My heater on my 2k2 SE has been performing poorly this winter, taking long to warm up and to some extent just being erratic. My coolant levels turned out to be low so I topped off the reservoir. This caused some swishing noises as fluid moved through the system. I figured this was caused by air bubbles and I burped the system, all appeared well.

Soon thereafter I noticed coolant spewing out over the engine a few times when transitioning from freeway driving to city stop/go traffic. This seems to cause more air bubbles and coolant loss, I assume this is what happened before I refilled it the first time.

The pattern I noticed is that the engine temp and heater don't warm up on freeway driving, then when I take an exit and hit city traffic the engine temp jumps up to the midpoint and the heater starts to get warm. At this point I've had coolant spew out a few times.

On closer inspection it looks like coolant might be leaking out of the top seams of the radiator. I don't see any other obvious leaks, hoses, radiator cap and reservoir look good. I also inspected the fans, both look good and appear to be working when I run the AC. I am getting engine codes P0328 (Knock Sensor 1 Circuit High Input) and P0128 (Coolant Temperature Below Thermostat Regulating Temperature). I assume the P0128 has to do either with the air bubbles in the cooling system or possibly a bad thermostat? This code goes away if I burp the system and refill the coolant. As for the knock sensor, I think this indicates a rough idle, possibly stemming from poor maintenance (100k miles w/ little to no engine work other than oil changes).

My best guess is to replace the radiator and thermostat, any ideas?

 

i'm having the same problem as you, minus the knock sensor thing.. i just bought a new radiator on Ebay and it only cost me 50 bucks shipped and hoping to install it sometimes next week.. i'm guessing the recent cold temperature plus the high miles on the car caused this problem, i'm sitting at around 110k as well.. hopefully this will fix it

 

While replacing the radiator. Flush the heater core out really good.

 

That pattern is normal. When u exit the highway and get into the city, engine revs, as well as the water pump speeds, slow down. Your cooling system will not be as effective at evacuating heat at slower city speeds, so the car gets warmer. The fans should kick in, though. Do they? But then again, they may not be kikcing in because your cooling system is losing pressure, giving the temp sensor bogus readings. So, fix the leak first.

Do you see anything on the seams? If so, replace the radiator. It's normal for the plastic seams to give out first when the radiator is done.

The fans may run when you put on the AC but they may not run when overheating. Your car is losing coolant. Fix that first.

Because you are losing coolant, the car is not maintaining pressure in the cooling system. That's why you got the code. I would concentrate on replacing the radiator and radiator cap (OEM cap) and find the leak before looking at the thermostat.

Nope. If everything else in your car is fine, the only thing you will notice with the knock sensor is the car not feeling as powerful as it normally is. The ECU, noticing that the knock sensor is not functioning properly, uses more modest engine settings, less aggressive engine timing, air/fuel ratio etc. You can drive the car forever with a bad knock sensor, no engine damage will occur, but the car will be less powerful.

....and OEM radiator cap. Good luck.

 

I believed you need to replace, the radiator. I just replaced mine with Koyo Radiator because the oem is expensive. The Knock sensor and Coolant Radiator Sensor must need to be replaced with oem sensors.

 

i have these exact codes after driving in a storm yesterday

P0128 Thermostat Function
P0328 Knock Sensor Circuit High Input


I replaced the radiator with a koyo February 2015 - I havent checked the coolant levels since doing that.

Any input guys? Are these two codes associated ? I noticed the moment it came on driving in a very strong rain storm, yesterday just did a 60k tune up w belts and sparks.

I am 1000 miles over an oil change interval, but oil level is fine, checked this am.