The bleed screw is #12.

 

The problem came back ....

Coolant reservoir was emptied out when I came back from like a 15min trip.
Remember, I replaced the thermoswitch near the thermostat housing (the green/gold plug in picture 1)

1 thing I notice is that the lower hose is cold while the upper radiator hose is piping hot. Then I said to myself, this shouldnt happen! I opened the air bleed valve on the right of the thermostat and the coolant that it shot out was HOT! The fluid on the left of the thermostat, which is the fluid in the lower radiator hose is cold!

Does this mean it is faulty thermostat?

The fans dont come on unless AC is turned on.

In the second picture, is there also a thermostat there (where the upper hose meets the engine block)?

Please help.

Pat

http://people.ucsc.edu/~pau/03252008144.jpg

http://people.ucsc.edu/~pau/03252008143.jpg

 

My bad for the huge pictures,

just click these links:
http://people.ucsc.edu/~pau/03252008143.jpg
http://people.ucsc.edu/~pau/03252008144jpg

 

I would replace the thermostat. Get it only from a Honda Dealership. It is ~$20 vs the risk of overheating the engine.

There is only one thermostat. The housing is at the end of the lower radiator hose on your car.

Here is what I find strange: If the thermostat was stuck closed, the temp gauge should have the gauge read that the engine is overheating. The engine coolant temp sending unit might be bad. That is different than the sensor that you replaced. The ECT sending unit has one red wire going to it. In the DIY section, the link in the thread ACC 5th gen... has a shop manual that you can download to help you do some tests.

I wonder if it is possible that the fins of the water pump are worn down enough that it doesn't efficiently push coolant through the engine. I have no idea how to test this. Another posibility is that there is a lot of corrosion in the system. A radiator flush from any parts store would take care of that.

Do the cheap fix (thermostat plus radiator flush) first, then worry about the expensive one (water pump).

 

Aradiator core plugged up with crud & scale will have very low flow rate, consequently the lower hose will be pretty cool. The flow rate is small so it may be sufficient cooling for some circumstances.

I've heard of waterpumps (rarely) getting so corroded there's no fins left on the impeller. I suppose you could run the engine with the radiator cap off, wait for the thermostat to open, then you'll see motion in the liquid inside the radiator. It's not avery good test, but ???

Most times there's 2 ways for a waterpump to fail. Bearings start making lots of noise, or the seals begin leaking.

 

This sounds like a faulty thermostat is most likely.

 

I always use Hond Geniune stuff, such as coolant and parts. I will go ahead and replace that thermostat. The cool system is very clean, no corrision. Thanks everyone.

Pat

 

Putting in new theromostat doesnt help. Please help again.

Symptoms are the same. I also noticed that there is a temperature difference in the upper radiator hose: The half that is closer to the engine block is 1.5times hotter than the half that is closer to the radiator. I used a stethoscope to listen for fluid flow and I can only hear the fluid flowing in the upper radiator hose and not lower.

Pat

 

Also....

I want to mention that I topped off the radiator and the resevoir. I also bled the air out of the system using the bleed valve near the thermostat.

With the car off and engine warmed. I jumped the temperature sensor near upper hose, and it kicked on one of the fans.

 

So no fluid circulation. I can think of 2 things:

Something in the radiator that clogging it.
The water pump isnt pumping.

Any suggestions on how to test these at home?