Intermittent Overheat
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Cross-Country
Joined: Aug 2011
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Intermittent Overheat
79 Bronco with a 460 (mid 70s lincoln numbers)
occasionally makes out temp guage, drops back to normal very quickly when I rev it up. The radiator and tstat have been replaced. Fan seems to blow hard.... any other thoughts before I throw a water pump and fan clutch at it?
I bled it again recently and it seemed to work for about 30 minutes before it started doing it again. That's when I noticed that revving it up immediately drops the temp back to normal.
occasionally makes out temp guage, drops back to normal very quickly when I rev it up. The radiator and tstat have been replaced. Fan seems to blow hard.... any other thoughts before I throw a water pump and fan clutch at it?
I bled it again recently and it seemed to work for about 30 minutes before it started doing it again. That's when I noticed that revving it up immediately drops the temp back to normal.
Logistics Pro
Joined: Jul 2005
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When it does this, watch your fuel gauge, and oil pressure gauge if it has one. Do they also go up the same amount the temp gauge does? If so, then it's your Instrument Panel Voltage Regulator. You can try pulling the cluster out, and cleaning the connections to the gauge - or every connection you can get to...
Moderator & parts slinger
Joined: Feb 2007
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From: S/W Missouri, Polk county
Fan shroud installed? So it has a fixed place fan now, 5 or 7 blade? X2 check sender condition (clean single wire elec contact) and consider replacing the sending unit. Do not use/wrap thread tape on all the threads on the new sender. It being installed in the block is one of the contacts. Do you have a 3 or 4 port vacume controlled valve on the T stat neck by chance? Or just down stream of it?
Hotshot
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From: The Shenandoah Valley
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Cross-Country
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Has stock fan clutch and fan. It smells hot and spits coolant out everytime it overheats and all of the other guages work so I don't think it's the guage. I'll have to check on the vacum ports.
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Thread Starter
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Cross-Country
Joined: Aug 2011
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Fan shroud installed? So it has a fixed place fan now, 5 or 7 blade? X2 check sender condition (clean single wire elec contact) and consider replacing the sending unit. Do not use/wrap thread tape on all the threads on the new sender. It being installed in the block is one of the contacts. Do you have a 3 or 4 port vacume controlled valve on the T stat neck by chance? Or just down stream of it?
nope. Should it?
Lead Driver
Joined: Oct 2018
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Being intermittent sounds like a thermostat, but if you replaced it that's unlikely.
A bad radiator would do it. slipping belts, or a rusted out backing plate. but it shouldn't be intermittent.
385 series engines have a backing plate behind the water pump. without one they'll overheat every time fast. a bad one would cause some sort of issues I'm sure.
A bad radiator would do it. slipping belts, or a rusted out backing plate. but it shouldn't be intermittent.
385 series engines have a backing plate behind the water pump. without one they'll overheat every time fast. a bad one would cause some sort of issues I'm sure.
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Cross-Country
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I pulled the fan. When I heat the clutch with a heat gun and engage it it doesn't feel any harder to spin by hand than when it's cold... does this indicate it's bad or does it have to be spinning fast to work right?
Logistics Pro
Joined: Jun 2004
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From: South Central Utah
You might use a laser temp gun to verify the engine and coolant system temperature changes at different points.
Thermostat housing, upper and lower radiator hoses and top and bottom radiator temperatures.
Thermostat housing, upper and lower radiator hoses and top and bottom radiator temperatures.