i dont think its a circulation problem just the fact thats its cooling it too much we will see. and i havent tried a new cap, the mishimoto rad. has a larger mouth than the OEM so i would have to order the blitz one off the net.

 

Well GUESS WHAT!?!! My brand new Mishimoto Rad Cap is SHOT!

I started my car today, heater cranked, let it sit for 30 minutes and only revved it a few times. My cabin heat started working as it should, the car reached operating temperature as it should. The top hose was HOT, the bottom of the rad was still cold. 20 minutes or so into it the bottom of the rad started to warm up, and then sure enough, the bottom of the hose started getting warm. 30 minutes passed and my rad cap started leaking... I'm assuming once the cooling system reached pressure, my defective rad cap couldn't keep it in any longer.

The fans never circulated, but my running temp was perfect, and I'm only assuming since the bottom of the rad and the bottom rad hose were starting to get warm, that it would have been just a matter of time. I'm also assuming that since the other times that I drove it, the weather was so cold that it was over-cooling as mentioned and the fluid in the bottom of the rad was simply cold enough that the hose wouldn't show any signs of warmth, hence why the fans never needed to cycle.

I never thought I would be happy to have a bad rad cap .

~Cam

 

s2kVTAK: Don't rule out the cap just yet. For all I know, it could have been causing my spiking issues too, letting in air!

Many guys run the Mishimoto rad with zero problems. Don't give up on it yet - although you did just order a new OEM rad...

 

I just checked my system with a hand held infrared thermometer and this is what I found. Upper hose 178F, lower hose 120F. This was after a 20 minute drive on the highway with a few VTEC runs up to speed from a stop in 58F weather. The roads are dry here so I was able load the car up enough to raise coolant flow thus the warm hose. In colder weather the radiators would transfer more heat and under a lower load the coolant flow would be slow enough to allow more heat transfer. You should be seeing less than 120F in your conditions.

 

I should look into getting one of these thermometers... how much do they go for? (average price)

 

ss04- it sounds like your system is working like it should. When I had the car sitting the lower radiator hose started to heat up slowly since there was no air flow through the radiator.

A leaking cap would give you problems and could let in air the system. A normal cap will allow the pressure in the system to build to about 15psi. Once it reaches 15psi the cap will relieve some of the coolant into the overflow bottle to maintain the system at 15psi. When the system cools down the pressure will drop and a vacuum poppet valve in the cap will pull coolant from the overflow bottle. If your cap is leaking then it will pull in air instead.

 

I got mine a few years ago for about $100. It looks like you can get them for about $30 now.

http://www.harborfreight.com/cpi/ctaf/disp...temnumber=96451

 

i found my mishi cap bad too now i just have a generic one. thats why i havent bought another yet.

 

hmm interesting i see what you mean

 

UPDATE:

So I just received my replacement rad cap in the mail from Mishimoto (great customer service BTW, didn't even hesitate to send me a new one). My cooling system is now functioning perfectly. I idled the engine for 25 minutes tonight before the fans were triggered. The ambient temperature was low enough to cool the coolant significantly so it took a while for the fans to cycle. The lower rad hose did not warm up until 25-30 minutes as well (makes sense).

After letting the fans cycle and engine idle for 40 minutes (with the odd rev here and there), there were no spikes or leaks. Coolant reservoir increased so I knew rad cap was working as designed.Then I took it for a drive. 20 minutes, of hard driving, multiple vtec runs and a lot of heavy throttle, holding it constant at high rpm's etc. Running temp remained steady, no spikes.

Pulled into the driveway, and felt the upper and lower rad hoses. Lower one was COLD, upper was HOT. My only conclusion here is that air cooling and the rad efficiency is fantastic. I then let it sit in the driveway again for another 10 minutes, and the lower hose slowly started to warm up and the fans would cycle.

My conclusion is that this is 100% normal (as others have mentioned). I actually feel kind of silly for posting this in the first place now. I hope this thread serves as quality information for other S owners