petrosar

Hi guys,
I have a 96 civic LX automatic that has about 200k miles on it and when it runs normally, is a great smooth two owner car. I acquired it from family because it was overheating slightly. I noticed the radiator was full of deposits and rust so I changed it with a new one along with a new thermostat which replaced one that appeared to be the original one. 50/50 coolant / water mix and the car seemed to not over heat until I drove it about 30 miles on the highway and upon exiting the temp gauge started to creep up towards red. Turned on the heater and cold air followed first minute or so then kicked in with heat and the temp came down.

Figured there's air in the system so let it run. A few times w without the Radiator cap during idle. Added coolant accordingly drove the car back another 30 miles or so and then the second it hit the hell that is about 2 miles long it started to overheat halfway up the hill going about 30 mph

This time it overheated all the way until you red but I had no choice I'm slowly drove it home with the heater on. Afterwards added water since all the coolant have completely drained out of the system but the water only coolant mixture appear to overheat the car I just idle. Drained the entire water from system and added 1 gallon of undilute it coolant. Also changed the coolant temp and fan temp sensors, idled the car for 15 minute under 3k rpm and temperature was perfect. Car idled for 3 hours and again perfect. I drive it to work the next day and history repeats itself on the way back home.

I'm out of ideas. Water pump was also done last year.

Some or saying headgasket but if that's the case why is is good sometimes and not others times. Would it not have overheated under 3k load for 15 minutes if it was the head?

Any thoughts would be truly appreciated!!

Former User

Was there water rather than coolant in the cooling system when you obtained the car? Tf so, you should flush the cooling system.

Then add 50:50 coolant and bleed like this:

https://honda-tech.com/honda-civic-d.../#post39830585

If overheating continues, rent a block tester kit from AutoZone.

tony_2018

80% sure you have a headgasket leak. Might wanna check for combustion in the coolant/water. Oh and water is not something you wanna use as coolant because it has a low boiling point.

chrysler kid

Replace your radiator and heater hoses. The back U shape one probably has a small leak that only happens when driving. Happened to my HX, I couldn't even tell it had a leak until I saw a couple of small drip spots on the back of the engine bay

Baby99EX

does the cooling fan turn on at idle??

DumpdEJ6

It should eventually. Fill the radiator directly when cold, let the car idle until the system is pressurised, and check every hose for leaks. IME the hose that goes to the cylinder head that leads to directly underneath the distributor tends to get oil leaking onto it from the distributor o-ring, which causes it to swell and crack. Also the hoses on the back of the cylinder head tend to crack as chryslerkid mentioned. If all the hoses are good, look at your radiator, especially around the top where the hundreds of tiny metal tabs keep the top plastic part held onto the aluminum cooling fins. If there is wetness there, you may just need to replace the radiator.

Don't start with the most expensive option first (head gasket). But do be aware that you have overheated the head at least twice, and the aluminum head warps easily. I have had bad luck with most of the Hondas I have owned, head gaskets went bad on 4/6 of them, one of them twice, although that was do to my own installation error.

axis11

Head lift!
Slightly warped head but does not leak at idling pressures.
Happens only when pressures in the cylinders are high like when your accelerating. Head and block clearance increase just a bit and high pressure exhaust gases enters the jacket water chambers. Then the gas is trapped in the thermostat housing, then the thermoswitch fails to operate properly. Now your fan operation is delayed, water boils and goes out the radiator.

Test for signs of exhaust gases in the coolant to verify HG leak.

eghatch9295

iTrader: (1)

head issues are less likely than an improper bleed or tired water pump. if the previous owners put a bunch of stop leak crap in the car, it could have gummed the pump up and or the entire cooling system. flush, and at those miles it is likely due for a new pump anyways.