High Temperature

[omar77]

Hi All,

I'v 02 Explorer XLT V6 4.0L, and I had just conclude a long distance travel (4500 miles trip), during I'd faced many troubles regarding a high temp alarm, when I stopped to check I found the coolant is boiling, then I wait for the engine to cool down, then increase the coolant to the indicated range, then it goes ok, it seems the coolant level sometimes goes low and makes this problem, but sometimes even in a high temp weather and when driving for a long distance also when I check the coolant level it seems ok and there is no high temp alarm. Also I noticed that after starting up the car from a cold state (like morning) and during the first few miles temp goes high for a while then calm to normal (middle), although Ford dealer had checked my truck before saying there is no leak using pressure test, but during my experience I had to add the coolant every 5-7 days, also I had changed the thermostat but nothing had changed yet, something else I noticed is that when I stop on traffic signals and during waiting when I shift the gear from Drive to Nutral the rpm is going more than usual (i.e. more than 1,000 rpm), usually it is below 1,000 rpm.

Any one could advice me, cause my ford dealer making no good help here?

Thanks in advance.

OK

 

[mawrazen]

Bad heads or head gasket?

 

[gijoecam]

It sounds like a simple overheat, so we start with the basics.

First, check the thermostat. Personally, I'd replace it myself. I don't trust shops to change something so simple without screwing it up.

Second, check the coolant mixture. I hope that when you added coolant, you added a 50/50 mixture of water and antifreeze. If it's too thick on the coolant side, it can cause overheating.

Third, the increased idle when hot is normal. The ECU changes the idle speed and shift strategy to aid in cooling the engine.

4th thing on my list would be the radiator cap. The place that pressure tested the system: Did they pressure test the cap as well? A cap that fails to hold pressure can cause it to boil over.

Finally, the coolant loss could be due to the overheating itself. The mixture boils, the water boils off as steam, and the level drops. The more it boils over, the higher the concentration of coolant in the system, and the less cooling capacity it has, the more it overheats, etc, etc, etc. It's a vicious cycle.

 

[omar77]

Thanks Gijoecam,

This looks logical & helpful, I'll check all of these and may get back to you, thanks again.

OMAR

It sounds like a simple overheat, so we start with the basics.

First, check the thermostat. Personally, I'd replace it myself. I don't trust shops to change something so simple without screwing it up.

Second, check the coolant mixture. I hope that when you added coolant, you added a 50/50 mixture of water and antifreeze. If it's too thick on the coolant side, it can cause overheating.

Third, the increased idle when hot is normal. The ECU changes the idle speed and shift strategy to aid in cooling the engine.

4th thing on my list would be the radiator cap. The place that pressure tested the system: Did they pressure test the cap as well? A cap that fails to hold pressure can cause it to boil over.

Finally, the coolant loss could be due to the overheating itself. The mixture boils, the water boils off as steam, and the level drops. The more it boils over, the higher the concentration of coolant in the system, and the less cooling capacity it has, the more it overheats, etc, etc, etc. It's a vicious cycle.