2001 Civic EX overheated going up the summit and radiator melted where cap meets rad.
New radiator and cap installed
ever since, heater would take long to heat up and only be warm when revved up
1 month later car randomly starts to overheat every once in a while. i watch it like a hawk and when it happens, i have to top up fluid directly to rad
rad does not pull fluid from radiator
can fill radiator up with coolant and it will work well again for a while but then overhead again randomly. sometimes after 70km, or sometimes after 300km. sometimes up or down a hill, but even just sitting flat and idling one time.
once it started to overheat and I revved up the engine, and it stopped rising in temp and levelled off as if plugged.
shop treated it as an air pocket and it worked for about 70km but then began to heat up again
Changed thermostat
same symptoms

any ideas?

could the thermostat be in the wrong way? when rad full of coolant, it stays at perfect operating temp according to guage on dash - just below half way mark
no fluid underneath car
no smell of coolant from heater core when driving
no loss of power
head gasket was redone before i purchased car
i had water pump replaced while timing belt/chain was done 6 months before first time it overheated

I'm thiking a flush of entire system including heater core, but any other thoughts? im planning a long trip soon.

Thanks


Jason
jbaris @ @ hotmail.com

 

overheating sucks...

that being said...

if you need to keep filling the radiator then you have a leak, somewhere.

Could be a seal somewhere, including water pump seal or head gasket or any of the hoses or even the thermostat housing (which should get a liquid gasket when being put back on). If you can leave the car parked and look for water/coolant dripping under the car and find the source that would be your best bet. If you cannot find anything then you are likely loosing fluid in vapor form which could be head gasket (with coolant you will get white smoke from tailpipe) or radiator cap (but you just replaced it) so sounds likely to be a bad hose that is only leaking under pressure ie when the system gets hot. You can let the car get hot then turn it off and listen around the engine bay for a leak in a hose, I found several when going through overheating problems.

If you do not need to keep filling the radiator then you have two paths of problems. 1) overheating when you are not moving which would equal a problem with the fan system (fan motor, fan switch, fan wiring, fan relay, fan fuse). 2) air in the system which just needs to be bled out (normal bleeding will bleed the entire car, heater core and all), when i bled my car I parked on a curb AND jacked up the car to do it (not sure if 01s have a bleeder valve, my 97 does not).

Outside of these problems you can replace the thermostat, water pump, head gasket. A leak down/compression test would help rule out the head. I forget how to check the water pump.

Hope something helps.

ps. remember that one problem can cause others, so what ever caused the problem the first time you replaced the radiator does not sound like it was fixed thus it is continuing to cause the problem, so it is possible that it has already warped the radiator cap again (not saying it has though). Overheating is something you want to fix in one shot otherwise is it likely to cause problems in other areas and make it seem like a never ending problem. I choose to replace all my hoses, switches, thermostat, radiator cap, ect all at once after my problem came back twice. And I have been good so far as I can tell now. Luckily all those parts are pretty cheap.

 

Thanks for the quick reply.

Had a guy test and there is coolant getting into combustion chamber, so it's a head/head gasket issue. NO coolant in oil though which is good.

I think I'll try take the head off myself and see if I can fix!

Cheers

 

both head and head gasket are not that difficult to replace if you are confident in your abilities. a gasket is much cheaper than the head itself, but if you do the gasket and it is the head then you are going to need to replace the gasket twice which is a waste so just be sure one what you need to do.

Good Luck!