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Discussion Starter · #1 ·
Hey guys,

I have no overheating issues at all driving around town, even with the A/C blasting. Temps in the 80's. The gauge doesn't even raise slightly. Recently however, when I am on the highway for say 30 miles or so, my truck starts to get hot. This is at sustained speeds of around 70 or 80. I had the A/C going and turning it off helped some but really when the RPMS drop and I drive slower, like 50 to 60 the temp also drops. Im having a hard time deciding what is causing this. I am going to start with the thermostat but what else should I look for?

Its a 2000 4.7L with 230K on it.

thanks for the help
 

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Belt on the water pump possibly slipping?
 

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Hey guys,

I have no overheating issues at all driving around town, even with the A/C blasting. Temps in the 80's. The gauge doesn't even raise slightly. Recently however, when I am on the highway for say 30 miles or so, my truck starts to get hot. This is at sustained speeds of around 70 or 80. I had the A/C going and turning it off helped some but really when the RPMS drop and I drive slower, like 50 to 60 the temp also drops. Im having a hard time deciding what is causing this. I am going to start with the thermostat but what else should I look for?

Its a 2000 4.7L with 230K on it.

thanks for the help
possibly a soft radiator hose on the suction side---with the engine at operating temp open the hood and hold the engine at 3000rpm and check both hoses to see if one is collapsing. this will severely restrict the coolant flow and cause overheating. Good luck
 

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I would say that clutch is not working properly. Our trucks can drive with out mechanical fan up to 60mph - without overheating. As soon as you go over 60mph it needs additional air flow.
 

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Is there enough coolant in the system?
is there any blokkage in the system (clogged)
Is your radiator whole?
Is your waterpump good?

I don't think it's your fan, because at 70 Mph, your fan doesn't suck more air in than the drivewind.
 

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Thermostat is an easy, cheap fix, and may fix the problem. However, at freeway speeds there is sufficient air flow across radiator. Suspect inefficient radiator, such as plugged. This assumes water pump, thermostat, etc are in good order. Finally, too high antifreeze concentration reduces heat transfer.
 

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Is there enough coolant in the system?
is there any blokkage in the system (clogged)
Is your radiator whole?
Is your waterpump good?

I don't think it's your fan, because at 70 Mph, your fan doesn't suck more air in than the drivewind.

I've actually tested on my own truck and on GX470 (anything past 60mph with out fan, you will overheat). If you don't believe try it on your own truck :rolleyes:
 

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I've actually tested on my own truck and on GX470 (anything past 60mph with out fan, you will overheat). If you don't believe try it on your own truck :rolleyes:
I was just getting ready to tell him the same thing. I know it sounds like a contradiction but you are right. Anything past 60 and the engine starts to get hot without the fan. I think it could be a fan clutch, a loose belt on the water pump, or a collapsed radiator hose - in that order.
 

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Discussion Starter · #10 ·
ok thanks everyone.

I have tested and I dont hear or see any kind of belt slippage. Everything looks great and no other problems with accessories.
The radiator is about a year old but I have no had any issues with it. The level is good. I have taken many long distance trips with it since I have installed it and this problem has just started in the last week or so.
I also could see no evidence of a hose collapsing. The hoses look great but I may replace them anyway.

I was just reading about redoing the clutch fan fluid, I may give that a chance as well as the thermostat.

thanks for all the help guys
 

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Discussion Starter · #11 ·
I just went out and moved my fan by hand and it moves very easily. It has some resistance but very little. Does this sound like the culprit?

thanks
 

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I just went out and moved my fan by hand and it moves very easily. It has some resistance but very little. Does this sound like the culprit?

thanks
Yep, sounds like it to me.
 

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Can you give us more info? You say that around town, "The gauge doesn't even raise slightly." What are you saying? ... that it doesn't even rise off the C on the gauge, or that it rises to a normal operating level and remains there? That's important.

Second, you say that at highway speeds the truck start to "get hot." Again, what are you saying? ... that the temp gauge rises a bit, or that it runs up into the overheat range ... up to the H?

This is a situation in which a ScanGauge comes in handy. It will tell you exactly what your coolant temp is at all times. It should be around 190-195 deg. F at all times after the engine has warmed up, which only takes a few miles. If your engine is operating much below 190, or above 195, you need to get it checked out. If all you see is your temp gauge rise and fall a little bit while always remaining pretty much in the center of the gauge range, you don't have a problem. But if it's normally operating down around the C, then rising to the H at highway speeds, you need to get it checked out.
 

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Discussion Starter · #14 ·
Can you give us more info? You say that around town, "The gauge doesn't even raise slightly." What are you saying? ... that it doesn't even rise off the C on the gauge, or that it rises to a normal operating level and remains there? That's important.

Second, you say that at highway speeds the truck start to "get hot." Again, what are you saying? ... that the temp gauge rises a bit, or that it runs up into the overheat range ... up to the H?

This is a situation in which a ScanGauge comes in handy. It will tell you exactly what your coolant temp is at all times. It should be around 190-195 deg. F at all times after the engine has warmed up, which only takes a few miles. If your engine is operating much below 190, or above 195, you need to get it checked out. If all you see is your temp gauge rise and fall a little bit while always remaining pretty much in the center of the gauge range, you don't have a problem. But if it's normally operating down around the C, then rising to the H at highway speeds, you need to get it checked out.
The truck will go to normal operating temp around town. Everything seems normal. It stays right in the middle of the gauge. When on the highway it will begin to slowly creep up. If I catch it and turn the AC off I can get it to stay just above normal or have it creep back down. The other day though it raised and kept raising almost to red but I pulled over to let it cool down. When I turned off the AC and pulled over it went back down to normal pretty quickly. It will idle all day with the AC on and not over heat.
 

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When was the last time you had the block back flushed?
 

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The truck will go to normal operating temp around town. Everything seems normal. It stays right in the middle of the gauge. When on the highway it will begin to slowly creep up. If I catch it and turn the AC off I can get it to stay just above normal or have it creep back down. The other day though it raised and kept raising almost to red but I pulled over to let it cool down. When I turned off the AC and pulled over it went back down to normal pretty quickly. It will idle all day with the AC on and not over heat.

I had similar issue. Its 99% that your clutch is no good.
 

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Discussion Starter · #17 ·
awesome, thanks. I will try that first. Is it worth buying a whole new one or just replenishing the silicone inside?
 

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Some people here just replaced silicone <=$50 vs +$200 for the clutch assembly. I remember seeing the threads here were people changed the silicone in fluid and even part numbers for silicone but don't remember who did it.
 

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Discussion Starter · #19 ·
thanks. I found the thread. I couldnt really find anything saying whether it made it as good as a new one or not though. I will probably try it for the price.

thanks
 

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