Heating Up In Traffic

[Jansen]

General question;

 

We hit 95ºF yesterday in Cincinnati and while sitting in traffic, I noticed three things:

 

1. The coolant temp climbed from 192ºF to 215ºF

2. The trans temp went from 176º to 198ºF

2. The A/C temp went from ~55ºF to 70ºF

 

This is after 8-10 minutes of sitting at a dead stop. I shut the A/C down and the coolant temp started to drop almost immediately. I use a scan gauge to watch the trans and coolant. I have an old meat thermometer in one of the vents (used to prove compressor problem to GM in 2005).

 

 

I know to expect things to heat up in the summer when idling at a dead stop, but the the rising temps showed no signs of stopping. I don't know if they would have leveled off at some point. Anyone notice anything similar? I figure if all three are rising maybe the fan isn't working correctly.

 

Jansen

[2007VictoryRed]

How many miles? Maybe you need to flush the coolant? Also check the thermostat, If its opened at the right temp, But being that the whole drivetrian is hot, I would look at the coolant

[Jansen]

sorry, it is a 2004 Ext Cab, 4x4, 5.3L V8, 65,500 miles.

[2005LT]

I'm assuming it doesn't have electric fans right? In any case, how clean is your rad? Do you have a bug screen or anything that helps to keep the rad clear? If not then that's where I would look first. A good power washing (careful not to bend the fins) with that plastic shroud off may help out.

[Jansen]

Mechanical fan.

[Jansen]

one other item to add. The overflow hose from the reservoir tank is constantly wet on my truck. i think the valve in the cap is bad.

[superjim]

one other item to add. The overflow hose from the reservoir tank is constantly wet on my truck. i think the valve in the cap is bad.

 

 

Have the cap tested or replace the cap if you have any doubt about it. It is cheap.

Coolant will boil at a lower temp if the pressure is the cooling system is lower than it should be.

 

The heating up may not be all that abnormal, since you were sitting at a dead stop at 95 degrees, for 10 minutes, at a slow idle, with the AC on.

Thats a pretty severe test.

 

The condenser in front of the radiator gets pretty hot when the AC is running.

Your fan is not turning very fast when you are sitting stopped with the truck in gear, therefore not much air is being drawn thru the radiator and what air IS coming thru is getting heated up more by the AC condenser.

 

This will affect both the temp of the air coming from the AC unit and the cooling ability of the radiator to cool your truck.

 

I am in Texas where it routinely gets well over 100 degrees in the summer.

When I am caught in traffic, in my truck, for a while, and the ac is not blowing real cold, I slip it into NEUTRAL and speed up the RPM's just a little.

It really helps... both the AC cooling and the temp of the engine.

My truck also has a mechanical fan...like yours.

[txab]

Check cap and fan clutch.

[superjim]

Check cap and fan clutch.

 

 

Agreed...I forgot to mention to also check the fan clutch.

[c4cruiser]

The fan clutch would be a good suspect. If the clutch is not working properly, then the fan will not rotate fast enough to bring enough air through the radiator at lower vehicle speeds or at idle. Idling at high ambient air temps can cause some increase in coolant temps, but 8-10 minutes at idle should not be a problem. But 215 degrees on the coolant temp is not that bad on a hot day. If it went to 230 or higher, then there would be reason to suspect something that's not right.

 

If you have not done a coolant flush with 65K on the truck, it should be done soon. Dex-cool should be replaced at 50K miles or 5 years.

[Bish]

If your fan clutch is fully engaging, you can hear it as it sounds like a damn airplane engine. I had one go on my 01 Tahoe at similar mileage and replaced it with a Hayden HD.

[pm26]

If your fan clutch is fully engaging, you can hear it as it sounds like a damn airplane engine. I had one go on my 01 Tahoe at similar mileage and replaced it with a Hayden HD.

 

 

I had a bad fan clutch on my 95 Nissan pickup and it stayed engaged even at low coolant temperatures and it did sound like a vacuum cleaner when the engine was revved up. There was also noticeable power drain from the engine with the clutch engaged. Electric fans are a much better system that fan clutches on mechanical fans.

 

One way to check a fan clutch for proper functioning is to run the engine until it is hot then let it idle with A/C on for a while. The fan clutch should be engaged at this point. Blow compressed air with a blow gun onto the fan blades against the direction of the fan rotation. If the clutch is engaged, the fan will keep rotating. If not, the air stream will stop the fan.

[bigredmariner]

My 2 cents, replace your rad cap, and the clutch. Probably time and you don't want to screw around and overheat it and crack a head. Oh yeah and the flush is a good idea too. Good luck.

[Jansen]

I plan to order a new cap and check the fan clutch this weekend. The truck turns 5 in December, hopefully I will have time to flush it over the 4th. Will post results as soon as they are available.