Last fall I bought a '95 3.8 V6 mustang. When I first bought it there was an overheating problem due to a bad thermostat and faulty radiator fan, that worsened into a head gasket problem. After 2 weeks in the shop and a hefty fee, my problem was fixed. Or so I thought...

Within the last month my car has started back up with it's overheating issue. The first time it overheated after the repairs, it oddly purged out quite a bit of my coolant. I'm aware that It is low on actual coolant at this time, I have been using water while attempting to troubleshoot the issue in order to conserve money. I notice that when the car overheats now that the water will boil (natural when there is not enough engine coolant). It usually only does this during the very hot parts of the day, or after prolonged driving. I'd really appreciate anything that could help me resolve this issue before another gasket is blown, or worse damage occurs.

Thanks!

 

Thermostat again. Or maybe even the fan still. My trans-Am would over heat in hot city driving or lots of red lights. When I'd check the fan would be on and I had trouble finding it. turned out the fan was not on as much as it should be. I had a guy straight wire it so when the ignition was on then the fan was on too. It fixed my problem.

 

The thermostat and fan are checking out fine. I started with those again once the problem started back up.

 

Do compression check and coolant jacket checks. Mine revealed a head gasket leak on cyl. 3 into the coolant. It would boil off coolant and inject an air bubble into the coolant system, displacing coolant so it would then convienently overheat.
Here is how I found it - my #3 cylinder did the exact same thing as in this video: http://youtu.be/qIgOg9HSEow

 

Found the problem. Discovered a slight leak in my water pump. I will be replacing it shortly. Thank you guys for the advice! Double checked my thermostat and fan again. When I refilled everything I noticed just a tiny drip coming from my water pump.

 

The thermostat has to have a relief hole drilled into it to operate correctly, also needs to be installed with hole at 12 o'clock high. See here:http://www.miracerros.com/mustang/thermo.htm
Radiator cap and overflow tank cap should have tight seal. When filling or adding coolant, always remove coolant system vent plug. Squeeze lower and upper hoses to get air bubbles out, start cool engine, fill to top of vent plug hole.

 

also im not sure on the mustang but on most cars there are two thermostats, one is for a temp reading to kick on your fan, the other thermostat is actually a valve in your cooling system, and when it gets to a certain temp (like the little red tabs you put in turkeys when you bake them) it pops open allowing the coolant to be cycled and then is closes again.

 

Mustangs only have one thermostat. Sometimes two coolant temperature sending units.
**Fan operation is controlled by the PCM and the Constant Control Relay Module (CCRM), which incorperates the fan relay and the AC relay. The coolant temperature sensor signals the PCM of the engine temperature, and the CCRM turns the fan on at 221 degrees and off at 200 degrees. CCRM turns on the fan when AC MAX is on also.