A few weeks ago one of the hoses broke and I replaced all of them. My mechanic replaced the top hose, the ones that run behind the motor and I replaced the bottom hose. My mechanic also replaced the thermostat. It's a 2000 accord SE, automatic 4cl.

Yesterday was a fairly hot day about 96°. I was parked and idling for about 45mins with the AC running about 3/4 of the way up. I noticed my temp spiked and went from where it usually sits at 1/3 to 1/2 way. I started driving and turned the AC off and the temp went back down. I let the car cool a while and checked the engine. The coolant level was still normal and no signs of leakage. I drove it again for about 10mins on the drive home and the temp stayed normal with the AC running. I'm stumped.

 

Does coolant get drawn back into the rad from the resivior when engine is off(cold)?

 

I think so, the reservoir is just above the low line after it cools off for a while.

 

When the car starts to overheat check that both fans are working.

 

I'll check that, does each fan have its own switch?

 

No, when the ignition is ever in the on position and they are commanded to come on they will always both come on. The only time one will come on is when the ignition is on the off position. They are commanded to come on from either the fan switch on the thermostat housing or when the ac compressor is cycled on.

 

What does it mean if only one comes on?

 

It means that likely one fan is dead. You would then use alligator test leads to apply direct power from the battery to the fan's connector. If the fan doesn't run then then the fan itself is dead.

 

When the car starts to overheat you can check to see if the lower radiator hose that runs towards the back of the engine is still cold. If it is, then the thermostat is stuck closed and bad.

 

Did you bleed the air out of the system?