hi everybody im new here and using google i discover this great forum maybe u guys can help me i have a 94 honda civic dx my car has been loosing coolant i first replace the thermostat it kept getting hot so i replace the water pump i bleed the system out so i got all the air out did a compression test i i taught it could be the head gasket but it held the pressure just fine after that i took a trip to another city got on the highway and it got hot again and when i was slowing down the temperature gauge move down like it was cooling so i notice that it gets hotter in the highway faster than on the street also it starts blowing steam thru the reservoir any help would be appreciated

 

Your head gasket could be leaking only under load. I believe a radiator shop can test your coolant for signs of combustion gasses. Some other possibilities:

Bad radiator cap
Thermostat is in backwards

 

Get the radiator as full as you can. With the engine COLD, start the engine with the radiator cap off and rev it. If coolant and / or air blow out of the radiator, the head gasket is bad.

 

sounds like HG, mine was bad and it passed compression AND leak down test (according to a mechanic, how knows if he really did the test)...

 

ok thanks everybody for the quick response ill star with the cheapest radiator cap and check the thermostat and test radiator fluid than head gasket ill keep u guys posted thanks again