My 03 Duratec overheats only once in a while. It can be a 70 degree day and it will overheat just once in 50 mles or so, very random. Then I can go for a few hundred miles with no problem, then it will do it again, very random. Someone said it may be the cat converter? I replaced the t-stat already, had 2 different mechanics lokk everythng else over. I even had the radiator back flushed. They and I are stumped.

anyone may contact me via email dennis@horgansales.com

 

Any CEL when this occurs? A "HANGING CLOSED" EGR valve can cause overheating by not allowing exhaust gases to "LEAK" into the intake to cool the combustion chamber. The amount of exhaust gas leaked into the intake manifold is only about 6 to 10% of the total, but it's enough to dilute the air/fuel mixture just enough to have a "cooling effect" on combustion temperatures. This keeps combustion temperatures below 2800 degrees F.

 

What is the CEL? What about the cat converter if it's somewhat clogged, remember this thing has 250K miles and it's all original.

I'm just a tourist.

 

OK, a CEL is the Check Engine Light. You never said that the vehicle has 250K miles on it. Normally a clogged or patially clogged converter will make the engine run like crap as it wouldn't be able to get a good clean Air/Fuel charge into the cylinders. Also a clogged/partially cligged converter will normally pop the silicone line off going to the DPFE sensor as an exhaust escape route. You can do a vacuum test to check for a clogged/partially clogged converter.

 

There is no CEL that comes on. When I did a test run today I was able to force an overheat by pounding it a little on the highway with the AC on and after about 10 minutes I stopped, shut off the car, there was a distinct bubbling sound coming from the drivers side of the engine compartment and the about 1 minute later the anti freeze was starting to come out the brand new filler cap on the expantion tank, the fluid was not foamy. Sound more now like the cooling fans or t-stat for the fans? Just ran another test, started the car which was somewhat still warm, turned on the AC and the 2 fans came on right away, shut off the AC and the fans shut off about a minute later.

By the way, Thank you for your help on this. If anyone needs help on security electronics, cameras, fire alarms etc. see me.

 

I'm still overheating once in a while.....anymore thoughts?

 

You could also have a head gasket going on you. This guess is based on the bubbling sound you're describing. This will cause an over heating issue that may come and go untill the gasket finally blows out. How does the engine run? Does it still pull strong? A partially clogged/plugged CAT will cause performance to go south. Your local Ford dealership should have a test kit to check for exhaust in the coolant. This will either confirm or eliminate a head gasket issue.

 

The engine pulls strong even when I get on it. Sounds more like the head gasket partial failure, I thought a bad head gasket would fail period, not come and go. I'll check with the ford guy for a test kit, do you know the part or part number?

 

The test kit is an actual tool that the Dealership should own and have on hand. These were used during the 3.8L Essex head gasket fiasco to test for failing/failed head gaskets. The tester gets connected to the radiator in place of the cap. In your case, the overflow tank. Then the engine is run while you check for the presense of exhaust in the coolant. You can also get a test kit from NAPA. Their part number is 700-1006.

http://www.napaonline.com/NOLPPSE/(S...006_0244767691

 

If my gasket was failing would'nt there be some coolant in the oil? So far there is no sign of contamination.