Hi all!

I bought an 04 Ram 1500 w/ 4.7L in November. All was well until recently. The other day outdoor temps reached excess of 80 degrees and my truck overheated on the way home from work. I wasn't paying attention to the gauges, but the "Check Gauges" light and warning bell caught my attention and I noticed the temp gauge just below the RED. I immediately exited the freeway and cranked the heater. The temps came back down to normal in a few minutes.

Normal has always been when the temp gauge needle is just below the half-way mark.

It seems as though this only happens when it is warmer (~70 degrees plus) and at higher speeds (~65mph+).
Driving in town at slower speeds or idling the temp gauge runs at a normal level.

Here is what I have done so far...

- Checked coolant level. OK.
- Replaced thermostat.
- Replaced water pump.
- Checked hoses. Seem to be OK. No leaks or blockage or collapsing..
- Removed radiator and flushed internally with a hose. Flow seemed OK.
- Cleaned radiator exterior of any debris.
- Burped system. (Purged air).
- Ran for 5+ hours with a radiator Super Clean/Flush product.

After all of this it has not overheated to the point that the "Check Gauges" light comes on, but it does run warmer at times (~3/4 mark on the temp gauge). Of course at this point I usually slow down, crank the heater, or pull over to keep it from getting any hotter, so i am not sure if it would truly overheat now.

My next steps will be:

- Checking the new thermostat (in a pan of boiling water with a thermometer to make sure it opens correctly).
- Possibly the fan clutch (although I would think that the air flow caused by the truck moving at 65 mph would be enough)
- Lastly a radiator.

One more side note...I have been running straight water (no antifreeze) due to all of the work I have been doing on it. (Didn;t want to spend a bunch of money on antifreeze, just to drain it later) I know antifreeze/coolant has better thermal transfer than plain water, but I don't think that coolant would keep it from overheating at reasonable temperatures and normal daily driving. Am I wrong inthinking this?

Is there anything that I am missing/overlooking or other words of advice?

Thanks,

Jared

 

I'm waking up from a hangover, looks like you've done a good amount of testing.

Fan clutch is a likely cause.

However the boiling point with out antifreeze differs, also their may not be enough pressure in their to keep it from boiling now thatthe boiling temp has changed.
Lastly when you do finally fill it up with anti freeze and water, make sure you buy distilled water if your hose water is hard water. Here in span antonio we have very hard water and that can clog the rad. How sure are you that all the air is out?
man theres been a lot of 4.7 over heating lately.

Also if your replace the fan look into an e fan.

 

I will check into a fan clutch. I compared the turning resistance (with motor off of course) with another vehicle and it felt similar, but it is hard to say what it does at higher speeds and temps.

I'm pretty darn sure all the air is out. When I refilled the radiator I let it warm up and run with the heater on full blast and the radiator cap off. I kept adding water as the water level went down. I have been driving it to/from work for the past 4 days (~1 hr each way) and I checkthe waer levelevery night. The level isn't changing in the radiator or overflow. So, I'm guessing all the air is out.

Never thought about the boiling point changing...good point.

Is there a good way to test the fan clutch or radiator flow without special equipment?

Thanks,

Jared

 

I would check inlet and outlet temperature of radiator under load to make sure someone didn't put stop leak in it preventing proper heat transfer.
I would think that running 65 or 70 on a 70 or 80 degree day the fan clutch should not even engage due to air already going accross the radiator....but I am a newbie and may be an idiot!![8D]

 

I knowthe fan clutch is engagedin the morning for a short bit (loud fan noise). After it warms up alll I have heard isthe electric fanon the AC condenser.I do not remember hearing the radiator fan noise once it heats up, whether I am going fast or slow.

I think I am going to try hitting the fan clutch with a heat gun tonight after work and see if I can get it to engage.
It is hot here today (> 90 degress), so I'll pay special attention to the fan noise if my temp starts to rise.

I'll post my results...

 

as a sorta fix you ought to buy a 180dual stage tstat. That way itll at least take longer to overheat.

 

It just occurred to me... You may yet have a collapsing hose. I've heard of that before. Give this a shot: With the motor hot, have someone wind the motor up pretty tight and see if one of the radiator hoses is collapsing. The item I read it was the top hose, but I guess either of 'em could do that.