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Discussion Starter #1 (Edited)
Ok. For the last several months I've been overheating while idling and the truck would overheat shortly after turning off the engine. I do courier work in Phoenix so that means lots of 10-15 minute stops, by the time I get back and start her up again, the temp gauge is off the chart. I never, ever had heat issues while at cruising speeds. Talked it over with my mechanic and figured it had to be a flow issue in the radiator (137K miles, factory radiator). This weekend, I replaced the radiator. The whole process went very smoothly.

However, now I am overheating at highway speeds if the A/C is on and when going up hills but NOT when idling (A/C on) and NOT after shutting off the engine. In other words, the exact OPPOSITE problem I faced before.

I've pretty much ruled out the fan clutch. The fan blows strong and it has passed a few different tests I put it through that some folks recommended. Also checked for air bubbles in the cooling system, came up with nothing.

I'm stumped at this point. Any thoughts? Thanks folks.


2002 V6 A/T 2WD No Supercharger
 

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It seems like this would have caused problems before, but: are all of the radiator's rubber or foam "gaskets" in place around the perimeter of the radiator?

What mix of anti-freeze / water are you using?
 

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with 137,000 miles you should have done a timing belt by now which should have done a water pump and thermostat change. Have you done any of those items?
 

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The two overheat problems are inapposite, so it is confusing.

Your current problem, overheat at highway speeds or uphill climb, suggest that the heat removal system (i.e. radiator) has insufficient heat transfer capability. It's brand new so it can't be the surfaces. That leaves coolant flowrate or coolant level.

If the radiator is full, (most likely) then that leaves the thermostat or water pump as the suspects. Water pumps fail by leaking, rather than stoppage of coolant flow. I think you should change out the thermostat.

Another remote possibility is a collapsed coolant line. There are two, upper and lower, and are subjected to vacuum when the engine cools down. They are reinforced to resist collapsing due to internal vacuum. But due to age and heat, they can break down. A simple inspection will uncover this fault.
 

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Did your mechanic bleed out the air from the cooling system after changing the radiator? There is a bleeder on the intake manifold to get all the air out after you get it re-filled and running.
These are my two thoughts on it, mainly the cooling system not being "burped", and a possible weak waterpump. If the system has air trapped in it, it wil cause te waterpump to cavitate, which in turn means no circulation of coolant. You need to remedy this quickly as you will in turn cause warped heads and a blown head gasket.
 

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Discussion Starter #8
These are my two thoughts on it, mainly the cooling system not being "burped", and a possible weak waterpump. If the system has air trapped in it, it wil cause te waterpump to cavitate, which in turn means no circulation of coolant. You need to remedy this quickly as you will in turn cause warped heads and a blown head gasket.
I have been trying to locate the bleeder valve for the last two days. When I was unable to find it, I went ahead and (while cool) removed the radiator cap, ran the engine for half an hour and tried to see if I could burp the system that way. If I could locate that bleeder it might make things easier.


My mechanic is out of town until Tuesday and can't be reached so I don't have the luxury of asking him questions about the installation procedure etc.


jerryp58 said:
It seems like this would have caused problems before, but: are all of the radiator's rubber or foam "gaskets" in place around the perimeter of the radiator?

What mix of anti-freeze / water are you using?
Are you talking about the large strips of foam that sit between the heater core and the radiator? The foam strip on the drivers side fell off when replacing the radiator and there appears to be no easy way to put it back. Do you really think that would affect air flow enough to do something like this?

By the way, I'm using pre-mixed 50/50 Prestone. Always have.
 

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I have been trying to locate the bleeder valve for the last two days. When I was unable to find it, I went ahead and (while cool) removed the radiator cap, ran the engine for half an hour and tried to see if I could burp the system that way. If I could locate that bleeder it might make things easier.


My mechanic is out of town until Tuesday and can't be reached so I don't have the luxury of asking him questions about the installation procedure etc.



