overheating issue
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New User
Joined: Jul 2013
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overheating issue
Hello-I have a 1968 F-100 with a 360 V8 automatic. It runs hot. I installed a new fan shroud yesterday as it was missing the old one along with a new thermostat. Coolant is flowing fine-hoses are almost new and there are no leaks. What could be causing the running hot issue?
Posting Guru
Joined: May 2010
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From: Alton, MO
I would look at the fan location in the shroud. The blades should be centered in the shroud. In other words half in the shroud & half out. Are you running a fixed fan or a clutch type? Any play in the water pump shaft? It is a 45 yr old truck maybe time for a new radiator. Core support. Is it a big block core support or 6cyl? If a 6 cyl you will need to cut the opening out to match the radiator. I am assuming you have a big block radiator in it & not a 6 cyl.
What is "running hot"? All the time or only at speeds or idle? If at idle only it is related to air flow. If at speeds it is related to capacity. That is general.
What is "running hot"? All the time or only at speeds or idle? If at idle only it is related to air flow. If at speeds it is related to capacity. That is general.
Junior User
Joined: May 2013
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Start with the lower cost items, temp sender, after market gauge and sender for testing. The radiator could have many tubes blocked and still allow coolant to flow but at a velocity that does not allow time for it to release heat.
Thread Starter
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New User
Joined: Jul 2013
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I would look at the fan location in the shroud. The blades should be centered in the shroud. In other words half in the shroud & half out. Are you running a fixed fan or a clutch type? Any play in the water pump shaft? It is a 45 yr old truck maybe time for a new radiator. Core support. Is it a big block core support or 6cyl? If a 6 cyl you will need to cut the opening out to match the radiator. I am assuming you have a big block radiator in it & not a 6 cyl.
What is "running hot"? All the time or only at speeds or idle? If at idle only it is related to air flow. If at speeds it is related to capacity. That is general.
What is "running hot"? All the time or only at speeds or idle? If at idle only it is related to air flow. If at speeds it is related to capacity. That is general.
Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
Next time it is running that warm feel the grille side of the radiator core while idling. Top to bottom and all over. Where water is flowing it will feel hot. If it is partially plugged it will feel not as hot where water is not flowing.
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Posting Guru
Joined: May 2010
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From: Alton, MO
I know the truck has a V8 I was talking about the radiator & core support.
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Logistics Pro
Joined: Jan 2011
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From: Antelope Valley ,CA
these old gauges are not accurate , get a new sending unit (like $9.99 ) see what temp is . if it hasn't changed then you need to start checking radiator for clogs , flush radiator/block . etc
Lead Driver
Joined: Aug 2003
Posts: 7,592
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From: **** hole San Jose ca.
So, I assuming you've been driving this vehicle with no problems until now?
Or you just noticed where the temp is a little higher now that's it's summer, time verses your winter time driving.. Most radaitors slowly plug in the lower end of the core tubes and less at the top tank. Being that's where you can't see it. I'd say it's time to have your radaitor rodded out and maybe back flush your whole cooling system. The ole skool stuff that most people don't do or want to pay to have done any more. Also I'd install a manual gauge so you really know the temp. Check for lose belts, your's don't sound like it's running hot. But if your over filling your rad like most guys do until they learn or look for the (fill too Line) which is about 2" below the cap filler hole..
Coolent will get pushed out after the motor is shut off from heat expansion.. orich
Or you just noticed where the temp is a little higher now that's it's summer, time verses your winter time driving.. Most radaitors slowly plug in the lower end of the core tubes and less at the top tank. Being that's where you can't see it. I'd say it's time to have your radaitor rodded out and maybe back flush your whole cooling system. The ole skool stuff that most people don't do or want to pay to have done any more. Also I'd install a manual gauge so you really know the temp. Check for lose belts, your's don't sound like it's running hot. But if your over filling your rad like most guys do until they learn or look for the (fill too Line) which is about 2" below the cap filler hole..
Coolent will get pushed out after the motor is shut off from heat expansion.. orich
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
festusmo Welcome to FTE & the Bumpside Forum. 
Many guys come here comparing these 50 year old design to todays standards. Theses old trucks have a huge frontal opening and don't require a fan shroud. As long as the truck is moving forward 20 miles an hour it does not need a fan. The one thing they will not do is sit and idle and this is where the shroud & fan comes in. I have been around these trucks since they were new, my 66 has same basic setup as yours, it never has had a shroud, I did use a larger fan when I rebuilt the engine 12 years ago.
Are you loosing coolant?
John
Many guys come here comparing these 50 year old design to todays standards. Theses old trucks have a huge frontal opening and don't require a fan shroud. As long as the truck is moving forward 20 miles an hour it does not need a fan. The one thing they will not do is sit and idle and this is where the shroud & fan comes in. I have been around these trucks since they were new, my 66 has same basic setup as yours, it never has had a shroud, I did use a larger fan when I rebuilt the engine 12 years ago.
Are you loosing coolant?
John
More Turbo
Joined: Jun 2003
Posts: 686
Likes: 80
Air and water flow are critical for sure. If it runs normal temps at speed, then both air and water flow are at higher rates and that fits with normal operating temps.
The same is true of ignition timing. I don't know the details of your distributor advance mechanism(s), but if the engine isn't seeing at least some degree of static ignition advance in that 500-800 rpm zone, then this kind of hot running can occur. I have seen this on more than one occasion.
Does the distributor have centrifugal advance? Is it equipped with a Loadomatic vacuum advance? How is the distributor connected to vacuum?
Somebody more versed in this particular engine can tell you what a good initial advance is.
The same is true of ignition timing. I don't know the details of your distributor advance mechanism(s), but if the engine isn't seeing at least some degree of static ignition advance in that 500-800 rpm zone, then this kind of hot running can occur. I have seen this on more than one occasion.
Does the distributor have centrifugal advance? Is it equipped with a Loadomatic vacuum advance? How is the distributor connected to vacuum?
Somebody more versed in this particular engine can tell you what a good initial advance is.