Should I drill holes into the thermostat? I have seen people do that before.

 

Nah .... if you take it out, it's not there to cause a problem .... if there's a lot of pressure on the lower hose without the stat, while the car is running, then I'd expect that your rad is clogged and needs to be replaced ..... the fact that there is pressure tells me that the pump is ok.

Can a tech verify that the water pump is a simple centrifugal type? I'm 98+% certain that it is.

 

ok, it cant be the pump, check out the picture I took this morning, notice the fluid at the thermoswitch hole. The fluid made it up there, the pump has to be working in order to pump that fluid up.

http://people.ucsc.edu/~pau/03282008146.jpg

Falk, Thanks fo rsticking around to help

 

Can a bad radiator cap cause this?

 

I doubt it. The cap just holds the pressure or if it gets too high, allows the coolant to get out so the rad doesn't blow apart. Coolant should flow without the cap even on. If you open the drain and put a hose on top, does water get through the radiator? That could be a way to check this thing out.Engine off on this one. I'm expecting a clog that's completely sealing the radiator.

If there is flow, but very little, you could try filling it with half vinegar and half water ..... leave the car with that mix in it for 3-4 hours, then start it up without the cap and see if the flow improves. If it does, let it run for 15 minutes, then drain it and refill it with vinear and water again and run that for another 15-20 minutes. After that, do the same with water 3 times, but you only need to wait for 5-10 minutes ...... then refill with coolant and you're done.

 

Well, I switched out the rad cap with another honda thats a year old, didnt fix the problem. So not the cap.

I will do a drain on the radiator. Seems like unhooking the lower radiator hose is more effective. wouldnt it?

 

Sure .... I just figured that the drain is a bit easier to contain.

 

took the upper radiator hose off, no clog there. I will be checking the radiator.

 

LOL .... the upper hose won't tell you anything ..... We're looking for a blockage in the rad itself. I'm taking off. I'll check in later tonight. Good luck!!!

 

I drained the radiator by using the drain plug, coolant came out, didnt notie any abnormal color or rust. I poured water straight into the rad neck, water came right out of the drain hole. Does that sound like no clog?