Cooling System and/or Fans
 

99 Accord EX 2.3 - Car is overheating, and this is what I have figured out.

I know the t-stat isn't working properly, the lower hose stays cool, even when the temp gauge reaches about 7/8th's. The t-stat was replaced about 8 months ago, so I wonder if there was another problem that caused the t-stat to fail quickly?

Also confused about the fans. Both kick on and run fine when the air is on, before the temp gauge reaches halfway. If I turn the air off, only the driver side fan kicks on once the temp has climbed about 7/8th's of the way up.

Could the fans cause the car to run hotter, thus causing the t-stat to fail sooner? Is there an unrelated issue with the fans, or maybe the bad t-stat is causing them to run incorrectly?

Are there any other thing I should check, that may cause the t-stat to fail so soon, or just chalk it up to a bad part?

Thanks for any help!

Make sure the coolant system is free of air as this willl cause overheating or indications of overheating.

Pour coolant in very slowling if radiator is not fully filled w/ cold engine. Look for air bleeder on topside of engine, but I'm not sure if V6 has one.

Replace thermostat is system is full of coolant. Recommend OEM thermostat as some aftermarkets are notoriously poor.

good luck

could be the sender for the engine fan as well

Get the stat replaced....Test thermo A. Sounds like thermo B is working fine.

Yes the V6's in this gen have the A and B set up :)

Original poster said 2.3 liter, which is the 4-cyl. Coolant bleed screw is at the thermostat housing - LOWER radiator hose. And there's no 2nd fan switch; the fan won't run after turning off the engine.

When the engine is running, AC turned off, high temperature should cause BOTH fans to run. Something's not right if only one runs.

Even if the T-stat is OK, a cold lower hose while the engine overheats might be a plugged radiator core. With severely restricted flow through the radiator, the water gets nice & cool. But there isn't enough flow to cool the engine.

Dang......I've got to read better. I think I keyed off TX comment about the V6.....sorry about that.

thanks for all the help! I am working on the car today. Should I replace t-stat, flush radiator, then retest fans? If fans still aren't working once flow restored to lower radiator, am I looking at a fan relay replacement?

Thanks again.

First try this test before doing the radiator flush...
- Disconnect the wire for the fan switch - located in the radiator housing.
- Jumper the wires together with a paperlip or something.
- Key ON, that should make BOTH fans run.
If not, then check fan relay, etc. Maybe even a bad fan motor. I'm guessing this, because you said only one fan runs when it gets hot. The fan switch is supposed to trigger both fans together.

(When you switch on the AC, both fans run regardless of the antifreeze temperature)

Since you said the fan doesn't run until the temperature gets up to 7/8, you might think about replacing that fan switch anyway. (Not sure how much they cost?) Seems like it should trigger the fan sooner, maybe 5/8 or so.

Easiest time to replace that fan switch is when you replace the thermostat.

Don't forget to check for a plugged radiator (plugged water channels inside). If you need a new radiator, you should do that before you put fresh antifreeze in.

Question for JimBlake
 

will try the fan test mentioned. You also said the fan switch? Are you referring to the relay, or is there another switch to be concerned with? I think fan motors are good, both run when A/C is on, and they seem fine - smooth quiet, plenty of RPM.

Sorry JimBlake, I see the temp switch for the fans are up near the t-stat, and the relay is in the fuse panel. I was hoping the fan was sampling temps near the lower hose, which would cause the temp sample to be low with the t-stat not working.