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Jimm

Jimm 5/16/2014

2003 Ford Ranger XLT 6 Cyl 4.00L

Engine

Cooling system - hidden leak

Have an intermittent cooling system leak. Will drain / lose one quart or more in maybe one week time from the overflow tank. No visible leak path, and the cooling system holds pressure for at least 15 minutes with 16 psi applied with a handheld system tester to the radiator filler neck.
The following components have been replaced; upper and lower radiator hoses (with new clamps), water pump bypass hose (with new clamps), radiator cap, lower thermostat housing (using Motorcraft pn RH144). Also, no visible indication nor weepage of coolant into the engine - no milky condition with the engine oil. Engine compression tested OK in all six cylinders. No white smoke upon startup nor loss of power - indicating a failed cylinder head gasket.

2 Answers


GT500Knights

GT500Knights 5/16/2014

Hmm...have you checked out the heater core? It's not located in the engine compartment....it's usually on the passenger side of the cabin area. Pull apart some ducting and see if you can find anything. Apply the pressure to the system for a longer period. 15 minutes might not be long enough. Also, it is normal for car to loose a very small amount of water from steam evaporation from the overflow tank. But a quart for a week seems a bit excessive. See if there is a fluorescent additive kit you can use. Put it in, drive around for a week, then use the light to trace it.

Oh, check transmission fluid/bell housing area. If one of the freeze plugs happens to develop a leak back there.....

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GT500Knights

Jimm 5/16/2014

Thanks for the suggestions. I've checked the heater core, and heater hoses at both ends - no leaks there. In addition, I've checked the rear of the engine freeze plugs and transmission area - pulled the inspection plate - no leakage, no stains and dry.

There is dye in the cooling system already - no visible signs of leakage - even pressurized at 30 minutes plus at 16 psi.

GT500Knights

GT500Knights 5/16/2014

Hopefully the dye will help out your situation. Oh another thought that comes to mind. If you have transmission and/or oil cooler lines that run to the radiator, it's possible that the coolant can leak into the transmission and oil coolers sitting in the radiator. Also check the exterior of the radiator front and back. I myself had a leak that was hardly detectable that was located right beneath the upper radiator hose connection. Hairline crack, but coolant was dripping from there

I found a thread that might be of some help, check it out. The guy there making a statement regarding the water pump leaking has a good point.

Also check the bottom of the page of the thread for what that guy found as his coolant leak, very interesting:

http://ths.gardenweb.com/.../msg080032143395.html

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