So out and about right now and getting off the freeway to get to where we need to be the water temp gauge spiked to almost to the max, engine went into limited power/limp mode and check engine light came on. The normal oil gauge was where it's normally at so a bit confused there. I added a quarter of oil yesterday and that topped it off fine. Coolant level is fine as well. So I popped the hood and double checked the oil and Coolant and both are fine. I had shut it off, just in case it was overheating, turned the key over to accessory and the temp gauge was still pegged to almost max, check engine light was on still and the red High temp/low oil light was still on. After a few minutes (about 3) it was fine, just a CEL on. Well I checked other forums for similar problems, no one really gave a definitive answer. One guy had it happen a week after he had his transmission rebuilt, and that turned out to be a faulty wire they pulled. Another that was on here, no one gave an answer.

The only major thing I did was I had to pass a line of slow moving vehicles on the road and got kind of hard (3,000-3,500rpm) and passed them doing about 85mph, which in my opinion should not have done anything. I still have that stupid high idle issue from when I changed out the IAC last year when it caused the engine to stall out, but if I start it right up after having it run for a bit, even after it sitting for an hour, it'll revv up to 2500rpm for about 15 seconds, drop down then Rev to 1000 drop to 600 a few times, or if I get on it kind of hard it'll stay at 1500rpm when I'm stopped, then abruptly drop to 550-600rpm.

So right now this 2003 4.6 Mountaineer is a bit of a mystery to me. I will be taking it to an auto store to read the CEL to see what it brings up, but I'm just wondering what usually causes this high temp light and for it to show its overheating...maybe a sensor that's faulty? I never bothered looking at the dash while driving cause I've never had to worry about the water or oil.

 

Codes are 1285 and 1299, both indicate cylinder head over heat temperature. Like I stated before, coolant level is good, while it is lower in the reservoir (about an inch below the middle) it's still cooling sufficiently. So it indicates the senor went bad or wiring shorted out somewhere. Are there places specifically to check for a short or where this sensor is at and how to test it to see if it's still good?

If the engine did overheat, it would have taken a hell of a lot longer to cool down than what it supposedly did, at minimum 1 hour and not 5 or so minutes. While I'm not surprised this happened considering its age, just a bit irritating.

 

You can get a SPIKE in the gauge if the sensor is not covered with coolant, but setting in an air pocket or exhaust gas pocket. .......... first thing I would do is get the coolant UP to the max cold mark on the tank. Monitor it for a few weeks and see if you are loosing coolant or have another problem... the air pocket / gas pocket came from somewhere, need to see where by monitoring.

 

I have filled it several times over the last year my fiance has owned it and I have no clue where the coolant is going. Fare as I can tell there's nothing under the vehicle leaking, hoses are good, and I've pulled the plugs a couple of times and found nothing that would indicate coolant in the cylinders. So I'm missing something for sure.

 

I think I may have a partly plugged heater core, not site if that could cause some of these issues. When it's in the teens, it gets as high as 120-130F with the recycle air on. Any lower and it barely gets above 110F, I'm talking heat from the vents, engine temp is fine. In fact I replaced the thermostat just a few months back. I also tested the new t-state in boiling water to make sure it was working and not faulty.

 

you probably have a small pin hole in a manifold gasket or head gasket. Your burning a very small amount of coolant over a long time. You will not see that on the plugs. You can monitor the level closely and add a little more often to keep the overheating from happening, or you can try a gasket sealer like Bars Leak Copper that mixes with the coolant and tries to plug cracks and holes in gaskets. I have a 2002 Explorer that uses a quart every 6 months... I just monitor and fill when its an inch low.... I had a F150 years ago that used a quart a week... time for BARS LEAK at that point.

 

When I have time, I'm going to have it taken in to have probably a dealer to flush the system and check the pressure. To see what they say. I'm possibly expecting the coolant reservoir cap to be part of the problem, since it is original to the vehicle, unless new Ford caps come with that sticker tag around it?

 

So it happened again today. I was going in front of a person thinking they were not going to get on the freeway on ramp, so I mashed the go pedal to get going. About 45 minutes later while on the freeway, I watched the water temp gauge hit about 260F really fast and it went into limp mode. Got to O'Rileys and same P1285 and 1299 codes. Talked to the guy there for the better part of 45 minutes spit balling what it was. Well it's possible the Head temperature sensor could be faulty, but considering this is the second time this has happened, they are thinking an air pocket in the coolant. So when I get a chance I'm going to pull the lower radiator hose off and drain that, refill it and let all the air bubbles out. If it happens again, I'm getting that sensor out and replacing it. The bugger is on the passenger side near the dang transmission bellhousing, so that'll be fun to pull.

