1992 Honda Civic over heating replace theormostat - still overheating air bubbles in overflow jug and in radiator when running with cap off...

1.take in a sample is the best method,2.to test a cap you need to put it under working presure

first check coolant level in radiator coolant level sound low.if coolant overflow jug empty.coolant sysyem low, when add coolant to coolant overflow jug coolant level should stay at full cold mark.if coolant level okay,engine overheat while sitting or moving in slow traffic either coolant fan relay or fuse could be bad.or engine coolant temperature sensor could be bad. coolant sensor turn on cooling fan at certain temperature.hot wire check to make sure cooling fan motor not bad or short in wires.if all is good have pcm check it controls fan relay to through the coolant temperature sensor signal when coolant get hot.

When was the last time you flushed your radiator?
Start with a radiator flush. Could be that simple

Pressure testing just tests that the radiator cap resists a certain amount of positive pressure. I assume you are saying that it is not drawing back from the overflow when the engine cools down. It is likely that the coolant is being blocked right inside the overflow jug by some dirt or debris. Remove the overflow jug and clean it out - and clean the overflow hose too, in case it is obstructed.

The most common overlook thing is you got a air pocket, so before you go spend your money turn Heather on full blast, open the radiator cap, car running look for air bubbles, takes patience cause you got to wait for the thermostat to open up, you must refill the coolant really really slow snail pace, some car have a bleeding valve others have two chamber on the overflow bottle,good luck, if that doesn't work change the thermostat first and if that doesn't work I'm afraid you may need to replace water pump. . water pump

YOU NEED BLEED AIR OUT THE COOLING SYSTEM.WAIT TO ENGINE COOL DOWN.YOUR VECHICLE YOU HAVE TO POUR COOLANT IN THE COOLANT OVERFLOW JUG UNTIL COOLANT LEVEL STAY AT THE FULL COLD MARK.THEN START ENGINE LET IT IDLE A FEW MINUTES WATCH COOLANT IN THE OVERFLOW JUG WHEN IT DROPS ADD MORE COOLANT UNTIL COOLANT LEVEL STAY AT FULL COLD MARK.WHEN COOLANT LEVEL STOP DROPPING IN OVERFLOW JUG.SCREW RADIATOR CAP BACK ON OVERFLOW JUG WATCH ENGINE COOLANT TEMPERATURE GAUGE AS COOLANT TEMPERATURE START CLIMBING TURN OFF ENGINE LET IT SET A WHILE KEEP FROM GETTING SCALDED.TAKE LARGE RAG PLACE OVER COOLANT OVERFLOW JUG CAP SLOWLY OPEN RADIATOR CAP A LITTLE AT A TIME UNTIL PRESSURE RELEASE.REMOVE OVER FLOW JUG CAP.ADD MORE COOLANT UNTIL COOLANT LEVEL AT THE FUL COLD MARK ON THE OVERFLOW JUG.THEN SCREW CAP BACK ON THE OVERFLOW JUG.START ENGINE LET IT IDLE AGAIN WATCH ENGINE COOLANT TEMPERATURE GAUGE WHEN TEMPERATURE GAUGE START CLIMBING.TURN OFF ENGINE WAIT A WHILE.CHECK COOLANT LEVEL IN THE OVER FLOW JUG.DO THIS PROCEDURE UNTIL THE COOLANT LEVEL IN THE COOLANT OVERFLOW JUG STOP DROPPING AND STAY AT FULL COLD MARK,WHEN THE TOP RADIATOR HOSE GET HOT THERMOSTAT OPENING AIR IS OUT THE COOLANT SYSTEM. WHEN ENGINE COOLS DOWN.CHECK COOLANT OVERFLOW JUG COOLANT MUST BE IN THE COOLANT OVER FLOW JUG AT THE FULL COLD MARK WHEN ENGINE COLD. DONT .DONT OVERFILL COOLANT OVERFLOW JUG.KEEP COOLANT IN THE OVERFLOW JUG IF YOU LET COOLANT OVERFLOW JUG RUN DRY AIR WILL BE DRAW IN COOLANT SYSTEM CAUSE ENGINE TO OVERHEAT.

