Coolant overpressure
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Senior User
Joined: May 2007
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Coolant overpressure
Fired up the 96 4.0 AWD Aerostar this morning, letting it idle to charge the battery (had to jump start it). After about 20 minutes notices steam blowing out. Observed the overflow tank distended, the steam was coming out of where the hose enters the tank. Temp gage was at max. Shut off the engine and let it cool down. Tank began to contract. Pulled the radiator cap and could hear the coolant bubbling inside the radiator. Radiator, cap, thermostat and upper/lower hoses are new (less than six months). Any ideas?
Post Fiend
Joined: Apr 2005
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From: Washington state
1. shot thermostatic fan clutch, free wheeling, no cooling while parked.
2. stuck thermostat. lots of fake knockoff imports out there that look good, auto parts stores are getting burned on them
3. impeller blades on water pump broken or corroded off, common on old pumps. example in old posts.
4. blown head gasket or cracked heads leaking into coolant system, known 4L weakness
2. stuck thermostat. lots of fake knockoff imports out there that look good, auto parts stores are getting burned on them
3. impeller blades on water pump broken or corroded off, common on old pumps. example in old posts.
4. blown head gasket or cracked heads leaking into coolant system, known 4L weakness
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The fan is not turning on. I have an after market electronicaly controlled fan that the previous owner added. There is a probe the goes in the upper radiator hose connection, which feeds feeds an adjustable thermostat. When I turn the thermostat, I can hear a solenoid or relay clicking on the fender wall (driver's side), but the fan does not run. I am getting voltage to the thermostat and through the thermostat when the relay clicks on. Tomorrow I'll pull the fan and check for bad wiring. I don't think it has worked since I changed the radiator, but here in Minnesota it has been cold much of the summer. Thanks for the ideas.
Elder User
Joined: Dec 2006
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From: Kitchener,Ontario,Canada
Dont buy anything yet. Run a jump lead from the battery to the fan, if it then fires up, you know that the thermistor which controls the fan to come on is likely shot or the positive lead to the fan is bad (have you checked the fuse?).
I had a Fiesta with a sensor controlled fan which came on TOO often, I bypassed this sensor with a manual switch for those traffic line ups where you need the fan on after 5-10 mins or so. It worked perfectly & no surprise spinning blades in the engine compartment. The flick of a switch reverted the fan back to automatic sensor operation.
I had a Fiesta with a sensor controlled fan which came on TOO often, I bypassed this sensor with a manual switch for those traffic line ups where you need the fan on after 5-10 mins or so. It worked perfectly & no surprise spinning blades in the engine compartment. The flick of a switch reverted the fan back to automatic sensor operation.
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I visited my local Aerostar grave yard and pulled the stock fan equipment and installed it in my 96. Fired it up and then discovered a leak in the radiator. Dumped some JB radiator stop leak in and things are running fine. Ran the vehicle for about five miles on the highway and then let it sit at idle for 20 minutes. No over heating, and no leaks.
I did test the electronic fan after pulling it out and it did run, and turning the thermostat up stopped it, turning it back down ran it again. I am going to hang on to it just in case my junkyard special loses a blade as it does have some cracking beginning.
Thanks for all the help guys.
I did test the electronic fan after pulling it out and it did run, and turning the thermostat up stopped it, turning it back down ran it again. I am going to hang on to it just in case my junkyard special loses a blade as it does have some cracking beginning.
Thanks for all the help guys.
Postmaster
Joined: Apr 2001
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Most if not all, fan blades on 4.0/3.0 engines have cracking issues. The blades are molded to a metal core inside. Mine were severely cracked yet never separated. I did finally replace it with a newer design. I pulled as hard as I could on some of the worst cracked blades on the old fan and could not get them to pull loose.
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Lead Driver
Joined: Sep 2003
Posts: 7,013
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From: SoCal
The cracks are usually in a part of the center "hat" that does not really support the blades. So I'm guessing that those cracks can look bad, but the fan will not disintigrate due to where the blades are supported.
Even so, I've searched through my local junkyard for replacements, and almost all of them are cracked. I came across a 1991 Aerostar that had a fan with no cracks. The plastic looked a little different than all the others, so I'm guessing Ford must have changed the design at some point. I'm still trying to decide whether to install it on my van now just to head off problems, or wait for the existing fan to get worse.
Even so, I've searched through my local junkyard for replacements, and almost all of them are cracked. I came across a 1991 Aerostar that had a fan with no cracks. The plastic looked a little different than all the others, so I'm guessing Ford must have changed the design at some point. I'm still trying to decide whether to install it on my van now just to head off problems, or wait for the existing fan to get worse.
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Postmaster
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Early fans had straight blades. Later design had 'hockey stick' style blades, where the last few inches angled out.
Lead Driver
Joined: Sep 2003
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From: SoCal
Actually, the shape of the blades on both fans were the same; a bend in the tips to reduce noise. I meant that the plastic of the newer fan looked more white; more so than fans I found in newer models in the junk yard. I guess it's possible that a previous owner replaced the original one with a newer unit. (But I doubt that, given the condition of the rest of the van.
Post Fiend
Joined: Apr 2005
Posts: 5,720
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From: Washington state
same fan blade used on FoMoCo Mustang, Ranger, Explorer products mid 80s thru mid 90s
tips bent over and in to reduce fan tip noise. still a loud fan blade.
FORD AEROSTAR (1990 - 1997)
FORD EXPLORER (1991 - 1994)
FORD MUSTANG COBRA 1993
FORD MUSTANG GT (1985 - 1993)
FORD MUSTANG LX (1985 - 1993)
FORD RANGER (1990 - 2004)
FORD RANGER SUPER (1990 - 1998)
MERCURY CAPRI (1985 - 1986)
tips bent over and in to reduce fan tip noise. still a loud fan blade.
FORD AEROSTAR (1990 - 1997)
FORD EXPLORER (1991 - 1994)
FORD MUSTANG COBRA 1993
FORD MUSTANG GT (1985 - 1993)
FORD MUSTANG LX (1985 - 1993)
FORD RANGER (1990 - 2004)
FORD RANGER SUPER (1990 - 1998)
MERCURY CAPRI (1985 - 1986)
Former ******
Joined: Nov 2004
Posts: 4,901
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From: Salt Lake City, Utah
The fan is not turning on. I have an after market electronicaly controlled fan that the previous owner added. There is a probe the goes in the upper radiator hose connection, which feeds feeds an adjustable thermostat. When I turn the thermostat, I can hear a solenoid or relay clicking on the fender wall (driver's side), but the fan does not run. I am getting voltage to the thermostat and through the thermostat when the relay clicks on. Tomorrow I'll pull the fan and check for bad wiring. I don't think it has worked since I changed the radiator, but here in Minnesota it has been cold much of the summer. Thanks for the ideas.
Everything these guys said is correct, but might i add, you should refill the system, then run the engine for a couple minutes. Look for small bubbles in the filler neck. If bubbles just seem to keep coming out even after the main pockets or air should have passed, you probably have a blown head gasket.
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