When I’m driving in freeway I hear a humming sound coming from under the hood as I go faster it gets louder. This morning when I went to work I saw the front lights coming and going. Could this be symptom of alternator?

 

My civic stalled when the alt. was going bad . A multi tester can be used to check the alt. if you have 14+ volts at the batt. it's good . Don't make a new alt. charge a dead/low batt. make sure it's charged . The humming could be a wheel bearing , they may quiet down on corners .

 

You think it may be the bearing on the alternator?
also my car seems to start over heating after driving it for over 1 hour in the freeway but these 2 days only in the morning not in the after noon. As soon as I turn the heater on the gauge goes back to normal. Car has 227,320 do you know what can it be?

 

A noisy pulley can be hard to locate , the alt. is below the power steering pump check the belt tension I guess . The over heating after 50 miles of driving is what my other honda was doing and I'm thinking a head gasket with a small leak , there would be little heat when it did and the gauge would usually go back to normal . But with sludge under the radiator cap it may not be as simple as an air pocket , your radiator may be a bit clogged , what I do is run a hose and get a flow rate then run it through the radiator and see if it is close . I time how long it takes to fill a gallon bucket . I was removing the heater hose behind the thermostat to see if the water pump is working but if there's an air pocket you can';t rely on that , found out the hard way by removing timing cover and replacing belt pump etc. A bad thermostat will act temperamental when coolant is full , I guess it depends on the behavior of the problem . Head gaskets are a common problem on these I've heard .

 

Ok thanks I’ll check these problems and hopefully it’s not a head gasket failure. Would a small leak on the head gasket can it be detected with test block fluid?

 

Not sure , I didn't think a head gasket could have a small leak I would think it would progress rapidly into a failure but with my one civic I've eliminated the rest and that's a remaining possibility .

 

Do you know by any chase what it means when I turn off my car kill the power and put the key back in but don’t start the car and the engine light comes on and it blinks 4 times and it erases. I tried to diagnose the car but no codes will come out.