REPLACE THERMOSTAT IF TOP COOLANT COOLANT HOSE GOING TO RADIATOR IS HOT TO TOUCH THERMOSTAT OPEN. TO BLEED COOLANT SYSTEM FIRST YOU NEED TO ADD COOLANT TO THE COOLANT OVER FLOW JUG UNTIL COOLANT LEVEL STOP DROPPING AND STAY AT FULL COLD MARK.WAIT 3 MINUTES IF COOLANT DROPS ADD MORE COOLANT UNTIL COOLANT STAY AT FULL COLD MARK.WITH RADIATOR OVER CAP OFF CRANK ENGINE FOR MINUTE WATCH COOLANT LEVEL AT OVERFLOW JUG.IF COOLANT DROPS ADD MORE COOLANT IN THE OVERFLOW JUG.WHEN COOLANT LEVEL STOP DROPPING IN OVERFLOW JUG.SCREW BACK ON THE RADIATOR CAP TO OVERFLOW JUG.WHILE ENGINE IDLING WATCH TEMPERATURE GAUGE WHEN TEMPERATURE START CLIMBING TURN OFF ENGINE WAIT A WHILE KEEP FROM GETTING SCALDED.WHEN COOLANT COOL DOWN SOME. PLACE A LARGE RAG OVER THE COOLANT OVERFLOW JUG OPEN CAP LITTLE AT A TIME UNTIL PRESSURE RELEASED, THEN REMOVE CAP ADD MORE COOLANT IN THE OVERFLOW JUG TO THE FULL COLD MARK.THEN REPEAT THE PROCESS SCREW BACK ON THE COOLANT OVERFLOW RADIATOR PRESSURE CAP.THEN START ENGINE WATCH TEMPERATURE GAUGE WATCH COOLANT TEMPERATURE GAUGE WHEN COOLANT TEMPERATURE START RISING TURN OFF ENGINE AGAIN WAIT UNTIL ENGINE COOL DOWN ENOUGH TO KEEP FROM GETTING SCALDED TAKE PLACE LARGE RAG OVER RADIATOR CAP WHICH IS THE COOLANT OVERFLOW JUG CAP OPEN CAP LITTLE AT A TIME UNTIL PRESSURE RELEASED ADD COOLANT UNTIL AT FULL COLD MARK. WHEN YOUR COOLANT LEVEL STOP DROPPING.AND TOP RADIATOR HOSE VERY HOT THERMOSTAT OPEN AND AIR IS OUT THE COOLANT SYSTEM. MAKE SURE YOUR COOLANT OVERFLOW JUG HAS COOLANT IN IT,WHEN ENGINE COOL DOWN CHECK COOLANT OVERFLOW JUG KEEP COOLANT LEVEL AT FULL COLD MARK.BECAUSE IF OVERFLOW JUG IS EMPTY THATS A SIGN RADIATOR COOLANT LEVEL LOW.WHEN OVERFLOW JUG EMPTY IT WILL ALLOW AIR GET IN THE COOLANT SYSTEM AND CAUSE CAR TO OVERHEAT.WHEN REPLACING THERMOSTAT ALSO REPLACE THE RADIATOR CAP ON THE COOLANT OVERFLOW JUG.

ADD COOLANT IN THE COOLANT OVERFLOW JUG UNTIL COOLANT LEVEL STOP DROPPING AND COOLANT LEVEL STAY AT THE FULL COLD MARK.PLACE COOLANT OVERFLOW JUG CAP BACK ON JUG.CRANK VECHICLE UNTIL ENGINE START WARMING UP. STOP ENGINE WAIT FOR A WHILE UNTIL COOLANT COOL DOWN TO KEEP FROM GETTING SCALDED. USE A LARGE RAG OVER THE OVERFLOW JUG CAP OPEN OVERFLOW JUG CAP A LITTLE AT A TIME REMOVE OVERJUG CAP CHECK COOLANT LEVEL ADD MORE. COOLANT IN THE OVERFLOW JUG.THEN START VECHICLE AGAIN.LET ENGINE IDLE UNTIL TOP RADIATOR GET HOT.THEN THERMOSTAT WILL BE OPEN.WHILE ENGINE IDLING WATCH THE TEMPERATURE GAUGE IN VECHICLE IF TEMPERATURE GAUGE START CLIMBING IN THE HOT ZONE.TURN OFF VECHICLE LET IT SET A WHILE THEN USE LARGE RAG REMOVE OVERFLOW JUG CAP.ADD MORE COOLANT, PLACE CAP BACK ON START VECHICLE AGAIN KEEP DOING THIS PROCEDURE UNTIL TEMPERATURE STOP CLIMBING HOT ZONE.AND WHEN COOLANT LEVEL STOP DROPPING IN THE COOLANT OVERFLOW JUG.AIR IS OUT THE SYSTEM, BUT KEEP COOLANT LEVEL IN THE COOLANT OVERFLOW JUG AT THE FULL COLD MARK.DONT OVERFILL.DONT LET COOLANT OVERFLOW JUG RUN DRY IF SO AIR WILL ENTER COOLANT SYSTEM BECAUSE COOLANT LEVEL WILL BE LOW ENGINE WILL START OVERHEATING.

You could have an airlock still in the system. Run the vehicle at idle and squeeze the top and bottom radiator hoses with the expansion bottle cap removed. Add fluid gradually to it keeping it under the full marker. The bubbling is super hot air caused by air trapped either in the engine block, or top of radiator. A little tip while doing this, have the heaters on in the car and on high heat with the fans running at high speed. If you notice the engine getting warm and the heating in the car stays cold, the airlock is going to need a bit more work. Eventually if you have replaced the head gasket correctly the air lock with come out. Hope this helped...