Hello,
I have 97 SOHC, 4.6 GT. In September 04, I had the new type of intake manifold (w/ metal base version) installed because it was cracked and leaking into the spark plug areas. It has been running fine, until just recently. Anti-freeze is going somewhere? I filled up one day, drive it about 40-50 miles, and the next morning, the reservior is empty!?! No sign of smoke, nothing on the driveway? And the funny thing is that it appears to be intermittent(sometimes it runs fine, and then I check it one morning and the tank is empty). I am currently attempting to run the engine without a thermostat. Maybe the thermostat was restricting the coolant, and it was evaporating out of the reservior cap while I am driving. Maybe I need a new reservior cap? Any ideas? Is it wise to run without a thermostat? I have tried the no thermostat thing during the summer months before on some of my other cars, and it seems to work fine. But the mustang always seems to be different. Any help/ideas would be appreciated.
Take care,
Mark

 

whats up? i have a 97 gt 5sp, my original intake is cracked too but i have the same prob, once in a while i have to fill it up,most of the garages i went to told me it was evaporation but i dont know if i believe that. did you notice a nice boost in performance from the new PI intake? i plan on that this month.
sorry i cant be much help, im new to the car game..

 

The evaporation theroy is BS. The system is closed. Loss of coolant means the system is no longer closed. If you don't see a leak around the engine look around the AC drain. A bad heater core would leak out there and also stink in the car. Other than that you might need to have a combustion leak test done.

 

You didn't really clarify if it is a PI or NPI manifold. You can get both with the updated aluminum xover. If it's PI, it may need some RTV to seal it to the NPI ports...but I doubt that's your problem. Don't run the car without a thermostat...the water moves too quickly and really doesn't absorb all the heat from the engine. It may be running hotter than you think or the gauge reads. Most people drill a small hole in the thermostat to help with bleeding the air out of the system.

Han Solo is right...it is a closed system, so it can't just evaporate. You have a leak somewhere. My suggestion is to fill it up, and let the car run until it reaches full operating temperature (I.E. when the fan kicks on) and check for drips on the driveway. It could be a multitude of things, from the radiator, to a hose fitting, heater core, freeze plug, radiator drain plug, or worst case scenario, a blown head gasket. Set a large piece of cardboard undr the car when you're hunting for it if you don't have relativley clean pavement to look for drips. If you cant seem to find anything, get a leak test done.