Bubbling in Overflow Reservore Related to Code P0118?

[mike1611]

Hi Everyone,
My Neon that I just bought is giving me a P0118 Code. I have done a little research and found that it has to do with the ECT sensor. Would this explain why the water in my overflow reservor bubbles like its overheating so easily?
My mechanic and I are going to replace the Thermostat tomorrow, but based on what I've found on the internet, I am assuming that it will not fix the problem. I would like abyone's feedback that knows anything about this problem. Thanks.

[Hatchtastic]

Bubbling in an overflow tank has several causes: faulty radiator cap, stuck closed thermostat, faulty water pump, air pockets in the system (turn your heater on when bleeding it), blown head gasket.

I don't think that your P0118 would have anything to do with this, since it is an electrical circuit fault, and air bubbling in your overflow is a mechanical cooling system problem. The PCM uses the ECT sensor to determine fuel trims, closed loop, etc. If there is a problem with the ECT sensor, it may be staying in open loop, and you will notice a drop in fuel economy.

I fixed a car today that had a stuck closed thermostat, incidentally. Boiled a bunch of coolant out within minutes!

[mike1611]

just switched out the thermostat and apperently it was stuck open, but it did not fix the problem. My mechanic says that he thinks it is the heater core because I have a leak right behind the overflow reservor, however, I noticed after I saw him while driving the car that it only leaks when the fan turns on. Is that normal, if not, what does it mean?

[Phantom]

I would pull the radiator cap off (when cold) and see what it looks like if it is all gummed up get a new one asap and have the system flushed and the lines that are leaking replaced since they are probable getting old.

What kind of temps would the car run at before the t-stat was replaced? I assume 120-130F. What temps is it showing now that the t-stat was replaced?

[gone-ot]

...uh, "bubbles" in the resevoir is commonly a symptom of a blown head gasket!

[mike1611]

I don't know what temperature it is suppose to be running and as the temperature gauge is broke (At least thats what I'm assuming since it never goes above 2/3rds).

I took the car back to my mechanic friend and he said the water that I was losing might be due to a crack on the reservor or busted hose around the heater core, so I went to autozone to buy a new one. The man I was talking to suggested that I had air in the line and to just put some more antifreeze n water and drive it around for another day before I start buying more parts. So far it has not overheated or even lost water. Based on that it must be that I do have a bad heater core (I forget to mention earlier that my buddy bypassed it when I 1st saw him when I replaced the thermostat as a temperary fix until I get paid next week) and it was bubbling still because of the air in the lines.

[gone-ot]

...does that have one of those cooling systems with an "air/bubble" vent value somewhere on the engine? What your mechanic friend described sounds like it does.

...the vent value is typically located at the "highest" spot in the engine/radiator location with todays' "low" engine designs. The vent value is used to "expel" any air bubbles that remain in the cooling system after a coolant cleaning, exchange or flush. Today's coolant systems don't tolerate "air bubbles" very well (localized 'hot spots').