we did that. i stated that previously in the post. we have done a pressure test on the coolant system for over 24 hrs. it didnt loose any pressure. we have done probably about 10 leak down tests. all came back with less than 10% on all cyl. we have done just as many lithium tests checking for hydrocarbons and again all were negative. thats why i feel that its an over cooling issue. since the weather is colder here as is ss04's weather i think thats why its showing up. i didnt have any probelms like this until we changed out the sticking thermostat when it started to get cold and now that the temps are staying between 20 and 40 i think thats whats causing this.

 

Ok, from what I can gather...plain and simple:

Your upper radiator hose is hot - that means your thermostat is flowing.

Your lower radiator hose is cold - that means your radiator is cooling the water flowing through.

Your fan switch is at the bottom of the radiator - who gives a crap if the fans don't come on if the temp isn't spiking.

If you're worried about your fans (who cares if the fans kick on as long as cold coolant is getting to the engine - the fans simply draw more air through the rad. Hell, the fans on my truck hardly ever kick on, even after driving all day, b/c of the outside air temps and aftermarket rad), then throw in a low-temp fan switch.

If you're getting temp spikes, then you have a coolant issue (air in the coolant lines).

The cooling system is actually pretty simple, yo.

 

Doesn't the thermostat control water flow from the bottom of the radiator back into the engine? Like the cold tap analogy somebody above came up with?

I believe the bottom hose is cool until the thermostat opens. The water flows through the radiator and although it is cooled it is still much hotter than ambient and can be felt to be warm.

If the lower pipe stays cool the thermostat is not opening and allowing flow. Why it is not opening is the question. If it is because it is stuffed then replace it. If it is because it is in an air pocket and not seeing heat then bleed.

Yesterday we did both.

 

I apologize, Wayne. I was thinking of the thermostat location on my truck (which is on top of the engine, at the upper rad hose).

You're correct that it is controlling flow of the cool water into the engine. I'd say swap in a lower temp thermostat and fan switch (if you haven't already) and see if that helps.

 

 

The lower hose could be cold even if everything is working correctly. The system is designed to cool the engine even if you are racing up a mountain, in the desert, in the middle of summer with the A/C on. The lower hose is going to be quite warm under those conditions but it will still be cooler than the upper hose. Driving around with a low load on the engine in ice cold weather will hardly stress the cooling system. The low coolant flow and icy cold air through the radiator will give the coolant plenty of time to cool off before it gets to the lower radiator hose.

 

This is not my experience in a stationary and controlled environment whilst bleeding the system. I'm referring to between 80-90C when the thermostat is open but the fans aren't on. When the thermostat opens hot water circulates from the top pipe, through the radiator (which has little air flowing through it as the car is stationary and the fans are off) and back through the bottom hose. At this point you should notice an increase in the temp of the bottom hose.

In fact even after the fans kick in (above 90C) the bottom pipe still shouldn't be cold. It has water at 80-90C running through it.

 

THe top hose should be at 80-90C but the bottom hose will be cooler. If the bottom hose is still at 80-90C then the radiator has not cooled the coolant at all.

I noticed last summer my lower hose was very warm but it was still much cooler than the upper hose. Now, in the winter, the lower hose gets very cool quickly.

 

burgman: you are correct the lower hose SHOULD be cooler than the top hose, but if i can place my hand on the top hose and its VERY hot and then touch the bottom hose and its AMBIENT temp. then something is wrong. a radiator should not and can not cool water from 185F to 50F in a matter of seconds. not possible. i work with heat transfer all day long doing air conditioning and there is just no way to do that. i do agree with everyone that has posted here that we do have a problem and i believe that everyone is now on the same page, but now we are just repeating ourselves.

as of last night i have ordered a new OEM radiator from Majestic Honda (www.hondaautomotiveparts.com) and it should be here in about 5 days. i do believe this SHOULD fix it, based on all of our discussion, but i still have that one question lingering in my mind that i just can not find an answer to. how am i getting air into the system, and why does this mainly happen only when engaging vtec several times? i didnt have any problems like this until the weather changed and my thermostat that was in the car stuck. i replaced it and now all this. i think that it is indeed that the radiator is just too efficient for my car that is still stock.

i will keep everyone informed on the progress, but if you have any more suggestions for ideas let me know please. thanks again everyone for all the help! its much appreciated! Lee

 

I really don't see how an OEM rad could fix it? A Mishimoto rad has a larger capacity, but it's still doing the same thing. The thermostat is what is controlling how much coolant from the rad makes it into the engine. I don't see a brand new Mishimoto rad having circulation issues either - but I guess anything is possible.

Have you not tried a new rad cap yet? I'm not familiar with how pressure tests work, but I imagine it'd be something that connects to the top of the rad. So if your pressure is fine and you're still getting air in the system, would this not point to a bad rad cap?

There have been guys that had defective Mishimoto rad caps before. It may solve your "air" problem without you having to swap anything.

I haven't started my car for a week now. I'll be playing with it for a couple hours today. We'll see if the bottom rad hose warms up at all...