wrong with the radiator relay.

Here is imy problem–I am on a very limited budget. Very. I can take my car to a repair shop, but I worry they will say the problem is more than a couple hundred bucks, and in the process of figuring out the problem, they will undo the manual override switch. I do not know how to re-do the switch myself. I doubt that they would reconnect it because, well, it is a bit of an odd fix. I do not have the money right now to fix it (though I probably will in the next few weeks—thank goodness for tax refunds!).

My worry is that:

  1. The non-working relay switch may be not working due to a bigger computer or electrical issue.

  2. That my check engine light not working (it lights up when I start the car–at least I can remember that it does) is tied into the relay issue, and may mean something more expensive and computer related

  3. That the manual override may impact my car. The person who fixed my car said he could make the switch permanent if I wanted to. I am not sure.

  4. Is the relay switch and the check engine light part of a larger system that involves the air bags?

My goal is to keep my car running for at least a few more years. So, I am not concerned if it doesn’t look fancy or have all of the bells and whistles, as long as my car is safe and dependable.

Thank you everybody for taking the time to help me with this.

Ps. I realize that I may be over simplifying my questions because I do listen to cartalk, and I have gotten used to the good advice that the brothers give to the callers, just by the caller making a sound and describing a situation without all of the technical terms. :slight_smile:

Honda civic 2000 dx
160,000 miles
radiator replaced less than 6 months ago
hoses have been checked – no leaks