OVERHEAT AT IDLE
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Joined: Jan 2001
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From: New England
OVERHEAT AT IDLE
I have a fresh rebuilt 400 , and it gets very hot at idle, my old 400 did the same thing, I checked the idle mixture over and over, timing set around 17 degrees , and the radiator is a heavy duty modine about 2-3 years old, I have one of those fly-swatter fans, could that be the cause??? give me some inexpensive tips to try first before suggesting a rebuild, and or plasti-gauge job
Fleet Owner
Joined: Jun 1999
Posts: 24,552
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From: Creedmoor, North Carolina
OVERHEAT AT IDLE
Sean, There is a thread about a mile long in the archives, from the guy that had a service truck that boiled on him when idling at stops. I really don't remember if there was a solution or not. We kicked around electric fans (blowing in & out) different thermostats, fan shrouds, you name it.
If you don't have one, try a fan shroud and an electric (large) fan. :-)
John
jowilker
[link:www.ford-trucks.net/users/jowilker|Club FTE since 01 01]
[link:www.ford-trucks.net/users/jowilker/NCFTE.html|NC Truck Owners]
66F100s Rule
In the cool still quite of night you can hear chevies rusting away.
If you don't have one, try a fan shroud and an electric (large) fan. :-)
John
jowilker
[link:www.ford-trucks.net/users/jowilker|Club FTE since 01 01]
[link:www.ford-trucks.net/users/jowilker/NCFTE.html|NC Truck Owners]
66F100s Rule
In the cool still quite of night you can hear chevies rusting away.
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From: Inthepast
OVERHEAT AT IDLE
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Why would someone suggest a rebuild on a fresh rebuilt motor? How fresh is the rebuild? Also, new rings generate more heat until break-in. That phenomena might be at work. Make sure you have a thermostat in the engine, running 50-50 mix of quality coolant, not just water and make sure you have a shroud on the radiator and a good fan. Not all fans are created equal as you already suspect.
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Why would someone suggest a rebuild on a fresh rebuilt motor? How fresh is the rebuild? Also, new rings generate more heat until break-in. That phenomena might be at work. Make sure you have a thermostat in the engine, running 50-50 mix of quality coolant, not just water and make sure you have a shroud on the radiator and a good fan. Not all fans are created equal as you already suspect.
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Senior User
Joined: Mar 2000
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OVERHEAT AT IDLE
you mentioned the timing is set at 17 isnt that a bit much? especially if the motor is stock. on my 352 wich is more than slightly built i only run my timing at 13-14btdc. it is possible it has too much timing.
Posting Guru
Joined: Aug 2000
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From: (near) Denver USA
OVERHEAT AT IDLE
fozzy,
I agree that 17 degrees BTDC at idle is excessive timing. Normal timing for the 400 is about 8-12 degrees BTDC. If the engine has a 351M damper instead of the 400 damper, the timing marks may be incorrect. I'd try to back the timing down to 10 degrees BTDC or so, and see if you can get a smooth idle with that timing.
Even though the radiator is only 2-3 years old, it could still be plugged. You should check that, maybe try flushing it. Fan shroud is also a good suggestion. I doubt an electric fan would improve things over what you've got.
Even though a new engine generates a little more heat than an engine that's already broken in, it shouldn't be significant if your cooling system is working properly.
As for overbore, that's a possible problem, but unlikely if it's not more than 0.030".
BubbaF250
1980 F250 4x4 Custom, 351M/NP435/NP208/D44HD-TTB/D60-FF/3.55s 6750 GVW, Rust & White.
I agree that 17 degrees BTDC at idle is excessive timing. Normal timing for the 400 is about 8-12 degrees BTDC. If the engine has a 351M damper instead of the 400 damper, the timing marks may be incorrect. I'd try to back the timing down to 10 degrees BTDC or so, and see if you can get a smooth idle with that timing.
Even though the radiator is only 2-3 years old, it could still be plugged. You should check that, maybe try flushing it. Fan shroud is also a good suggestion. I doubt an electric fan would improve things over what you've got.
Even though a new engine generates a little more heat than an engine that's already broken in, it shouldn't be significant if your cooling system is working properly.
As for overbore, that's a possible problem, but unlikely if it's not more than 0.030".
BubbaF250
1980 F250 4x4 Custom, 351M/NP435/NP208/D44HD-TTB/D60-FF/3.55s 6750 GVW, Rust & White.
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Fleet Mechanic
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From: Lower 48
OVERHEAT AT IDLE
Have you checked the basics like - Is the fan shroud intact? Thermostat?
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Senior User
Joined: Jan 2001
Posts: 380
Likes: 1
From: Meriden USA
OVERHEAT AT IDLE
The main reason it is overheating at idle is because it isnt getting any air pushed to the engine versus when its moving it gets air pushed to it. Id try a different thermostate that opens up earliyer or a less pound cap. Good Luck!
Anthony DiPietro
79 F150 Ranger
Anthony DiPietro
79 F150 Ranger
Post Fiend
Joined: Feb 2001
Posts: 6,624
Likes: 8
From: Missouri
OVERHEAT AT IDLE
How big of a problem is this? Does it only happen on hot days when it idles for a long time or is it getting hot sitting at stop light. We have 2 grain trucks at home with a 332 FE block and another off brand grain truck that i won't mention the name of with a 235 I6 and they will over heat if left idling for a real long time. I don't want to say that it is normal for extended idling to cause overheats but it does happen quite a bit with older trucks with older cooling systems.
Senior User
Joined: Jun 1999
Posts: 288
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OVERHEAT AT IDLE
Did you change the water pump and the thermostat? When I did my 400 rebuild the first therm. I put in didn't work. Had to go to a 180 degree therm. and then everything worked fine.
Also, my timing runs high too, 15 deg BTDC. If it's not pinging it shouldn't present any problems. However, you do want to check for correct installation of the distributor.
Good luck! Rick
Also, my timing runs high too, 15 deg BTDC. If it's not pinging it shouldn't present any problems. However, you do want to check for correct installation of the distributor.
Good luck! Rick
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More Turbo
Joined: Jan 2001
Posts: 574
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From: New England
OVERHEAT AT IDLE
well, It was a short block kit(now with 4.5k), so yes I put the head gaskets on correctly, the water pump is an old stock replacement with about 40k on it, I used a NEW 180 thermostat and a new 13lb. cap, I have the large 4 row radiator(2 years old)and I back flushed it with a water hose.
the cylinder walls were bored .040" over with silv-o-lite pistons, new rings, the works. I bought it from a reputable engine builder who has been established here for over 18 years.
I checked the distributor, I think the timing would have shown if it were a tooth off.
the fan shroud is in A++ shape, although I still have the OE fly-swatter fan.
UGHHH!!! summer is quickly on its way here in south TX!!!!
the cylinder walls were bored .040" over with silv-o-lite pistons, new rings, the works. I bought it from a reputable engine builder who has been established here for over 18 years.
I checked the distributor, I think the timing would have shown if it were a tooth off.
the fan shroud is in A++ shape, although I still have the OE fly-swatter fan.
UGHHH!!! summer is quickly on its way here in south TX!!!!