Hi all, I've got a 1999 3.0 that is losing coolant. I replaced my thermostat in May to fix a coolant overflow issue, and all went well until last week when I noticed fluctuations on the temperature gauge. I pulled in to the nearest gas station and noticed that the coolant level in the overflow tank was higher than it normally was when the engine was hot so I popped the rad cap and topped of the radiator with a few quarts of coolant that I carry around and went home. The next day I got up and bled the radiator, everything went fine and I figured all was well. I drove 150 miles back to my college with no issues. The next day I got up and drove a mile or so to the store and noticed the temp was off-scale cold and sure enough there was absolutely no fluid in the radiator. Once again I added water and went home to investigate. There is no mixing in the oil or trans fluid, also no water in the exhaust or strange smells in the coolant or exhaust. It may be worth noting that the radiator hoses aren't collapsed, and I can't see any leaks around the radiator or thermostat housing.

My first guess was that maybe coolant was being forced out through the gasket in the thermostat housing, but that doesn't seem to be the case. Any of you guys got any suggestions?

 

Welcome to the forum

Rent a cooling system pressure tester, about $10-$15
Its a radiator cap with a hand pump and pressure gauge
Install the cap on COLD engine with radiator topped up
Pump it up to 20psi pressure, system normally runs at 16psi after warm up
Wait and watch
Pressure will start to drop if there is a leak, and you should see coolant dripping down somewhere


When engine is warmed up leaking coolant will evaporate pretty fast, so leaks on to the ground are not seen


It is possible you have a head gasket leak or cracked head
With pressure gauge hooked up and pumped up to 20psi
Disable spark by unplugged the 4 wire connector on coil pack
Have some one crank over the engine while you watch pressure gauge
If gauge starts to go up and down you do have a head gasket leak or cracked head, bummer
You could pull one spark plug at a time and crank engine
When pressure gauge stops bouncing last spark plug removed was from the leaking cylinder
Not that it matters, both heads need to be removed, tested and then new head gaskets installed

 

Well I did the pressure test today and there wasn't any change in pressure after I let it sit or when I cranked it with the coil pack disabled. I'm thinking I'll take a look at the spark plugs tomorrow anyway and go from there