Hi,

My car has 187.000 miles on it. I had my radiator, water pump, thermostat changed about a year ago when I only had about 165,00 miles on my car. Right now it is overheating again and the mechanic changed my thermostat, we thought that did it but when I was on my home on traffic, it started to heat up again. The pin goes down if start to move, might be because of the air flow but when I stop, it starts to go up. It doesn't have nay leaks whatsoever except for the thing that when the car heats up, the coolant sneaks out the reserve tank. I also noticed that there is a lot of black sticky kind of gunk on the side walls of my reserve tank making it look black instead of white plastic inside. Do you think that the head gasket is blown or the head has a crack? Please help. Thank you.

If you aren't the original owner, it could be block or radiator sealer, which is difficult to get rid of and could be ruining your new radiator and life. I suspect blockage in the radiator from something.

Can you verify that your fan is working, I only recommend OEM Honda thermostats. I would at least get the cap pressure tested also, do you have a good mix af coolant/water, say 50/50. Anything like this black stuff in the coolant will reduce the heat exchange capability of the radiator. There are dyes that can test for a blown headgasket at your parts store.

The fan was working and at the right time too but I think it could not handle the heat of the engine that's why it goes up. The mechanic also tested the radiator and he said it was good. He said our next stop is to try to change the water pump and if it still doesn't work, he is going to try for the head gasket. He said that it is not the head gasket because there is no white smoke going out and there is no milky thing in the oil cap. I will ask him about the test with a dye tomorrow when I go back to him to cehck the water pump. There is also a 50/50 mix of coolant.

There does not have to be white smoke to have a bad head gasket and there does not have to be coolant in the oil (milky) to have a bad head gasket. From what you just stated about your mechanic, I am recommending that you get a second opinion. The car also needs to be checked from full cold until full hot and then a test drive or two so I would want to leave it at a shop.

This problem is not so difficult to test, but experience does help.

That's what he said also, it shouln't be the head gasket there is no white smoke coming out and no milky substance in the oil. I tried to drive my car earlier and just took in a slow ride even in the freeway. I was just running 65mph and about 2500 rpm but when I encountered a hill, my car started vibrating like it feels it's going to die down, then my check engine light started blinking and then went steady. This time I drove for 35mi but my engine did not overheat and just a small amount of coolant went out the reservoir. Thanks for the time. It's a good thing to have a lot of ideas on what's going on.

Don't trust your temperature gauge, the ECT sensor must have actual hot coolant on it for it to read correctly, if coolant is low and there is air trapped at the thermostat, the temp gauge will not show overheating until its way boiling and hot steam at the ECT sensor.

The sensor could be out of spec or the gauge could be out of calibration, no more driving my friend. Air in the system (coolant low) can create pressure and push coolant out the radiator cap and make the reserve tank overflow making it appear that the system was full and was overheated (over expanded) and overflowed. MAY BE DECEPTIVE, BEWARE.