KATOOM

I may be wrong but I'm betting that your thermostat started working better (for your situation) only because, for some unknown reason, its no longer opening at the same "cooler" temp than it was before. Maybe that 215* jump forced the thermostat to open fully and changed its set limits. Not saying that 215* is overheating but I have heard that overheating an engine sometimes means also having to change a damaged thermostat from the overheating. I still stand firm on my theory though..... I think the 190* thermostats are to cool for the 24v. But.....in saying that, I'm sure there is a reason a 190* is offered for the 24v. And that reason is probably for the HO application because HO engines run hotter cylinder head temperatures than SO's. Thats why they run different valve seats than the SO motors. So maybe the HO is more capable of maintaining the hotter temp and can get away with a 5* cooler thermostat.....but the SO cant. I am betting that if you install a 195* thermostat that your engine temperature fluctuations will stop.

Placing the thermostat in a pot of hot water may let you know what it doing unless its moving slower than you think and then you're not going to notice any differences. You'd think that there is no normal reason engine temp would fluctuate up and down either unless the thermostat was bogus, but logic would make you think that would be rare too since there isn't much to a thermostat.....so there is likely another reason this is going on.Unfortunately I didn't save the box when I replaced mine so I cant tell you positively what temp it was nor what brand it was but I want to say that I remember it being a 195* and I know it was a NAPA. I called the NAPA I bought it from and they can only say that they carry NAPA brand, but think that Stant makes them. I say 195* because I remember researching what temp to get simply because old school gut instinct was wanting me to get a cooler one, although I had to listen to reason while understanding the requirements of the 24v ISB being cold blooded (per say) and choose 195*. I'm glad I did and the truck runs 190* all the time unless I'm towing and then it will lean toward 195*, which is exactly like it should.What do you all think about this.....Maybe running a thermostat colder than 195* in the 24v is keeping the thermostat partially open to early and the excess circulation of the radiator water is causing such engine temp variations. I say that for good reason and follow me here as I try to explain what I mean..... In knowing that the 24v requires more head temp than the 12v because of the increase in airflow (which is the reason the 12v thermostats are available in colder rangers than 24v thermostats), maybe if the thermostat in a 24v isn't hot enough then the engine is no longer capable of maintaining a constant cylinder temp and is easily overcome by cooler radiator water. The thermostat being so close to the open/close setting of the thermostat could be allowing the thermostat to ride right in that "not really open but not really closed" state. Remember that even though cool air builds HP by creating a denser combustion charge, diesels need cylinder heat for proper combustion which means that they need the proper thermostat temp per the application to achieve correct cylinder head temperatures. So one would think that maybe what most of you engine temperature fluctuations guys are complaining about is a result of the wrong thermostat temp setting (to cold), and/or that the thermostat itself is simply opening sooner than its stamped setting. Just throwing that out there.....but it sounds completely logical to me. :)Edit: Backing my theory would be why all these thermostat issue arise in the colder weather.....because during warm weather, the engine is able to create enough heat to maintain cylinder head temps and the engine temperature should remain more constant.

I have the NAPA thermostat and it works perfect. No fluctuation, and it seems to run at 190* on the spot unless I'm really loaded in the summer and then I may get up around 195*-205* on hills. Cant tell you what specific brand thermostat it was either because when I bought it a couple years ago it came in a NAPA box and there wasn't a lot of talk about the necessity to have only a Cummins thermostat. I've always kinda thought NAPA carried fairly quality parts so..... On a side note, are you sure your cooling system is full and that you dont have any air bubbles possibly causing air locks since either one of those could cause engine temperature swing? If you read the FSM you'll see where it clearly states that ONLY the diesel engine has what they call a "jiggle pin" one way valve in the cooling system and that attempting to fill the cooling system with the engine running wont work because of that one way valve. Now I've asked what is this jiggle pin but it seems no one knows. So my point is that I've heard that having an air lock isnt to uncommon. Just a thought.

Gotta admit that I've never heard this saying before.

Honestly I never cared much about battery hoopla. Talking batteries always turns into an oil thread..... Sure if I had the money I'd probably buy Interstates just because they've always been great but what I seem to look for now is simply where I can get a quick replacement if I have trouble and/or away from home. That would be a benefit for using Walmart since they're everywhere.

True that to many holes would affect warm up time and hamper the thermostats ability to keep the engine temp normal under no load situations. But for whatever reason, some thermostats do cause this wide range of temperature fluctuation. I've heard that guys claim its normal but I dont buy it. I would never consider a 10*-20* swing in engine temp "normal". Matter of fact, I cant imagine it being good for the engine either since there would be a constant expansion and contraction of metals and tolerances. But all I meant was that I've read somewhere that drilling a couple small holes in the side of the thermostat is supposed to stop any temp swing but I couldn't tell you what thermostat they were talking about.

I read somewhere that you could fix that by drilling a couple small holes in the thermostat. Not sure how big or where so.....

Just out of curiosity I just pulled up the Consumer Reports website and to find out this all so important rating information requires being a member. Whats that all about? On another website, the NAPA battery was rated best. I understand that all batteries are built by only a couple battery manufacturing plants but they build those batteries for specific brand names as per that brands requirements.

Anyone ever hear of the "jiggle pin" in the coolant system that the FSM refers to? Not sure what it is or where it is but it cautions not to fill a running engine because of this one way valve. I didn't have any problems that I know of but I'm just curious.Update..... Now the truck takes considerably longer to warm up than it did before and now every time the engine warms after sitting all night, the engine temp will slowly climb to about 195* and then drop to about 185* and remain steady there throughout the day. Maybe this always happened but I never paid attention. I'm curious how what it will run in the hot summer months.

I'm just shocked you got 10 years..... Hope those Walmart batteries last for you too because I've heard to many times that they're garbage. But you seem pretty particular about battery upkeep. So keep us posted.

