Acura Repair: Overheating, radiator hoses, impeller blade

Question
My son has a 93 Integra with approx 150k miles.  It has a new radiator from an accident he had, last year it needed a water pump (I think)and I now put a new radiator cap on it.
It seems to only overheat on long trips.  First the heat starts blowing cold then it overheats.  My son drove from Atlanta to Phila and it was fine for approx the first 2-3 hours then he had major problems but as long as he drove at certain speeds he could keep the temp. gauge in a reasonable range.  When he got home the radiator hoses were compressed inwards.  My neighbor who is a auto mechanic said it sounded like a bad radiator cap.  I replaced it and my son drove to NYC and back (approx. 2.5 hrs each way) with no problem. My daughter yesterday drove it to Va. and said it worked fine for about 3 hours and then started overheating.
Do you have any idea what this could be?  It has plenty of antifreeze.  It doesn't sound like a thermostat issue to me since I would think that any overheating would occur in the first .5 to 1 hour range.  Is the water pump 1 piece or could have someone istalled an impeller blade backwards?  I am perplexed so I am looking for some insight.  While I am asking questions the car runs good but vibrates pretty bad when idling in gear (stopped at a traffic light).  do you have any suggestions for this issue?
Thank you

Answer
by the sounds of it the first thing i think of is a head gasket. there is a way for you to check this. take all the spark plugs out, keep them in order so you know where they came out, look at the plugs for one that is very clean. if you find one like that than it is a head gasket. this test is best done right after it overheats, shut it off, let it cool down than check the plugs.
 the only other thing i think is an air lock in the cooling system but that is not the likely cause.
 one other symptom of a head gasket is slow in town it does not over heat but on the highway it does. or the harder you drive the car the faster it overheats than drive it easy and slow and it cools down.