Hey everyone. I own a nice 94 3.8 Mustang and I just started (for the past 3 weekes)having poor coolant circulation. My temp. needle keepsmoving back and forward (to the hot then back to the cold). When it's high it's not in the red zone, but stays on the letter L of the word normaL. Okay, first off, I notice I had a leak coming from the timing chain cover. So, a guy that I know told me that was the problem. So, I spent over $500.00 in labor and $120.00 for parts to replace the water pump and timing chain. Well, after everything was done I started driving the car to my house. Everything was fine...I was getting nice warm heat. Well, later that day when I started driving the car again, the needle started moving back and forward again. The guy that fix my car told me I might have a bad head gasket, but I did like 4 to 5 pressure test, and check my oil (for milkshake like color) and everything was ok. Now, I just happen to notice that my high water hose is nice and hot, but my low water hose was not. So, I went and did 3 flush (2 that I did and one from Tire Plus) and change out the thermostat (replace with a Ford brand). Now when I flush the system...everything is somewhat fine. I get nice warm heat, but after the car sits for a while and I drive it again...the needle keeps moving for hot to cold, cold to hot. Does anyone have a clue what is going on here? I'm clueless and tired of spending money on something this crazy.THANKS!

 

i had the same problem with my car...im swapping motors right now but mine was the head gasket

 

It is difficult to determine what the FLOW
of a cooling system is. As the heater core hose
is really a bypass of the main cooling system
It should have little effect on the cooling.
Since you have replaced all the main parts
of the cooling system, and even some not
related I would suspect the obvious.
The temperature gauge is supposed to
have a heavy damper on it to smooth out
major fluctuations. It probably is your
temperature gauge.

 

Sounds like your baby needs a burp... Probably have an air buble in your system, very possible with the work you've done... Take the radiator cap off and let it run for a little bit, the air will work it's way out...

 

I'd jack the front of the car up so that the rad cap is higher than anyother point in the coolant system and open the cap, let the car warm to temp and squeze the crap out of those hoses til she birps out that air. Or else the temp sensor may be shot... that'd be my next point of attack.