I have a 1990 Mustang GT and it overheats when sitting in traffic, but only when the A/C is on. The car runs cool with the A/C off when moving or in traffic. Even if I'm moving with the A/C on it runs cool, but in traffic it will start to heat up. I have the stock fan with clutch, but some of the shroud is broken off at the bottom and the fan blade tips have been cut a little bit. I was wondering if replacing the fan and the shroud would solve the problem or should I spend the money on an electric fan instead. My 2003 F-150 has a fan clutch and it works perfectly, so I was wondering if a new mustang fan and shroud would work just as good. I'd perfer not to get an electric fan if it isn't necessary.
Overheating with A/C on
- Thread starter twinsnakes23
- Start date
It depends upon where you live (ambient temps) and what mods and state of tune the car is in. It sounds like a fresh fan and clutch could be just enough to get you coolagain, esp if the existing clutch isn't locked up.
Check your motor mounts while you're in there. They are probably the reason the fan hit the bottom of the shroud and cracked the fan. I went with a metal replacement fan blade and like it for hot climates.
Check your motor mounts while you're in there. They are probably the reason the fan hit the bottom of the shroud and cracked the fan. I went with a metal replacement fan blade and like it for hot climates.
Had this exact problem myself last week. The fan clutch is probably getting sloppy on your car, as it was on mine. Get the car up to operating temp sometime and then shut it off and pop the hood. Give the fan a spin by hand. If it spins pretty freely, then yeah, your fan clutch is shot. I replaced mine with a "heavy duty" fan clutch and all is well again. 
DO NOT get the "severe duty" fan clutch, though, unless you want your car to sound like a giant Hoover vacuum cleaner; those things are like having the fan permanently engaged rather than the fan clutch allowing the fan to "slip" a bit above a certain RPM, so it makes it noisy as hell and will affect your horsepower and even your gas mileage (I lost about 2 MPG while I was running one).
You can tell it apart from the standard OEM-replacement fan clutch visually and by feel. It's way thicker than the stock fan clutch, and it's reeeeeally stiff when trying to turn it by hand. Oddly enough, it was also $7 CHEAPER than the OEM replacement fan clutch for some reason. 
Having a trimmed fan shroud and/or a few nicks out of the fan blades may or may not make a difference, but it won't be enough to make it overheat. (Not having a shroud AT ALL might do that, though.) Probably wouldn't a bad idea to replace the fan at the same time while you've got it off to replace the fan clutch. Old plastic fans tend to crack around the center hub, and you don't want that coming apart at high RPM and sending pieces of plastic into your radiator and everywhere else.
DO NOT get the "severe duty" fan clutch, though, unless you want your car to sound like a giant Hoover vacuum cleaner; those things are like having the fan permanently engaged rather than the fan clutch allowing the fan to "slip" a bit above a certain RPM, so it makes it noisy as hell and will affect your horsepower and even your gas mileage (I lost about 2 MPG while I was running one).
You can tell it apart from the standard OEM-replacement fan clutch visually and by feel. It's way thicker than the stock fan clutch, and it's reeeeeally stiff when trying to turn it by hand. Oddly enough, it was also $7 CHEAPER than the OEM replacement fan clutch for some reason. Having a trimmed fan shroud and/or a few nicks out of the fan blades may or may not make a difference, but it won't be enough to make it overheat. (Not having a shroud AT ALL might do that, though.) Probably wouldn't a bad idea to replace the fan at the same time while you've got it off to replace the fan clutch. Old plastic fans tend to crack around the center hub, and you don't want that coming apart at high RPM and sending pieces of plastic into your radiator and everywhere else.
The car was in a front end crash and the radiator support was reused which is the reason the misalignment issues. I live in Houston, Texas so it's pretty hot right now. And like I said it does not heat up unless the A/C is on and only then it heat up very slowly. The only time it really becomes a problem is when I'm waiting on someone, sitting in my car with the A/C on, or if I'm in a traffic jam. Driving around in the city waiting on a light isn't enough to overheat. So it's a small problem I want to get fixed before it gets worse.
If it literally only happens while idling for an extended period, are you sure it's not a coolant flow or fan RPM issue that is about as good as it can get? For instance, if you hold the idle at about 1K RPM, does it stay cooler?
In any case, I would renew or retrofit parts so you're not using broken stuff. The route you go (even if just a new blade but the old clutch) is up to you.
In any case, I would renew or retrofit parts so you're not using broken stuff. The route you go (even if just a new blade but the old clutch) is up to you.
Have you really inspected the fan blade or noted how tight the fan clutch is when hot and the car is off (like Dave outlined)? That will help you decide if fresh parts will help and how much.
Clutches tend to either get real tight (at all times) when they crap out, or they get loose. The former is more common when you have a leak (the clutch uses a bimetallic spring that shutters a fluid orifice for the viscous coupling).
Clutches tend to either get real tight (at all times) when they crap out, or they get loose. The former is more common when you have a leak (the clutch uses a bimetallic spring that shutters a fluid orifice for the viscous coupling).
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