I took the car out today and noticed it wasn't warming up. After driving 1-2 miles I got a CEL light. I ended up driving about 5 miles and it never got more than one bar on the coolant guage. I got home pulled the code and it was P0128 (two times), which is cooling system malfunction. Heat coming out of the vents was warm, not hot. Radiator was hot, top hose was warm, lower hose was cool. My rad cap temperature guage says the fluid in the rad is about 150 degrees F.

The car just turned 100,000 kilometres (63k miles). I took it to a track lapping event 2 weeks ago and it ran great, I haven't driven it since up until today. No other codes accompanied the P0128. Shop manual says to change thermostat. Is this just a thermostat that is stuck open ?. Sucks because I put in new fluid about 6 months ago. I have a Mishimoto radiator and samco hoses but I've been running those items for one year without issue. Any opinions on this ?, thanks for reading.

 

Sounds like a stuck open thermostat. This would explain the warm heat out of the vents and the coolant not getting to operating temperature.

Better then a stuck closed thermostat!

 

thanks for the reply, I always wondered if the Honda thermostats would be fail safe and remain open, that might be the case. I'll try to get it opened up in the coming days and see how it looks.

 

I got the thermostat housing opened up after removing a half-dozen parts. Thanks to the Mishimoto radiator company I had a nice piece of aluminum weld stuck in the thermostat which was keeping it open. I bought a new thermostatI've got it installed after Honda got done raping me for that damn part at a ridiculous cost. The only good part is that the weld material didn't make it to the water pump or it may have caused some damage perhaps. Mishimoto gives you a magnetic radiator plug with their radiators, too bad everythng is made of aluminum and the magnetic plug won't pick up aluminum weld material. Bunch of idiots, I guess that is what you get when you buy the lowest cost radiator. It worked fine other than this issue, but still pisses me off. Now I have to work on putting the car back together and doing another fill and bleed procedure. Just a pain if nothing else.

 

Wow...

That is unbelieveable....and unacceptable.

Mishimoto rad can now go on my list next to the omni master cylinder, and the axle spacers.

 

Yeah I think so too. I might post up a picture of the thermostat later today if I can snap a picture. When I got the radiator I heard a bit of a rattle inside of it, but I couldn't fish out any particle. I figured it was stuck inside one of the core rows. Looks like the piece made its way out and it got stuck in the thermostat.

 

I put in a new Honda thermostat and the car runs like a top now. I think there is something to be said about the oem engine/rad temps, the car ran like crap with an open thermostat and cooler engine temps, it felt very weak. Now that I'm running a properly functioning oem thermostat the car has more power. People who go all out and put in colder thermostats and fan switches might be doing themselves a dis-service, cooler coolant temps can result in loss of power, it was quite noticeable for me, even when the temps got up to 3 bars.

 

glad you got it figured out