AusS2000, Sounds like you do have a malfunctioning thermostat or a lot of air in the system.

 

The thermostat does the same job as the cold water valve on your shower. When you first turn on the shower you keep the cold water valve off until the water warms up. Once it warms up you turn the cold water valve a little to keep the water warm. If the water starts to get hotter you open the valve some more. If the water starts to get cold you start to close the cold water valve.

The thermostat will vary how much cooled water it allows into the engine from the lower radiator hose to keep the engine at the proper temperature. In cold air with no load on the engine the thermostat will not need much flow to keep the engine at operating temperature. In hot weather with a heavy load on the engine (racing, high speed) the thermostat will have to flow allot to keep the engine at temperature.

I hope this helps.

 

this makes since except like i stated earlier if i drive the car normally (under 5000 rpms) the car is perfectly fine. if i drive more aggressive (into vtec and up to about 8500rpms several times) the car will spike in temp. sometimes after this i can park the car for a couple hours allowing it to cool off completely and go drive it again and it will be fine. if it does it again i can go home, jack the front WAY up and bleed air from the system (usually quite a bit) and it will be fine again until i drive aggressive. originally we thought the air was coming from a bad HG, but since it will not fail a lithium test for hydrocarbons this has been ruled out. these tests are very sensitive, s i dont believe that its just a bad test. still i havent come up with a full theory of where i am getting the air into the system.

this is my theory at this point. the only thing i can come up with is that the rad. is over cooling and not allowing the t-stat to open fully, this is also why i loose heat when i get my spike in temp, this is causing the system to get too hot and causing the water to flash to steam causing an air pocket.

now that we are showing all these cases with the same radiator with the same issues and side effect i can only believe we have something wrong with this radiator. even a full time attack s2k from GT Motoring has had an issue with it.

 

Your fans are going to run less because the radiator is more efficient, if the engine overheats and the upper hose is hot the thermostat is working. Rebleed the system and road test, you more than likely have air in the system.

 

i have bleed the system for air now for about 2 months is its got air in it still then honda REALLY screwed up on the design of this car. i know that after i bleed it i have all the air out. its a little more than just an air pocket moving around. i am getting air into the system from somewhere or the car is producing it. one or the other i am just trying to figure out which.

 

Stevharr and I did a major bleed of the system and he kept on finding more pockets of vapour. I say vapour because I'm not sure it was air. May well have been steam which would happen if the thermostat was closed and the water superheated.

I've done a pressure test and gas test and both came out fine.

 

i forgot to add that as well. the coolant system on my car was on pressure for over 24 hrs and didnt loose anything.

 

s2kVTAK: Seems as though you are having more issues than I am. After bleeding my system I seem to no longer have spiking, and I have all of my cabin heat working steadily. The only thing I could suggest is massaging all of the coolant lines. I did this while I was bleeding my system. Maybe this helped get out a stubborn air pocket?

Judging from the responses in this thread, it seems as though I may not have any problem at all, and I am truly chasing a problem that doesn't exist.

I'll take the car for some longer drives, and push her a bit more to see if she spikes or if I lose my heat. That will have to be once the snow melts though.

I must say thanks to everyone for all this great information. There is a lot of good info in this thread.

 

S2kVTAK, You might have a bad radiator cap. The cap is designed to allow pressure to build in the system. Coolant under pressure has a higher boiling point than coolant without pressure. If the cap does not hold enough pressure, the coolant could boil and cause air in the system. The water pump can not pump air so you will quickly gain water temperature and loose flow to your heater.

The thermostat is controled from the coolant on the hot, engine side of the thermostat housing so it does not matter how cold the coolant is from the radiator. A thermostat that will not open fully could be the problem. Under a low load the engine is not going to need a lot of coolant flow to stay at operating temperature. A higher load is going to need more flow and if your thermostat is not opening enough then it could overheat.

 

Question:

If there is air trapped in the system, couldn't the ECT Sensor give a false reading? Is it possible that your block could actually be overheating while your temp gauge is giving you an inaccurate temp?