V6 (1994-2004) MustangsTechnical discussions on the 3.8L and 3.9L V6 torque monsters Sponsored by Optima Batteries
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Quick history: Car started to overheat during traffic conditions and when I would turn the AC on the car would cool down. Since I have warranty on a few cooling items I changed out the radiator and waterpump. In addition I replaced the thermostat with a high performance stat, added new hoses, replaced both coolant and temp sending switches, and changed the original radiator fan. Flushed out the system and added new 50/50 coolant while properly bleeding out the system of air. However the car's temp continues to move just passed the A. I did noticed that the fan takes longer to turn on at times, and shuts off a little to early. I need some help here, I have run out of ideas.
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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. but im not sure on mustangs.
Your words are key here; "when I would turn the AC on the car would cool down". that's because the fan is controlled by the AC relay as well as the thermal switch that senses the coolant temperature. You turn on the AC, you're turning on the fan. This sounds like just the thermal switch is crusty or corroded or crappy wire connection causing it to not come on soon enough. I would either replace it with another FMCo stock one OR you could go a little cooler with an aftermarket one (maybe 10* F cooler) & get a head start on it, especially for all the stop & go you get in Cali
Thanks GT Katie, I decided to by pass the original fan wiring with a thermostatic adjustment switch and set the fan to turn on at 160. While in park the temperature has stabilized during normal idle or while I rev up the engine, again while in park. However, when I take it out to the road to test drive the car, it drives well for a little while (5min), then I notice a slight loss of power and the needle begins to move to the hot side. I parked the car still keeping it in drive and it begins to cool down. So the car is heating up only during acceleration while driving. Is it possible that my catalytic converter is clogging up and the back pressure it creates is overheating the car?
Good idea on the electrical thermal switch for the fan. I put one of those on my truck & they are infinitely adjustable for summer, winter, towing etc.
Yes it could be a clogged cat. They are fairly easy to check & since you're now indicating that you're feeling a loss of power when the temp guage rises, that could be it. Have a helper sit in the car while you check the flow at the exhaust pipe. There should be a dicernable difference in pressure between idle & say 3,000, 4,000 RPM. If it's plugged you may also hear some odd noises like whistling or wheezing at the tail pipe as the exhaust is trying to force it's way through the passages that are still open in the cat.
If it's not a plugged cat, & since you now have the fan problem sorted out, then one other thing is a possible leak in the combustion chamber (leaking head gasket or cracked head)
Have you ever looked for bubbles in the radiator when it's running? This would be a good indication of a C.C. leak. When you have a leak here the pressure & heat from the C.C. gets forced into the coolant passages in the head & block & will raise the temp of the coolant. If the leak is big it will also overheat at idle. A smaller leak that's just getting started would give symptoms like you're having with the overheating only happening at higher RPMs. You can also have your cooling system pressure checked at a shop (requires a special guage). Just make sure that they check it when it's hot & at the upper RPMs where you're experiencing the overheat problem. Many times a mech will do a static test with the engine shut off & that will only find large leaks at 15-18 P.S.I. You may be able to buy a press guage for the same $$ or less than what the shop will charge you for the price of the test & then you would have it in your tool box for the next time :-)
They come with adapters so will work on a lot of different cars.
edit: Does this "loss of power" feel like a miss, or is it a smooth loss of power like someone is putting on the brakes?
Is there a chance the accessory belt is loose or a weak tensioner. Not knowing the 95 well enough if it's a distributor engine your timing advance springs could be weak allowing for very advanced timing. Option 2 is low fuel pressure beyond what injector timing can handle causing a lean condition producing higher combustion chamber temps. Last thought is a collapsing rad house limiting coolant flow.
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