Thats right. Keeping it real.

Obviously I agree with you but given the fact that the FSM lists the overflow valve setting as "approximately" 14 psi and goes on to say that it should flow at 14-16 psi, I figure 15 psi is safer than 14 psi. That being said, how accurate is everyone's fuel pressure gauge? Well for example, my electronic fuel pressure gauge used to read 19.5 psi at idle but after changing to my new mechanical fuel pressure gauge, I was now reading 17.5 psi at idle. So I compared with a fuel pressure test gauge to find that my mechanical was within 1/2 a psi of the tester which means that I can only figure I wasn't getting accurate fuel pressure readings from my electrical gauge. My fault for trusting it for all those years, which is why I plumbed in a test port this time around so I can always confirm my mechanical gauge. Now I know I'm really getting 19.5 psi at idle. Point being is, I would advise someone to either test their fuel pressure gauge or set their regulator so that they never get below 16 psi.....just to be sure. Not worth the risk.

This is exactly correct. Yes, excess fuel running through the VP is what removes the heat but using the "if more is good then a lot is better" mentality by just cranking up the fuel pressure could potentially work against you. We know how the VP is cooled and we know at what psi the VP is cooled but we dont know at what psi could be causing the return line to run under pressure and if that happening will affect the return process or affect VP performance or reliability. More research with more people running well over 20 psi may yield more answers to this but at the moment, staying between 15-20 psi at all times seems to be best. In saying this, we have yet to hear of someone who ruined their VP from "to much" fuel pressure.

Taking off the front driveshaft would only help on non-CAD front axles because on full time 4wd systems the front tires are always turning the front axles which are turning the carrier which is turning the driveshaft which is spinning bearings in the transfer case. As Mike stated, that rotational mass and drag could affect fuel mileage. There would be no point in removing the driveshaft off a CAD axle since everything is basically disconnected in 2wd.

Thanks bcbigfoot for the post since thats exactly what I'm talking about. When every faucet in my house has white stalagmites hanging from them.....ya, I'm a little concerned to introduce any to my coolant system.

I dont have any pictures of my house faucets but if I did, you'd see a lot of white buildup. I also use a teapot on the stove for humidity but its not as clean as yours. Seriously, the water here is so full of minerals that you cant wash off the cars and drive away fast enough before ending up with water spots. Towel drying is a must. I love all the minerals for taste and for watering plants but its hard on faucets, water heater, and washing cars.

I wouldn't be so worried but where I live, there is a lot of minerals in the water. But just to be clear of my concerns..... I have to use hose water to flush the system and I know that getting all what I've put in there with the hose out will be impossible so even when I completely refill with 50/50, there will still be some contaminating hose water in there. Is this reason for concern? And also so I dont have to make more than one trip to the parts store, how much coolant does the system hold?

Anyone have any opinions on what to use and how to go about this process? Thanks.

I find mine pulls the strongest at around 2200 RPM which happens to be around 55-60 mph in 4th. Thats not to say that 1700-2199 isn't also impressive but just noting where it will pull just about any hill with any load (I've had) without much, if any, speed loss.

Hmmm.....That is funny. Darn Discovery channel.

No worries Mike. Didn't think you ever indicated that you mistreat your ride. And yes, I'm sure your 1 mile dash to the station wasn't good for anything but simply being there in a hurry to help. Thus the reason why fire truck engines are strictly scrutinized and are replaced frequently. No time for warm up for them.

As Mike stated, both speed and aerodynamics play a role in fuel mileage. Speed because mathematically the drag coefficient of a vehicle increases exponentially. Meaning it takes four times the HP to double the speed. So you can only imagine how much more fuel it takes to go from 55 to 75 MPH. This is all exaggerated while towing because of increased rolling resistance from the combined weight and the extra drag from whatever you're towing. TT's and 5th wheels are generally anything but aerodynamic so you're really just shoving them down the road. The more aerodynamic the trailer is and the amount of energy it takes to move it along will reduce. I can tow a heavy boat down the freeway and not even know its there but when towing a travel trailer, I rarely need to use the brakes because letting off the throttle slows me fast enough. Now some engines are simply more efficient at a certain work load and the Cummins excels in that department which is why we get such great fuel mileage. All engines can tow but how hard they have to work to accomplish the same task is whats important.

This is about me to the tee. Although I happen to live where it takes me about 10 minutes of light driving to get to town or the freeway. "Exact" idling time can be irrelevant unless you're actually sitting in the cab waiting to drive off. What I do is before I'm completely ready, I go outside, start 'er up, let it idle for a minute or two or three, and then drive away. That may not be an option for people in the city. Long idle times aren't necessary nor are they good but its just important to make sure the oil has had enough time to fully circulate and become thin enough so you're assured that all moving parts are being lubricated. Depending on the outside temp and if the trucks been plugged in will both determine how long you should let it idle before placing a load on the engine. If a trucks been sitting outdoors in zero degree weather without being plugged in, then you can be sure the oil is as thick as mud. And remember its not just the oil that you have to worry about either but that engines are designed with specification clearances ONLY meant for normal running temps. That means that all the moving parts clearances will not be right until everything is at normal running temperature. Point being is if you care to keep your truck running in good condition for a long time then treat it right and keep your engine load to a minimum until as everyone stated, the engine temp is around 160* and the oil pressure is not spiking the gauge.

Bummer.

I've noticed that the '03 towing mirrors are identical to the 2nd gen towing mirror but the '03's come heated. Will the '03's fit on the 2nd gen? I haven't looked but I cant imagine that Dodge would make many multiple different wiring looms for the very few available model options so I'm betting that there is a connector already in the door for heated mirrors and all I'd need is a headlight switch with the heated mirror button.