351M Overheating
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Cross-Country
Joined: Aug 2003
Posts: 50
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From: Winnie, Texas
351M Overheating
Looking for help! I have changed the thermostat(MotorcraftRT-139 DOAZ_8575-A)waterpump and replaced the radaitor with a new one,set the timing at 12 degrees BTDC with vacum advance hose disconnected using a timing light,adjusted the air to fuel adjusting screws on the bottom of the 2 barrell carb.,no bubbles in radiatorto indicate bad head gasket,no pressure build up either,flushed cooling system with Prestone super flush and then flushed again with thier 2 part flush with the neutralizer,removed A/C coil from front of radiator. thanks alot.
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Joined: Aug 2002
Posts: 1,214
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From: Minneapolis, MN
351M Overheating
How hot is it actually getting and when does it overheat? If it is boiling the coolant, does it do it at any time or mainly while idling in traffic? If only in traffic (slow speeds) I'd be looking at the fan shroud and/or fan. If the shroud is missing, installing one should do it. If it's there, check all the small flaps on the radiator support that direct the airflow through the radiator. Most aftermarket fans, especially the flex fans, don't pull as much air as the factory fan with the fan clutch. There's another possibility...the fan clutch. If you're relying on the factory gauge, they're notorious for being inaccurate. You could try an aftermarket gauge to see exactly what temps you're running.
Just my 2¢
Greg
Just my 2¢
Greg
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Cross-Country
Joined: Aug 2003
Posts: 50
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From: Winnie, Texas
351M Overheating
Thanks for your reply! I have replaced the guage with a new mechanicle one. The thermostat is a 195 degree one and the truck is running 210 degrees without pulling my trailer with my tractor on it. The truck is a 1977 one ton dually. The fan is the factory one and the fan clutch checks out. The fan shroud is on the truck.
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Joined: Dec 2002
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From: chicago burbs
351M Overheating
so it's not spewing coolant or doing anything else to indicate an undriveable condition? 210 is not really overheating, the pressure cap increases the boiling point of the system. i have seen my mech gauge as high as 240-250 and it wasn't spewing! temp indicated also depends on where the temp is being taken from. the 195 deg thermostat is a minimum temperature. thats when the Tstat will open. the engine may continue to get hotter than the T stat temp rating. you said you have the timing at 12 deg advanced, just for an experiment , back it down a little and see if your indicated temp doesn't drop. advancing(or retarding) the timing will have an effect on the running temp.
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Joined: Aug 2002
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From: Minneapolis, MN
351M Overheating
I agree, 210 isn't that hot. If you're running an automatic tranny you might want to consider a tranny cooler as the tranny cools through the radiator also. Especially if you're pulling a load.
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Joined: Dec 2002
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From: chicago burbs
351M Overheating
i forgot to say, i use the A/C condenser for a trans cooler. for year round use you could route the fluid through the condenser, then through the radiator to make sure it isn't "overcooled"
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Cross-Country
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From: Winnie, Texas
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Joined: Jul 2003
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351M Overheating
210 isn't that hot and it is normal for the old 351M and 400M.I have my dad's old 77' woody wagon and it always ran 215.When I would tow with it then it would run 235 to 240.The car has 165,000 miles and still runs and has never had a problem with head gaskets or cracked heads.those two engines always ran hot but I am not sure why.Poor cooling passages I guess.Don't worry about it.
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Joined: Dec 2002
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From: Halifax, NS
351M Overheating
i didnt like how hot mine was running with a 195 either. right now, i have a 160 high flow in it. as a the weather gets colder, i'll put in a 180.
my truck seems to dig the 160 fine.
my truck seems to dig the 160 fine.
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