I have a 2002 1500 4.7L with 120K miles and are having an overheating problem...

Replaced the Thermostat.
Flushed the Radiator.
Made sure there was no air in the system.

Still overheating. Now this is question one...as soon as I start up the truck when it is cold, the fan starts spinning...is it supposed to do that or has the fan clutch seized?

Questions 2...And how can I tell if the water pump is bad?

And lastly, there is what seems like an overflow hose that feeds into the reservoir from the upper coolant hose...there is a constant flow from that hose when the engine is running...is that supposed to be like that?

Any help would be greatly appreciated.

R

 

R,

1) Check the radiator, it should not have any cool spots when the engine is up to temp.
Yes, the fan should spin when the engine starts. It is designed to slip at higher rpm to free up power, but should always be turning when the engine is running.

2) They usually either leak or have a wobble from a bad bearing when bad. rarely, the impeller fins wear away and it won't push coolant properly.


My guess, is that you have a blown head gasket allowing compression into the cooling system. This seems to be a common problem on 4.7L engines.

 

Does the radiator cap hold pressure? It's another cheap replacement you can try.

 

Well, there actually are some cool spots on the radiator...I ran the engine up to temp and there are parts of the radiator I can not keep my hand on due to heat, and there is a pretty good chunk of the radiator that I can keep my hand on. Pretty much the bottom half....

So I am thinking the radiator is plugged up with gunk...so I am going to take it out and take it to the Radiator shop so that they can give it a good cleaning. What do yall think about that? For $65, lets try the cleaning before $$$ for a new one...

Thanks for the help. Does anyone have a PDF of the service manual?

R

 

It should generally feel cooler towards the bottom. Hot fluid flows in through the top hose and then cools down as it reaches the bottom hose.

 

I just got done dealing with a blown head gasket in my 4.7. Apparently that is a pretty common problem with them. Hopefully it isn't that, but your story sounds exactly like mine...Are you losing coolant at all? When you start the truck up for the first time in a while do you see white smoke coming out of the exhaust?


Is your CEL even on?

There are things that are making me think that that is what it is, but then there are things that are making me think otherwise

 

Yeah, it was real hot on the top of the Radiator, and cool on the bottom half.

So, yall are thinking it is not the radiator?

CRAP...I need to get this fixed. I don't see any white smoke when the truck starts, and I usually drive it once or twice a week. And I really didn't pay attention to the coolant level until it started to overheat.

It overheats almost instantly, I mean like from the time that the temp gauge hits the middle of the gauge, then if you drive it for 5 minutes, the temp is spiked.

Here is something I have not mentioned...I can have the truck sit and idle for an hour and the temp stays right where it needs to be, but when I start driving it, BAM, temp starts going UP!!! I am not sure that means anything....

How can I tell if there is a head gasket leak?

 

What is a CEL?

Also....this hose is constantly spilling hot coolant into the reservoir, so for that same reason I am thinking that the radiator is blocked up....

What do yall think?

 

CEL=Check Engine Light.

Are you leaking coolant at all? Honestly, I wouldn't drive the truck unless it is to a mechanic. If it is a blown head gasket/cracked head you dont want coolant getting in to the engine.

Your situation literally sounds exactly like mine...I was fine when it was sitting, but if I drove 5 minutes to O'Reilly it would be almost spiked and when I was stopped sitting at stoplights sometimes it would cool down if it was a cool day out. On hot days (most days here in texas lol) it would cool up a bit as I drove-I figured from air passing through.

It also never got hot if I filled the radiator back up (There were a few times when I HAD to drive it to my job, and then to the mechanic obv)

 

If the heat is spiking that quickly, there is a major cooling issue, either with the radiator or the engine. The 4.7 is known to have cooling system issues due to the cooling channels being close to the cylinders. drain a tiny bit of oil out, and see if there is coolant in your oil.