ECT sensor, coolant leak, or... something else.
06-23-2013, 04:32 PM
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ECT sensor, coolant leak, or... something else.
Haven't made any posts for quite a while. Between the OBD scanner, the Haynes manual, and pre-existing posts on the forum, I've been able to solve all my truck's problems thus far. But now I've encountered some confusion.
First off as I was driving one day the engine appeared to be overheating. Just before the gauge hit the red line, it dropped back into the normal range. When I got home I checked the coolant level and it was low, so I added a gallon.
A few days later I got a check engine light and popped a code P0125. I checked the coolant again and it was still pretty low. I added another gallon and cleared the code.
A day or so later, the light came back on - same code. So having ruled out a low coolant level as the culprit, I proceed to other possible causes. I'm confident that the thermostat is in working order since I replaced it several months ago. According to the ODB website, the other possible cause would be the ECT sensor.
The engine temp gauge is showing that I'm running cool all the time. It's not showing that I'm dead cold as if I had just started the engine, so the sensor is reading something. But obviously, this reading is inaccurate.
Also, being that I put in a full two gallons of coolant, I began to suspect a leak. I checked all the hoses for damage and found none. I didn't find any puddles on the ground or any drips from the rear side underneath the engine. However, there is some coolant pooled up in the "valley" area of the engine block mostly on the passenger side and it's wet with coolant on the underside of the thermostat housing. It seems that there is a leak somewhere, I just haven't been able to locate it precisely. But I don't believe the coolant level is low enough yet to pop the code again.
So - before I go removing the alternator or the intake manifold to access the ECT sensor, which may not even be the problem, does anyone have any insight or suggestions as to ways to proceed or other areas to investigate?
First off as I was driving one day the engine appeared to be overheating. Just before the gauge hit the red line, it dropped back into the normal range. When I got home I checked the coolant level and it was low, so I added a gallon.
A few days later I got a check engine light and popped a code P0125. I checked the coolant again and it was still pretty low. I added another gallon and cleared the code.
A day or so later, the light came back on - same code. So having ruled out a low coolant level as the culprit, I proceed to other possible causes. I'm confident that the thermostat is in working order since I replaced it several months ago. According to the ODB website, the other possible cause would be the ECT sensor.
The engine temp gauge is showing that I'm running cool all the time. It's not showing that I'm dead cold as if I had just started the engine, so the sensor is reading something. But obviously, this reading is inaccurate.
Also, being that I put in a full two gallons of coolant, I began to suspect a leak. I checked all the hoses for damage and found none. I didn't find any puddles on the ground or any drips from the rear side underneath the engine. However, there is some coolant pooled up in the "valley" area of the engine block mostly on the passenger side and it's wet with coolant on the underside of the thermostat housing. It seems that there is a leak somewhere, I just haven't been able to locate it precisely. But I don't believe the coolant level is low enough yet to pop the code again.
So - before I go removing the alternator or the intake manifold to access the ECT sensor, which may not even be the problem, does anyone have any insight or suggestions as to ways to proceed or other areas to investigate?
06-23-2013, 05:51 PM
#2
Ford Owner
I would say that you should try first to find the leak and fix it. If you were low on coolant, it would cause your PCM to throw the P0125 code and since you put in a lot of coolant, you were in fact low. Fix the leak and see if you are good to go after that.
Regarding the leak, since it is at the passanger side, it could be the heater hoses where the quick disconnect fittings fit into the heater core at the firewall. New hoses are low cost and easy to change.
As a point of information, you have a ECT sensor and a engine temperature indicator that is hooked up to your temperature indicator. the sensor tells the PCM the temp of the coolant but does not register the temperature on your temp gauge.
Regarding the leak, since it is at the passanger side, it could be the heater hoses where the quick disconnect fittings fit into the heater core at the firewall. New hoses are low cost and easy to change.
As a point of information, you have a ECT sensor and a engine temperature indicator that is hooked up to your temperature indicator. the sensor tells the PCM the temp of the coolant but does not register the temperature on your temp gauge.
Last edited by Frank_Ford; 06-23-2013 at 05:54 PM.
07-06-2013, 03:35 PM
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Thanks, Frank.
I still haven't done anything as of yet, other than poke around under the hood and scratch my head.
As for the leak it does appear that coolant is coming from the thermostat housing. If I'm not mistaken I replaced the thermostat recently enough that it should be under warranty, so it might be worth a shot to replace it as it's a lot easier to access than the ECT sensor.
I've been doing some more research and it sounds like the thermostat being stuck open could also throw up the P0125 code. Do you think a leaky housing could contribute to this problem, or would a bad thermostat be the only explanation? And would the thermostat being stuck open cause the extremely slow warm up (or what the PCM seems to think is a slow warm up)?
Also, I've been getting some hard starts occasionally which, from what I've read, could also be a symptom of incorrect temp. readings. Does it sound like I'm on the right track to you, Frank, or anyone else?
I still haven't done anything as of yet, other than poke around under the hood and scratch my head.
As for the leak it does appear that coolant is coming from the thermostat housing. If I'm not mistaken I replaced the thermostat recently enough that it should be under warranty, so it might be worth a shot to replace it as it's a lot easier to access than the ECT sensor.
I've been doing some more research and it sounds like the thermostat being stuck open could also throw up the P0125 code. Do you think a leaky housing could contribute to this problem, or would a bad thermostat be the only explanation? And would the thermostat being stuck open cause the extremely slow warm up (or what the PCM seems to think is a slow warm up)?
Also, I've been getting some hard starts occasionally which, from what I've read, could also be a symptom of incorrect temp. readings. Does it sound like I'm on the right track to you, Frank, or anyone else?