 

Pulling the lower hose off, draining, and refilling, is not likely to get the air out, but rather to create new air pockets. Your best bet is to work the air out that is currently in there.

Pasted below is what the Ford service manual recommends:

1. Fill the radiator through the degas bottle until the coolant level is at the COLD FILL range mark.
2. Install and tighten the pressure relief cap until it clicks twice.
3. Select the maximum heater temperature and blower motor speed settings. Position the control to discharge air from the A/C vents to the instrument panel.
4. CAUTION: If the air discharge remains cool and the engine coolant temperature gauge does not move, the engine coolant level is low in the engine and must be filled. Stop the engine, allow it to cool and fill the cooling system.
   Run the engine until it reaches operating temperature.
5. WARNING: To avoid personal injury, do not unscrew the coolant pressure relief cap while the engine is operating or hot. The cooling system is under pressure; steam and hot liquid can come out forcefully when the cap is loosened slightly. Failure to follow these instructions may result in personal injury.
   Turn off the engine and allow the cooling system to cool. When the pressure has been released, remove the pressure relief cap.
6. Add more coolant mixture to the degas bottle until the coolant level is at the COLD FILL range mark.
7. Install and tighten the pressure relief cap until it clicks twice.
8. Start the engine and allow it to idle. While the engine is idling, feel for hot air from the A/C vents.
   • Hot air should discharge from the A/C vents. The engine coolant temperature gauge should maintain a stabilized reading in the middle of the NORMAL range and the upper radiator hose should feel hot to the touch.
9. Check the engine coolant level in the degas bottle and fill it as necessary.
10. Repeat previous five steps as necessary.

 

Well, having the issue all over again. Been working fine for well over a month, then today while driving around it went to this. However when I just drove around and limped it home, was able to get a thermometer into the reservoir and coolant temp maxed out at 210 or 212F. When it first happened today, I added a full gallon of coolant. Well when I got it home, it was maybe half inch from the bottom of the reservior.

This last time maybe 20 minutes ago, before I drove it around, I filled it back up and had the cap off for a good 15 minutes with the engine running. It was just below the cold line, raised up above the cold line after a bit then dropped to the seam between the two halves. So this is really irritating me, cause it's not happening consiststently. When I got it home, coolant was at the cap and starting to purge out. Would a sensor cause this whole issue? Or what's causing this thing to say it's overheating, cause the coolant to overflow and then drop off to 1/2" from the bottom of the Really? Coolant is going back into the engine somehow. I checked the plugs and it's not burning it. It's possibly leaking coolant a small bit at a gasket that's below where the thermostat sits, did see a small bit sitting near it.

 

Reading over symptoms of a Cylinder Head Temp Sensor, it's pretty much everything I'm dealingwith to a T. Low coolant level and overheating. Long as I can keep the intake manifold in place to take it out I'll be a happy clam. Question is, will I have to add more coolant or will the level return to normal?

 

Replaced the Cylinder Head temperature sensor and same thing still occurring. So there is either an air pocket, or the wiring is shot. Anyone know how much resistance there should be? I'm getting 3.14 ohms with my multimeter running at the 20k setting.

 

So far as I can decides it was not the sensor. Ordered a wiring harness which is all of maybe 8" of wire with 2 connectors and if that isn't the issue then I have no idea what on God's green earth is the issue.

 

Well replaced the wiring from the sensor and that did not fix it. Pulled the t-stat out and put it in boiling water and it remained closed. So at this point I'm at a loss for what to do at this point.

 

I'll know more in a couple hours, but it appears as though part of the issue stems from either air pockets, but low on coolant, or a combination their of. Ran the engine for a little bit yesterday on water and Prestone chemical flush, and never had the over heating issue. So fingers crossed this is what the issue is and nothing overly stupid.

Edit: As of right now after doing a flush and refilled the while engine and radiator, it's running normally. Drive over 15 miles today, which is 3x as many as I could when this issue became more prevalent last weekend. I'll keep this updated for the next week or so, in case something comes up. If something does come up, we are taking it to a shop and let them go over it, kind of tired of working on it at this point.