Overheat - not thermostat, fans, or hoses

fatsodoctor

New Member
Thanks to everyone posting on this topic here. I've read most of the relevant posts, and they've helped focus the diagnosis.

Civic begins to overheat slowly at idle - not aggressively and not consistently. Overheating can be arrested by switching off recirculation in the cab. Temp returns almost immediately to normal if I turn on the heater in the cab.

Replaced the thermostat a few weeks ago. Bled the system. Both fans operate normally. Upper and lower radiator hoses carry fluid. Nothing white in the exhaust.

Can it be...

...layers of crud in the radiator itself, inhibiting the cooling of fluid by air flow over the radiator?

...water pump?

...temperature sensor?

...something I don't know anything about?

Thanks for the help.
 

Ej8Turbo

New Member
fatsodoctor said:
Thanks to everyone posting on this topic here. I've read most of the relevant posts, and they've helped focus the diagnosis.

Civic begins to overheat slowly at idle - not aggressively and not consistently. Overheating can be arrested by switching off recirculation in the cab. Temp returns almost immediately to normal if I turn on the heater in the cab.

Replaced the thermostat a few weeks ago. Bled the system. Both fans operate normally. Upper and lower radiator hoses carry fluid. Nothing white in the exhaust.

Can it be...

...layers of crud in the radiator itself, inhibiting the cooling of fluid by air flow over the radiator?

...water pump?

...temperature sensor?

...something I don't know anything about?

Thanks for the help.
Click to expand...
Waterpumps when they fail to start leaking, temp sensor wouldnt cause your car to overheat.
Eventhough you say no white smoke, Headgasket is very proboble.
 


2NRSTV

Team Exile/ADO Garage
Registered VIP
^x2

Do you have to refill your coolant every now and then?
 

fatsodoctor

New Member
No Leaks

No leaks that I can find from the radiator. I don't have to top off the coolant. The system seems tight.

How would I diagnose a failed head gasket without simply replacing it to see if it works? Would it be worth the time to backflush the radiator before going after the head gasket?
 

Ej8Turbo

New Member
fatsodoctor said:
No leaks that I can find from the radiator. I don't have to top off the coolant. The system seems tight.

How would I diagnose a failed head gasket without simply replacing it to see if it works? Would it be worth the time to backflush the radiator before going after the head gasket?
Click to expand...
Whats the condition of your rad cap? The syspmtoms are very simialr
 

tonyhatchetman

New Member
Try bleeding the system ....and test ur thermostat by hanging it in a pan of boiling water with a cooking thermometer to see if it opens at the temp its supost to... do this to deturmon it is good .... I had 2 new ones in a row that did not open fully ......hope this helps

If not let us know
 

fatsodoctor

New Member
Thanks, everyone, for the comments.

I bled the system well. In fact, yesterday I flushed the system with the Prestone "Flush" stuff, then ran water through the system, then refilled it, and bled it. It hasn't overheated since, but it's only been a day.

If it overheats again, I'll take out the thermostat we installed and test it.

I bought one of those 'backflush' kits, but did not install or use it. Is the whole 'backflushing" thing worthwhile therapy?
 

fatsodoctor

New Member
Thermostat Checks Out

Took out the thermostat and boiled it. Began to open at 180°. Fully open by 195°. The thermostat itself was imprinted with 170°, but I'm assuming that 180° - 190° is well within spec. Put the thermostat back in. Topped off the coolant. Bled the system.

While bleeding the system, the heater (which I had on full) was blowing hot air.

Took the car for a longer drive this afternoon. Let it idle in the driveway when I got back. Temperature began to climb again. Turned on the heater to bring the temperature down. Only blew cold air. Temperature continued to climb until I thought it unwise to let it climb anymore. Never got any heat out of the heater.

Given these symptoms, at this point, do I:

A) Replace the head gasket?
B) Replace the radiator?
C) Steal someone else's car?

Thanks.
 

fatsodoctor

New Member
Update: I replaced the radiator. Drove it quite a bit over the course of the day, and it's very hot here, these days. No trouble so far. But I still have to take it for a longer drive followed by extended idling.
 

fatsodoctor

New Member
Dadgummit. Overheated again. Fan not working this time (was certainly working prior to another, electrical, issue over the weekend). Tested the fan (direct to battery). Fan works. Tested the wiring from the ACT to the fan. Also working. Replaced the ECT sensor. Fan still not coming on. And, hot air from the heater faded. Replaced the ECU (happened to have a spare). Fan came on when engine warmed up.

Maybe all this time an ECU problem. More tests tomorrow.
 
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