Low Coolant - No leaks, GOOD head gasket

[hbirring]

Hey Everyone,
I'm posting here because I'm completely puzzled at this one! I have a 2004 ford explorer xlt, v6, 4.0L with 120,000 miles on it. This past summer my car started to overheat (I sit in a lot of stop and go traffic). I had noticed for a while before it started to overheat that my coolant level was getting low so I always just added some and kept on moving. Well, when it started overheating I looked into it further and noticed my upper thermostat housing was cracked and leaking coolant. I replaced the upper and lower thermostat housing as well as the thermostat but, I was still losing coolant. I found a small leak in a hose that feeds the heater core so I replaced the clamp on it and it stopped. I'm still losing coolant. A lot of it! and my car runs warmer than it used to before. Before the temp gauge would get to about half way between the halfway mark and the mark below it. Now It gets exactly to the halfway mark and sometimes a little above it. I have checked for leaks and even did a leak down test to make sure no exhaust gasses were in the coolant system and even had a coolant flush done. Nothing was found by multiple shops. My coolant fan seems to be working properly and my radiator was only replaced a year ago.

I have no clue what could be the cause. Any help is greatly appreciated.

 

[Drewmcg]

Can you put a dye in the coolant and use a black light to see where it may be leaking? Lots of hoses; water pump; heater core . . .

 

[TechGuru]

Overheating in traffic is usually a sign of a bad fan clutch.

 

[Joe in NY]

Check to make sure your pressure cap is good. Ford is known for pressure caps going bad. When this happens the system is no longer under pressure and is allowed to boil at a much lower temp than specified. When this occurs you lose coolant due to the water boiling away.

 

[Turdle]

Could the transmission heat exchanger be leaking coolant into transmission? Is the transmission over full if checked?

 

[Joe in NY]

These do not have transmission coolers integrated into the engine cooling system. They are separate.

 

[TechGuru]

Check to make sure your pressure cap is good. Ford is known for pressure caps going bad. When this happens the system is no longer under pressure and is allowed to boil at a much lower temp than specified. When this occurs you lose coolant due to the water boiling away.

If it's the cap get a proper MOTORCRAFT RS527 not Stant crap. http://www.rockauto.com/en/moreinfo.php?pk=1833080

 

[Hugh Janus]

Just one other thing: I've had problems with Spectra radiators - a common Chinese low-cost replacement radiator. They usually develop a leak at the tank/core seam. Small at first, then eventually a torrent. The radiator cannot be repaired.

 

[Tech By Trade]

Its probably the rad, It will run down the seams and pool on the cross member. It wont drip on the ground until you drive away. Hard to catch. i bet if you crawl underneath and look by the drain valve, or where the drain valve would be on the passenger side, one of them will be damp.