Are you talking about the large strips of foam that sit between the heater core and the radiator? The foam strip on the drivers side fell off when replacing the radiator and there appears to be no easy way to put it back. Do you really think that would affect air flow enough to do something like this?

By the way, I'm using pre-mixed 50/50 Prestone. Always have.


How To Remove Air From Automotive Cooling System
 

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Are you talking about the large strips of foam that sit between the heater core and the radiator? The foam strip on the drivers side fell off when replacing the radiator and there appears to be no easy way to put it back. Do you really think that would affect air flow enough to do something like this?

By the way, I'm using pre-mixed 50/50 Prestone. Always have.
That's them. I don't know about these trucks, but previous vehicles I have owned have responded poorly to allowing air to flow around the radiator rather than through it and I think that effect is amplified at higher speeds. My truck had lost about 20% of the top foam and some of the side foam had fallen out of place. I saw no ill effects on my truck, but I only have 50k miles.

50/50 is the recommended I suppose. The more anti-freeze and less water, the less efficient the cooling, but 50/50 should be fine.

I can't tell where it is from the pic, but I have a pic of the bleeder I'll try to PM you; if that's doable.
OK, can't do that... here's the pic from my service manual...

 

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Like Jerry pic shows. Remove the bleeder cap when engine is cool. Then run engine till hot. Make sure you are a level surface too. If no coolant flows out of the bleeder then squeeze the upper radiator hose to see how low the fluid is. Then add some when engine cools off.
 

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Discussion Starter #14
Like Jerry pic shows. Remove the bleeder cap when engine is cool. Then run engine till hot. Make sure you are a level surface too. If no coolant flows out of the bleeder then squeeze the upper radiator hose to see how low the fluid is. Then add some when engine cools off.
Found it. Opened the bleeder valve and coolant is flowing out of it at a steady pace while idling. I'm not getting actual bubbles, just cooling seeping out. No air in there?
 

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I forgot to mention that you should turn on your heat in the cabin too. That will circulate the coolant through the heater core and pull the air out through the bleeder. Sorry, forgot to mention that.

However, sounds like you are getting the air out. Take it for a test drive and see how it responds. If it acts up I would replace the thermostat next. I replaced mine when I flushed the coolant at 45,000 miles.
 

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I'd replace the radiator cap and go from there. With the engine at operating temp., shut it off, wait a while, and see if you can hear a "hiss" at the cap. Poor man's pressure test.
 

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Discussion Starter #17
Ok. New / previously unknown symptom.

The vehicle runs hot even during regular city street driving (30-45Mph) but it takes a lot longer to get hot than it does when I drive uphill or at highway speeds.

The temperature stays right around operating range IF I leave the A/C off.

I'm getting plenty of hot air when I turn on the heater and naturally, the system stays nice and cool as long as I leave it running. Of course, since I don't want to die of heat exhaustion, this isn't really an option.

Next step seems to be to look at the thermostat, I suppose.
 

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Could it be a bad Radiator? Even if it is new, there could be an issue with the flow, Maybe bad quality control? It would seem that way to me if the heater is keeping it cool and the radiator isn't. Just because a part is new doesn't mean it it is good, I've scratched my head more than once with a new "bad" part.
 

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Discussion Starter #19
Could it be a bad Radiator? Even if it is new, there could be an issue with the flow, Maybe bad quality control? It would seem that way to me if the heater is keeping it cool and the radiator isn't. Just because a part is new doesn't mean it it is good, I've scratched my head more than once with a new "bad" part.
That possibility keeps getting closer and closer to the top of the list. That wouldn't be so terrible I suppose. I've got this drain/fill down to a science myself.
 

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Loosen, and turn out of range, the micro switch behind the air flow selector knob. This'll let you run with the heater on and blowing on the windshield, w/o the a/c kicking on.
I once ran 18 months with the heater on to help a bum radiator. One summer of that was enough. It was a dry heat, tho. :)
 
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