My, 01, 1500, 4x4, 5.9, tranny heat exchanger, isrunning hot while towing (boat or utility trailer), both about 4500lbs loaded. Ive only had the truck a few weeks so i dont have a history for it. Runs fine when not towing, but occasionally hear water sounds around my ac/heater box on passenger side. Ive done the searches and read that maybe there is air in system.

I have only tried the removing of the fill cap and watching for the thermostatto open, which it does but when it opens fluid starts flowing over the filler opening. Not very fast but it starts flowing over, I have to idle the engine a little to have the level pull down below the filler opening. Does any one know what might be causing thatto happen? With past trucks Iwould be able to watch the coolant flow withoutit overflowing.

Ive replaced the radiator cap.Ensured proper coolant level. Ran it with capoff until therm opensand then let it cool down. Seems as though the thermostat is operating correctly. I do have alot of flow when the thermo opens. The water pump looks to be fairly new. The pump is alot cleaner/shinerthan rest of engine.

Concernedabout the coolant coming out of the fill opening after thermo opens. Not sure if that is right. Makes me question a combustion leak, which in turn could be adding air/fumes to the coolant system.

Anyone with a good technique for burping the system or flushing the air out im taking all suggestions.

Im still troubleshooting the system but thought i would run this by you guys. Ive read alot of good feedback on some of the other posts.

thanks mayfly

 

I just drivethe frontup on ramps, try to make the fillopening the highest point on the coolant system. I usually have to let it idle with the heat on full for about 8 min before all the bubbles go away.

I wonder if the previous owner put in a high flow water pump? Never had one myself, but it might be the reason the coolant is "boiling" out at you. Do you ever notice a coolant leak under the truck? It's possibleone of the hoses has a leak or bad seal, check nearest the newpump first. The hose might have gotten cracked or split shoving it back on the new pump.

If you still can't get the heat down and you can't find any other problems, try a cooler thermostat (180*) or a 12" electric fanpulling air over the radiator, that should pull the temp down.

 

No one has yet explained how a 180º thermostat is going to make a truck run cooler. All it does is open at 180º rather than 195º.

 

by putting in a 180 it will open at that temp as opposed to the 195 stock (15* cooler) should keep the temp down. thats how that would work.

 

But opening sooner is not going to make the engine run cooler.

 

....yea it will, thats the whole concept of the thermostat. The thermostat traps water in the block until it reaches the thermostat opening temperature, at which point cooler water is allowed to fill the block and the thermostat closes again. I had my thermostat break in the open position and I couldn't even get the temperature guage to read anything. After driving for an hour the temp guage was still bottomed out so I popped the hood and the engine was much cooler than normal...barely hot to the touch.

 

My problem/issue is that the Dodge was built stock with a 195º thermostat and rated at the towing capacity most of us barely touch. I am certain that the transmission adds a certain amount of heat, hence part of the reason a transmission cooler is helpful. However, I believe there are underlying issues why an engine will run hot. In my case, I had not replaced the fiberboard that goes on either side of the radiator shroud (I had only replaced it on one side), and my truck was running hot as the summer approached. Once I replaced the missing piece, it ceased being a problem with the exception of the occasional bouncing of the needle, which I suspect to be air in the system. I am trying my best to get all of the air bled.

 

Sorry, I wasn't trying to say a lower thermostat would fix his problem. Only that a lower temp thermostat allows the engine to run at a cooler temperature. Regardless of what temp thermostat you run, your engine should maintain a steady temperature unless you are in the most extreme of circumstances. There is probably some other problem related to his towing...likely a water pump or fan clutch.

As to your problem, the typical reason for a bouncing temperature needle is as you stated air in your line or a bad fan clutch. If your engine temp gets hot at low speed driving but is fine at highway speed, then you should look into replacing the fan clutch. As for air trapped in the system, an old trick is to drill two small vent holes in the thermostat that will let air pass through. (It also lets water pass through but usually a negligable amount if the hole is small enough). Note: this doesn't let water leak out of the system, only lets air and a small amount of water pass even when the thermostat is closed.

 

I understand. I don't buy the drilling holes in the t-stat. Never done it before on a vehicle. BTW - I have replaced my fan clutch. Also note that at speeds over 35mph, the fan clutch no longer needs to run. Only at low or idle speeds.

 

Jeez guys,

I didn't mean ot start a t-stat war. [sm=oopssign.gif]