96 Mustang GT cooling fan question

CCM POWER

MEMBER
1996 FORD MUSTANG

Good morning. I have a 96 Mustang Gt with about 70,000 miles on it. Runs great. 2 weeks ago I put a new OEM intake manifold on it to replace the old one that ford has had problems with. Everything is hooked up right and no leaks. My car does have a hypertech power module on the computer so I've always had a hypertech cooler thermostat to go with it. I used to run the 160 degree but put in a new 180 degree thermostat. Now, when my car warms up the cooling fan turns on and stays on all the time and seems like its in "overdrive" mode because its moving at a very high speed. It doesnt shut off until I shut the car off. Now I know that if you run a stock thermostat with that power module that this will happen and thats why they recommend you use a cool thermostat but Im confused as to why this is happening with their 180 thermostat. Should I maybe take power module off and let the computer reset then put it back on? Any help would be appreciated. As I said before I double checked everything and its all hooked up correctly. Thanks guys.

Brian

5 Replies

BUBBA_KOSKI

MECHANIC
129 POSTS

I recommend just going with the degree thermostat, but it might not hurt going with a higher one, now you have a GT which is a 4.65l 305 I believe, with a V8, try checking the radiator fan motor and ground cables leading up to it.

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Thursday, September 28th, 2006 AT 12:06 PM

NOS

MECHANIC
320 POSTS

The coolant sensors are calibrated to run at a certian temp. If there is quit a varance in temp it messes with the fan. The temp sensor is what tells the computer what the temp is, it does it by voltages the computer kicks the cooling fans on threw the relays. Now the rest of this story is the chips adv the timing curv and the colder thermostat makes the temp register cold and the map sensor also reads this voltage and richens the fuel so more power. You can do that with any car just use a colder themostat and let the cars computer do the rest. Best way to see my point is to start the car and pull the wires off the temp sensor the fans should go into bypass mode and come on. The problem ford had with the 4.6 L intake was the alternator would get so hot that it would melt the plastic and blow coolant every where, thermostat houseings would crack causeing plug misfires, the tower at the back corner where the heater hose hooks up breaks the plastic and water goes into the plug hole causeing a misfire. (NOS) 8)

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Thursday, September 28th, 2006 AT 9:26 PM

BUBBA_KOSKI

MECHANIC
129 POSTS

NOS is correct about the temp sensor but it dont mean nothin if themotor dont work, it can tell it all it wants but the fan wont kick on.

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Thursday, September 28th, 2006 AT 10:19 PM

NOS

MECHANIC
320 POSTS

I was under the impression that all that was working cause he said he just changed the intake manifold and now the fan don't work. Did I read something?(NOS) 8)

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Thursday, September 28th, 2006 AT 10:50 PM

CCM POWER

MEMBER
4 POSTS

I went over everything with a fine tooth comb. No fuel leaks or coolant leaks. So that was good. I ended up actually taking the Hypertech power module off the computer and leaving the 180 thermostat on the engine. Car runs great now. The fan only kicks in when it needs to(which isnt very often) and when it does run it runs normal and not at super high speeds. As it turns out my car feels just as strong now as it did with that other computer in it so Im pretty happy with the end result here. Just a tip for anyone out there who does happen to have a hypertech power module for their 96-98 model mustang GT. The 160 thermostat will work fine but the 180 thermostat will run the fan all the time. I even called Hypertech about this and the guy on the phone seemed pretty ignorant about this claiming that their "low temp" thermostats shouldnt run the fan all the time. I have news for them. When you put on a 180 degree unit it will. Like I said though, car still seems very strong and runs cooler now without the fan constantly churning away. :D