Hi guys I need help trying to figure out my 03 civix is overheating, i put in a new thermostat last weekend, topped up the coolant everything was working fine until i was on the highway noticed that the car temp was a little higher than usual, it overheated, I checked the radiator hoses and the top one was extremely hot but the bottom one was cool, so i got home took out the stat and made sure it opened and it did and i also did a coolant flush, put everything back in, engine keeps overheating, tried bleeding the system, made sure everything was topped off. nothing seems to work the lower radiator hose is still cold

 

Did you put the thermostat in backwards ? Are the fans running when it gets hot ? Is there white goop under the oil fill cap ? Is the exhaust whitish ? For bleeding I pull the small hose from above the thermostat housing and put it in a jug of coolant , keep it submerged , then a clear hose on the nipple it came off of and put that in the jug .It will draw from the small hose going to the back of the engine and come out from the nipple . I would say maybe the thermostat is junk but it opened when you tested it , a bad stat will usually be temperamental . The sensor below the thermostat runs the fans and there's another (sending unit ) on top of the motor that runs the temp gauge . . Top off the radiator when cool and perhaps it will burp any air in the system . I go with honda OEM parts . This problem is not uncommon with these and can cause hair loss .

 

could very well be the water pump and it’s one of those while your in there things get a timing water pump kit it’s like $70 easy to time being a single cam but definitely check the thermostat again and make sure there isn’t exhaust gases in your coolant system

 

If you bleed it out like I said it will show if the water pump is bad , Replacing the water pump , timing belt and tensioner is an operation so you want to make sure . How ever replacing the timing belt is a preventive maintenance and I believe the 1.7 is an interference engine

 

I didn’t put it in backwards but i took it out and left it out because the fans wouldn’t turn once once it overheated, now with the thermostat out the fans do turn on but it still overheats. lower hose is only warm by the thermostat housing the rest is cold when the engine is warmed up, i’ll try do what you suggest later today after work.

 

mad sure the thermostat worked after i took it out, took it to some boiling water and it opens, i ended up leaving it out but you’re probably right about the water pump, just want to make sure there are other options to why it may be overheating.

 

 

You shouldn't run it without the thermostat it won't warm up properly and the ECM won't know W.T.F. is going on , Boiling water is 212f , the stat opens at like 195 so it may still be a P.O.S. I would also advise against a bargain water pump/timing belt/tensioner kit . If the fans aren't working then replace the sensor below/at the thermostat housing if the gauge doesn't drop at cruising speeds , Get the air out of the system , top off the radiator when cool .

 

the fans work fine, but before i took out the thermostat the wouldn’t turn on once engine started to overheat. after i took out the stat the fans would then on but the engine still overheats.

 

You should do a compression test , don't tighten the gauge hose too much or it may not want to come back out , Only slightly snug , The fans turn on when the ECM tells them to , the sensor tells the ECM when things are hot . The thermostat may be a P.O.S. and cause problems down the road but do the comprssion test before you spend any more money .