Originally Posted by Moonshinestang
New member! My 1996 mustang is overheating majorly. Unless I have defrost or mix on my temp. Gauge goes all the way to hot. I need help on what this could be?
First a couple questions. Have you noticed any coolant leaking? Any sweet smelling smoke (coolant burning)?
How many miles on the motor?
A thermostat failure will not cause the motor to overheat. Thermostats are designed so that when they break, they stay stuck open. The car will usually run hotter when this happens yes but not overheat. I suspect you may need to replace the water pump. This is easy to do and usually can take a day if you're up to the task. The pump can still need replacing even if it hasn't failed completely--the problem lies with the pumps ability to move enough fluid fast enough so the coolant does it's job and absorbs the heat and gets out of the hot motor. If you have a pump that's on the verge of failing or failed completely, you're not moving the coolant, thus causing the motor to overheat.
The other issue could be a blocked radiator. Check to see that the fins are not clogged with debris. Also make sure then didn't get damaged or bent. When I say damaged or bent--I mean the majority if the rad.
If you have no leaks and you're not burning coolant and/or the system is full of fluid and no visible damage to the rad, then the only thing I can think of is the water pump.
Go to a decent shop and have them do a system pressure test to make sure you have no leaks.
If it's the pump, have it replaced with an factory pump or get a performance pump--Edelbrock has a good one for less than $200. Make sure you have the thermostat replaced as well and get the system completely flushed out and replaced with new coolant.
Stop leak should only be used short term not as a permanent fix and it should only be used if you actually detect a leak. I believe your mechanic friend must have meant for you to use a conditioner that helps preserve the system and prevent rust.
Hope this helps. Let us know what you find out.