2004 silverado crew cab z71 overheating while idle

[04z71crew]

Looking for some help here, I've got an 04 z71 crew cab with the 5.3 and recently it has been overheating when the truck is sitting at idle with the ac on. What I have done : installed a fan clutch last year, and cleaned the condenser and radiator out. While driving it sits at 195 but today it did jump to 212 even while moving and cutting the ac off brings it back down. When its sitting the fan just doesn't seem as loud as it should be in these 100+ temps here in oklahoma. The other day i left it running for 20 minutes to cool it off and when i left the house it was sitting at 250 with the engine coolant hot warning. Revving it up to 3K for about 2 minutes brought it back down to normal. It seems like an airflow issue, isn't the fan supposed to be pretty damn loud? I know my 94 z71 was. Is the radiator going to sh*$? thermostat sticking? water pump weak? where should i start to diagnose it? Thanks.

[kstruckcountry]

The water pump, thermostat, and fan clutch are cheap and all have to be replaced at some point, I'd start there if it was me.

[txab]

Sounds like a weak fan clutch

[arcasey]

I would suggest replacing the thermostat first. They are cheap and relatively easy to get too. If that doesn't fix it then I would look at the fan clutch. In my experience water pumps don't typically get weak, they just fail.

 

If you really want to be thorough, you can removed the thermostat and put it in a pot of hot water on the stove with a thermometer and check to make sure it is opening at the correct temperature. They're usually only about $5-$10 so I would go ahead and replace it to eliminate it from being the culprit of the problem. Thermostat should start to open between 180-195 degrees. If I recall correctly those trucks OEM thermostat were rated at 186 degrees.

[MonsterCrewCab]

I have the same problem with the same truck!

 

At idle for 12 mins it over heats with ac on. Kill ac it cools back down or rev to 2500 and it coola back down.

 

So far

New clutch fan

New thermostat

New waterpump

Checked radiator and around same temp at all points

Checked AC freon and level is where it should be.

 

My plan is to so e-fan conversion with factory fans and factory pcm stand alone so my pcm can control fans not a relay or switch.

 

Truck has 6" suspension and 3" body

 

The fan shroud currently is 3" lower on the radiator but is still installed on truck

 

My thoughts are the body lift pulled the fan further from the radiator causing the issue.

 

However neighbor has the same lift set up on a tahoe same fan and shroud and has zero issues!

 

On other thing truck does not burn oil and i do not lose engine coolant either.

 

Any ideas?

[GM_Lover]

Anyone figure anything out with this issue? My truck (same truck) is struggling in this Kansas heat.. Hell its not even hot really.. I work on a pipeline so I’m in my truck a great deal of the day with the A/C on at an idle. I’ve replaced the fan clutch twice, water pump, thermostat, had the cooling system flushed, cleaned the condenser with oven cleaner and pressure washed it out.. If I lift the hood it’ll cool right back down or if I get the rpms up to 1500+ it’ll cool down.. No other issues at all.. I would put the electric fans and larger radiator in it but I don’t have anyone to tune the computer for the fans. I’m beating my head against the wall trying to figure this out.. I’m new here by the way so if I step out of line or repeat myself just let me know. Thanks 

[CamGTP]

I'd almost suspect the radiator having poor circulation. When you rev the engine it's able to force more coolant flow through the system and cool it back down.

 

How hot is it actually getting?

 

The dash is not a good way to judge real temp as the temp sensor to cluster read outs tend to be 10-15+ degrees different. When the cluster reads 210, they tend to be 195-200 at the temp sensor.

[GM_Lover]

Well it says 195 normally and it slowly makes its way to 235 but I haven’t let it get over that.. I’m sitting in it right now with the ac on and the hood up.. it’s sitting at 195. When I had it flushed, the clear hose on the machine had a steady solid flow of coolant coming out and the tech said in his experience if there is a clog then it will be a “half full” or “less than full” hose. I don’t know the guy and can’t say he knows shit for sure so I guess this weekend I’ll replace the radiator. I was also considering installing an AC Delco fan clutch since I’ve changed it twice and still having an issue. I happened to have read somewhere that they replaced an after market clutch with a delco and that fixed their issue.. Heck I appreciate the help bud. Radiator and hoses this week I guess.. question, if the radiator is clogged, why when I open the hood it cools back down? 

[txab]

Some aftermarket fan clutches aren't as good as OEM for some vehicles. You could have a tube or several tubes in the radiator that are blocked or partially blocked also.

 

Are all your shrouds still in place? These ensure the air is being pulled through the radiator and just recirculating underhood air. Have you got anything that would block airflow on the front end. Extra light bars, winch, bull bar, brush guards?

 

Mine idles in the heat too and I can't get it to overheat. AC performance doesn't suffer at idle either

[GM_Lover]

Everything up front is stock. The shrouds are all in place. Maybe upgrade to a Delco clutch and replace the radiator will do it for me. I’ll try those for sure. The radiator is literally the only thing I have not replaced so it appears that could be the culprit but I’d feel better if I upgraded the clutch as well.. I’ve read a lot about aftermarket clutches not pulling enough air, even being replaced multiple times with sub par results. Thanks again buddy

[sefiroxx]

I've had the same problem on 04 Sierra in Texas for the past 10 years. Have replaced clutch, water pump and radiator. Plan on converting to an electric fan next.

I assume an engineering problem of some sort.

[Sierra89]

I had a similar issue.  Turns out a rodent  made a nest under the fuse panel and relay box under the hood and was dining on my wiring.  Judging from all the damage he did by eating wires I'm amazed that the overheating at idle because the fans were not kicking on was the only sign of the problem.  This was earlier this week, I'm sorting out and fixing the wires as we speak.

Best of luck sorting it out, remember to check for animal damage too.

Edited May 15, 2020 by Sierra89

[CKentC]

I’ve got the same problem on 2004 z71. In Texas with hot summer temps. Has suspension and 3” body lift that has raised the radiator about 3 inches above the top of fan shroud. Has anyone figured out a solution beside throwing parts at it? Seems like everyone saying water pump, thermo, and clutch are still having issues. Is this just a GM engineering flaw, like the 2-3 gear clunk I’ve also got?

[davester]

How is it a GM engineering problem when your radiator is no longer entirely within the shroud?  Is there a plug along the bottom of the radiator, to fill the gap below the radiator, so the air is forced to go through the radiator instead of just going around it?

[txab]

You've got to get the airflow across/through all the radiator, otherwise your cooling capacity is being wasted. Modify all the shroud and baffles to insure all the air going through the grill is passing through all the radiator. If you've got a 3"gap between the backside of the radiator and fan shroud, you're just sucking air through that gap which is sizable

 

I have no issues with mine in Texas heat at idle for extended period of times.

 

Arriving at parking spot. Clutch fan

 

 

 

 

 

After 40 minutes parked and running, with AC on and very comfortable.

 

 

Edited August 30, 2020 by txab